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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Mobile Ad hoc Networks Working Group R. Taylor 3 Internet-Draft Airbus Defence & Space 4 Intended status: Standards Track S. Ratliff 5 Expires: February 21, 2019 VT iDirect 6 August 20, 2018 8 DLEP Link Identifier Extension 9 draft-ietf-manet-dlep-lid-extension-03 11 Abstract 13 There exists a class of modems that wish to support the Dynamic Link 14 Exchange Protocol (DLEP) [RFC8175] but do not present a single Layer 15 2 network domain as required by DLEP. Such devices may be: 17 o Modems that maintain a varying link to some upstream backbone 18 network infrastructure, where the ability to announce link state 19 and DLEP metrics is desired, but the concept of a DLEP destination 20 router for the backbone does not apply. Examples of such devices 21 can include LTE modems, IEEE 802.11 stations not in ad-hoc mode, 22 and some satellite terminals. 24 o Modems that provide Layer 3 wide area network connectivity between 25 devices, where individual DLEP destinations do exist, but are not 26 directly reachable by MAC address. 28 This document introduces an optional extension to the core DLEP 29 specification, allowing DLEP to be used between routers and modems 30 that operate in this way. 32 Note: 34 o This document is intended as an extension to the core DLEP 35 specification, and readers are expected to be fully conversant 36 with the operation of core DLEP. 38 Status of This Memo 40 This Internet-Draft is submitted in full conformance with the 41 provisions of BCP 78 and BCP 79. 43 Internet-Drafts are working documents of the Internet Engineering 44 Task Force (IETF). Note that other groups may also distribute 45 working documents as Internet-Drafts. The list of current Internet- 46 Drafts is at https://datatracker.ietf.org/drafts/current/. 48 Internet-Drafts are draft documents valid for a maximum of six months 49 and may be updated, replaced, or obsoleted by other documents at any 50 time. It is inappropriate to use Internet-Drafts as reference 51 material or to cite them other than as "work in progress." 53 This Internet-Draft will expire on February 21, 2019. 55 Copyright Notice 57 Copyright (c) 2018 IETF Trust and the persons identified as the 58 document authors. All rights reserved. 60 This document is subject to BCP 78 and the IETF Trust's Legal 61 Provisions Relating to IETF Documents 62 (https://trustee.ietf.org/license-info) in effect on the date of 63 publication of this document. Please review these documents 64 carefully, as they describe your rights and restrictions with respect 65 to this document. Code Components extracted from this document must 66 include Simplified BSD License text as described in Section 4.e of 67 the Trust Legal Provisions and are provided without warranty as 68 described in the Simplified BSD License. 70 Table of Contents 72 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 73 1.1. Requirements . . . . . . . . . . . . . . . . . . . . . . 3 74 2. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 75 2.1. Identifier Restrictions . . . . . . . . . . . . . . . . . 4 76 2.2. Negotiation . . . . . . . . . . . . . . . . . . . . . . . 4 77 3. New Data Items . . . . . . . . . . . . . . . . . . . . . . . 5 78 3.1. Link Identifier Length Data Item . . . . . . . . . . . . 5 79 3.2. Link Identifier Data Item . . . . . . . . . . . . . . . . 6 80 4. Security Considerations . . . . . . . . . . . . . . . . . . . 6 81 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 82 6. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 83 6.1. Normative References . . . . . . . . . . . . . . . . . . 7 84 6.2. Informative References . . . . . . . . . . . . . . . . . 7 85 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 87 1. Introduction 89 The Dynamic Link Exchange Protocol (DLEP) [RFC8175] describes a 90 protocol for modems to advertise the status of wireless links between 91 reachable destinations to attached routers. The core specification 92 of the protocol assumes that every modem in the radio network has an 93 attached DLEP router, and requires that the MAC address of the DLEP 94 interface on the attached router is used to identify the destination 95 in the network for purposes of reporting the state and quality of the 96 link to that destination. 98 This document describes a DLEP Extension allowing modems that do not 99 meet the strict requirement that DLEP must be implemented on a single 100 Layer 2 domain to use DLEP to describe link availability and quality 101 to one or more destinations reachable beyond a local or remote device 102 on the Layer 2 domain. A router can use this knowledge to influence 103 any routing or flow-control decisions regarding traffic to this 104 destination, understanding that such traffic flows via Layer 3. 