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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 IETF S. Brim 2 Internet Draft B. Carpenter 3 October 1999 F. Le Faucheur 5 Per Hop Behavior Identification Codes 7 Copyright Notice 9 Placeholder for ISOC copyright. 11 Abstract 13 draft-ietf-diffserv-phbid-00.txt 14 (updates draft-brim-diffserv-phbid-00.txt) 16 This document defines a 16 bit encoding mechanism for the identification 17 of differentiated services Per Hop Behaviors in protocol messages. 19 Status of this Memo 21 This document is an Internet-Draft and is in full conformance with 22 all provisions of Section 10 of RFC2026. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF), its areas, and its working groups. Note that 26 other groups may also distribute working documents as Internet- 27 Drafts. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet- Drafts as reference 32 material or to cite them other than as "work in progress." 34 The list of current Internet-Drafts can be accessed at 35 http://www.ietf.org/ietf/1id-abstracts.txt 37 The list of Internet-Draft Shadow Directories can be accessed at 38 http://www.ietf.org/shadow.html. 40 Table of Contents: 42 Status of this Memo.............................................1 43 1. Introduction.................................................3 44 1.1. Usage Scenarios............................................3 45 2. Encoding.....................................................4 46 3. IANA Considerations..........................................5 47 4. Security considerations......................................6 48 Acknowledgements................................................6 49 References......................................................6 50 Authors' Addresses..............................................6 51 Intellectual Property...........................................7 52 Full Copyright Statement........................................7 54 1. Introduction 56 Differentiated Services [RFC 2474, RFC 2475] introduces the notion of 57 Per Hop Behaviors (PHBs) that define how traffic belonging to a 58 particular behavior aggregate is treated at an individual network 59 node. In IP packet headers, PHBs are not indicated as such; instead 60 Differentiated Services Codepoint (DSCP) values are used. There are 61 only 64 possible DSCP values, but there is no such limit on the 62 number of PHBs. In a given network domain, there is a locally defined 63 mapping between DSCP values and PHBs. Standardized PHBs recommend a 64 DSCP mapping, but network operators may choose alternative mappings. 66 In some cases it is necessary or desirable to identify a particular 67 PHB in a protocol message, such as a message negotiating bandwidth 68 management or path selection, especially when such messages pass 69 between management domains. Examples where work is in progress 70 include communication between bandwidth brokers, and MPLS support of 71 diffserv. 73 In certain cases, what needs to be identified is not an individual 74 PHB, but a set of PHBs. One example is a set of PHBs that must follow 75 the same physical path to prevent re-ordering. An instance of this 76 is the set of three PHBs belonging to a single Assured Forwarding 77 class, such as the PHBs AF11, AF12 and AF13 [RFC 2597]. 79 This document defines a binary encoding to uniquely identify PHBs 80 and/or sets of PHBs in protocol messages. This encoding MUST be used 81 when such identification is required. 83 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 84 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 85 document are to be interpreted as described in [RFC2119]. 87 1.1. Usage Scenarios 89 Diffserv services are expected to be supported over various 90 underlying technologies which we broadly refer to as "link layers" 91 for the purpose of this discussion. For the transport of IP packets, 92 some of these link layers make use of connections or logical 93 connections where the forwarding behavior supported by each link 94 layer device is a property of the connection. In particular, within 95 the link layer domain, each link layer node will schedule traffic 96 depending on which connection the traffic is transported in. Examples 97 of such "link layers" include ATM and MPLS. 99 For efficient support of diffserv over these link layers, one model 100 is for different Behavior Aggregates (BAs) (or sets of Behavior 101 Aggregates) to be transported over different connections so that they 102 are granted different (and appropriate) forwarding behaviors inside 103 the link layer cloud. When those connections are dynamically 104 established for the transport of diffserv traffic, it is very useful 105 to communicate at connection establishment time what forwarding 106 behavior(s) is(are) to be granted to each connection by the link 107 layer device so that the BAs transported experience consistent 108 forwarding behavior inside the link layer cloud. This can be achieved 109 by including in the connection establishment signaling messages the 110 encoding of the corresponding PHB, or set of PHBs, as defined in this 111 document. Details on proposed usage of PHB encodings by some MPLS 112 label distribution protocols (RSVP and LDP) for support of Diff-Serv 113 over MPLS, can be found in [MPLS-DS]. 