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draft-clausen-lln-loadng-10.txt:

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  Miscellaneous warnings:
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  == The copyright year in the IETF Trust and authors Copyright Line does not
     match the current year

  == Line 655 has weird spacing: '...-length  is an...'

  == Line 660 has weird spacing: '...seq-num  is an...'

  == Line 664 has weird spacing: '...ic-type  is an...'

  == Line 667 has weird spacing: '...-metric  is a ...'

  == Line 672 has weird spacing: '...p-count  is an...'

  == (30 more instances...)

  == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD',
     or 'RECOMMENDED' is not an accepted usage according to RFC 2119.  Please
     use uppercase 'NOT' together with RFC 2119 keywords (if that is what you
     mean).
     
     Found 'MUST not' in this paragraph:
     
    
     +-------------------+-------------------+---------------------------+ |  
      RREQ Element   |  RFC5444-Element  | Considerations            |
     +-------------------+-------------------+---------------------------+ | 
     RREQ.addr-length | <msg-addr-length> | Supports addresses from   | |     
                  |                   | 1-16 octets               | |   
     RREQ.seq-num   |   <msg-seq-num>   | 16 bits, hence MAXVALUE   | |       
                |                   | (Section 8) is 65535.     | |           
            |                   | MUST be included          | | 
     RREQ.metric-type |   METRIC Message  | Encoded by way of the     | |     
                  |        TLV        | Type-Extension of a       | |         
              |                   | Message-Type-specific     | |             
          |                   | Message TLV of type       | |                 
      |                   | METRIC, defined in        | |                   | 
                      | Table 8. A LOADng Router  | |                   |     
                  | generating an RREQ (as    | |                   |         
              | specified in              | |                   |             
          | Section 12.1) when using  | |                   |                 
      | the HOP_COUNT metric,     | |                   |                   |
     MUST NOT add the METRIC   | |                   |                   |
     Message TLV to the RREQ   | |                   |                   | (in
     order to reduce       | |                   |                   |
     overhead, as the hop      | |                   |                   |
     count value is already    | |                   |                   |
     encoded in                | |                   |                   |
     RREQ.hop-count). LOADng   | |                   |                   |
     Routers receiving an RREQ | |                   |                   |
     without METRIC Message    | |                   |                   | TLV
     assume that           | |                   |                   |
     RREQ.metric-type is       | |                   |                   |
     HOP_COUNT, and MUST not   | |                   |                   | add
     the METRIC Message    | |                   |                   | TLV
     when forwarding the   | |                   |                   |
     message. Otherwise,       | |                   |                   |
     exactly one METRIC TLV    | |                   |                   |
     MUST be included in each  | |                   |                   |
     RREQ message.             | | RREQ.route-metric |   METRIC Message  |
     Encoded as the value      | |                   |     TLV value     |
     field of the METRIC TLV.  | |                   |                   |
     (LOADng Routers           | |                   |                   |
     generating RREQs when     | |                   |                   |
     using the HOP_COUNT       | |                   |                   |
     metric do not need need   | |                   |                   | to
     add the METRIC Message | |                   |                   | TLV,
     as specified above   | |                   |                   | for the
     RREQ.metric-type  | |                   |                   | field.)    
                   | |   RREQ.hop-limit  |  <msg-hop-limit>  | 8 bits. MUST be
     included  | |                   |                   | in an RREQ message 
           | |   RREQ.hop-count  |  <msg-hop-count>  | 8 bits, hence          
       | |                   |                   | MAX_HOP_COUNT is 255.     |
     |                   |                   | MUST be included in an    | |  
                     |                   | RREQ message.             | | 
     RREQ.originator  |  <msg-orig-addr>  | MUST be included in an    | |     
                  |                   | RREQ message.             | | 
     RREQ.destination |     Address in    | Encoded by way of an      | |     
                  |   Address-Block   | address in an address     | |         
              |       w/TLV       | block, with which a       | |             
          |                   | Message-Type-specific     | |                 
      |                   | Address Block TLV of type | |                   | 
                      | ADDR-TYPE and with        | |                   |     
                  | Type-Extension            | |                   |         
              | DESTINATION is            | |                   |             
          | associated, defined in    | |                   |                 
      | Table 9. An RREQ MUST     | |                   |                   |
     contain exactly one       | |                   |                   |
     address with a TLV of     | |                   |                   |
     type ADDR-TYPE and with   | |                   |                   |
     Type-Extension            | |                   |                   |
     DESTINATION associated.   |
     +-------------------+-------------------+---------------------------+

  == Using lowercase 'not' together with uppercase 'MUST', 'SHALL', 'SHOULD',
     or 'RECOMMENDED' is not an accepted usage according to RFC 2119.  Please
     use uppercase 'NOT' together with RFC 2119 keywords (if that is what you
     mean).
     
     Found 'MUST not' in this paragraph:
     
    
     +-------------------+-------------------+---------------------------+ |  
      RREP Element   |  RFC5444-Element  | Considerations            |
     +-------------------+-------------------+---------------------------+ | 
     RREP.addr-length | <msg-addr-length> | Supports addresses from   | |     
                  |                   | 1-16 octets               | |   
     RREP.seq-num   |   <msg-seq-num>   | 16 bits, hence MAXVALUE   | |       
                |                   | (Section 8) is 65535.     | |           
            |                   | MUST be included          | | 
     RREP.metric-type |   METRIC Message  | Encoded by way of the     | |     
                  |        TLV        | Type-Extension of a       | |         
              |                   | Message-Type-specific     | |             
          |                   | Message TLV of type       | |                 
      |                   | METRIC, defined in        | |                   | 
                      | Table 12. A LOADng Router | |                   |     
                  | generating an RREP (as    | |                   |         
              | specified in              | |                   |             
          | Section 13.1) when using  | |                   |                 
      | the HOP_COUNT metric,     | |                   |                   |
     MUST NOT add the METRIC   | |                   |                   |
     Message TLV to the RREP   | |                   |                   | (in
     order to reduce       | |                   |                   |
     overhead, as the hop      | |                   |                   |
     count value is already    | |                   |                   |
     encoded in                | |                   |                   |
     RREP.hop-count). LOADng   | |                   |                   |
     Routers receiving an RREP | |                   |                   |
     without METRIC Message    | |                   |                   | TLV
     assume that           | |                   |                   |
     RREP.metric-type is       | |                   |                   |
     HOP_COUNT, and MUST not   | |                   |                   | add
     the METRIC Message    | |                   |                   | TLV
     when forwarding the   | |                   |                   |
     message. Otherwise,       | |                   |                   |
     exactly one METRIC TLV    | |                   |                   |
     MUST be included in each  | |                   |                   |
     RREP message.             | | RREP.route-metric |   METRIC Message  |
     Encoded as the value      | |                   |     TLV value     |
     field of the METRIC TLV.  | |                   |                   |
     (LOADng Routers           | |                   |                   |
     generating RREPs when     | |                   |                   |
     using the HOP_COUNT       | |                   |                   |
     metric do not need need   | |                   |                   | to
     add the METRIC Message | |                   |                   | TLV,
     as specified above   | |                   |                   | for the
     RREP.metric-type  | |                   |                   | field.)    
                   | |  RREP.ackrequired | FLAGS Message TLV | Encoded by way
     of a       | |                   |                   |
     Message-Type-specific     | |                   |                   |
     Message TLV of type       | |                   |                   |
     FLAGS, defined in         | |                   |                   |
     Table 13. A TLV of type   | |                   |                   |
     FLAGS MUST always be      | |                   |                   |
     included in an RREP       | |                   |                   |
     message.                  | |   RREP.hop-limit  |  <msg-hop-limit>  | 8
     bits. MUST be included  | |                   |                   | in an
     RREQ message        | |   RREP.hop-count  |  <msg-hop-count>  | 8 bits,
     hence             | |                   |                   |
     MAX_HOP_COUNT is 255.     | |                   |                   |
     MUST be included in an    | |                   |                   |
     RREP message.             | |  RREP.originator  |  <msg-orig-addr>  |
     MUST be included in an    | |                   |                   |
     RREP message.             | |  RREP.destination |     Address in    |
     Encoded by way of an      | |                   |   Address-Block   |
     address in an address     | |                   |       w/TLV       |
     block, with which a       | |                   |                   |
     Message-Type-specific     | |                   |                   |
     Address Block TLV of type | |                   |                   |
     ADDR-TYPE and with        | |                   |                   |
     Type-Extension            | |                   |                   |
     DESTINATION is            | |                   |                   |
     associated, defined in    | |                   |                   |
     Table 14. An RREP MUST    | |                   |                   |
     contain exactly one       | |                   |                   |
     address with a TLV of     | |                   |                   |
     type ADDR-TYPE and with   | |                   |                   |
     Type-Extension            | |                   |                   |
     DESTINATION associated.   |
     +-------------------+-------------------+---------------------------+

  -- The document date (October 18, 2013) is 3843 days in the past.  Is this
     intentional?


  Checking references for intended status: Proposed Standard
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     to lower-maturity documents in RFCs)

  == Outdated reference: A later version (-06) exists of
     draft-sheffer-running-code-01


     Summary: 1 error (**), 0 flaws (~~), 10 warnings (==), 2 comments (--).

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--------------------------------------------------------------------------------


2	Network Working Group                                         T. Clausen
3	Internet-Draft                                      A. Colin de Verdiere
4	Intended status: Standards Track                                   J. Yi
5	Expires: April 21, 2014                         LIX, Ecole Polytechnique
6	                                                              A. Niktash
7	                                               Maxim Integrated Products
8	                                                             Y. Igarashi
9	                                                                H. Satoh
10	                                        Hitachi, Ltd., Yokohama Research
11	                                                              Laboratory
12	                                                              U. Herberg
13	                                         Fujitsu Laboratories of America
14	                                                               C. Lavenu
15	                                                                 EDF R&D
16	                                                                  T. Lys
17	                                                                    ERDF
18	                                                                 J. Dean
19	                                               Naval Research Laboratory
20	                                                        October 18, 2013

22	The Lightweight On-demand Ad hoc Distance-vector Routing Protocol - Next
23	                          Generation (LOADng)
24	                      draft-clausen-lln-loadng-10

26	Abstract

28	   This document describes the Lightweight Ad hoc On-Demand - Next
29	   Generation (LOADng) distance vector routing protocol, a reactive
30	   routing protocol intended for use in Mobile Ad hoc NETworks (MANETs).

32	Status of This Memo

34	   This Internet-Draft is submitted in full conformance with the
35	   provisions of BCP 78 and BCP 79.  This document may not be modified,
36	   and derivative works of it may not be created, except to format it
37	   for publication as an RFC or to translate it into languages other
38	   than English.

40	   Internet-Drafts are working documents of the Internet Engineering
41	   Task Force (IETF).  Note that other groups may also distribute
42	   working documents as Internet-Drafts.  The list of current Internet-
43	   Drafts is at http://datatracker.ietf.org/drafts/current/.

45	   Internet-Drafts are draft documents valid for a maximum of six months
46	   and may be updated, replaced, or obsoleted by other documents at any
47	   time.  It is inappropriate to use Internet-Drafts as reference
48	   material or to cite them other than as "work in progress."
49	   This Internet-Draft will expire on April 21, 2014.

51	Copyright Notice

53	   Copyright (c) 2013 IETF Trust and the persons identified as the
54	   document authors.  All rights reserved.

56	   This document is subject to BCP 78 and the IETF Trust's Legal
57	   Provisions Relating to IETF Documents
58	   (http://trustee.ietf.org/license-info) in effect on the date of
59	   publication of this document.  Please review these documents
60	   carefully, as they describe your rights and restrictions with respect
61	   to this document.  Code Components extracted from this document must
62	   include Simplified BSD License text as described in Section 4.e of
63	   the Trust Legal Provisions and are provided without warranty as
64	   described in the Simplified BSD License.

66	Table of Contents

68	   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  5
69	   2.  Terminology and Notation . . . . . . . . . . . . . . . . . . .  6
70	     2.1.  Message and Message Field Notation . . . . . . . . . . . .  6
71	     2.2.  Variable Notation  . . . . . . . . . . . . . . . . . . . .  7
72	     2.3.  Other Notation . . . . . . . . . . . . . . . . . . . . . .  7
73	     2.4.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  7
74	   3.  Applicability Statement  . . . . . . . . . . . . . . . . . . .  8
75	   4.  Protocol Overview and Functioning  . . . . . . . . . . . . . .  9
76	     4.1.  Overview . . . . . . . . . . . . . . . . . . . . . . . . .  9
77	     4.2.  LOADng Routers and LOADng Interfaces . . . . . . . . . . . 10
78	     4.3.  Information Base Overview  . . . . . . . . . . . . . . . . 11
79	     4.4.  Signaling Overview . . . . . . . . . . . . . . . . . . . . 12
80	   5.  Protocol Parameters  . . . . . . . . . . . . . . . . . . . . . 13
81	     5.1.  Protocol and Port Numbers  . . . . . . . . . . . . . . . . 13
82	     5.2.  Router Parameters  . . . . . . . . . . . . . . . . . . . . 13
83	     5.3.  Interface Parameters . . . . . . . . . . . . . . . . . . . 14
84	     5.4.  Constants  . . . . . . . . . . . . . . . . . . . . . . . . 14
85	   6.  Protocol Message Content . . . . . . . . . . . . . . . . . . . 15
86	     6.1.  Route Request (RREQ) Messages  . . . . . . . . . . . . . . 15
87	     6.2.  Route Reply (RREP) Messages  . . . . . . . . . . . . . . . 16
88	     6.3.  Route Reply Acknowledgement (RREP_ACK) Messages  . . . . . 17
89	     6.4.  Route Error (RERR) Messages  . . . . . . . . . . . . . . . 18
90	   7.  Information Base . . . . . . . . . . . . . . . . . . . . . . . 19
91	     7.1.  Routing Set  . . . . . . . . . . . . . . . . . . . . . . . 19
92	     7.2.  Local Interface Set  . . . . . . . . . . . . . . . . . . . 20
93	     7.3.  Blacklisted Neighbor Set . . . . . . . . . . . . . . . . . 20
94	     7.4.  Destination Address Set  . . . . . . . . . . . . . . . . . 21
95	     7.5.  Pending Acknowledgment Set . . . . . . . . . . . . . . . . 21
96	   8.  LOADng Router Sequence Numbers . . . . . . . . . . . . . . . . 22
97	   9.  Route Maintenance  . . . . . . . . . . . . . . . . . . . . . . 22
98	   10. Unidirectional Link Handling . . . . . . . . . . . . . . . . . 24
99	     10.1. Blacklist Usage  . . . . . . . . . . . . . . . . . . . . . 24
100	   11. Common Rules for RREQ and RREP Messages  . . . . . . . . . . . 25
101	     11.1. Identifying Invalid RREQ or RREP Messages  . . . . . . . . 26
102	     11.2. RREQ and RREP Message Processing . . . . . . . . . . . . . 26
103	   12. Route Requests (RREQs) . . . . . . . . . . . . . . . . . . . . 30
104	     12.1. RREQ Generation  . . . . . . . . . . . . . . . . . . . . . 30
105	     12.2. RREQ Processing  . . . . . . . . . . . . . . . . . . . . . 31
106	     12.3. RREQ Forwarding  . . . . . . . . . . . . . . . . . . . . . 31
107	     12.4. RREQ Transmission  . . . . . . . . . . . . . . . . . . . . 32
108	   13. Route Replies (RREPs)  . . . . . . . . . . . . . . . . . . . . 32
109	     13.1. RREP Generation  . . . . . . . . . . . . . . . . . . . . . 32
110	     13.2. RREP Processing  . . . . . . . . . . . . . . . . . . . . . 33
111	     13.3. RREP Forwarding  . . . . . . . . . . . . . . . . . . . . . 34
112	     13.4. RREP Transmission  . . . . . . . . . . . . . . . . . . . . 34
113	   14. Route Errors (RERRs) . . . . . . . . . . . . . . . . . . . . . 35
114	     14.1. Identifying Invalid RERR Messages  . . . . . . . . . . . . 36
115	     14.2. RERR Generation  . . . . . . . . . . . . . . . . . . . . . 36
116	     14.3. RERR Processing  . . . . . . . . . . . . . . . . . . . . . 37
117	     14.4. RERR Forwarding  . . . . . . . . . . . . . . . . . . . . . 38
118	     14.5. RERR Transmission  . . . . . . . . . . . . . . . . . . . . 38
119	   15. Route Reply Acknowledgments (RREP_ACKs)  . . . . . . . . . . . 39
120	     15.1. Identifying Invalid RREP_ACK Messages  . . . . . . . . . . 39
121	     15.2. RREP_ACK Generation  . . . . . . . . . . . . . . . . . . . 39
122	     15.3. RREP_ACK Processing  . . . . . . . . . . . . . . . . . . . 40
123	     15.4. RREP_ACK Forwarding  . . . . . . . . . . . . . . . . . . . 41
124	     15.5. RREP_ACK Transmission  . . . . . . . . . . . . . . . . . . 41
125	   16. Metrics  . . . . . . . . . . . . . . . . . . . . . . . . . . . 41
126	     16.1. Specifying New Metrics . . . . . . . . . . . . . . . . . . 41
127	   17. Implementation Status  . . . . . . . . . . . . . . . . . . . . 41
128	     17.1. Implementation of Ecole Polytechnique  . . . . . . . . . . 41
129	     17.2. Implementation of Fujitsu Laboratories of America  . . . . 42
130	     17.3. Implementation of Hitachi Yokohama Research Laboratory
131	           - 1  . . . . . . . . . . . . . . . . . . . . . . . . . . . 42
132	     17.4. Implementation of Hitachi Yokohama Research Laboratory
133	           -2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43
134	   18. Security Considerations  . . . . . . . . . . . . . . . . . . . 43
135	     18.1. Confidentiality  . . . . . . . . . . . . . . . . . . . . . 43
136	     18.2. Integrity  . . . . . . . . . . . . . . . . . . . . . . . . 44
137	     18.3. Channel Jamming and State Explosion  . . . . . . . . . . . 46
138	     18.4. Interaction with External Routing Domains  . . . . . . . . 47
139	   19. LOADng Specific IANA Considerations  . . . . . . . . . . . . . 47
140	     19.1. Error Codes  . . . . . . . . . . . . . . . . . . . . . . . 47
141	   20. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 48
142	   21. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . . 48
143	   22. References . . . . . . . . . . . . . . . . . . . . . . . . . . 49
144	     22.1. Normative References . . . . . . . . . . . . . . . . . . . 49
145	     22.2. Informative References . . . . . . . . . . . . . . . . . . 49
146	   Appendix A.  LOADng Control Messages using RFC5444 . . . . . . . . 50
147	     A.1.  RREQ-Specific Message Encoding Considerations  . . . . . . 51
148	     A.2.  RREP-Specific Message Encoding Considerations  . . . . . . 52
149	     A.3.  RREP_ACK Message Encoding  . . . . . . . . . . . . . . . . 54
150	     A.4.  RERR Message Encoding  . . . . . . . . . . . . . . . . . . 55
151	     A.5.  RFC5444-Specific IANA Considerations . . . . . . . . . . . 56
152	       A.5.1.  Expert Review: Evaluation Guidelines . . . . . . . . . 57
153	       A.5.2.  Message Types  . . . . . . . . . . . . . . . . . . . . 57
154	     A.6.  RREQ Message-Type-Specific TLV Type Registries . . . . . . 57
155	     A.7.  RREP Message-Type-Specific TLV Type Registries . . . . . . 59
156	     A.8.  RREP_ACK Message-Type-Specific TLV Type Registries . . . . 61
157	     A.9.  RERR Message-Type-Specific TLV Type Registries . . . . . . 61
158	   Appendix B.  LOADng Control Packet Illustrations . . . . . . . . . 62
159	     B.1.  RREQ . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
160	     B.2.  RREP . . . . . . . . . . . . . . . . . . . . . . . . . . . 64
161	     B.3.  RREP_ACK . . . . . . . . . . . . . . . . . . . . . . . . . 65
162	     B.4.  RERR . . . . . . . . . . . . . . . . . . . . . . . . . . . 66

164	1.  Introduction

166	   The Lightweight On-demand Ad hoc Distance-vector Routing Protocol -
167	   Next Generation (LOADng) is a routing protocol, derived from AODV
168	   [RFC3561] and extended for use in Mobile Ad hoc NETworks (MANETs).
169	   As a reactive protocol, the basic operations of LOADng include
170	   generation of Route Requests (RREQs) by a LOADng Router (originator)
171	   for when discovering a route to a destination, forwarding of such
172	   RREQs until they reach the destination LOADng Router, generation of
173	   Route Replies (RREPs) upon receipt of an RREQ by the indicated
174	   destination, and unicast hop-by-hop forwarding of these RREPs towards
175	   the originator.  If a route is detected to be broken, e.g., if
176	   forwarding of a data packet to the recorded next hop on the route
177	   towards the intended destination is detected to fail, a Route Error
178	   (RERR) message is returned to the originator of that data packet to
179	   inform the originator about the route breakage.

