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(See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (November 19, 2017) is 2342 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) ** Downref: Normative reference to an Informational RFC: RFC 4272 == Outdated reference: A later version (-23) exists of draft-ietf-sidr-bgpsec-protocol-07 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group R. Bush 3 Internet-Draft Internet Initiative Japan 4 Updates: 4271 (if approved) K. Patel 5 Intended status: Standards Track Arrcus, Inc. 6 Expires: May 23, 2018 D. Ward 7 Cisco Systems 8 November 19, 2017 10 Extended Message support for BGP 11 draft-ietf-idr-bgp-extended-messages-24 13 Abstract 15 The BGP specification mandates a maximum BGP message size of 4096 16 octets. As BGP is extended to support newer AFI/SAFIs and other 17 features, there is a need to extend the maximum message size beyond 18 4096 octets. This document updates the BGP specification RFC4271 by 19 providing an extension to BGP to extend its current maximum message 20 size from 4096 octets to 65535 octets for all except the OPEN 21 message. 23 Requirements Language 25 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 26 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" are to 27 be interpreted as described in [RFC2119] only when they appear in all 28 upper case. They may also appear in lower or mixed case as English 29 words, without normative meaning. 31 Status of This Memo 33 This Internet-Draft is submitted in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Internet-Drafts are working documents of the Internet Engineering 37 Task Force (IETF). Note that other groups may also distribute 38 working documents as Internet-Drafts. The list of current Internet- 39 Drafts is at https://datatracker.ietf.org/drafts/current/. 41 Internet-Drafts are draft documents valid for a maximum of six months 42 and may be updated, replaced, or obsoleted by other documents at any 43 time. It is inappropriate to use Internet-Drafts as reference 44 material or to cite them other than as "work in progress." 46 This Internet-Draft will expire on May 23, 2018. 48 Copyright Notice 50 Copyright (c) 2017 IETF Trust and the persons identified as the 51 document authors. All rights reserved. 53 This document is subject to BCP 78 and the IETF Trust's Legal 54 Provisions Relating to IETF Documents 55 (https://trustee.ietf.org/license-info) in effect on the date of 56 publication of this document. Please review these documents 57 carefully, as they describe your rights and restrictions with respect 58 to this document. Code Components extracted from this document must 59 include Simplified BSD License text as described in Section 4.e of 60 the Trust Legal Provisions and are provided without warranty as 61 described in the Simplified BSD License. 63 Table of Contents 65 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 66 2. BGP Extended Message . . . . . . . . . . . . . . . . . . . . 2 67 3. Extended message Capability for BGP . . . . . . . . . . . . . 3 68 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 3 69 5. Error Handling . . . . . . . . . . . . . . . . . . . . . . . 4 70 6. Changes to RFC4271 . . . . . . . . . . . . . . . . . . . . . 4 71 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 72 8. Security Considerations . . . . . . . . . . . . . . . . . . . 4 73 9. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 74 10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5 75 10.1. Normative References . . . . . . . . . . . . . . . . . . 5 76 10.2. Informative References . . . . . . . . . . . . . . . . . 5 77 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 79 1. Introduction 81 The BGP specification [RFC4271] mandates a maximum BGP message size 82 of 4096 octets. As BGP is extended to support newer AFI/SAFIs and 83 newer capabilities (e.g., [I-D.ietf-sidr-bgpsec-protocol]), there is 84 a need to extend the maximum message size beyond 4096 octets. This 85 draft provides an extension to BGP to extend its current message size 86 limit from 4096 octets to 65535 octetsfor all except the OPEN 87 message. 89 2. BGP Extended Message 91 A BGP message over 4096 octets in length is a BGP Extended Message. 93 BGP Extended Messages have maximum message size of 65535 octets. The 94 smallest message that may be sent consists of a BGP header without a 95 data portion (19 octets). 97 3. Extended message Capability for BGP 99 To advertise the BGP Extended Message Capability to a peer, a BGP 100 speaker uses BGP Capabilities Advertisement [RFC5492]. By 101 advertising the BGP Extended Message Capability to a peer, a BGP 102 speaker conveys that it is able to send, receive, and properly handle 103 BGP Extended Messages. 105 A peer which does not advertise this capability MUST NOT send BGP 106 Extended Messages, and BGP Extended Messages MUST NOT be sent to it. 108 The BGP Extended Message Capability is a new BGP Capability [RFC5492] 109 defined with Capability code 6 and Capability length 0. 