115 In another approach, the ATM Forum has a requirement to indicate 116 desired IP QOS treatments in ATM signaling, so that ATM switches can 117 be just as supportive of the desired service as are IP forwarders. 118 To do so the Forum is defining a new VC call setup information 119 element is which will carry PHB identification codes (although will 120 be generalized to do more if needed). 122 2. Encoding 124 PHBs and sets of PHBs are encoded in an unsigned 16 bit binary field. 126 The 16 bit field is arranged as follows: 128 Case 1: PHBs defined by standards action, as per [RFC 2474]. 130 The encoding for a single PHB is the recommended DSCP value for that 131 PHB, left-justified in the 16 bit field, with bits 6 through 15 set 132 to zero. Note that the recommended DSCP value MUST be used, even if 133 the network in question has chosen a different mapping. 135 The encoding for a set of PHBs is the numerically smallest of the set 136 of encodings for the various PHBs in the set, with bit 14 set to 1. 137 (Thus for the AF1x PHBs, the encoding is that of the AF11 PHB, with 138 bit 14 set to 1.) 140 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 141 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 142 | DSCP | 0 0 0 0 0 0 0 0 X 0 | 143 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 145 Case 2: PHBs not defined by standards action, i.e. experimental or 146 local use PHBs as allowed by [RFC 2474]. In this case an arbitrary 12 147 bit PHB identification code, assigned by the IANA, is placed left- 148 justified in the 16 bit field. Bit 15 is set to 1, and bit 14 is zero 149 for a single PHB or 1 for a set of PHBs. Bits 12 and 13 are zero. 151 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 152 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 153 | PHB id code | 0 0 X 1 | 154 +---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+---+ 156 Bits 12 and 13 are reserved either for expansion of the PHB 157 identification code, or for other use, at some point in the future. 159 3. IANA Considerations 161 IANA is requested to create a new assignment registry for "Per-Hop 162 Behavior Identification Codes", initially allowing values in the 163 range 0 to 4095 decimal. 165 Assignment of values in this field require: 167 -the identity of the assignee 168 -a brief description of the new PHB, with enough detail to 169 distinguish it from existing standardized and non-standardized 170 PHBs. In the case of a set of PHBs, this description should cover 171 all PHBs in the set. 172 -a reference to a stable document describing the PHB in detail. 174 During the first year of existence of this registry, IANA is 175 requested to refer all requests to the IETF diffserv WG for review. 176 Subsequently, requests should be reviewed by the IETF Transport Area 177 Directors or by an expert that they designate. 179 If the number of assignments begins to approach 4096, the Transport 180 Area Directors should be alerted. 182 4. Security considerations 184 This encoding in itself raises no security issues. However, users of 185 this encoding should consider that modifying a PHB identification 186 code may constitute theft or denial of service, so protocols using 187 this encoding must be adequately protected. 189 Acknowledgements 191 Useful comments were made by Francois Le Faucheur and others. 193 References 195 [RFC 2119] Key words for use in RFCs to Indicate Requirement Levels, 196 S. Bradner, RFC 2119, March 1997. 198 [RFC 2474] Definition of the Differentiated Services Field (DS Field) 199 in the IPv4 and IPv6 Headers. K. Nichols, S. Blake, F. Baker, D. 200 Black, RFC 2474, December 1998. 202 [RFC 2475] An Architecture for Differentiated Services. S. Blake, D. 203 Black, M. Carlson, E. Davies, Z. Wang, W. Weiss, RFC 2475, December 204 1998. 206 [RFC 2597] Assured Forwarding PHB Group, J. Heinanen, F. Baker, W. 207 Weiss, J. Wroclawski, RFC 2597, June 1999. 209 [MPLS-DS] , work in progress 211 Authors' Addresses 213 Scott W. Brim 214 146 Honness Lane 215 Ithaca, NY 14850 216 USA 218 E-mail: swb@newbridge.com 220 Brian E. Carpenter 221 IBM 222 c/o iCAIR 223 Suite 150 224 1890 Maple Avenue 225 Evanston, IL 60201 226 USA 228 E-mail: brian@icair.org 229 Francois Le Faucheur 230 Cisco Systems 231 Petra B - Les Lucioles 232 291, rue Albert Caquot 233 06560 Valbonne 234 France 236 E-mail: flefauch@cisco.com 238 Intellectual Property 240 PLACEHOLDER for full IETF IPR Statement if needed. 242 Full Copyright Statement 244 PLACEHOLDER for full ISOC copyright Statement if needed.