181	   Compared to [RFC3561], LOADng is simplified as follows:

183	   o  Only the destination is permitted to respond to an RREQ;
184	      intermediate LOADng Routers are explicitly prohibited from
185	      responding to RREQs, even if they may have active routes to the
186	      sought destination, and RREQ/RREP messages generated by a given
187	      LOADng Router share a single unique, monotonically increasing
188	      sequence number.  This also eliminates Gratuitous RREPs while
189	      ensuring loop freedom.  The rationale for this simplification is
190	      reduced complexity of protocol operation and reduced message
191	      sizes.

193	   o  A LOADng Router does not maintain a precursor list, thus when
194	      forwarding of a data packet to the recorded next hop on the route
195	      to the destination fails, an RERR is sent only to the originator
196	      of that data packet.  The rationale for this simplification is an
197	      assumption that few overlapping routes are in use concurrently in
198	      a given network.

200	   Compared to [RFC3561], LOADng is extended as follows:

202	   o  Optimized flooding is supported, reducing the overhead incurred by
203	      RREQ generation and flooding.  If no optimized flooding operation
204	      is specified for a given deployment, classical flooding is used by
205	      default.

207	   o  Different address lengths are supported - from full 16 octet IPv6
208	      addresses over 8 octet EUI64 addresss [EUI64], 6 octet MAC
209	      addresses and 4 octet IPv4 addresses to shorter 1 and 2 octet
210	      addresses such as [RFC4944].  The only requirement is, that within
211	      a given routing domain, all addresses are of the same address
212	      length.

214	   o  Control messages are carried by way of the Generalized MANET
215	      Packet/Message Format [RFC5444].

217	   o  Using [RFC5444], control messages can include TLV (Type-Length-
218	      Value) elements, permitting protocol extensions to be developed.

220	   o  LOADng supports routing using arbitrary additive metrics, which
221	      can be specified as extensions to this protocol.

223	2.  Terminology and Notation

225	   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
226	   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
227	   "OPTIONAL" in this document are to be interpreted as described in
228	   [RFC2119].

230	   Additionally, this document uses the notations in Section 2.1,
231	   Section 2.2, and Section 2.3 and the terminology defined in
232	   Section 2.4.

234	2.1.  Message and Message Field Notation

236	   LOADng Routers generate and process messages, each of which has a
237	   number of distinct fields.  For describing the protocol operation,
238	   specifically the generation and processing of such messages, the
239	   following notation is employed:

241	                   MsgType.field

243	   where:

245	   MsgType -  is the type of message (e.g., RREQ or RREP);

247	   field -  is the field in the message (e.g., originator).

249	   The different messages, their fields and their meaning are described
250	   in Section 6.  The encoding of messages for transmission by way of
251	   [RFC5444] packets/messages is described in Appendix A, and Appendix B
252	   illustrates the bit layout of LOADng control messages.

254	   The motivation for separating the high-level messages and their
255	   content from the low-level encoding and frame format for transmission
256	   is to allow discussions of the protocol logic to be separated from
257	   the message encoding and frame format - and, to support different
258	   frame formats.

260	2.2.  Variable Notation

262	   Variables are introduced into the specification solely as a means to
263	   clarify the description.  The following notation is used:

265	   MsgType.field -  If "field" is a field in the message MsgType, then
266	      MsgType.field is also used to represent the value of that field.

268	   bar -  A variable (not prepended by MsgType), usually obtained
269	      through calculations based on the value(s) of element(s).

271	2.3.  Other Notation

273	   This document uses the following additional notational conventions:

275	   a := b   An assignment operator, whereby the left side (a) is
276	      assigned the value of the right side (b).

278	   c = d   A comparison operator, returning TRUE if the value of the
279	      left side (c) is equal to the value of the right side (d).

281	2.4.  Terminology

283	   This document uses the following terminology:

285	   LOADng Router -  A router that implements this routing protocol.  A
286	      LOADng Router is equipped with at least one, and possibly more,
287	      LOADng Interfaces.

289	   LOADng Interface -  A LOADng Router's attachment to a communications
290	      medium, over which it receives and generates control messages,
291	      according to this specification.  A LOADng Interface is assigned
292	      one or more addresses.

294	   Link -  A link between two LOADng Interfaces exists if either can
295	      receive control messages, according to this specification, from
296	      the other.

298	   Message -  The fundamental entity carrying protocol information, in
299	      the form of address objects and TLVs.

301	   Link Metric -  The cost (weight) of a link between a pair of LOADng
302	      Interfaces.

304	   Route Metric -  The sum of the Link Metrics for the links that an
305	      RREQ or RREP has crossed.

307	3.  Applicability Statement

309	   LOADng is a reactive MANET protocol, i.e., routes are discovered only
310	   when a data packet is sent by a router (e.g., on behalf of an
311	   attached host), and when the router has no route for this
312	   destination.  In that case, the router floods Route Requests (RREQ)
313	   throughout the network for discovering the destination.  Reactive
314	   protocols require state only for the routes currently in use,
315	   contrary to proactive protocols, which periodically send control
316	   traffic and store routes to all destinations in the network.  As
317	   MANETs are often operated on wireless channels, flooding RREQs may
318	   lead to frame collisions and therefore data loss.  Moreover, each
319	   transmission on a network interface consumes energy, reducing the
320	   life-time of battery-driven routers.  Consequently, in order to
321	   reduce the amount of control traffic, LOADng (and in general reactive
322	   protocols) are most suitable under the following constraints:

324	   o  Few concurrent traffic flows in the network (i.e., traffic flows
325	      only between few sources and destinations);

327	   o  Little data traffic overall, and therefore the traffic load from
328	      periodic signaling (for proactive protocols) is greater than the
329	      traffic load from flooding RREQs (for reactive protocols);

331	   o  State requirements on the router are very stringent, i.e., it is
332	      beneficial to store only few routes on a router.

334	   In these specific use cases, reactive MANET protocols have shown to
335	   be beneficial, and may be preferable over the more general use case
336	   of proactive MANET protocols.

338	   Specifically, the applicability of LOADng is determined by its
339	   characteristics, which are that this protocol:

341	   o  Is a reactive routing protocol for Mobile Ad hoc NETworks
342	      (MANETs).

344	   o  Is designed to work in networks with dynamic topology in which the
345	      links may be lossy due to collisions, channel instability, or
346	      movement of routers.

348	   o  Supports the use of optimized flooding for RREQs.

350	   o  Enables any LOADng Router to discover bi-directional routes to
351	      destinations in the routing domain, i.e., to any other LOADng
352	      Router, as well as hosts or networks attached to that LOADng
353	      Router, in the same routing domain.

355	   o  Supports addresses of any length with integral number of octets,
356	      from 16 octets to a single octet.

358	   o  Is layer-agnostic, i.e., may be used at layer 3 as a "route over"
359	      routing protocol, or at layer 2 as a "mesh under" routing
360	      protocol.

362	   o  Supports per-destination route maintenance; if a destination
363	      becomes unreachable, rediscovery of that single (bi-directional)
364	      route is performed, without need for global topology
365	      recalculation.

367	4.  Protocol Overview and Functioning

369	   The objective of this protocol is for each LOADng Router to,
370	   independently:

372	   o  Discover a bi-directional route to any destination in the network.

374	   o  Establish a route only when there is data traffic to be sent along
375	      that route.

377	   o  Maintain a route only for as long as there is data traffic being
378	      sent along that route.

380	   o  Generate control traffic based on network events only: when a new
381	      route is required, or when an active route is detected broken.
382	      Specifically, this protocol does not require periodic signaling.

384	4.1.  Overview

386	   These objectives are achieved, for each LOADng Router, by performing
387	   the following tasks:

389	   o  When having a data packet to deliver to a destination, for which
390	      no tuple in the routing set exists and where the data packet
391	      source is local to that LOADng Router (i.e., is an address in the
392	      Local Interface Set or Destination Address Set of that LOADng
393	      Router), generate a Route Request (RREQ) encoding the destination
394	      address, and transmit this RREQ over all of its LOADng Interfaces.

396	   o  Upon receiving an RREQ, insert or refresh a tuple in the Routing
397	      Set, recording a route towards the originator address from the
398	      RREQ, as well as to the neighbor LOADng Router from which the RREQ
399	      was received.  This will install the Reverse Route (towards the
400	      originator address from the RREQ).

402	   o  Upon receiving an RREQ, inspect the indicated destination address:

404	      *  If that address is an address in the Destination Address Set or
405	         in the Local Interface Set of the LOADng Router, generate a
406	         Route Reply (RREP), which is unicast in a hop-by-hop fashion
407	         along the installed Reverse Route.

409	      *  If that address is not an address in the Destination Address
410	         Set or in the Local Interface Set of the LOADng Router,
411	         consider the RREQ as a candidate for forwarding.

413	   o  When an RREQ is considered a candidate for forwarding, retransmit
414	      it according to the flooding operation, specified for the network.

416	   o  Upon receiving an RREP, insert or refresh a tuple in the Routing
417	      Set, recording a route towards the originator address from the
418	      RREP, as well as to the neighbor LOADng Router, from which that
419	      RREP was received.  This will install the Forward Route (towards
420	      the originator address from the RREP).  The originator address is
421	      either an address from the Local Interface Set of the LOADng
422	      Router, or an address from its Destination Address Set (i.e., an
423	      address of a host attached to that LOADng Router).

425	   o  Upon receiving an RREP, forward it, as unicast, to the recorded
426	      next hop along the corresponding Reverse Route until the RREP
427	      reaches the LOADng Router that has the destination address from
428	      the RREP in its Local Interface Set or Destination Address Set.

430	   o  When forwarding an RREQ or RREP, update the route metric, as
431	      contained in that RREQ or RREP message.

433	   A LOADng Router generating an RREQ specifies which metric type it
434	   desires.  Routers receiving an RREQ will process it and update route
435	   metric information in the RREQ according to that metric, if they can.
436	   All LOADng Routers, however, will update information in the RREQ so
437	   as to be able to support a "hop-count" default metric.  If a LOADng
438	   Router is not able to understand the metric type, specified in an
439	   RREQ, it will update the route metric value to its maximum value, so
440	   as to ensure that this is indicated to the further recipients of the
441	   RREQ.  Once the route metric value is set to its maximum value, no
442	   LOADng Router along the path towards the destination may change the
443	   value.

445	4.2.  LOADng Routers and LOADng Interfaces

447	   A LOADng Router has a set of at least one, and possibly more, LOADng
448	   Interfaces.  Each LOADng Interface:

450	   o  Is configured with one or more addresses.

452	   o  Has a number of interface parameters.

454	   In addition to a set of LOADng Interfaces as described above, each
455	   LOADng Router:

457	   o  Has a number of router parameters.

459	   o  Has an Information Base.

461	   o  Generates and processes RREQ, RREP, RREP_ACK and RERR messages,
462	      according to this specification.

464	4.3.  Information Base Overview

466	   Necessary protocol state is recorded by way of five information sets:
467	   the "Routing Set", the "Local Interface Set", the "Blacklisted
468	   Neighbor Set", the "Destination Address Set", and the "Pending
469	   Acknowledgment Set".

471	   The Routing Set contains tuples, each representing the next-hop on,
472	   and the metric of, a route towards a destination address.
473	   Additionally, the Routing Set records the sequence number of the last
474	   message, received from the destination.  This information is
475	   extracted from the message (RREQ or RREP) that generated the tuple so
476	   as to enable routing.  The routing table is to be updated using this
477	   Routing Set. (A LOADng Router may choose to use any or all
478	   destination addresses in the Routing Set to update the routing table,
479	   this selection is outside the scope of this specification.)

481	   The Local Interface Set contains tuples, each representing a local
482	   LOADng Interface of the LOADng Router.  Each tuple contains a list of
483	   one or more addresses of that LOADng Interface.

485	   The Blacklisted Neighbor Set contains tuples representing neighbor
486	   LOADng Interface addresses of a LOADng Router with which
487	   unidirectional connectivity has been recently detected.

489	   The Destination Address Set contains tuples representing addresses,
490	   for which the LOADng Router is responsible, i.e., addresses of this
491	   LOADng Router, or of hosts and networks directly attached to this
492	   LOADng Router and which use it to connect to the routing domain.
493	   These addresses may in particular belong to devices which do not
494	   implement LOADng, and thus cannot process LOADng messages.  A LOADng
495	   Router provides connectivity to these addresses by generating RREPs
496	   in response to RREQs directed towards them.

498	   The Pending Acknowledgment Set contains tuples, representing
499	   transmitted RREPs for which an RREP_ACK is expected, but where this
500	   RREP_ACK has not yet been received.

502	   The Routing Set, the Blacklisted Neighbor Set and the Pending
503	   Acknowledgment Set are updated by this protocol.  The Local Interface
504	   Set and the Destination Address Set are used, but not updated by this
505	   protocol.

507	4.4.  Signaling Overview

509	   This protocol generates and processes the following routing messages:

511	   Route Request (RREQ) -  Generated by a LOADng Router when it has a
512	      data packet to deliver to a given destination, where the data
513	      packet source is local to that LOADng Router (i.e., is an address
514	      in the Local Interface Set or Destination Address Set of that
515	      LOADng Router), but where it does not have an available tuple in
516	      its Routing Set indicating a route to that destination.  An RREQ
517	      contains:

519	      *  The (destination) address to which a Forward Route is to be
520	         discovered by way of soliciting the LOADng Router with that
521	         destination address in its Local Interface Set or in its
522	         Destination Address Set to generate an RREP.

524	      *  The (originator) address for which a Reverse Route is to be
525	         installed by RREQ forwarding and processing, i.e., the source
526	         address of the data packet which triggered the RREQ generation.

528	      *  The sequence number of the LOADng Router, generating the RREQ.

530	      An RREQ is flooded through the network, according to the flooding
531	      operation specified for the network.

533	   Route Reply (RREP) -  Generated as a response to an RREQ by the
534	      LOADng Router which has the address (destination) from the RREQ in
535	      its Local Interface Set or in its Destination Address Set. An RREP
536	      is sent in unicast towards the originator of that RREQ.  An RREP
537	      contains:

539	      *  The (originator) address to which a Forward Route is to be
540	         installed when forwarding the RREP.

542	      *  The (destination) address towards which the RREP is to be sent.
543	         More precisely, the destination address determines the unicast
544	         route which the RREP follows.

546	      *  The sequence number of the LOADng Router, generating the RREP.

548	   Route Reply Acknowledgment (RREP_ACK) -  Generated by a LOADng Router
549	      as a response to an RREP, in order to signal to the neighbor that
550	      transmitted the RREP that the RREP was successfully received.
551	      Receipt of an RREP_ACK indicates that the link between these two
552	      neighboring LOADng Routers is bidirectional.  An RREP_ACK is
553	      unicast to the neighbor from which the RREP has arrived, and is
554	      not forwarded.  RREP_ACKs are generated only in response to an
555	      RREP which, by way of a flag, has explicitly indicated that an
556	      RREP_ACK is desired.

558	   Route Error (RERR) -  Generated by a LOADng Router when a link on an
559	      active route to a destination is detected as broken by way of
560	      inability to forward a data packet towards that destination.  An
561	      RERR is unicast to the source of the undeliverable data packet.

563	5.  Protocol Parameters

565	   The following parameters and constants are used in this
566	   specification.

568	5.1.  Protocol and Port Numbers

570	   When using LOADng as an IP routing protocol, the considerations of
571	   [RFC5498] apply.

573	5.2.  Router Parameters

575	   NET_TRAVERSAL_TIME -  is the maximum time that a packet is expected
576	      to take when traversing from one end of the network to the other.

578	   RREQ_RETRIES -  is the maximum number of subsequent RREQs that a
579	      particular LOADng Router may generate in order to discover a route
580	      to a destination, before declaring that destination unreachable.

582	   RREQ_MIN_INTERVAL -  is the minimal interval (in milliseconds) of
583	      RREQs that a particular LOADng Router is allowed to send.

585	   R_HOLD_TIME -  is the minimum time a Routing Tuple SHOULD be kept in
586	      the Routing Set after it was last refreshed.

588	   MAX_DIST -  is the value representing the maximum possible metric
589	      (R_metric field).

591	   B_HOLD_TIME -  is the time during which the link between the neighbor
592	      LOADng Router and this LOADng Router MUST be considered as non-
593	      bidirectional, and that therefore RREQs received from that
594	      neighbor LOADng Router MUST be ignored during that time
595	      (B_HOLD_TIME).  B_HOLD_TIME should be greater than 2 x
596	      NET_TRAVERSAL_TIME x RREQ_RETRIES, to ensure that subsequent RREQs
597	      will reach the destination via a route, excluding the link to the
598	      blacklisted neighbor.