106 A Layer 3 destination may be an attached DLEP router, in the case of 107 a modem that provides Layer 3 wide area network connectivity between 108 devices, or a logical destination that describes a set of attached 109 subnets, when referring to some upstream backbone network 110 infrastructure. 112 1.1. Requirements 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in BCP 14, RFC 2119. 118 2. Operation 120 To refer to a Layer 3 DLEP Destination, the DLEP session participant 121 adds a Link Identifier Data Item (Section 3.2) to the relevant 122 Destination Message, and (as usual) includes a MAC Address Data Item. 123 When paired with a Link Identifier Data Item, the MAC Address Data 124 Item MUST contain the MAC address of the last reachable node in the 125 Layer 2 domain beyond which the Layer 3 DLEP Destination resides. 126 For example, if the over-the-air network is not a single Layer 2 127 domain, the MAC Address Data Item might be the address of the LAN- 128 side interface of the local modem. Alternatively, when used with 129 some kind of backbone infrastructure, the MAC Address Data Item would 130 be the address of the last device reachable on the local Layer 2 131 domain. However, how such remote destinations are discovered is 132 beyond the scope of this specification. 134 As only modems are initially aware of Layer 3 DLEP Destinations, Link 135 Identifier Data Items referring to a new link MUST first appear in a 136 DLEP Destination Up Message from the modem to the router. Once a 137 link has been identified in this way, Link Identifier Data Items MAY 138 be used by either DLEP participant during the lifetime of a DLEP 139 session. Because of this, a router MUST NOT send a DLEP Destination 140 Announce Message containing a Link Identifier Data Item referring to 141 a link that has not been mentioned in a prior DLEP Destination Up 142 Message. 144 Because the MAC Address associated with any DLEP Destination Message 145 containing a Link Identifier Data Item is not the Layer 2 address of 146 the destination, all DLEP Destination Up Messages MUST contain Layer 147 3 information. In the case of modems that provide Layer 3 wide area 148 network connectivity between devices, this means one or more IPv4 or 149 IPv6 Address Data Items providing the Layer 3 address of the 150 destination. When referring to some upstream backbone network 151 infrastructure, this means one or more IPv4 or IPv6 Attached Subnet 152 Data Items, for example: '0.0.0.0/0' or '::/0'. This allows the DLEP 153 peer router to understand the properties of the link to those routes. 155 When the DLEP peer router wishes to forward packets to the Layer 3 156 destination or subnet, the MAC address associated with the link MUST 157 be used as the Layer 2 destination of the packet. 159 2.1. Identifier Restrictions 161 A link identifier is by default 4 octets in length. If a modem 162 wishes to use an identifier of a different length, it MUST be 163 announced using the Link Identifier Length Data Item (Section 3.1) 164 contained in the DLEP Session Initialization Response message sent by 165 the modem to the router. 167 During the lifetime of a DLEP session, the length of link identifiers 168 MUST remain constant, i.e. the Length field of the Link Identifier 169 Data Item MUST NOT differ between destinations. 171 The method for generating identifiers is a modem implementation 172 matter and out of scope of this document. Routers MUST NOT make any 173 assumptions about the meaning of identifiers, or how identifiers are 174 generated. 176 Within a single DLEP session, all link identifiers MUST be unique per 177 MAC Address. This means that a Layer 3 DLEP Destination is uniquely 178 identified by the pair: {MAC Address,Link Id}. 180 Identifiers MUST NOT be reused, i.e. a {MAC Address,Link Id} pair 181 that has been used to refer to one destination MUST NOT be recycled 182 to refer to a different destination within the lifetime of a single 183 DLEP session. 