111 4. Operation 113 A BGP speaker that is willing to send and receive BGP Extended 114 Messages with a peer SHOULD advertise the BGP Extended Message 115 Capability to the peer using BGP Capabilities Advertisement 116 [RFC5492]. A BGP speaker MAY send Extended Messages to its peer only 117 if it has received the Extended Message Capability from that peer. 119 The Extended Message Capability only applies to all messages except 120 for the OPEN message. This exception is reduce compexity of 121 providing backward compatibility 123 An implementation that advertises support for BGP Extended Messages 124 MUST be capable of receiving a message with a length up to and 125 including 65535 octets. 127 Applications generating information which might be encapsulated 128 within BGP messages MUST limit the size of their payload to take the 129 maximum message size into account. 131 A BGP announcement will, in the normal case, propagate throughout the 132 BGP speaking Internet; and there will undoubtedly be BGP speakers 133 which do not have the Extended Message capability. Therefore putting 134 an attribute which can not be decomposed to 4096 octets or less in an 135 Extended Message is a likely path to routing failure. 137 It is RECOMMENDED that BGP protocol developers and implementers are 138 conservative in their application and use of Extended Messages. 139 Future protocol specifications will need to describe how to handle 140 peers which can only accomodate 4096 octet messages. 142 5. Error Handling 144 A BGP speaker that has the ability to use Extended Messages but has 145 not advertised the BGP Extended Messages capability, presumably due 146 to configuration, SHOULD NOT accept an Extended Message. A speaker 147 MAY implement a more liberal policy and accept Extended Messages, 148 even from a peer to which it has not advertised the capability, in 149 the interest of preserving the BGP session if at all possible. 151 A BGP speaker that does not advertise the BGP Extended Messages 152 capability might also genuinely not support Extended Messages. Such 153 a speaker would be expected to follow the error handling procedures 154 of [RFC4271] if it receives an Extended Message. Similarly, any 155 speaker that treats an improper Extended Message as a fatal error, 156 MUST treat it similarly. 158 The inconsistency between the local and remote BGP speakers MUST be 159 flagged to the network operator through standard operational 160 interfaces. The information should include the NLRI and as much 161 relevant information as reasonably possible. 163 6. Changes to RFC4271 165 [RFC4271] states "The value of the Length field MUST always be at 166 least 19 and no greater than 4096." This document changes the latter 167 number to 65535 for all except the OPEN message. 169 [RFC4271] Sec 6.1, specifies raising an error if the length of a 170 message is over 4096 octets. For all messages except the OPEN 171 message, if the receiver has advertised the capability to receive 172 Extended Messages, this document raises that limit to 65535. 174 7. IANA Considerations 176 The IANA has made an early allocation for this new BGP BGP Extended 177 Message Capability referring to this document. 179 Registry: BGP Capability Code 181 Value Description Document 182 ----- ----------------------------------- ------------- 183 6 BGP-Extended Message [this draft] 185 8. Security Considerations 187 This extension to BGP does not change BGP's underlying security 188 issues; see [RFC4272]. 190 Section 5 allowed a receiver to accept an Extended Message even 191 though they had not advertised the capability. This slippery slope 192 will surely lead to sloppy implementations sending Extended Messages 193 when the receiver is not prepared to deal with them, e.g. to peer 194 groups. At best, this will result in errors; at worst, buffer 195 overflows. 197 Due to increased (over [RFC4272]) memory requirements for buffering, 198 there may be increased exposure to resource exhaustion, intentional 199 or unintentional. 201 9. Acknowledgments 203 The authors thank Alvaro Retana, Enke Chen, Susan Hares, John 204 Scudder, John Levine, and Job Snijders for their input; and Oliver 205 Borchert and Kyehwan Lee for their implementations and testing. 207 10. References 209 10.1. Normative References 211 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 212 Requirement Levels", BCP 14, RFC 2119, 213 DOI 10.17487/RFC2119, March 1997, 214 . 216 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 217 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 218 DOI 10.17487/RFC4271, January 2006, 219 . 221 [RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis", 222 RFC 4272, DOI 10.17487/RFC4272, January 2006, 223 . 225 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 226 with BGP-4", RFC 5492, DOI 10.17487/RFC5492, February 227 2009, . 229 10.2. Informative References 231 [I-D.ietf-sidr-bgpsec-protocol] 232 Lepinski, M., "BGPSEC Protocol Specification", draft-ietf- 233 sidr-bgpsec-protocol-07 (work in progress), February 2013. 235 Authors' Addresses 237 Randy Bush 238 Internet Initiative Japan 239 5147 Crystal Springs 240 Bainbridge Island, Washington 98110 241 United States of America 243 Email: randy@psg.com 245 Keyur Patel 246 Arrcus, Inc. 248 Email: keyur@arrcus.com 250 Dave Ward 251 Cisco Systems 252 170 W. Tasman Drive 253 San Jose, CA 95134 254 United States of America 256 Email: dward@cisco.com