600	   MAX_HOP_LIMIT -  is the maximum limit of the number of hops that
601	      LOADng routing messages are allowed to traverse.

603	5.3.  Interface Parameters

605	   Different LOADng Interfaces (on the same or on different LOADng
606	   Routers) MAY employ different interface parameter values and MAY
607	   change their interface parameter values dynamically.  A particular
608	   case is where all LOADng Interfaces on all LOADng Routers within a
609	   given LOADng routing domain employ the same set of interface
610	   parameter values.

612	   RREQ_MAX_JITTER -  is the default value of MAXJITTER used in
613	      [RFC5148] for RREQ messages forwarded by this LOADng Router on
614	      this interface.

616	   RREP_ACK_REQUIRED -  is a boolean flag, which indicates (if set) that
617	      the LOADng Router is configured to expect that each RREP it sends
618	      be confirmed by an RREP_ACK, or, (if cleared) that no RREP_ACK is
619	      expected for this interface.

621	   USE_BIDIRECTIONAL_LINK_ONLY -  is a boolean flag, which indicates if
622	      the LOADng Router only uses verified bi-directional links for data
623	      packet forwarding on this interface.  It is set by default.  If
624	      cleared, then the LOADng Router can use links which have not been
625	      verified to be bi-directional on this interface.

627	   RREP_ACK_TIMEOUT -  is the minimum amount of time after transmission
628	      of an RREP, that a LOADng Router SHOULD wait for an RREP_ACK from
629	      a neighbor LOADng Router, before considering the link to this
630	      neighbor to be unidirectional.

632	5.4.  Constants

634	   MAX_HOP_COUNT -  is the maximum number of hops as representable by
635	      the encoding that is used (e.g., 255 when using [RFC5444]).  It
636	      SHOULD NOT be used to limit the scope of a message; the router
637	      parameter MAX_HOP_LIMIT can be used to limit the scope of a LOADng
638	      routing message.

640	6.  Protocol Message Content

642	   The protocol messages, generated and processed by LOADng, are
643	   described in this section using the notational conventions described
644	   in Section 2.  The encoding of messages for transmission by way of
645	   [RFC5444] packets/messages is described in Appendix A, and Appendix B
646	   illustrates the bit layout of a selection of LOADng control messages.
647	   Unless stated otherwise, the message fields described below are set
648	   by the LOADng Router that generates the message, and MUST NOT be
649	   changed by intermediate LOADng Routers.

651	6.1.  Route Request (RREQ) Messages

653	   A Route Request (RREQ) message has the following fields:

655	   RREQ.addr-length  is an unsigned integer field, encoding the length
656	      of the originator and destination addresses as follows:

658	      RREQ.addr-length := the length of an address in octets - 1

660	   RREQ.seq-num  is an unsigned integer field, containing the sequence
661	      number (see Section 8) of the LOADng Router, generating the RREQ
662	      message.

664	   RREQ.metric-type  is an unsigned integer field and specifies the type
665	      of metric requested by this RREQ.

667	   RREQ.route-metric  is a unsigned integer field, of length defined by
668	      RREQ.metric-type, which specifies the route metric of the route
669	      (the sum of the link metrics of the links), through which this
670	      RREQ has traveled.

672	   RREQ.hop-count  is an unsigned integer field and specifies the total
673	      number of hops which the message has traversed from the
674	      RREQ.originator.

676	   RREQ.hop-limit  is an unsigned integer field and specifies the number
677	      of hops that the message is allowed to traverse.

679	   RREQ.originator  is an identifier of RREQ.addr-length + 1 octets,
680	      specifying the address of the LOADng Interface over which this
681	      RREQ was generated, and to which a route (the "reverse route") is
682	      supplied by this RREQ.  In case the message is generated by a
683	      LOADng Router on behalf of an attached host, RREQ.originator
684	      corresponds to an address of that host, otherwise it corresponds
685	      to an address of the sending LOADng Interface of the LOADng
686	      Router.

688	   RREQ.destination  is an identifier of RREQ.addr-length + 1 octets,
689	      specifying the address to which the RREQ should be sent, i.e., the
690	      destination address for which a route is sought.

692	   The following fields of an RREQ message are immutable, i.e., they
693	   MUST NOT be changed during processing or forwarding of the message:
694	   RREQ.addr-length, RREQ.seq-num, RREQ.originator, and
695	   RREQ.destination.

697	   The following fields of an RREQ message are mutable, i.e., they will
698	   be changed by intermediate routers during processing or forwarding,
699	   as specified in Section 12.2 and Section 12.3: RREQ.metric-type,
700	   RREQ.route-metric, RREQ.hop-limit, and RREQ.hop-count.

702	   Any additional field that is added to the message by an extension to
703	   this protocol, e.g., by way of TLVs, MUST be considered immutable,
704	   unless the extension specifically defines the field as mutable.

706	6.2.  Route Reply (RREP) Messages

708	   A Route Reply (RREP) message has the following fields:

710	   RREP.addr-length  is an unsigned integer field, encoding the length
711	      of the originator and destination addresses as follows:

713	      RREP.addr-length := the length of an address in octets - 1

715	   RREP.seq-num  is an unsigned integer field, containing the sequence
716	      number (see Section 8) of the LOADng Router, generating the RREP
717	      message.

719	   RREP.metric-type  is an unsigned integer field and specifies the type
720	      of metric, requested by this RREP.

722	   RREP.route-metric  is a unsigned integer field, of length defined by
723	      RREP.metric-type, which specifies the route metric of the route
724	      (the sum of the link metrics of the links) through which this RREP
725	      has traveled.

727	   RREP.ackrequired  is a boolean flag which, when set ('1'), at least
728	      one RREP_ACK MUST be generated by the recipient of an RREP if the
729	      RREP is successfully processed.  When cleared ('0'), an RREP_ACK
730	      MUST NOT be generated in response to processing of the RREP.

732	   RREP.hop-count  is an unsigned integer field and specifies the total
733	      number of hops which the message has traversed from
734	      RREP.originator to RREP.destination.

736	   RREP.hop-limit  is an unsigned integer field and specifies the number
737	      of hops that the message is allowed to traverse.

739	   RREP.originator  is an identifier of RREP.addr-length + 1 octets,
740	      specifying the address for which this RREP was generated, and to
741	      which a route (the "forward route") is supplied by this RREP.  In
742	      case the message is generated on a LOADng Router on behalf of an
743	      attached host, RREP.originator corresponds to an address of that
744	      host, otherwise it corresponds to an address of the LOADng
745	      Interface of the LOADng Router, over which the RREP was generated.

747	   RREP.destination  is an identifier of RREP.addr-length + 1 octets,
748	      specifying the address to which the RREP should be sent.  (I.e.,
749	      this address is equivalent to RREQ.originator of the RREQ that
750	      triggered the RREP.)

752	   The following fields of an RREP message are immutable, i.e., they
753	   MUST NOT be changed during processing or forwarding of the message:
754	   RREP.addr-length, RREP.seq-num, RREP.originator, and
755	   RREP.destination.

757	   The following fields of an RREP message are mutable, i.e., they will
758	   be changed by intermediate routers during processing or forwarding,
759	   as specified in Section 13.2 and Section 13.3: RREP.metric-type,
760	   RREP.route-metric, RREP.ackrequired, RREP.hop-limit, and RREP.hop-
761	   count.

763	   Any additional field that is added to the message by an extension to
764	   this protocol, e.g., by way of TLVs, MUST be considered immutable,
765	   unless the extension specifically defines the field as mutable.

767	6.3.  Route Reply Acknowledgement (RREP_ACK) Messages

769	   A Route Reply Acknowledgement (RREP_ACK) message has the following
770	   fields:

772	   RREP_ACK.addr-length  is an unsigned integer field, encoding the
773	      length of the destination and originator addresses as follows:

775	      RREP_ACK.addr-length := the length of an address in octets - 1

777	   RREP_ACK.seq-num  is an unsigned integer field and contains the value
778	      of RREP.seq-num from the RREP for which this RREP_ACK is sent.

780	   RREP_ACK.destination  is an identifier of RREP_ACK.addr-length + 1
781	      octets and contains the value of the RREP.originator field from
782	      the RREP for which this RREP_ACK is sent.

784	   RREP_ACK messages are sent only across a single link and are never
785	   forwarded.

787	6.4.  Route Error (RERR) Messages

789	   A Route Error (RERR) message has the following fields:

791	   RERR.addr-length  is an unsigned integer field, encoding the length
792	      of RERR.destination and RERR.unreachableAddress, as follows:

794	      RERR.addr-length := the length of an address in octets - 1

796	   RERR.errorcode  is an unsigned integer field and specifies the reason
797	      for the error message being generated, according to Table 1.

799	   RERR.unreachableAddress  is an identifier of RERR.addr-length + 1
800	      octets, specifying an address, which has become unreachable, and
801	      for which an error is reported by way of this RERR message.

803	   RERR.originator  is an identifier of RERR.addr-length + 1 octets,
804	      specifying the address of the LOADng Interface over which this
805	      RERR was generated by a LOADng Router.

807	   RERR.destination  is an identifier of RERR.address-length + 1 octets,
808	      specifying the destination address of this RERR message.
809	      RERR.destination is, in general, the source address of a data
810	      packet, for which delivery to RERR.unreachableAddress failed, and
811	      the unicast destination of the RERR message is the LOADng Router
812	      which has RERR.destination listed in a Local Interface Tuple or in
813	      a Destination Address Tuple.

815	   RERR.hop-limit  is an unsigned integer field and specifies the number
816	      of hops that the message is allowed to traverse.

818	   The following fields of an RERR message are immutable, i.e., they
819	   MUST NOT be changed during processing or forwarding of the message:
820	   RERR.addr-length, RERR.errorcode, RERR.unreachableAddress,
821	   RERR.originator and RERR.destination.

823	   The following fields of an RERR message are mutable, i.e., they will
824	   be changed by intermediate routers during processing or forwarding,
825	   as specified in Section 14.3 and Section 14.4: RERR.hop-limit.

827	   Any additional field that is added to the message by an extension to
828	   this protocol, e.g., by way of TLVs, MUST be considered immutable,
829	   unless the extension specifically defines the field as mutable.

831	7.  Information Base

833	   Each LOADng Router maintains an Information Base, containing the
834	   information sets necessary for protocol operation, as described in
835	   the following sections.  The organization of information into these
836	   information sets is non-normative, given so as to facilitate
837	   description of message generation, forwarding and processing rules in
838	   this specification.  An implementation may choose any representation
839	   or structure for when maintaining this information.

841	7.1.  Routing Set

843	   The Routing Set records the next hop on the route to each known
844	   destination, when such a route is known.  It consists of Routing
845	   Tuples:

847	   (R_dest_addr, R_next_addr, R_metric, R_metric_type, R_hop_count,
848	      R_seq_num, R_bidirectional, R_local_iface_addr, R_valid_time)

850	   where:

852	   R_dest_addr -  is the address of the destination, either an address
853	      of a LOADng Interface of a destination LOADng Router, or an
854	      address of an interface reachable via the destination LOADng
855	      Router, but which is outside the routing domain.

857	   R_next_addr -  is the address of the "next hop" on the selected route
858	      to the destination.

860	   R_metric -  is the metric associated with the selected route to the
861	      destination with address R_dest_addr.

863	   R_metric_type -  specifies the metric type for this Routing Tuple -
864	      in other words, how R_metric is defined and calculated.

866	   R_hop_count -  is the hop count of the selected route to the
867	      destination with address R_dest_addr.

869	   R_seq_num -  is the value of the RREQ.seq-num or RREP.seq-num field
870	      of the RREQ or RREP which installed or last updated this tuple.
871	      For the Routing Tuples installed by previous hop information of
872	      RREQ or RREP, R_seq_num MUST be set to -1.

874	   R_bidirectional -  is a boolean flag, which specifies if the Routing
875	      Tuple is verified as representing a bi-directional route.  Data
876	      traffic SHOULD only be routed through a routing tuple with
877	      R_bidirectional flag equals TRUE, unless the LOADng Router is
878	      configured as accepting routes without bi-directionality
879	      verification explicitly by setting USE_BIDIRECTIONAL_LINK_ONLY to
880	      FALSE of the interface with R_local_iface_address.

882	   R_local_iface_addr -  is an address of the local LOADng Interface,
883	      through which the destination can be reached.

885	   R_valid_time -  specifies the time until which the information
886	      recorded in this Routing Tuple is considered valid.

888	7.2.  Local Interface Set

890	   A LOADng Router's Local Interface Set records its local LOADng
891	   Interfaces.  It consists of Local Interface Tuples, one per LOADng
892	   Interface:

894	               (I_local_iface_addr_list)

896	   where:

898	   I_local_iface_addr_list -  is an unordered list of the network
899	      addresses of this LOADng Interface.

901	   The implementation MUST initialize the Local Interface Set with at
902	   least one tuple containing at least one address of an LOADng
903	   Interface.  The Local Interface Set MUST be updated if there is a
904	   change of the LOADng Interfaces of a LOADng Router (i.e., a LOADng
905	   Interface is added, removed or changes addresses).

907	7.3.  Blacklisted Neighbor Set

909	   The Blacklisted Neighbor Set records the neighbor LOADng Interface
910	   addresses of a LOADng Router, with which connectivity has been
911	   detected to be unidirectional.  Specifically, the Blacklisted
912	   Neighbor Set records neighbors from which an RREQ has been received
913	   (i.e., through which a Forward Route would possible) but to which it
914	   has been determined that it is not possible to communicate (i.e.,
915	   forwarding Route Replies via this neighbor fails, rendering
916	   installing the Forward Route impossible).  It consists of Blacklisted
917	   Neighbor Tuples:

919	               (B_neighbor_address, B_valid_time)

921	   where:

923	   B_neighbor_address -  is the address of the blacklisted neighbor
924	      LOADng Interface.

926	   B_valid_time -  specifies the time until which the information
927	      recorded in this tuple is considered valid.

929	7.4.  Destination Address Set

931	   The Destination Address Set records addresses, for which a LOADng
932	   Router will generate RREPs in response to received RREQs, in addition
933	   to its own LOADng Interface addresses (as listed in the Local
934	   Interface Set).  The Destination Address Set thus represents those
935	   destinations (i.e., hosts), for which this LOADng Router is providing
936	   connectivity.  It consists of Destination Address Tuples:

938	               (D_address)

940	   where:

942	   D_address -  is the address of a destination (a host or a network),
943	      attached to this LOADng Router and for which this LOADng Router
944	      provides connectivity through the routing domain.

946	   The Destination Address Set is used for generating signaling, but is
947	   not itself updated by signaling specified in this document.  Updates
948	   to the Destination Address Set are due to changes of the environment
949	   of a LOADng Router - hosts or external networks being connected to or
950	   disconnected from a LOADng Router.  The Destination Address Set may
951	   be administrationally provisioned, or provisioned by external
952	   protocols.

954	7.5.  Pending Acknowledgment Set

956	   The Pending Acknowledgment Set contains information about RREPs which
957	   have been transmitted with the RREP.ackrequired flag set, and for
958	   which an RREP_ACK has not yet been received.  It consists of Pending
959	   Acknowledgment Tuples:

961	               (P_next_hop, P_originator, P_seq_num,
962	                P_ack_received, P_ack_timeout)

964	   where:

966	   P_next_hop -  is the address of the neighbor LOADng Interface to
967	      which the RREP was sent.

969	   P_originator -  is the address of the originator of the RREP.

971	   P_seq_num -  is the RREP.seq-num field of the sent RREP.

973	   P_ack_received -  is a boolean flag, which specifies the tuple has
974	      been acknowledged by a corresponding RREP_ACK message.  The
975	      default value is FALSE.

977	   P_ack_timeout -  is the time after which the tuple MUST be expired.

979	8.  LOADng Router Sequence Numbers

981	   Each LOADng Router maintains a single sequence number, which must be
982	   included in each RREQ or RREP message it generates.  Each LOADng
983	   Router MUST make sure that no two messages (both RREQ and RREP) are
984	   generated with the same sequence number, and MUST generate sequence
985	   numbers such that these are monotonically increasing.  This sequence
986	   number is used as information for when comparing routes to the LOADng
987	   Router having generated the message.

989	   However, with a limited number of bits for representing sequence
990	   numbers, wrap-around (that the sequence number is incremented from
991	   the maximum possible value to zero) can occur.  To prevent this from
992	   interfering with the operation of the protocol, the following MUST be
993	   observed.  The term MAXVALUE designates in the following the largest
994	   possible value for a sequence number.  The sequence number S1 is said
995	   to be "greater than" (denoted '>') the sequence number S2 if:

997	      S2 < S1 AND S1 - S2 <= MAXVALUE/2 OR

999	      S1 < S2 AND S2 - S1 > MAXVALUE/2

1001	9.  Route Maintenance

1003	   Tuples in the Routing Set are maintained by way of five different
1004	   mechanisms:

1006	   o  RREQ/RREP exchange, specified in Section 12 and Section 13.

1008	   o  Data traffic delivery success.

1010	   o  Data traffic delivery failure.

1012	   o  External signals indicating that a tuple in the Routing Set needs
1013	      updating.

1015	   o  Information expiration.

1017	   Routing Tuples in the Routing Set contain a validity time, which
1018	   specifies the time until which the information recorded in this tuple
1019	   is considered valid.  After this time, the information in such tuples
1020	   is to be considered as invalid, for the processing specified in this
1021	   document.

1023	   Routing Tuples for actively used routes (i.e., routes via which
1024	   traffic is currently transiting) SHOULD NOT be removed, unless there
1025	   is evidence that they no longer provide connectivity - i.e., unless a
1026	   link on that route has broken.

1028	   To this end, one or more of the following mechanisms (non-exhaustive
1029	   list) MAY be used:

1031	   o  If a lower layer mechanism provides signals, such as when delivery
1032	      to a presumed neighbor LOADng Router fails, this signal MAY be
1033	      used to indicate that a link has broken, trigger early expiration
1034	      of a Routing Tuple from the Routing Set, and to initiate Route
1035	      Error Signaling (see Section 14).  Conversely, absence of such a
1036	      signal when attempting delivery MAY be interpreted as validation
1037	      that the corresponding Routing Tuple(s) are valid, and their
1038	      R_valid_time refreshed correspondingly.  Note that when using such
1039	      a mechanism, care should be taken to prevent that an intermittent
1040	      error (e.g., an incidental wireless collision) triggers corrective
1041	      action and signaling.  This depends on the nature of the signals,
1042	      provided by the lower layer, but can include the use of a
1043	      hysteresis function or other statistical mechanisms.

1045	   o  Conversely, for each successful delivery of a packet to a neighbor
1046	      or a destination, if signaled by a lower layer or a transport
1047	      mechanism, or each positive confirmation of the presence of a
1048	      neighbor by way of an external neighbor discovery protocol, MAY be
1049	      interpreted as validation that the corresponding Routing Tuple(s)
1050	      are valid, and their R_valid_time refreshed correspondingly.  Note
1051	      that when refreshing a Routing Tuple corresponding to a
1052	      destination of a data packet, the Routing Tuple corresponding to
1053	      the next hop toward that destination SHOULD also be refreshed.