185 2.2. Negotiation 187 To use this extension, as with all DLEP extensions, the extension 188 MUST be announced during DLEP session initialization. A router 189 advertises support by including the value 'Link Identifiers' (TBD1), 190 Section 5, in the Extension Data Item within the Session 191 Initialization Message. A modem advertises support by including the 192 value 'Link Identifiers' (TBD1) in the Extension Data Item within the 193 Session Initialization Response Message. If both DLEP peers 194 advertise support for this extension then the Link Identifier Data 195 Item MAY be used. 197 If a modem requires support for this extension in order to describe 198 destinations, and the router does not advertise support, then the 199 modem MUST NOT include a Link Identifier Data Item in any DLEP 200 Message. However, the modem SHOULD NOT immediately terminate the 201 DLEP session, rather it SHOULD use session-wide DLEP Data Items to 202 announce general information about all reachable destinations via the 203 modem. By doing this, a modem allows a router not supporting this 204 extension to at least make a best guess at the state of any reachable 205 network. A modem MUST NOT attempt to re-use the MAC Address Data 206 Item to perform some kind of sleight-of-hand, assuming that the 207 router will notice the DLEP Peer Type of the modem is special in some 208 way. 210 3. New Data Items 212 This extension introduces two new DLEP Data Items: the Link 213 Identifier Data Item (Section 3.2) used to identify a Layer 3 link at 214 or beyond a destination, and the Link Identifier Length Data Item 215 (Section 3.1) used to announce the length of Link Identifiers at 216 session initialization. 218 3.1. Link Identifier Length Data Item 220 The Link Identifier Length Data Item MUST be used by a DLEP modem 221 implementation to define the length of Link Identifier Data Items if 222 it does not with to use the default value of 4 octets. 224 The Link Identifier Length Data Item MAY be used during Session 225 Initialization, contained in a Session Initialization Response 226 Message. 228 0 1 2 3 229 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 1 230 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 231 | Data Item Type | Length | 232 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 233 | Link Identifier Length | 234 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 236 Data Item Type: TBD2, Section 5 238 Length: 2 239 Link Identifier Length: The length, in octets, of Link Identifiers 240 used by the DLEP modem for this session. 242 3.2. Link Identifier Data Item 244 The Link Identifier Data Item MAY be used wherever a MAC Address Data 245 Item is defined as usable in core DLEP. 247 0 1 2 3 248 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 1 249 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 250 | Data Item Type | Length | 251 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 252 | Link Identifier... : 253 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 255 Data Item Type: TBD3, Section 5 257 Length: The length of the Data Item, by default 4, but may be 258 different if a Link Identifier Length Data Item (Section 3.1) has 259 been announced during session initialization. 261 Link Identifier: The unique identifier of the Layer 3 destination. 262 This identifier has no implicit meaning and is only used to 263 discriminate between multiple links. 265 4. Security Considerations 267 As an extension to the core DLEP protocol, the security 268 considerations of that protocol apply to this extension. This 269 extension adds no additional security mechanisms or features. 271 None of the features introduced by this extension require extra 272 consideration by an implementation. 274 5. IANA Considerations 276 Upon approval of this document, IANA is requested to: 278 o Assign a new value (TBD1) from the Specification Required section 279 of the DLEP Extensions Registry, named "Link Identifiers". 281 o Assign a new value (TBD2) from the Specification Required section 282 of the DLEP Data Item Type Values Registry, named "Link Identifier 283 Length". 285 o Assign a new value (TBD3) from the Specification Required section 286 of the DLEP Data Item Type Values Registry, named "Link 287 Identifier". 289 6. References 291 6.1. Normative References 293 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 294 Requirement Levels", BCP 14, RFC 2119, 295 DOI 10.17487/RFC2119, March 1997, 296 . 298 [RFC8175] Ratliff, S., Jury, S., Satterwhite, D., Taylor, R., and B. 299 Berry, "Dynamic Link Exchange Protocol (DLEP)", RFC 8175, 300 DOI 10.17487/RFC8175, June 2017, 301 . 303 6.2. Informative References 305 [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an 306 IANA Considerations Section in RFCs", RFC 5226, 307 DOI 10.17487/RFC5226, May 2008, 308 . 310 Authors' Addresses 312 Rick Taylor 313 Airbus Defence & Space 314 Quadrant House 315 Celtic Springs 316 Coedkernew 317 Newport NP10 8FZ 318 UK 320 Email: rick.taylor@airbus.com 322 Stan Ratliff 323 VT iDirect 324 13861 Sunrise Valley Drive, Suite 300 325 Herndon, VA 20171 326 USA 328 Email: sratliff@idirect.net