1055	   Furthermore, a LOADng Router may experience that a route currently
1056	   used for forwarding data packets is no longer operational, and must
1057	   act to either rectify this situation locally (Section 13) or signal
1058	   this situation to the source of the data packets for which delivery
1059	   was unsuccessful (Section 14).

1061	   If a LOADng Router fails to deliver a data packet to a next-hop, it
1062	   MUST generate an RERR message, as specified in Section 14.

1064	10.  Unidirectional Link Handling

1066	   Each LOADng Router MUST monitor the bidirectionality of the links to
1067	   its neighbors and set the R_bidirectional flag of related routing
1068	   tuples when processing Route Replies (RREP).  To this end, one or
1069	   more of the following mechanisms MAY be used (non exhaustive list):

1071	   o  If a lower layer mechanism provides signals, such as when delivery
1072	      to a presumed neighbor LOADng Router fails, this signal MAY be
1073	      used to detect that a link to this neighbor is broken or is
1074	      unidirectional; the LOADng Router MUST then blacklist the neighbor
1075	      (see Section 10.1).

1077	   o  If a mechanism such as NDP [RFC4861] is available, the LOADng
1078	      Router MAY use it.

1080	   o  A LOADng Router MAY use a neighborhood discovery mechanism with
1081	      bidirectionality verification, such as NHDP [RFC6130].

1083	   o  RREP_ACK message exchange, as described in Section 15.

1085	   o  Upper-layer mechanisms, such as transport-layer acknowledgments,
1086	      MAY be used to detect unidirectional or broken links.

1088	   When a LOADng Router detects, via one of these mechanisms, that a
1089	   link to a neighbor LOADng Router is unidirectional or broken, the
1090	   LOADng Router MUST blacklist this neighbor (see Section 10.1).
1091	   Conversely, if a LOADng Router detects via one of these mechanisms
1092	   that a previously blacklisted LOADng Router has a bidirectional link
1093	   to this LOADng Router, it MAY remove it from the blacklist before the
1094	   B_valid_time of the corresponding tuple.

1096	10.1.  Blacklist Usage

1098	   The Blacklist is maintained according to Section 7.3.  When an
1099	   interface of neighbor LOADng Router is detected to have a
1100	   unidirectional link to the LOADng Router, it is blacklisted, i.e., a
1101	   tuple (B_neighbor_address, B_valid_time) is created thus:

1103	   o  B_neighbor_address := the address of the blacklisted neighbor
1104	      LOADng Router interface

1106	   o  B_valid_time := current_time + B_HOLD_TIME

1108	   When a neighbor LOADng Router interface is blacklisted, i.e., when
1109	   there is a corresponding (B_neighbor_address, B_valid_time) tuple in
1110	   the Blacklisted Neighbor Set, it is temporarily not considered as a
1111	   neighbor, and thus:

1113	   o  Every RREQ received from this neighbor LOADng Router interface
1114	      MUST be discarded;

1116	11.  Common Rules for RREQ and RREP Messages

1118	   RREQ and RREP messages, both, supply routes between their recipients
1119	   and the originator of the RREQ or RREP message.  The two message
1120	   types therefore share common processing rules, and differ only in the
1121	   following:

1123	   o  RREQ messages are multicast or broadcast, intended to be received
1124	      by all LOADng Routers in the network, whereas RREP messages are
1125	      all unicast, intended to be received only by LOADng Routers on a
1126	      specific route towards a specific destination.

1128	   o  Receipt of an RREQ message by a LOADng router, which has the
1129	      RREQ.destination address in its Local Interface Set or Destination
1130	      Address Set MUST trigger the procedures for generation of an RREP
1131	      message.

1133	   o  Receipt of an RREP message with RREP.ackrequired set MUST trigger
1134	      generation of an RREP_ACK message.

1136	   For the purpose of the processing description in this section, the
1137	   following additional notation is used:

1139	   received-route-metric  is a variable, representing the route metric,
1140	      as included in the received RREQ or RREP message, see Section 16.

1142	   used-metric-type  is a variable, representing the type of metric used
1143	      for calculating received-route-metric, see Section 16.

1145	   previous-hop  is the address of the LOADng Router, from which the
1146	      RREQ or RREP message was received.

1148	   >  is the comparison operator for sequence numbers, as specified in
1149	      Section 8.

1151	   MSG  is a shorthand for either an RREQ or RREP message, used for when
1152	      accessing message fields in the description of the common RREQ and
1153	      RREP message processing in the following subsections.

1155	   hop-count  is a variable, representing the hop-count, as included in
1156	      the received RREQ or RREP message.

1158	   hop-limit  is a variable, representing the hop-limit, as included in
1159	      the received RREQ or RREP message.

1161	   link-metric  is a variable, representing the link metric between this
1162	      LOADng Router and the LOADng Router from which the RREQ or RREP
1163	      message was received, as calculated by the receiving LOADng
1164	      Router, see Section 16.

1166	   route-metric  is a variable, representing the route metric, as
1167	      included in the received RREQ or RREP message, plus the link-
1168	      metric for the link, over which the RREQ or RREP was received,
1169	      i.e., the total route cost from the originator to this LOADng
1170	      Router.

1172	11.1.  Identifying Invalid RREQ or RREP Messages

1174	   A received RREQ or RREP message is invalid, and MUST be discarded
1175	   without further processing, if any of the following conditions are
1176	   true:

1178	   o  The address length specified by this message (i.e., MSG.addr-
1179	      length + 1) differs from the length of the address(es) of this
1180	      LOADng Router.

1182	   o  The address contained in MSG.originator is an address of this
1183	      LOADng Router.

1185	   o  There is a tuple in the Routing Set where:

1187	      *  R_dest_addr = MSG.originator

1189	      *  R_seq_num > MSG.seq-num

1191	   o  For RREQ messages only, an RREQ MUST be considered invalid if the
1192	      previous-hop is blacklisted (i.e., its address is in a tuple in
1193	      the Blacklisted Neighbor Set, see Section 10.1).

1195	   A LOADng Router MAY recognize additional reasons for identifying that
1196	   an RREQ or RREP message is invalid for processing, e.g., to allow a
1197	   security protocol to perform verification of integrity check values
1198	   and prevent processing of unverifiable RREQ or RREP message by this
1199	   protocol.

1201	11.2.  RREQ and RREP Message Processing

1203	   A received, and valid, RREQ or RREP message is processed as follows:

1205	   1.  Included TLVs are processed/updated according to their
1206	       specification.

1208	   2.  Set the variable hop-count to MSG.hop-count + 1.

1210	   3.  Set the variable hop-limit to MSG.hop-limit - 1.

1212	   4.  If MSG.metric-type is known to this LOADng Router, and if
1213	       MSG.metric-type is not HOP_COUNT, then:

1215	       *  Set the variable used-metric-type to the value of MSG.metric-
1216	          type.

1218	       *  Determine the link metric over the link over which the message
1219	          was received, according to used-metric-type, and set the
1220	          variable link-metric to the calculated value.

1222	       *  Compute the route metric to MSG.originator according to used-
1223	          metric-type by adding link-metric to the received-route-metric
1224	          advertised by the received message, and set the variable
1225	          route-metric to the calculated value.

1227	   5.  Otherwise:

1229	       *  Set the variable used-metric-type to HOP_COUNT.

1231	       *  Set the variable route-metric to MAX_DIST, see Section 16.

1233	       *  Set the variable link-metric to MAX_DIST.

1235	   6.  Find the Routing Tuple (henceforth, Matching Routing Tuple)
1236	       where:

1238	       *  R_dest_addr = MSG.originator

1240	   7.  If no Matching Routing Tuple is found, then create a new Matching
1241	       Routing Tuple (the "reverse route" for RREQ messages or "forward
1242	       route" for RREP messages) with:

1244	       *  R_dest_addr := MSG.originator

1246	       *  R_next_addr := previous-hop

1248	       *  R_metric_type := used-metric-type

1250	       *  R_metric := MAX_DIST
1251	       *  R_hop_count := hop-count

1253	       *  R_seq_num := -1

1255	       *  R_valid_time := current time + R_HOLD_TIME

1257	       *  R_bidirectional := FALSE

1259	       *  R_local_iface_addr := the address of the LOADng Interface
1260	          through which the message was received.

1262	   8.  The Matching Routing Tuple, existing or new, is compared to the
1263	       received RREQ or RREP message:

1265	       1.  If

1267	           +  R_seq_num = MSG.seq-num; AND

1269	           +  R_metric_type = used-metric-type; AND

1271	           +  R_metric > route-metric

1273	           OR

1275	           +  R_seq_num = MSG.seq-num; AND

1277	           +  R_metric_type = used-metric-type; AND

1279	           +  R_metric = route-metric; AND

1281	           +  R_hop_count > hop-count

1283	           OR

1285	           +  R_seq_num = MSG.seq-num; AND

1287	           +  R_metric_type does not equal to used-metric-type; AND

1289	           +  R_metric_type = HOP_COUNT

1291	           OR

1293	           +  R_seq_num < MSG.seq-num

1295	           Then:

1297	           12.  The message is used for updating the Routing Set. The
1298	                Routing Tuple, where:

1300	                -  R_dest_addr = MSG.originator;

1302	                is updated thus:

1304	                -  R_next_addr := previous-hop

1306	                -  R_metric_type = used-metric-type

1308	                -  R_metric := route-metric

1310	                -  R_hop_count := hop-count

1312	                -  R_seq_num := MSG.seq-num

1314	                -  R_valid_time := current time + R_HOLD_TIME

1316	                -  R_bidirectional := TRUE, if the message being
1317	                   processed is an RREP.

1319	           13.  If previous-hop is not equal to MSG.originator, and if
1320	                there is no Matching Routing Tuple in the Routing Set
1321	                with R_dest_addr = previous-hop, create a new Matching
1322	                Routing Tuple with:

1324	                -  R_dest_addr := previous-hop

1326	                -  R_next_addr := previous-hop

1328	           14.  The Routing Tuple with R_dest_addr = previous-hop,
1329	                existing or new, is updated as follows

1331	                -  R_metric_type := used-metric-type

1333	                -  R_metric := link-metric

1335	                -  R_hop_count := 1

1337	                -  R_seq_num := -1

1339	                -  R_valid_time := current time + R_HOLD_TIME

1341	                -  R_bidirectional := TRUE, if the processed message is
1342	                   an RREP, otherwise FALSE.

1344	                -  R_local_iface_addr := the address of the LOADng
1345	                   Interface through which the message was received.

1347	       2.  Otherwise, if the message is an RREQ, it is not processed
1348	           further and is not considered for forwarding.  If it is an
1349	           RREP and if RREP.ackrequired is set, an RREP_ACK message MUST
1350	           be sent to the previous-hop, according to Section 15.2.  The
1351	           RREP is not considered for forwarding.

1353	12.  Route Requests (RREQs)

1355	   Route Requests (RREQs) are generated by a LOADng Router when it has
1356	   data packets to deliver to a destination, where the data packet
1357	   source is local to that LOADng Router (i.e., is an address in the
1358	   Local Interface Set or Destination Address Set of that LOADng
1359	   Router), but for which the LOADng router has no matching tuple in the
1360	   Routing Set. Furthermore, if there is a matching tuple in the Routing
1361	   Set with the R_bidirectional set to FALSE, and the parameter
1362	   USE_BIDIRECTIONAL_LINK_ONLY of the interface with
1363	   R_local_iface_address equals TRUE, an RREQ MUST be generated.

1365	   After originating an RREQ, a LOADng Router waits for a corresponding
1366	   RREP.  If no such RREP is received within 2*NET_TRAVERSAL_TIME
1367	   milliseconds, the LOADng Router MAY issue a new RREQ for the sought
1368	   destination (with an incremented seq_num) up to a maximum of
1369	   RREQ_RETRIES times.  Two consequent RREQs generated on an interface
1370	   of a LOADng Router SHOULD be separated at least RREQ_MIN_INTERVAL.

1372	12.1.  RREQ Generation

1374	   An RREQ message is generated according to Section 6 with the
1375	   following content:

1377	   o  RREQ.addr-length set to the length of the address, as specified in
1378	      Section 6;

1380	   o  RREQ.metric-type set to the desired metric type;

1382	   o  RREQ.route-metric := 0.

1384	   o  RREQ.seq-num set to the next unused sequence number, maintained by
1385	      this LOADng Router;

1387	   o  RREQ.hop-count := 0;

1389	   o  RREQ.hop-limit := MAX_HOP_LIMIT;

1391	   o  RREQ.destination := the address to which a route is sought;

1393	   o  RREQ.originator := one address of the LOADng Interface of the
1394	      LOADng Router that generates the RREQ.  If the LOADng Router is
1395	      generating RREQ on behalf of a host connected to this LOADng
1396	      Router, the source address of the data packet, generated by that
1397	      host, is used;

1399	12.2.  RREQ Processing

1401	   The variables hop-count and hop-limit have been updated in
1402	   Section 11.2 (when processing the message) and are used in this
1403	   section.  On receiving an RREQ message, a LOADng Router MUST process
1404	   the message according to this section:

1406	   1.  If the message is invalid for processing, as defined in
1407	       Section 11.1, the message MUST be discarded without further
1408	       processing.  The message is not considered for forwarding.

1410	   2.  Otherwise, the message is processed according to Section 11.2.

1412	   3.  If RREQ.destination is listed in I_local_iface_addr_list of any
1413	       Local Interface Tuple, or corresponds to D_address of any
1414	       Destination Address Tuple of this LOADng Router, the RREP
1415	       generation process in Section 13.1 MUST be applied.  The RREQ is
1416	       not considered for forwarding.

1418	   4.  Otherwise, if hop-count is less than MAX_HOP_COUNT and hop-limit
1419	       is greater than 0, the message is considered for forwarding
1420	       according to Section 12.3.

1422	12.3.  RREQ Forwarding

1424	   The variables used-metric type, hop-count, hop-limit and route-metric
1425	   have been updated in Section 11.2 (when processing the message) and
1426	   are used in this section to update the content of the message to be
1427	   forwarded.  An RREQ, considered for forwarding, MUST be updated as
1428	   follows, prior to it being transmitted:

1430	   1.  RREQ.metric-type := used-metric-type (as set in Section 11.2)

1432	   2.  RREQ.route-metric := route-metric (as set in Section 11.2)

1434	   3.  RREQ.hop-count := hop-count (as set in Section 11.2)

1436	   4.  RREQ.hop-limit := hop-limit (as set in Section 11.2)

1438	   An RREQ MUST be forwarded according to the flooding operation,
1439	   specified for the network.  This MAY be by way of classic flooding, a
1440	   reduced relay set mechanism such as [RFC6621], or any other
1441	   information diffusion mechanism such as [RFC6206].  Care must be
1442	   taken that NET_TRAVERSAL_TIME is chosen so as to accommodate for the
1443	   maximum time that may take for an RREQ to traverse the network,
1444	   accounting for in-router delays incurring due to or imposed by such
1445	   algorithms.

1447	12.4.  RREQ Transmission

1449	   RREQs, whether initially generated or forwarded, are sent to all
1450	   neighbor LOADng Routers through all interfaces in the Local Interface
1451	   Set.

1453	   When an RREQ is transmitted, all receiving LOADng Routers will
1454	   process the RREQ message and as a consequence consider the RREQ
1455	   message for forwarding at the same, or at almost the same, time.  If
1456	   using data link and physical layers that are subject to packet loss
1457	   due to collisions, such RREQ messages SHOULD be jittered as described
1458	   in [RFC5148], using RREQ_MAX_JITTER, in order to avoid such losses.

1460	13.  Route Replies (RREPs)

1462	   Route Replies (RREPs) are generated by a LOADng Router in response to
1463	   an RREQ (henceforth denoted "corresponding RREQ"), and are sent by
1464	   the LOADng Router which has, in either its Destination Address Set or
1465	   in its Local Interface Set, the address from RREQ.destination.  RREPs
1466	   are sent, hop by hop, in unicast towards the originator of the RREQ,
1467	   in response to which the RREP was generated, along the Reverse Route
1468	   installed by that RREQ.  A LOADng Router, upon forwarding an RREP,
1469	   installs the Forward Route towards the RREP.destination.

1471	   Thus, with forwarding of RREQs installing the Reverse Route and
1472	   forwarding of RREPs installing the Forward Route, bi-directional
1473	   routes are provided between the RREQ.originator and RREQ.destination.

1475	13.1.  RREP Generation

1477	   At least one RREP MUST be generated in response to a (set of)
1478	   received RREQ messages with identical (RREP.originator, RREP.seq-
1479	   num).  An RREP MAY be generated immediately as a response to each
1480	   RREQ processed, in order to provide shortest possible route
1481	   establishment delays, or MAY be generated after a certain delay after
1482	   the arrival of the first RREQ, in order to use the "best" received
1483	   RREQ (e.g., received over the lowest-cost route) but at the expense
1484	   of longer route establishment delays.  A LOADng Router MAY generate
1485	   further RREPs for subsequent RREQs received with the same
1486	   (RREP.originator, RREP.seq-num) pairs, if these indicate a better
1487	   route, at the expense of additional control traffic being generated.
1488	   In all cases, however, the content of an RREP is as follows:

1490	   o  RREP.addr-length set to the length of the address, as specified in
1491	      Section 6;

1493	   o  RREP.seq-num set to the next unused sequence number, maintained by
1494	      this LOADng Router;

1496	   o  RREP.metric-type set to the same value as the RREQ.metric-type in
1497	      the corresponding RREQ if the metric type is known to the router.
1498	      Otherwise, RREP.metric-type is set to HOP_COUNT;

1500	   o  RREP.route-metric := 0

1502	   o  RREP.hop-count := 0;

1504	   o  RREP.hop-limit := MAX_HOP_LIMIT;

1506	   o  RREP.destination := the address to which this RREP message is to
1507	      be sent; this corresponds to the RREQ.originator from the RREQ
1508	      message, in response to which this RREP message is generated;

1510	   o  RREP.originator := the address of the LOADng Router, generating
1511	      the RREP.  If the LOADng Router is generating an RREP on behalf of
1512	      the hosts connected to it, or on behalf of one of the addresses
1513	      contained in the LOADng Routers Destination Address Set, the host
1514	      address is used.

1516	   The RREP that is generated is transmitted according to Section 13.4.

1518	13.2.  RREP Processing

1520	   The variables hop-count and hop-limit have been updated in
1521	   Section 11.2 (when processing the message) and are used in this
1522	   section.  On receiving an RREP message, a LOADng Router MUST process
1523	   the message according to this section:

1525	   1.  If the message is invalid for processing, as defined in
1526	       Section 11.1, the message MUST be discarded without further
1527	       processing.  The message is not considered for forwarding.

1529	   2.  Otherwise, the message is processed according to Section 11.2.

1531	   3.  If RREP.ackrequired is set, an RREP_ACK message MUST be sent to
1532	       the previous-hop, according to Section 15.2.

1534	   4.  If hop-count is equal to MAX_HOP_COUNT or hop-limit is equal to
1535	       0, the message is not considered for forwarding.

1537	   5.  Otherwise, if RREP.destination is not listed in
1538	       I_local_iface_addr_list of any Local Interface Tuple and does not
1539	       correspond to D_address of any Destination Address Tuple of this
1540	       LOADng Router, the RREP message is considered for forwarding
1541	       according to Section 13.3.

1543	13.3.  RREP Forwarding

1545	   The variables used-metric type, hop-count, hop-limit and route-metric
1546	   have been updated in Section 11.2 (when processing the message) and
1547	   are used in this section to update the content of the message to be
1548	   forwarded.  An RREP message, considered for forwarding, MUST be
1549	   updated as follows, prior to it being transmitted:

1551	   1.  RREP.metric-type := used-metric-type (as set in Section 11.2)

1553	   2.  RREP.route-metric := route-metric (as set in Section 11.2)

1555	   3.  RREP.hop-count := hop-count (as set in Section 11.2)

1557	   4.  RREP.hop-limit := hop-limit (as set in Section 11.2)

1559	   5.  The RREP is transmitted, according to Section 13.4.

1561	   The RREP message is then unicast to the next hop towards
1562	   RREP.destination.

1564	13.4.  RREP Transmission

1566	   An RREP is, ultimately, destined for the LOADng Router which has the
1567	   address listed in the RREP.destination field in either of its Local
1568	   Interface Set, or in its Destination Address Set. The RREP is
1569	   forwarded in unicast towards that LOADng Router.  The RREP MUST,
1570	   however, be transmitted so as to allow it to be processed in each
1571	   intermediate LOADng Router to:

1573	   o  Install proper forward routes; AND

1575	   o  Permit that RREP.hop-count be updated to reflect the route.

1577	   RREP Transmission is accomplished by the following procedure:

1579	   1.  Find the Routing Tuple (henceforth, the "Matching Routing Tuple")
1580	       in the Routing Set, where:

1582	       *  R_dest_addr = RREP.destination

1584	   2.  Find the Local Interface Tuple (henceforth, "Matching Interface
1585	       Tuple), where:

1587	       *  I_local_iface_addr_list contains R_local_iface_addr from the
1588	          Matching Routing Tuple

1590	   3.  If RREP_ACK_REQUIRED is set for the LOADng Interface, identified
1591	       by the Matching Interface Tuple:

1593	       *  Create a new Pending Acknowledgment Tuple with:

1595	          +  P_next_hop := R_next_addr from the Matching Routing Tuple

1597	          +  P_originator := RREP.originator

1599	          +  P_seq_num := RREP.seq-num

1601	          +  P_ack_received := FALSE

1603	          +  P_ack_timeout := current_time + RREP_ACK_TIMEOUT

1605	       *  RREP.ackrequired := TRUE

1607	   4.  Otherwise:

1609	       *  RREP.ackrequired := FALSE

1611	   5.  The RREP is transmitted over the LOADng Interface, identified by
1612	       the Matching Interface Tuple to the neighbor LOADng Router,
1613	       identified by R_next_addr from the Matching Routing Tuple.

1615	   When a Pending Acknowledgement Tuple expires, if P_ack_received =
1616	   FALSE, the P_next_hop address MUST be blacklisted by creating a
1617	   Blacklisted Neighbor Tuple according to Section 7.3

1619	14.  Route Errors (RERRs)

1621	   If a LOADng Router fails to deliver a data packet to a next hop or a
1622	   destination, and if neither the source nor destination address of
1623	   that data packet belongs to the Destination Address Set of that
1624	   LOADng Router, it MUST generate a Route Error (RERR).  This RERR MUST
1625	   be sent along the Reverse Route towards the source of the data packet
1626	   for which delivery was unsuccessful (to the last LOADng Router along
1627	   the Reverse Route, if the data packet was originated by a host behind
1628	   that LOADng Router).

1630	   The following definition is used in this section:

1632	   o  "EXPIRED" indicates that a timer is set to a value clearly
1633	      preceding the current time (e.g., current time - 1).

1635	14.1.  Identifying Invalid RERR Messages

1637	   A received RERR is invalid, and MUST be discarded without further
1638	   processing, if any of the following conditions are true:

1640	   o  The address length specified by this message (i.e., RERR.addr-
1641	      length + 1) differs from the length of the address(es) of this
1642	      LOADng Router.

1644	   o  The address contained in RERR.originator is an address of this
1645	      LOADng Router.

1647	   A LOADng Router MAY recognize additional reasons, external to this
1648	   specification, for identifying that an RERR message is invalid for
1649	   processing, e.g., to allow a security protocol to perform
1650	   verification of signatures and prevent processing of unverifiable
1651	   RERR message by this protocol.

1653	14.2.  RERR Generation

1655	   A packet with an RERR message is generated by the LOADng Router,
1656	   detecting the link breakage, with the following content:

1658	   o  RERR.error-code := the error code corresponding to the event
1659	      causing the RERR to be generated, from among those recorded in
1660	      Table 1;

1662	   o  RERR.addr-length := the length of the address, as specified in
1663	      Section 6;

1665	   o  RERR.unreachableAddress := the destination address from the
1666	      unsuccessfully delivered data packet.

1668	   o  RERR.originator := one address of the LOADng Interface of the
1669	      LOADng Router that generates the RERR.

1671	   o  RERR.destination := the source address from the unsuccessfully
1672	      delivered data packet, towards which the RERR is to be sent.

1674	   o  RERR.hop-limit := MAX_HOP_LIMIT;

1676	14.3.  RERR Processing

1678	   For the purpose of the processing description below, the following
1679	   additional notation is used:

1681	   previous-hop  is the address of the LOADng Router, from which the
1682	      RERR was received.

1684	   hop-limit  is a variable, representing the hop-limit, as included in
1685	      the received RERR message.

1687	   Upon receiving an RERR, a LOADng Router MUST perform the following
1688	   steps:

1690	   1.  If the RERR is invalid for processing, as defined in
1691	       Section 14.1, the RERR MUST be discarded without further
1692	       processing.  The message is not considered for forwarding.

1694	   2.  Included TLVs are processed/updated according to their
1695	       specification.

1697	   3.  Set the variable hop-limit to RERR.hop-limit - 1.

1699	   4.  Find the Routing Tuple (henceforth "matching Routing Tuple") in
1700	       the Routing Set where:

1702	       *  R_dest_addr = RERR.unreachableAddress

1704	       *  R_next_addr = previous-hop

1706	   5.  If no matching Routing Tuple is found, the RERR is not processed
1707	       further, but is considered for forwarding, as specified in
1708	       Section 14.4.

1710	   6.  Otherwise, if one matching Routing Tuple is found:

1712	       1.  If RERR.errorcode is 0 ("No available route", as specified in
1713	           Section 19.1), this matching Routing Tuple is updated as
1714	           follows:

1716	           +  R_valid_time := EXPIRED

1718	           Extensions to this specification MAY define additional error
1719	           codes in the Error Code IANA registry, and MAY insert
1720	           processing rules here for RERRs with that error code.

1722	       2.  If hop-limit is greater than 0, the RERR message is
1723	           considered for forwarding, as specified in Section 14.4

1725	14.4.  RERR Forwarding

1727	   An RERR is, ultimately, destined for the LOADng Router which has, in
1728	   either its Destination Address Set or in its Local Interface Set, the
1729	   address from RERR.originator.

1731	   An RERR, considered for forwarding is therefore processed as follows:

1733	   1.  RERR.hop-limit := hop-limit (as set in Section 14.3)

1735	   2.  Find the Destination Address Tuple (henceforth, matching
1736	       Destination Address Tuple) in the Destination Address Set where:

1738	       *  D_address = RERR.destination

1740	   3.  If one or more matching Destination Address Tuples are found, the
1741	       RERR message is discarded and not retransmitted, as it has
1742	       reached the final destination.

1744	   4.  Otherwise, find the Local Interface Tuple (henceforth, matching
1745	       Local Interface Tuple) in the Local Interface Set where:

1747	       *  I_local_iface_addr_list contains RERR.destination.

1749	   5.  If a matching Local Interface Tuple is found, the RERR message is
1750	       discarded and not retransmitted, as it has reached the final
1751	       destination.

1753	   6.  Otherwise, if no matching Destination Address Tuples or Local
1754	       Interface Tuples are found, the RERR message is transmitted
1755	       according to Section 14.5.

1757	14.5.  RERR Transmission

1759	   An RERR is, ultimately, destined for the LOADng Router which has the
1760	   address listed in the RERR.destination field in either of its Local
1761	   Interface Set, or in its Destination Address Set. The RERR is
1762	   forwarded in unicast towards that LOADng Router.  The RERR MUST,
1763	   however, be transmitted so as to allow it to be processed in each
1764	   intermediate LOADng Router to:

1766	   o  Allow intermediate LOADng Routers to update their Routing Sets,
1767	      i.e., remove tuples for this destination.

1769	   RERR Transmission is accomplished by the following procedure:

1771	   1.  Find the Routing Tuple (henceforth, the "Matching Routing Tuple")
1772	       in the Routing Set, where:

1774	       *  R_dest_addr = RERR.destination

1776	   2.  Find the Local Interface Tuple (henceforth, "Matching Interface
1777	       Tuple), where:

1779	       *  I_local_iface_addr_list contains R_local_iface_addr from the
1780	          Matching Routing Tuple

1782	   3.  The RERR is transmitted over the LOADng Interface, identified by
1783	       the Matching Interface Tuple to the neighbor LOADng Router,
1784	       identified by R_next_addr from the Matching Routing Tuple.

1786	15.  Route Reply Acknowledgments (RREP_ACKs)

1788	   A LOADng Router MUST signal in a transmitted RREP that it is
1789	   expecting an RREP_ACK, by setting RREP.ackrequired flag in the RREP.
1790	   When doing so, the LOADng Router MUST also add a tuple (P_next_hop,
1791	   P_originator, P_seq_num, P_ack_timeout) to the Pending Acknowledgment
1792	   Set, and set P_ack_timeout to current_time + RREP_ACK_TIMEOUT, as
1793	   described in Section 13.4.

1795	   The following definition is used in this section:

1797	   o  "EXPIRED" indicates that a timer is set to a value clearly
1798	      preceding the current time (e.g., current_time - 1).

1800	15.1.  Identifying Invalid RREP_ACK Messages

1802	   A received RREP_ACK is invalid, and MUST be discarded without further
1803	   processing, if any of the following conditions are true:

1805	   o  The address length specified by this message (i.e., RREP_ACK.addr-
1806	      length + 1) differs from the length of the address(es) of this
1807	      LOADng Router.

1809	   A LOADng Router MAY recognize additional reasons, external to this
1810	   specification, for identifying that an RREP_ACK message is invalid
1811	   for processing, e.g., to allow a security protocol to perform
1812	   verification of signatures and prevent processing of unverifiable
1813	   RREP_ACK message by this protocol.

1815	15.2.  RREP_ACK Generation

1817	   Upon reception of an RREP message with the RREP.ackrequired flag set,
1818	   a LOADng Router MUST generate at least one RREP_ACK and send this
1819	   RREP_ACK in unicast to the neighbor which originated the RREP.

1821	   An RREP_ACK message is generated by a LOADng Router with the
1822	   following content:

1824	   o  RREP_ACK.addr-length := the length of the address, as specified in
1825	      Section 6;

1827	   o  RREP_ACK.seq-num := the value of the RREP.seq-num field of the
1828	      received RREP;

1830	   o  RREP_ACK.destination := RREP.originator of the received RREP.

1832	15.3.  RREP_ACK Processing

1834	   On receiving an RREP_ACK from a LOADng neighbor LOADng Router, a
1835	   LOADng Router MUST do the following:

1837	   1.  If the RREP_ACK is invalid for processing, as defined in
1838	       Section 15.1, the RREP_ACK MUST be discarded without further
1839	       processing.

1841	   2.  Find the Routing Tuple (henceforth, Matching Routing Tuple)
1842	       where:

1844	       *  R_dest_addr = previous-hop;

1846	       The Matching Routing Tuple is updated as follows:

1848	       *  R_bidirectional := TRUE

1850	   3.  If a Pending Acknowledgement Tuple (henceforth, Matching Pending
1851	       Acknowledgement Tuple) exists, where:

1853	       *  P_next_hop is the address of the LOADng Router from which the
1854	          RREP_ACK was received.

1856	       *  P_originator = RREP_ACK.destination

1858	       *  P_seq_num = RREP_ACK.seq-num

1860	       Then the RREP has been acknowledged.  The Matching Pending
1861	       Acknowledgement Tuple is updated as follows:

1863	       *  P_ack_received := TRUE

1865	       *  P_ack_timeout := EXPIRED

1867	15.4.  RREP_ACK Forwarding

1869	   An RREP_ACK is intended only for a specific direct neighbor, and MUST
1870	   NOT be forwarded.

1872	15.5.  RREP_ACK Transmission

1874	   An RREP_ACK is transmitted, in unicast, to the neighbor LOADng Router
1875	   from which the RREP was received.

1877	16.  Metrics

1879	   This specification enables the use of different metrics for when
1880	   calculating route metrics.

1882	   Metrics as defined in LOADng are additive, and the routes that are to
1883	   be created are those with the minimum sum of the metrics along that
1884	   route.

1886	16.1.  Specifying New Metrics

1888	   When defining a metric, the following considerations SHOULD be taken
1889	   into consideration:

1891	   o  The definition of the R_metric field, as well as the value of
1892	      MAX_DIST.

1894	17.  Implementation Status

1896	   This section records the status of known implementations of the
1897	   protocol defined by this specification, and is based on a proposal
1898	   described in [I-D.sheffer-running-code].  According to
1899	   [I-D.sheffer-running-code], "this will allow reviewers and working
1900	   groups to assign due consideration to documents that have the benefit
1901	   of running code and potentially reward the documented protocols by
1902	   treating the documents with implementations preferentially".

1904	   In the following subsections, each publicly-known implementation of
1905	   LOADng is listed.  There are currently four publicly-known
1906	   implementations of LOADng.  These have been tested for
1907	   interoperability in at least three interop events, as described in
1908	   [I-D.loadng-interop-report].

1910	17.1.  Implementation of Ecole Polytechnique

1912	   This implementation is developed by the Networking Group at Ecole
1913	   Polytechnique.  It can run over real network interfaces, and can also
1914	   be integrated with the network simulator NS2.  It is a Java
1915	   implementation, and can be used on any platform that includes a Java
1916	   virtual machine.

1918	   The implementation has been maintained since the 00 revision of
1919	   LOADng, and is quite mature.  It has been tested in interoperability
1920	   events with other implementations (as described in
1921	   [I-D.loadng-interop-report]), and in large-scale network simulations
1922	   with up to 1000 routers.  There have been several scientific
1923	   publications based on this implementation, such as [IEEE_VTC2012]
1924	   [IEEE_WiCom2012] [IEEE_ICWITS2012].

1926	   All the protocol functions of this revision (-08) of the
1927	   specification, including RREQ/RREP/RREP-ACK/RERR generation,
1928	   processing, forwarding and transmission, as well as blacklisting, are
1929	   implemented.

1931	   The latest implementation conforms to the LOADng-07 revision as
1932	   documented in this specification.  This software is currently closed
1933	   source.

1935	17.2.  Implementation of Fujitsu Laboratories of America

1937	   This implementation is developed by Fujitsu Laboratories of America.
1938	   It is a Java implementation, structured in multiple separate modules,
1939	   notably a [RFC5444] generator and parser, and integration module in
1940	   the network simulator Ns-2, a kernel module for integrating the
1941	   implementation in a Linux kernel (not yet completed), and the
1942	   protocol core.

1944	   The implementation is mature and has been tested both in
1945	   interoperability tests with other implementations
1946	   [I-D.loadng-interop-report], as well as large-scale simulations with
1947	   hundreds of routers.  The implementation is not currently used in
1948	   deployments.  The implementation supports all LOADng functions (RREQ,
1949	   RREP, RREP-ACK generation, processing, forwarding and transmission),
1950	   and conforms to the LOADng-06 specification.  The software is
1951	   currently closed source.

1953	17.3.  Implementation of Hitachi Yokohama Research Laboratory - 1

1955	   This implementation is developed by Hitachi, Ltd. Yokohama Research
1956	   Laboratory.  It can run over real embedded devices.  It is a C
1957	   implementation.  The implementation is maintained since the 00
1958	   revision of LOADng.  It was tested in the first interoperability
1959	   event with other implementations, as described in
1960	   [I-D.loadng-interop-report].

1962	   This implementation is alpha version, mainly for performance test and
1963	   evaluations.  All the functions of the protocol, including RREQ/RREP/
1964	   RREP-ACK/RERR generation, processing, forwarding and transmission,
1965	   blacklisting, have been implemented.  Also a RFC5444 generator and
1966	   parser have been implemented.  The latest implementation conforms to
1967	   LOADng-06 revision.  This software is currently closed source.

1969	17.4.  Implementation of Hitachi Yokohama Research Laboratory -2

1971	   This implementation is developed by Hitachi, Ltd. Yokohama Research
1972	   Laboratory.  It can run over real network interface, and can also be
1973	   integrated with network simulator NS2.  It is a C++ implementation.

1975	   The implementation is mature and maintained since the 00 revision of
1976	   LOADng.  It was tested in large-scale network simulations up to 500
1977	   routers.

1979	   All the functions of the protocol, including RREQ/RREP/RREP-ACK/RERR
1980	   generation, processing, forwarding and transmission, blacklisting,
1981	   have been implemented.  The latest implementation conforms to the
1982	   LOADng-05 revision.  This software is currently closed source.

1984	18.  Security Considerations

1986	   Currently, this protocol does not specify any special security
1987	   measures.  As a reactive routing protocol, this protocol is a
1988	   potential target for various attacks.  Various possible
1989	   vulnerabilities are discussed in this section.

1991	   By way of (i) enabling inclusion of TLVs and (ii) permitting that
1992	   LOADng recognizes external reasons for rejecting RREQ, RREP, RREP_ACK
1993	   and RERR messages, development of security measures, appropriate for
1994	   a given deployment, is however supported.  This architecture is a
1995	   result of the observation that with respect to security in LOADng
1996	   routed networks, "one size rarely fits all".  This, as LOADng
1997	   deployment domains have varying security requirements ranging from
1998	   "unbreakable" to "virtually none", depending on, e.g., physical
1999	   access to the network, or on security available on other layers.  The
2000	   virtue of this approach is that LOADng routing protocol
2001	   specifications (and implementations) can remain "generic", with
2002	   extensions providing proper deployment-domain specific security
2003	   mechanisms.

2005	18.1.  Confidentiality

2007	   This protocol floods Route Requests (RREQs) to all the LOADng Routers
2008	   in the network, when there is traffic to deliver to a given
2009	   destination.  Hence, if used in an unprotected network (such as an
2010	   unprotected wireless network):

2012	   o  Part of the network topology is revealed to anyone who listens,
2013	      specifically (i) the identity (and existence) of the source LOADng
2014	      Router; (ii) the identity of the destination; and (iii) the fact
2015	      that a path exists between the source LOADng Router and the LOADng
2016	      Router from which the RREQ was received.

2018	   o  The network traffic patterns are revealed to anyone who listens to
2019	      the LOADng control traffic, specifically which pairs of devices
2020	      communicate.  If, for example, a majority of traffic originates
2021	      from or terminates in a specific LOADng Router, this may indicate
2022	      that this LOADng Router has a central role in the network.

2024	   This protocol also unicasts Route Replies (RREPs) from the
2025	   destination of an RREQ to the originator of that same RREQ.  Hence,
2026	   if used in an unprotected network (such as an unprotected wireless
2027	   network):

2029	   o  Part of the network topology is revealed to anyone who is near or
2030	      on the unicast path of the RREP (such as within radio range of
2031	      LOADng Routers on the unicast path in an unprotected wireless
2032	      network), specifically that a path from the originator (of the
2033	      RREP) to the destination (of the RREP) exists.

2035	   Finally, this protocol unicasts Route Errors (RERRs) when an
2036	   intermediate LOADng Router detects that the path from a source to a
2037	   destination is no longer available.  Hence, if used in an unprotected
2038	   network (such as an unprotected wireless network):

2040	   o  A disruption of the network topology is revealed to anyone who is
2041	      near or on the unicast path of the RERR (such as within radio
2042	      range of LOADng Routers on the unicast path in an unprotected
2043	      wireless network), specifically that a path from the originator
2044	      (of the RERR) to the destination (of the RERR) has been disrupted.

2046	   This protocol signaling behavior enables, for example, an attacker to
2047	   identify central devices in the network (by monitoring RREQs) so as
2048	   to target an attack, and (by way of monitoring RERRs) to measure the
2049	   success of an attack.

2051	18.2.  Integrity

2053	   A LOADng Router injects topological information into the network by
2054	   way of transmitting RREQ and RREP messages, and removes installed
2055	   topological information by way of transmitting RERR messages.  If
2056	   some LOADng Routers for some reason, malice or malfunction, inject
2057	   invalid control traffic, network integrity may be compromised.
2058	   Therefore, message authentication is recommended.

2060	   Different such situations may occur, for instance:

2062	   1.  A LOADng Router generates RREQ messages, pretending to be another
2063	       LOADng Router;

2065	   2.  A LOADng Router generates RREP messages, pretending to be another
2066	       LOADng Router;

2068	   3.  A LOADng Router generates RERR messages, pretending to be another
2069	       LOADng Router;

2071	   4.  A LOADng Router generates RERR messages, indicating that a link
2072	       on a path to a destination is broken;

2074	   5.  A LOADng Router forwards altered control messages;

2076	   6.  A LOADng Router does not forward control messages;

2078	   7.  A LOADng Router forwards RREPs and RREQs, but does not forward
2079	       unicast data traffic;

2081	   8.  A LOADng Router "replays" previously recorded control messages
2082	       from another LOADng Router.

2084	   Authentication of the originator LOADng Router for control messages
2085	   (for situations 1, 2 and 3) and on individual links announced in the
2086	   control message (for situation 2 and 4) may be used as a
2087	   countermeasure.  However, to prevent routers from repeating old (and
2088	   correctly authenticated) information (situation 8), temporal
2089	   information is required, requiring a router to positively identify
2090	   such a delayed message.

2092	   In general, integrity check values and other required security
2093	   information may be transmitted as a separate Message Type, or
2094	   signatures and security information may be transmitted within the
2095	   control messages, using the TLV mechanism.  Either option permits
2096	   that "secured" and "unsecured" routers can coexist in the same
2097	   network, if desired.

2099	   Specifically, if LOADng is used on the IP layer, the authenticity of
2100	   entire control messages can be established through employing IPsec
2101	   authentication headers, whereas authenticity of individual links
2102	   (situations 2 and 4) require additional security information to be
2103	   distributed.

2105	18.3.  Channel Jamming and State Explosion

2107	   A reactive protocol, LOADng control messages are generated in
2108	   response to network events.  For RREQs, such an event is that a data
2109	   packet is present in a router which does not have a route to the
2110	   destination of the data packet, or that the router receives an RERR
2111	   message, invalidating a route.  For RREPs, such an event is the
2112	   receipt of an RREQ corresponding to a destination owned by the LOADng
2113	   Router.  A router that forwards an RREQ records the reverse route
2114	   state.  A router that forwards an RREP records the forward route
2115	   state.  If some routers for some reason, malice or malfunction,
2116	   generates excessive RREQ, RREP or RERRs, otherwise correctly
2117	   functioning LOADng Routers may fall victim to either "indirect
2118	   jamming" (being "tricked" into generating excessive control traffic)
2119	   or an explosion in the state necessary for maintaining protocol state
2120	   (potentially, exhausting the available memory resources).

2122	   Different such situations may occur, for instance:

2124	   1.  A router, within a short time, generates RREQs to an excessive
2125	       amount of destinations in the network (possibly all destinations,
2126	       possibly even destinations not present in the network), causing
2127	       intermediate routers to allocate state for the forward routes.

2129	   2.  A router generates excessively frequent RREQs to the same
2130	       (existing) destination, causing the corresponding LOADng Router
2131	       to generate excessive RREPs.

2133	   3.  A router generates RERRs for a destination to the source LOADng
2134	       Router for traffic to that destination, causing that LOADng
2135	       Router to flood renewed RREQs.

2137	   For situation 1, the state required for recording forward and/or
2138	   reverse routes may exceed the memory available in the intermediate
2139	   LOADng Routers - to the detriment of being able of recording state
2140	   for other routes.  This, in particular, if a LOADng Router generates
2141	   RREQs for destinations "not present in the network".

2143	   A router which, within a short time, generates RREPs to an excessive
2144	   amount of destinations in the network (possibly all destinations,
2145	   possibly even destinations not present in the network), will not have
2146	   the same network-wide effect: an intermediate router receiving an
2147	   RREP for a destination for which no reverse route exists will neither
2148	   attempt forwarding the RREP nor allocate state for the forward route.

2150	   For situations 1, 2, and 3, a possible countermeasure is to rate-
2151	   limit the number of control messages that a LOADng Router forwards on
2152	   behalf of another LOADng Router.  Such a rate limit should take into
2153	   consideration the expected normal traffic for a given LOADng
2154	   deployment.  Authentication may furthermore be used so as to prohibit
2155	   a LOADng Router from forwarding control traffic from any non-
2156	   authenticated router (with the assumption being that an authenticated
2157	   router is not expected to exhibit such rogue behavior).

2159	18.4.  Interaction with External Routing Domains

2161	   This protocol does provide a basic mechanism for a LOADng Router to
2162	   be able to discover routes to external routing domains: a LOADng
2163	   Router configured to "own" a given set of addresses will respond to
2164	   RREQs for destinations with these addresses, and can - by whatever
2165	   protocols governing the routing domain wherein these addresses exist
2166	   - provide paths to these addresses.

2168	   When operating routers connecting a LOADng domain to an external
2169	   routing domain, destinations inside the LOADng domain can be injected
2170	   into the external domain, if the routing protocol governing that
2171	   domain so permits.  Care MUST be taken to not allow potentially
2172	   insecure and untrustworthy information to be injected into the
2173	   external domain.

2175	   In case LOADng is used on the IP layer, a RECOMMENDED way of
2176	   extending connectivity from an external routing domain to a LOADng
2177	   routed domain is to assign an IP prefix (under the authority of the
2178	   routers/gateways connecting the LOADng routing domain with the
2179	   external routing domain) exclusively to that LOADng routing domain,
2180	   and to statically configure gateways to advertise routes for that
2181	   prefix into the external domain.  Within the LOADng domain, gateways
2182	   SHOULD only generate RREPs for destinations which are not part of
2183	   that prefix; this is in particularly important if a gateway otherwise
2184	   provides connectivity to "a default route".

2186	19.  LOADng Specific IANA Considerations

2188	19.1.  Error Codes

2190	   IANA is requested to create a new registry for Error Codes, with
2191	   initial assignments and allocation policies as specified in Table 1.

2193	           +---------+--------------------+-------------------+
2194	           |   Code  | Description        | Allocation Policy |
2195	           +---------+--------------------+-------------------+
2196	           |    0    | No available route |                   |
2197	           |  1-251  | Unassigned         | Expert Review     |
2198	           | 252-255 | Unassigned         | Experimental Use  |
2199	           +---------+--------------------+-------------------+
2200	                           Table 1: Error Codes

2202	20.  Contributors

2204	   This specification is the result of the joint efforts of the
2205	   following contributors - listed alphabetically.

2207	   o  Alberto Camacho, LIX, France, <alberto@albertocamacho.com>

2209	   o  Thomas Heide Clausen, LIX, France, <T.Clausen@computer.org>

2211	   o  Axel Colin de Verdiere, LIX, France, <axel@axelcdv.com>

2213	   o  Kenneth Garey, Maxim Integrated Products, USA,
2214	      <kenneth.garey@maxim-ic.com>

2216	   o  Ulrich Herberg, Fujitsu Laboratories of America, USA
2217	      <ulrich.herberg@us.fujitsu.com>

2219	   o  Yuichi Igarashi, Hitachi Ltd, Yokohama Research Laboratory, Japan,
2220	      <yuichi.igarashi.hb@hitachi.com>

2222	   o  Cedric Lavenu, EDF R&D, France, <cedric-2.lavenu@edf.fr>

2224	   o  Afshin Niktash, Maxim Integrated Products, USA,
2225	      <afshin.niktash@maxim-ic.com>

2227	   o  Charles E. Perkins, Futurewei Inc, USA, <charliep@computer.org>

2229	   o  Hiroki Satoh, Hitachi Ltd, Yokohama Research Laboratory, Japan,
2230	      <hiroki.satoh.yj@hitachi.com>

2232	   o  Thierry Lys, ERDF, France, <thierry.lys@erdfdistribution.fr>

2234	   o  Jiazi Yi, LIX, France, <jiazi@jiaziyi.com>

2236	21.  Acknowledgments

2238	   The authors would like to acknowledge the team behind AODV [RFC3561].
2239	   The authors would also like to acknowledge the efforts of K. Kim
2240	   (picosNet Corp/Ajou University), S. Daniel Park (Samsung
2241	   Electronics), G. Montenegro (Microsoft Corporation), S. Yoo (Ajou
2242	   University) and N. Kushalnagar (Intel Corp.) for their work on an
2243	   initial version of a specification, from which this protocol is
2244	   derived.

2246	22.  References
2247	22.1.  Normative References

2249	   [RFC2119]                    Bradner, S., "Key words for use in RFCs
2250	                                to Indicate Requirement Levels",
2251	                                RFC 2119, BCP 14, March 1997.

2253	   [RFC5444]                    Clausen, T., Dean, J., Dearlove, C., and
2254	                                C. Adjih, "Generalized Mobile Ad Hoc
2255	                                Network (MANET) Packet/Message Format",
2256	                                RFC 5444, February 2009.

2258	   [RFC5498]                    Chakeres, I., "IANA Allocations for
2259	                                Mobile Ad Hoc Network (MANET)
2260	                                Protocols", RFC 5498, March 2009.

2262	22.2.  Informative References

2264	   [I-D.sheffer-running-code]   Sheffer, Y. and A. Farrel, "Improving
2265	                                "Rough Consensus" with Running Code",
2266	                                draft-sheffer-running-code-01 (work in
2267	                                progress), December 2012.

2269	   [I-D.loadng-interop-report]  Clausen, T., Camacho, A., Yi, J., Colin
2270	                                de Verdiere, A., Igarashi, Y., Satoh,
2271	                                H., Morii, Y., Heropberg, U., and C.
2272	                                Lavenu, "Interoperability Report for the
2273	                                Lightweight On-demand Ad hoc Distance-
2274	                                vector Routing Protocol - Next
2275	                                Generation (LOADng)", draft-lavenu-lln-
2276	                                loadng-interoperability-report-04 (work
2277	                                in progress), December 2012.

2279	   [RFC3561]                    Perkins, C., Belding-Royer, E., and S.
2280	                                Das, "Ad hoc On-Demand Distance Vector
2281	                                (AODV) Routing", RFC 3561, July 2003.

2283	   [RFC4861]                    Narten, T., Nordmark, E., Simpson, W.,
2284	                                and H. Soliman, "Neighbor Discovery for
2285	                                IP version 6 (IPv6)", RFC 4861,
2286	                                September 2007.

2288	   [RFC4944]                    Montenegro, G., Kushalnagar, N., Hui,
2289	                                J., and D. Culler, "Transmission of IPv6
2290	                                Packets over IEEE 802.15.4 Networks",
2291	                                RFC 4944, September 2007.

2293	   [RFC5148]                    Clausen, T., Dearlove, C., and B.
2294	                                Adamson, "Jitter Considerations in
2295	                                Mobile Ad Hoc Networks (MANETs)",
2296	                                RFC 5148, February 2008.

2298	   [RFC6130]                    Clausen, T., Dean, J., and C. Dearlove,
2299	                                "MANET Neighborhood Discovery Protocol
2300	                                (NHDP)", RFC 6130, April 2011.

2302	   [RFC6206]                    Levis, P., Clausen, T., Gnawali, O., and
2303	                                J. Ko, "The Trickle Algorithm",
2304	                                RFC 6206, March 2011.

2306	   [RFC6621]                    Macker, J., "Simplified Multicast
2307	                                Forwarding", RFC 6621, May 2012.

2309	   [EUI64]                      IEEE, "Guidelines for 64-bit Global
2310	                                Identifier (EUI-64) Registration
2311	                                Authority".

2313	   [IEEE754-2008]               IEEE, "IEEE 754-2008: IEEE Standard for
2314	                                Floating-Point Arithmetic", 2008.

2316	   [IEEE_VTC2012]               Clausen, T., Yi, J., and A. Coline de
2317	                                Verdiere, "Towards AODV Version 2",
2318	                                Proceedings of IEEE VTC 2012 Fall, IEEE
2319	                                76th Vehicular Technology Conference,
2320	                                2012.

2322	   [IEEE_WiCom2012]             Yi, J., Clausen, T., and A. Coline de
2323	                                Verdiere, "Efficient Data Acquisition in
2324	                                Sensor Networks:Introducing (the) LOADng
2325	                                Collection Tree Protocol",
2326	                                Proceedings of IEEE WiCom 2012, The 8th
2327	                                IEEE International Conference on
2328	                                Wireless Communications, Networking and
2329	                                Mobile Computing., 2012.

2331	   [IEEE_ICWITS2012]            Yi, J., Clausen, T., and A. Bas, "Smart
2332	                                Route Request for On-demand Route
2333	                                Discovery in Constrained Environments",
2334	                                Proceedings of IEEE ICWITS 2012, IEEE
2335	                                International Conference on Wireless
2336	                                Information Technology and Systems.,
2337	                                2012.

2339	Appendix A.  LOADng Control Messages using RFC5444

2341	   This section presents how the abstract LOADng messages, used
2342	   throughout this specification, are mapped into [RFC5444] messages.

2344	A.1.  RREQ-Specific Message Encoding Considerations

2346	   This protocol defines, and hence owns, the RREQ Message Type.  Thus,
2347	   as specified in [RFC5444], this protocol generates and transmits all
2348	   RREQ messages, receives all RREQ messages and is responsible for
2349	   determining whether and how each RREQ message is to be processed
2350	   (updating the Information Base) and/or forwarded, according to this
2351	   specification.  Table 2 specifies how RREQ messages are mapped into
2352	   [RFC5444]-elements.

2354	   +-------------------+-------------------+---------------------------+
2355	   |    RREQ Element   |  RFC5444-Element  | Considerations            |
2356	   +-------------------+-------------------+---------------------------+
2357	   |  RREQ.addr-length | <msg-addr-length> | Supports addresses from   |
2358	   |                   |                   | 1-16 octets               |
2359	   |    RREQ.seq-num   |   <msg-seq-num>   | 16 bits, hence MAXVALUE   |
2360	   |                   |                   | (Section 8) is 65535.     |
2361	   |                   |                   | MUST be included          |
2362	   |  RREQ.metric-type |   METRIC Message  | Encoded by way of the     |
2363	   |                   |        TLV        | Type-Extension of a       |
2364	   |                   |                   | Message-Type-specific     |
2365	   |                   |                   | Message TLV of type       |
2366	   |                   |                   | METRIC, defined in        |
2367	   |                   |                   | Table 8. A LOADng Router  |
2368	   |                   |                   | generating an RREQ (as    |
2369	   |                   |                   | specified in              |
2370	   |                   |                   | Section 12.1) when using  |
2371	   |                   |                   | the HOP_COUNT metric,     |
2372	   |                   |                   | MUST NOT add the METRIC   |
2373	   |                   |                   | Message TLV to the RREQ   |
2374	   |                   |                   | (in order to reduce       |
2375	   |                   |                   | overhead, as the hop      |
2376	   |                   |                   | count value is already    |
2377	   |                   |                   | encoded in                |
2378	   |                   |                   | RREQ.hop-count). LOADng   |
2379	   |                   |                   | Routers receiving an RREQ |
2380	   |                   |                   | without METRIC Message    |
2381	   |                   |                   | TLV assume that           |
2382	   |                   |                   | RREQ.metric-type is       |
2383	   |                   |                   | HOP_COUNT, and MUST not   |
2384	   |                   |                   | add the METRIC Message    |
2385	   |                   |                   | TLV when forwarding the   |
2386	   |                   |                   | message. Otherwise,       |
2387	   |                   |                   | exactly one METRIC TLV    |
2388	   |                   |                   | MUST be included in each  |
2389	   |                   |                   | RREQ message.             |
2390	   | RREQ.route-metric |   METRIC Message  | Encoded as the value      |
2391	   |                   |     TLV value     | field of the METRIC TLV.  |
2392	   |                   |                   | (LOADng Routers           |
2393	   |                   |                   | generating RREQs when     |
2394	   |                   |                   | using the HOP_COUNT       |
2395	   |                   |                   | metric do not need need   |
2396	   |                   |                   | to add the METRIC Message |
2397	   |                   |                   | TLV, as specified above   |
2398	   |                   |                   | for the RREQ.metric-type  |
2399	   |                   |                   | field.)                   |
2400	   |   RREQ.hop-limit  |  <msg-hop-limit>  | 8 bits. MUST be included  |
2401	   |                   |                   | in an RREQ message        |
2402	   |   RREQ.hop-count  |  <msg-hop-count>  | 8 bits, hence             |
2403	   |                   |                   | MAX_HOP_COUNT is 255.     |
2404	   |                   |                   | MUST be included in an    |
2405	   |                   |                   | RREQ message.             |
2406	   |  RREQ.originator  |  <msg-orig-addr>  | MUST be included in an    |
2407	   |                   |                   | RREQ message.             |
2408	   |  RREQ.destination |     Address in    | Encoded by way of an      |
2409	   |                   |   Address-Block   | address in an address     |
2410	   |                   |       w/TLV       | block, with which a       |
2411	   |                   |                   | Message-Type-specific     |
2412	   |                   |                   | Address Block TLV of type |
2413	   |                   |                   | ADDR-TYPE and with        |
2414	   |                   |                   | Type-Extension            |
2415	   |                   |                   | DESTINATION is            |
2416	   |                   |                   | associated, defined in    |
2417	   |                   |                   | Table 9. An RREQ MUST     |
2418	   |                   |                   | contain exactly one       |
2419	   |                   |                   | address with a TLV of     |
2420	   |                   |                   | type ADDR-TYPE and with   |
2421	   |                   |                   | Type-Extension            |
2422	   |                   |                   | DESTINATION associated.   |
2423	   +-------------------+-------------------+---------------------------+

2425	                      Table 2: RREQ Message Elements

2427	A.2.  RREP-Specific Message Encoding Considerations

2429	   This protocol defines, and hence owns, the RREP Message Type.  Thus,
2430	   as specified in [RFC5444], this protocol generates and transmits all
2431	   RREP messages, receives all RREP messages and is responsible for
2432	   determining whether and how each RREP message is to be processed
2433	   (updating the Information Base) and/or forwarded, according to this
2434	   specification.  Table 3 describes how RREP messages are mapped into
2435	   [RFC5444]-elements.

2437	   +-------------------+-------------------+---------------------------+
2438	   |    RREP Element   |  RFC5444-Element  | Considerations            |
2439	   +-------------------+-------------------+---------------------------+
2440	   |  RREP.addr-length | <msg-addr-length> | Supports addresses from   |
2441	   |                   |                   | 1-16 octets               |
2442	   |    RREP.seq-num   |   <msg-seq-num>   | 16 bits, hence MAXVALUE   |
2443	   |                   |                   | (Section 8) is 65535.     |
2444	   |                   |                   | MUST be included          |
2445	   |  RREP.metric-type |   METRIC Message  | Encoded by way of the     |
2446	   |                   |        TLV        | Type-Extension of a       |
2447	   |                   |                   | Message-Type-specific     |
2448	   |                   |                   | Message TLV of type       |
2449	   |                   |                   | METRIC, defined in        |
2450	   |                   |                   | Table 12. A LOADng Router |
2451	   |                   |                   | generating an RREP (as    |
2452	   |                   |                   | specified in              |
2453	   |                   |                   | Section 13.1) when using  |
2454	   |                   |                   | the HOP_COUNT metric,     |
2455	   |                   |                   | MUST NOT add the METRIC   |
2456	   |                   |                   | Message TLV to the RREP   |
2457	   |                   |                   | (in order to reduce       |
2458	   |                   |                   | overhead, as the hop      |
2459	   |                   |                   | count value is already    |
2460	   |                   |                   | encoded in                |
2461	   |                   |                   | RREP.hop-count). LOADng   |
2462	   |                   |                   | Routers receiving an RREP |
2463	   |                   |                   | without METRIC Message    |
2464	   |                   |                   | TLV assume that           |
2465	   |                   |                   | RREP.metric-type is       |
2466	   |                   |                   | HOP_COUNT, and MUST not   |
2467	   |                   |                   | add the METRIC Message    |
2468	   |                   |                   | TLV when forwarding the   |
2469	   |                   |                   | message. Otherwise,       |
2470	   |                   |                   | exactly one METRIC TLV    |
2471	   |                   |                   | MUST be included in each  |
2472	   |                   |                   | RREP message.             |
2473	   | RREP.route-metric |   METRIC Message  | Encoded as the value      |
2474	   |                   |     TLV value     | field of the METRIC TLV.  |
2475	   |                   |                   | (LOADng Routers           |
2476	   |                   |                   | generating RREPs when     |
2477	   |                   |                   | using the HOP_COUNT       |
2478	   |                   |                   | metric do not need need   |
2479	   |                   |                   | to add the METRIC Message |
2480	   |                   |                   | TLV, as specified above   |
2481	   |                   |                   | for the RREP.metric-type  |
2482	   |                   |                   | field.)                   |
2483	   |  RREP.ackrequired | FLAGS Message TLV | Encoded by way of a       |
2484	   |                   |                   | Message-Type-specific     |
2485	   |                   |                   | Message TLV of type       |
2486	   |                   |                   | FLAGS, defined in         |
2487	   |                   |                   | Table 13. A TLV of type   |
2488	   |                   |                   | FLAGS MUST always be      |
2489	   |                   |                   | included in an RREP       |
2490	   |                   |                   | message.                  |
2491	   |   RREP.hop-limit  |  <msg-hop-limit>  | 8 bits. MUST be included  |
2492	   |                   |                   | in an RREQ message        |
2493	   |   RREP.hop-count  |  <msg-hop-count>  | 8 bits, hence             |
2494	   |                   |                   | MAX_HOP_COUNT is 255.     |
2495	   |                   |                   | MUST be included in an    |
2496	   |                   |                   | RREP message.             |
2497	   |  RREP.originator  |  <msg-orig-addr>  | MUST be included in an    |
2498	   |                   |                   | RREP message.             |
2499	   |  RREP.destination |     Address in    | Encoded by way of an      |
2500	   |                   |   Address-Block   | address in an address     |
2501	   |                   |       w/TLV       | block, with which a       |
2502	   |                   |                   | Message-Type-specific     |
2503	   |                   |                   | Address Block TLV of type |
2504	   |                   |                   | ADDR-TYPE and with        |
2505	   |                   |                   | Type-Extension            |
2506	   |                   |                   | DESTINATION is            |
2507	   |                   |                   | associated, defined in    |
2508	   |                   |                   | Table 14. An RREP MUST    |
2509	   |                   |                   | contain exactly one       |
2510	   |                   |                   | address with a TLV of     |
2511	   |                   |                   | type ADDR-TYPE and with   |
2512	   |                   |                   | Type-Extension            |
2513	   |                   |                   | DESTINATION associated.   |
2514	   +-------------------+-------------------+---------------------------+

2516	                      Table 3: RREP Message Elements

2518	A.3.  RREP_ACK Message Encoding

2520	   This protocol defines, and hence owns, the RREP_ACK Message Type.
2521	   Thus, as specified in [RFC5444], this protocol generates and
2522	   transmits all RREP_ACK messages, receives all RREP_ACK messages and
2523	   is responsible for determining whether and how each RREP_ACK message
2524	   is to be processed (updating the Information Base), according to this
2525	   specification.  Table 4 describes how RREP_ACK Messages are mapped
2526	   into [RFC5444]-elements.

2528	   +----------------------+-------------------+------------------------+
2529	   |   RREP_ACK Element   |  RFC5444-Element  | Considerations         |
2530	   +----------------------+-------------------+------------------------+
2531	   | RREP_ACK.addr-length | <msg-addr-length> | Supports addresses     |
2532	   |                      |                   | from 1-16 octets       |
2533	   |   RREP_ACK.seq-num   |   <msg-seq-num>   | 16 bits, hence         |
2534	   |                      |                   | MAXVALUE (Section 8)   |
2535	   |                      |                   | is 65535. MUST be      |
2536	   |                      |                   | included               |
2537	   | RREP_ACK.destination |     Address in    | Encoded by way of an   |
2538	   |                      |   Address-Block   | address in an address  |
2539	   |                      |       w/TLV       | block, with which a    |
2540	   |                      |                   | Message-Type-specific  |
2541	   |                      |                   | Address Block TLV of   |
2542	   |                      |                   | type ADDR-TYPE and     |
2543	   |                      |                   | with Type-Extension    |
2544	   |                      |                   | DESTINATION is         |
2545	   |                      |                   | associated, defined in |
2546	   |                      |                   | Table 17. An RREP_ACK  |
2547	   |                      |                   | MUST contain exactly   |
2548	   |                      |                   | one address with a TLV |
2549	   |                      |                   | of type ADDR-TYPE and  |
2550	   |                      |                   | with Type-Extension    |
2551	   |                      |                   | DESTINATION            |
2552	   |                      |                   | associated.            |
2553	   +----------------------+-------------------+------------------------+

2555	                    Table 4: RREP_ACK Message Elements

2557	A.4.  RERR Message Encoding

2559	   This protocol defines, and hence owns, the RERR Message Type.  Thus,
2560	   as specified in [RFC5444], this protocol generates and transmits all
2561	   RERR messages, receives all RERR messages and is responsible for
2562	   determining whether and how each RERR message is to be processed
2563	   (updating the Information Base) and/or forwarded, according to this
2564	   specification.  Table 5 describes how RERR Messages are mapped into
2565	   [RFC5444]-elements.

2567	   +------------------------+------------------+-----------------------+
2568	   |      RERR Element      |  RFC5444-Element | Considerations        |
2569	   +------------------------+------------------+-----------------------+
2570	   |    RERR.addr-length    | <msg-addr-length | Supports addresses    |
2571	   |                        |         >        | from 1-16 octets      |
2572	   |     RERR.hop-limit     |  <msg-hop-limit> | 8 bits. MUST be       |
2573	   |                        |                  | included in an RREQ   |
2574	   |                        |                  | message               |
2575	   |     RERR.errorcode     |   Address Block  | According to          |
2576	   |                        |     TLV Value    | Section 19.1.         |
2577	   | RERR.unreachableAddres |    Address in    | Encoded by way of an  |
2578	   |            s           |   Address-Block  | address in an address |
2579	   |                        |       w/TLV      | block, with which a   |
2580	   |                        |                  | Message-Type-specific |
2581	   |                        |                  | Address Block TLV of  |
2582	   |                        |                  | type ADDR-TYPE and    |
2583	   |                        |                  | with Type-Extension   |
2584	   |                        |                  | ERRORCODE is          |
2585	   |                        |                  | associated, defined   |
2586	   |                        |                  | in Table 20.          |
2587	   |     RERR.originator    |  <msg-orig-addr> | MUST be included in   |
2588	   |                        |                  | an RERR message.      |
2589	   |    RERR.destination    |    Address in    | Encoded by way of an  |
2590	   |                        |   Address-Block  | address in an address |
2591	   |                        |       w/TLV      | block, with which a   |
2592	   |                        |                  | Message-Type-specific |
2593	   |                        |                  | Address Block TLV of  |
2594	   |                        |                  | type ADDR-TYPE and    |
2595	   |                        |                  | with Type-Extension   |
2596	   |                        |                  | DESTINATION is        |
2597	   |                        |                  | associated, defined   |
2598	   |                        |                  | in Table 20. An RERR  |
2599	   |                        |                  | MUST contain exactly  |
2600	   |                        |                  | one address with a    |
2601	   |                        |                  | TLV of type ADDR-TYPE |
2602	   |                        |                  | and with              |
2603	   |                        |                  | Type-Extension        |
2604	   |                        |                  | DESTINATION           |
2605	   |                        |                  | associated.           |
2606	   +------------------------+------------------+-----------------------+

2608	                      Table 5: RERR Message Elements

2610	A.5.  RFC5444-Specific IANA Considerations

2612	   This specification defines four Message Types, which must be
2613	   allocated from the "Message Types" repository of [RFC5444], two
2614	   Message TLV Types, which must be allocated from the "Message TLV
2615	   Types" repository of [RFC5444], and four Address Block TLV Types,
2616	   which must be allocated from the "Address Block TLV Types" repository
2617	   of [RFC5444].

2619	A.5.1.  Expert Review: Evaluation Guidelines

2621	   For the registries where an Expert Review is required, the designated
2622	   expert should take the same general recommendations into
2623	   consideration as are specified by [RFC5444].

2625	A.5.2.  Message Types

2627	   This specification defines four Message Type, to be allocated from
2628	   the 0-223 range of the "Message Types" namespace defined in
2629	   [RFC5444], as specified in Table 6.

2631	         +------+-----------------------------------------------+
2632	         | Type | Description                                   |
2633	         +------+-----------------------------------------------+
2634	         | TBD1 | RREQ: Route Request Message                   |
2635	         | TBD1 | RREP: Route Reply Message                     |
2636	         | TBD1 | RREP_ACK: Route Reply Acknowledgement Message |
2637	         | TBD1 | RERR: Route Error Message                     |
2638	         +------+-----------------------------------------------+

2640	                     Table 6: Message Type assignment

2642	A.6.  RREQ Message-Type-Specific TLV Type Registries

2644	   IANA is requested to create a registry for Message-Type-specific
2645	   Message TLVs for RREQ messages, in accordance with Section 6.2.1 of
2646	   [RFC5444], and with initial assignments and allocation policies as
2647	   specified in Table 7.

2649	               +---------+-------------+-------------------+
2650	               |   Type  | Description | Allocation Policy |
2651	               +---------+-------------+-------------------+
2652	               |   128   | METRIC      |                   |
2653	               | 129-223 | Unassigned  | Expert Review     |
2654	               +---------+-------------+-------------------+

2656	           Table 7: RREQ Message-Type-specific Message TLV Types

2658	   Allocation of the METRIC TLV from the RREQ Message-Type-specific
2659	   Message TLV Types in Table 7 will create a new Type Extension
2660	   registry, with assignments as specified in Table 8.

2662	   +--------+------+-----------+------------------------+--------------+
2663	   |  Name  | Type |    Type   | Description            | Allocation   |
2664	   |        |      | Extension |                        | Policy       |
2665	   +--------+------+-----------+------------------------+--------------+
2666	   | METRIC |  128 |     0     | HOP_COUNT:             |              |
2667	   |        |      |           | MSG.hop-count is used  |              |
2668	   |        |      |           | instead of the METRIC  |              |
2669	   |        |      |           | TLV Value. MAX_DIST is |              |
2670	   |        |      |           | 255.                   |              |
2671	   | METRIC |  128 |     1     | DIMENSIONLESS: A       |              |
2672	   |        |      |           | 32-bit, dimensionless, |              |
2673	   |        |      |           | additive metric,       |              |
2674	   |        |      |           | single precision       |              |
2675	   |        |      |           | float, formatted       |              |
2676	   |        |      |           | according to           |              |
2677	   |        |      |           | [IEEE754-2008].        |              |
2678	   | METRIC |  128 |   2-251   | Unassigned             | Expert       |
2679	   |        |      |           |                        | Review       |
2680	   | METRIC |  128 |  252-255  | Unassigned             | Experimental |
2681	   +--------+------+-----------+------------------------+--------------+

2683	               Table 8: Message TLV Type assignment: METRIC

2685	   IANA is requested to create a registry for Message-Type-specific
2686	   Address Block TLVs for RREQ messages, in accordance with Section
2687	   6.2.1 of [RFC5444], and with initial assignments and allocation
2688	   policies as specified in Table 9.

2690	               +---------+-------------+-------------------+
2691	               |   Type  | Description | Allocation Policy |
2692	               +---------+-------------+-------------------+
2693	               |   128   | ADDR-TYPE   | Expert Review     |
2694	               | 129-223 | Unassigned  | Expert Review     |
2695	               +---------+-------------+-------------------+

2697	        Table 9: RREQ Message-Type-specific Address Block TLV Types

2699	   Allocation of the ADDR-TYPE TLV from the RREQ Message-Type-specific
2700	   Address Block TLV Types in Table 9 will create a new Type Extension
2701	   registry, with assignments as specified in Table 10.

2703	   +-----------+------+----------------+-------------+-----------------+
2704	   |    Name   | Type | Type Extension | Description | Allocation      |
2705	   |           |      |                |             | Policy          |
2706	   +-----------+------+----------------+-------------+-----------------+
2707	   | ADDR-TYPE |  128 |        0       | DESTINATION |                 |
2708	   | ADDR-TYPE |  128 |      2-255     | Unassigned  | Expert Review   |
2709	   +-----------+------+----------------+-------------+-----------------+
2710	          Table 10: Address Block TLV Type assignment: ADDR-TYPE

2712	A.7.  RREP Message-Type-Specific TLV Type Registries

2714	   IANA is requested to create a registry for Message-Type-specific
2715	   Message TLVs for RREP messages, in accordance with Section 6.2.1 of
2716	   [RFC5444], and with initial assignments and allocation policies as
2717	   specified in Table 11.

2719	               +---------+-------------+-------------------+
2720	               |   Type  | Description | Allocation Policy |
2721	               +---------+-------------+-------------------+
2722	               |   128   | METRIC      |                   |
2723	               |   129   | FLAGS       |                   |
2724	               | 130-223 | Unassigned  | Expert Review     |
2725	               +---------+-------------+-------------------+

2727	          Table 11: RREP Message-Type-specific Message TLV Types

2729	   Allocation of the METRIC TLV from the RREP Message-Type-specific
2730	   Message TLV Types in Table 11 will create a new Type Extension
2731	   registry, with assignments as specified in Table 12.

2733	   +--------+------+-----------+------------------------+--------------+
2734	   |  Name  | Type |    Type   | Description            | Allocation   |
2735	   |        |      | Extension |                        | Policy       |
2736	   +--------+------+-----------+------------------------+--------------+
2737	   | METRIC |  128 |     0     | HOP_COUNT:             |              |
2738	   |        |      |           | MSG.hop-count is used  |              |
2739	   |        |      |           | instead of the METRIC  |              |
2740	   |        |      |           | TLV Value. MAX_DIST is |              |
2741	   |        |      |           | 255.                   |              |
2742	   | METRIC |  128 |     1     | DIMENSIONLESS: A       |              |
2743	   |        |      |           | 32-bit, dimensionless, |              |
2744	   |        |      |           | additive metric,       |              |
2745	   |        |      |           | single precision       |              |
2746	   |        |      |           | float, formatted       |              |
2747	   |        |      |           | according to           |              |
2748	   |        |      |           | [IEEE754-2008].        |              |
2749	   | METRIC |  128 |   2-251   | Unassigned             | Expert       |
2750	   |        |      |           |                        | Review       |
2751	   | METRIC |  128 |  252-255  | Unassigned             | Experimental |
2752	   +--------+------+-----------+------------------------+--------------+

2754	               Table 12: Message TLV Type assignment: METRIC

2756	   Allocation of the FLAGS TLV from the RREP Message-Type-specific
2757	   Message TLV Types in Table 11 will create a new Type Extension
2758	   registry, with assignments as specified in Table 13.

2760	   +-------+------+-----------+---------------------------+------------+
2761	   |  Name | Type |    Type   | Description               | Allocation |
2762	   |       |      | Extension |                           | Policy     |
2763	   +-------+------+-----------+---------------------------+------------+
2764	   | FLAGS |  129 |     0     | Bit 0 represents the      |            |
2765	   |       |      |           | ackrequired flag (i.e.,   |            |
2766	   |       |      |           | ackrequired is TRUE when  |            |
2767	   |       |      |           | bit 0 is set to 1 and     |            |
2768	   |       |      |           | FALSE when bit 0 is 0.).  |            |
2769	   |       |      |           | All other bits are        |            |
2770	   |       |      |           | reserved for future use.  |            |
2771	   | FLAGS |  129 |   1-255   | Unassigned                | Expert     |
2772	   |       |      |           |                           | Review     |
2773	   +-------+------+-----------+---------------------------+------------+

2775	               Table 13: Message TLV Type assignment: FLAGS

2777	   IANA is requested to create a registry for Message-Type-specific
2778	   Address Block TLVs for RREP messages, in accordance with Section
2779	   6.2.1 of [RFC5444], and with initial assignments and allocation
2780	   policies as specified in Table 14.

2782	               +---------+-------------+-------------------+
2783	               |   Type  | Description | Allocation Policy |
2784	               +---------+-------------+-------------------+
2785	               |   128   | ADDR-TYPE   | Expert Review     |
2786	               | 129-223 | Unassigned  | Expert Review     |
2787	               +---------+-------------+-------------------+

2789	       Table 14: RREP Message-Type-specific Address Block TLV Types

2791	   Allocation of the ADDR-TYPE TLV from the RREP Message-Type-specific
2792	   Address Block TLV Types in Table 14 will create a new Type Extension
2793	   registry, with assignments as specified in Table 15.

2795	   +-----------+------+----------------+-------------+-----------------+
2796	   |    Name   | Type | Type Extension | Description | Allocation      |
2797	   |           |      |                |             | Policy          |
2798	   +-----------+------+----------------+-------------+-----------------+
2799	   | ADDR-TYPE |  128 |        0       | DESTINATION |                 |
2800	   | ADDR-TYPE |  128 |      1-255     | Unassigned  | Expert Review   |
2801	   +-----------+------+----------------+-------------+-----------------+

2803	          Table 15: Address Block TLV Type assignment: ADDR-TYPE

2805	A.8.  RREP_ACK Message-Type-Specific TLV Type Registries

2807	   IANA is requested to create a registry for Message-Type-specific
2808	   Message TLVs for RREP_ACK messages, in accordance with Section 6.2.1
2809	   of [RFC5444], and with initial assignments and allocation policies as
2810	   specified in Table 16.

2812	               +---------+-------------+-------------------+
2813	               |   Type  | Description | Allocation Policy |
2814	               +---------+-------------+-------------------+
2815	               | 128-223 | Unassigned  | Expert Review     |
2816	               +---------+-------------+-------------------+

2818	        Table 16: RREP_ACK Message-Type-specific Message TLV Types

2820	   IANA is requested to create a registry for Message-Type-specific
2821	   Address Block TLVs for RREP_ACK messages, in accordance with Section
2822	   6.2.1 of [RFC5444], and with initial assignments and allocation
2823	   policies as specified in Table 17.

2825	               +---------+-------------+-------------------+
2826	               |   Type  | Description | Allocation Policy |
2827	               +---------+-------------+-------------------+
2828	               |   128   | ADDR-TYPE   | Expert Review     |
2829	               | 129-223 | Unassigned  | Expert Review     |
2830	               +---------+-------------+-------------------+

2832	     Table 17: RREP_ACK Message-Type-specific Address Block TLV Types

2834	   Allocation of the ADDR-TYPE TLV from the RREP_ACK Message-Type-
2835	   specific Address Block TLV Types in Table 17 will create a new Type
2836	   Extension registry, with assignments as specified in Table 18.

2838	   +-----------+------+----------------+-------------+-----------------+
2839	   |    Name   | Type | Type Extension | Description | Allocation      |
2840	   |           |      |                |             | Policy          |
2841	   +-----------+------+----------------+-------------+-----------------+
2842	   | ADDR-TYPE |  128 |        0       | DESTINATION |                 |
2843	   | ADDR-TYPE |  128 |      2-255     | Unassigned  | Expert Review   |
2844	   +-----------+------+----------------+-------------+-----------------+

2846	          Table 18: Address Block TLV Type assignment: ADDR-TYPE

2848	A.9.  RERR Message-Type-Specific TLV Type Registries

2850	   IANA is requested to create a registry for Message-Type-specific
2851	   Message TLVs for RERR messages, in accordance with Section 6.2.1 of
2852	   [RFC5444], and with initial assignments and allocation policies as
2853	   specified in Table 19.

2855	               +---------+-------------+-------------------+
2856	               |   Type  | Description | Allocation Policy |
2857	               +---------+-------------+-------------------+
2858	               | 128-223 | Unassigned  | Expert Review     |
2859	               +---------+-------------+-------------------+

2861	          Table 19: RERR Message-Type-specific Message TLV Types

2863	   IANA is requested to create a registry for Message-Type-specific
2864	   Address Block TLVs for RERR messages, in accordance with Section
2865	   6.2.1 of [RFC5444], and with initial assignments and allocation
2866	   policies as specified in Table 20.

2868	               +---------+-------------+-------------------+
2869	               |   Type  | Description | Allocation Policy |
2870	               +---------+-------------+-------------------+
2871	               |   128   | ADDR-TYPE   | Expert Review     |
2872	               | 129-223 | Unassigned  | Expert Review     |
2873	               +---------+-------------+-------------------+

2875	     Table 20: RREP_ACK Message-Type-specific Address Block TLV Types

2877	   Allocation of the ADDR-TYPE TLV from the RERR Message-Type-specific
2878	   Address Block TLV Types in Table 20 will create a new Type Extension
2879	   registry, with assignments as specified in Table 21.

2881	   +-----------+------+----------------+-------------+-----------------+
2882	   |    Name   | Type | Type Extension | Description | Allocation      |
2883	   |           |      |                |             | Policy          |
2884	   +-----------+------+----------------+-------------+-----------------+
2885	   | ADDR-TYPE |  128 |        0       | DESTINATION |                 |
2886	   | ADDR-TYPE |  128 |        1       | ERRORCODE   |                 |
2887	   | ADDR-TYPE |  128 |      2-255     | Unassigned  | Expert Review   |
2888	   +-----------+------+----------------+-------------+-----------------+

2890	          Table 21: Address Block TLV Type assignment: ADDR-TYPE

2892	Appendix B.  LOADng Control Packet Illustrations

2894	   This section presents example packets following this specification.

2896	B.1.  RREQ

2898	   RREQ messages are instances of [RFC5444] messages.  This
2899	   specification requires that RREQ messages contain RREQ.msg-seq-num,
2900	   RREQ.msg-hop-limit, RREQ.msg-hop-count and RREQ.msg-orig-addr fields.

2902	   It supports RREQ messages with any combination of remaining message
2903	   header options and address encodings, enabled by [RFC5444] that
2904	   convey the required information.  As a consequence, there is no
2905	   single way to represent how all RREQ messages look.  This section
2906	   illustrates an RREQ message, the exact values and content included
2907	   are explained in the following text.

2909	   The RREQ message's four bit Message Flags (MF) field has value 15
2910	   indicating that the message header contains originator address, hop
2911	   limit, hop count, and message sequence number fields.  Its four bit
2912	   Message Address Length (MAL) field has value 3, indicating addresses
2913	   in the message have a length of four octets, here being IPv4
2914	   addresses.  The overall message length is 30 octets.

2916	   The message has a Message TLV Block with content length 6 octets
2917	   containing one TLV.  The TLVs is of type METRIC and has a Flags octet
2918	   (MTLVF) value 144, indicating that it has a Value, a type extension,
2919	   but no start and stop indexes.  The Value Length of the METRIC TLV is
2920	   2 octets.

2922	   The message has one Address Block.  The Address Block contains 1
2923	   address, with Flags octet (ATLVF) value 0, hence with no Head or Tail
2924	   sections, and hence with a Mid section with length four octets.  The
2925	   following TLV Block (content length 2 octets) contains one TLV.  The
2926	   TLV is an ADDR_TYPE TLV with Flags octet (ATLVF) value 0, indicating
2927	   no Value and no indexes.  Thus, the address is associated with the
2928	   Type ADDR_TYPE, i.e., it is the destination address of the RREQ.

2930	      0                   1                   2                   3
2931	      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
2932	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2933	     |     RREQ      | MF=15 | MAL=3 |      Message Length = 30      |
2934	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2935	     |                      Originator Address                       |
2936	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2937	     |   Hop Limit   |   Hop Count   |    Message Sequence Number    |
2938	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2939	     | Message TLV Block Length = 6  |    METRIC     |  MTLVF = 144  |
2940	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2941	     |  Type Ext.    | Value Len = 2 |       Value (metric)          |
2942	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2943	     | Num Addrs = 1 |    ABF = 0    |             Mid               |
2944	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2945	     |            Mid                | Address TLV Block Length = 2  |
2946	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2947	     |   ADDR-TYPE   |   ATLVF = 0   |
2948	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

2950	B.2.  RREP

2952	   RREP messages are instances of [RFC5444] messages.  This
2953	   specification requires that RREP messages contain RREP.msg-seq-num,
2954	   RREP.msg-hop-limit, RREP.msg-hop-count and RREP.msg-orig-addr fields.
2955	   It supports RREP messages with any combination of remaining message
2956	   header options and address encodings, enabled by [RFC5444] that
2957	   convey the required information.  As a consequence, there is no
2958	   single way to represent how all RREP messages look.  This section
2959	   illustrates an RREP message, the exact values and content included
2960	   are explained in the following text.

2962	   The RREP message's four bit Message Flags (MF) field has value 15
2963	   indicating that the message header contains originator address, hop
2964	   limit, hop count, and message sequence number fields.  Its four bit
2965	   Message Address Length (MAL) field has value 3, indicating addresses
2966	   in the message have a length of four octets, here being IPv4
2967	   addresses.  The overall message length is 34 octets.

2969	   The message has a Message TLV Block with content length 10 octets
2970	   containing two TLVs.  The first TLV is of type METRIC and has a Flags
2971	   octet (MTLVF) value 144, indicating that it has a Value, a type
2972	   extension, but no start and stop indexes.  The Value Length of the
2973	   METRIC TLV is 2 octets.  The second TLV is of type FLAGS and has a
2974	   Flags octet (MTLVF) value of 16, indicating that it has a Value, but
2975	   no type extension or start and stop indexes.  The Value Length of the
2976	   FLAGS TLV is 1 octet.  The TLV value is 0x80 indicating that the
2977	   ackrequired flag is set.

2979	   The message has one Address Block.  The Address Block contains 1
2980	   address, with Flags octet (ATLVF) value 0, hence with no Head or Tail
2981	   sections, and hence with a Mid section with length four octets.  The
2982	   following TLV Block (content length 2 octets) contains one TLV.  The
2983	   TLV is an ADDR_TYPE TLV with Flags octet (ATLVF) value 0, indicating
2984	   no Value and no indexes.  Thus, the address is associated with the
2985	   Type ADDR_TYPE, i.e., it is the destination address of the RREP.

2987	      0                   1                   2                   3
2988	      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
2989	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2990	     |     RREP      | MF=15 | MAL=3 |      Message Length = 34      |
2991	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2992	     |                      Originator Address                       |
2993	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2994	     |   Hop Limit   |   Hop Count   |    Message Sequence Number    |
2995	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2996	     | Message TLV Block Length = 10 |    METRIC     |  MTLVF = 144  |
2997	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
2998	     |  Type Ext.    | Value Len = 2 |        Value (metric)         |
2999	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3000	     |     FLAGS     |   MTLVF = 16  | Value Len = 1 | Value (0x80)  |
3001	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3002	     | Num Addrs = 1 |    ABF = 0    |             Mid               |
3003	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3004	     |              Mid              |  Address TLV Block Length = 2 |
3005	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3006	     |   ADDR-TYPE   |   ATLVF = 0   |
3007	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3009	B.3.  RREP_ACK

3011	   RREP_ACK messages are instances of [RFC5444] messages.  This
3012	   specification requires that RREP_ACK messages contains RREP_ACK.msg-
3013	   seq-num.  It supports RREP_ACK messages with any combination of
3014	   remaining message header options and address encodings, enabled by
3015	   [RFC5444] that convey the required information.  As a consequence,
3016	   there is no single way to represent how all RREP_ACK messages look.
3017	   This section illustrates an RREP_ACK message, the exact values and
3018	   content included are explained in the following text.

3020	   The RREP_ACK message's four bit Message Flags (MF) field has value 1
3021	   indicating that the message header contains the message sequence
3022	   number field.  Its four bit Message Address Length (MAL) field has
3023	   value 3, indicating addresses in the message have a length of four
3024	   octets, here being IPv4 addresses.  The overall message length is 18
3025	   octets.

3027	   The message has a Message TLV Block with content length 0 octets
3028	   containing zero TLVs.

3030	   The message has one Address Block.  The Address Block contains 1
3031	   address, with Flags octet (ATLVF) value 0, hence with no Head or Tail
3032	   sections, and hence with a Mid section with length four octets.  The
3033	   following TLV Block (content length 2 octets) contains one TLV.  The
3034	   TLV is an ADDR_TYPE TLV with Flags octet (ATLVF) value 0, indicating
3035	   no Value and no indexes.  Thus, the address is associated with the
3036	   Type ADDR_TYPE, i.e., it is the destination address of the RREP_ACK.

3038	      0                   1                   2                   3
3039	      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3040	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3041	     |   RREP_ACK    | MF=1  | MAL=3 |      Message Length = 18      |
3042	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3043	     |    Message Sequence Number    | Message TLV Block Length = 0  |
3044	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3045	     | Num Addrs = 1 |    ABF = 0    |               Mid             |
3046	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3047	     |               Mid             | Address TLV Block Length = 2  |
3048	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3049	     |   ADDR-TYPE   |   ATLVF = 0   |
3050	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3052	B.4.  RERR

3054	   RERR messages are instances of [RFC5444] messages.  This
3055	   specification supports RERR messages with any combination of message
3056	   header options and address encodings, enabled by [RFC5444] that
3057	   convey the required information.  As a consequence, there is no
3058	   single way to represent how all RERR messages look.  This section
3059	   illustrates an RERR message, the exact values and content included
3060	   are explained in the following text.

3062	   The RERR message's four bit Message Flags (MF) field has value 12
3063	   indicating that the message header contains RERR.msg-orig-addr field
3064	   and RERR.msg-hop-limit field.  Its four bit Message Address Length
3065	   (MAL) field has value 3, indicating addresses in the message have a
3066	   length of four octets, here being IPv4 addresses.  The overall
3067	   message length is 30 octets.

3069	   The message has a Message TLV Block with content length 0 octets
3070	   containing zero TLVs.

3072	   The message has one Address Block.  The Address Block contains 2
3073	   addresses, with Flags octet (ATLVF) value 128, hence with a Head
3074	   section (with length 3 octets), but no Tail section, and hence with
3075	   Mid sections with length one octet.  The following TLV Block (content
3076	   length 9 octets) contains two TLVs.  The first TLV is an ADDR_TYPE
3077	   TLV with Flags octet (ATLVF) value 64, indicating a single index of
3078	   0, but no Value.  Thus, the first address is associated with the Type
3079	   ADDR_TYPE and Type Extension DESTINATION, i.e., it is the destination
3080	   address of the RERR.  The second TLV is an ADDR_TYPE TLV with Flags
3081	   octet (ATLVF) value 208, indicating Type Extension, Value, and single
3082	   index.  Thus, the second address is associated with the Type
3083	   ADDR_TYPE, Type Extension ERRORCODE, and Value 0, i.e., it is
3084	   associated with error code 0.

3086	      0                   1                   2                   3
3087	      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
3088	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3089	     |     RERR      | MF=12 | MAL=3 |      Message Length = 30      |
3090	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3091	     |                      Originator Address                       |
3092	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3093	     |   Hop Limit   | Message TLV Block Length = 0  | Num Addrs = 2 |
3094	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3095	     |  ABF = 128    | Head Len = 3  |       Head                    |
3096	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3097	     |    Head       |             Mid               | Address TLV   |
3098	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3099	     |Block Length= 9|   ADDR-TYPE   |   ATLVF = 64  |  Index = 0    |
3100	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3101	     |   ADDR-TYPE   |  ATLVF = 208  |TypEx=ERRORCODE|  Index = 1    |
3102	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
3103	     | Value Len = 1 |  Value = 0    |
3104	     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

3106	Authors' Addresses

3108	   Thomas Heide Clausen
3109	   LIX, Ecole Polytechnique

3111	   Phone: +33 6 6058 9349
3112	   EMail: T.Clausen@computer.org
3113	   URI:   http://www.ThomasClausen.org/

3115	   Axel Colin de Verdiere
3116	   LIX, Ecole Polytechnique

3118	   Phone: +33 6 1264 7119
3119	   EMail: axel@axelcdv.com
3120	   URI:   http://www.axelcdv.com/
3121	   Jiazi Yi
3122	   LIX, Ecole Polytechnique

3124	   Phone: +33 1 6933 4031
3125	   EMail: jiazi@jiaziyi.com
3126	   URI:   http://www.jiaziyi.com/

3128	   Afshin Niktash
3129	   Maxim Integrated Products

3131	   Phone: +1 94 9450 1692
3132	   EMail: afshin.niktash@maxim-ic.com
3133	   URI:   http://www.Maxim-ic.com/

3135	   Yuichi Igarashi
3136	   Hitachi, Ltd., Yokohama Research Laboratory

3138	   Phone: +81 45 860 3083
3139	   EMail: yuichi.igarashi.hb@hitachi.com
3140	   URI:   http://www.hitachi.com/

3142	   Hiroki Satoh
3143	   Hitachi, Ltd., Yokohama Research Laboratory

3145	   Phone: +81 44 959 0205
3146	   EMail: hiroki.satoh.yj@hitachi.com
3147	   URI:   http://www.hitachi.com/

3149	   Ulrich Herberg
3150	   Fujitsu Laboratories of America

3152	   Phone: +1 408 530 4528
3153	   EMail: ulrich@herberg.name
3154	   URI:   http://www.herberg.name/

3156	   Cedric Lavenu
3157	   EDF R&D

3159	   Phone: +33 1 4765 2729
3160	   EMail: cedric-2.lavenu@edf.fr
3161	   URI:   http://www.edf.fr/
3162	   Thierry Lys
3163	   ERDF

3165	   Phone: +33 1 8197 6777
3166	   EMail: thierry.lys@erdfdistribution.fr
3167	   URI:   http://www.erdfdistribution.fr/

3169	   Justin Dean
3170	   Naval Research Laboratory

3172	   EMail: jdean@itd.nrl.navy.mil
3173	   URI:   http://cs.itd.nrl.navy.mil/