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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 4 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group E. Chen 3 Internet Draft S. Sangli 4 Expiration Date: June 6, 2012 Cisco Systems 5 December 5, 2011 7 Dynamic Capability for BGP-4 8 draft-ietf-idr-dynamic-cap-14.txt 10 Status of this Memo 12 This Internet-Draft is submitted to IETF in full conformance with the 13 provisions of BCP 78 and BCP 79. 15 Internet-Drafts are working documents of the Internet Engineering 16 Task Force (IETF), its areas, and its working groups. Note that 17 other groups may also distribute working documents as Internet- 18 Drafts. 20 Internet-Drafts are draft documents valid for a maximum of six months 21 and may be updated, replaced, or obsoleted by other documents at any 22 time. It is inappropriate to use Internet-Drafts as reference 23 material or to cite them other than as "work in progress." 25 The list of current Internet-Drafts can be accessed at 26 http://www.ietf.org/1id-abstracts.html 28 The list of Internet-Draft Shadow Directories can be accessed at 29 http://www.ietf.org/shadow.html 31 This Internet-Draft will expire on June 6, 2012. 33 Copyright Notice 35 Copyright (c) 2011 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (http://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Abstract 50 This document defines a new BGP capability termed "Dynamic 51 Capability", which would allow the dynamic update of capabilities 52 over an established BGP session. This capability would facilitate 53 non-disruptive capability changes by BGP speakers. 55 1. Introduction 57 Currently BGP capabilities [RFC5492] are only advertised in the OPEN 58 message during the session initialization. In order to enable a new 59 capability or remove an existing capability (such as an Address 60 Family support [RFC4760]), an established session needs to be reset, 61 which may disrupt other services running over the session. 63 This document defines a new BGP capability termed "Dynamic 64 Capability", which would allow the dynamic update of capabilities 65 over an established BGP session. This capability would facilitate 66 non-disruptive capability changes by BGP speakers. 68 1.1. Specification of Requirements 70 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 71 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 72 document are to be interpreted as described in [RFC2119]. 74 2. Dynamic Capability 76 The Dynamic Capability is a new BGP capability [RFC5492]. The 77 Capability Code for this capability is specified in the "IANA 78 Considerations" section of this document. The Capability Value field 79 consists of a list of capability codes (one-octet for each) that 80 specify the capabilities that MAY be revised dynamically by the 81 remote speaker. 83 By advertising the Dynamic Capability to a peer in the OPEN, a BGP 84 speaker conveys to the peer that the speaker is capable of receiving 85 and properly handling the CAPABILITY message (as defined in the next 86 Section) from the peer after the BGP session has been established. 88 3. Capability Message 90 The CAPABILITY Message is a new BGP message type with type code 6. 91 In addition to the fixed-size BGP header [RFC4271], the CAPABILITY 92 message contains one or more of the following tuples of capability 93 revisions: 95 +------------------------------+ 96 | Init/Ack (1 bit) | 97 +------------------------------+ 98 | Ack Request (1 bit) | 99 +------------------------------+ 100 | Reserved (5 bits) | 101 +------------------------------+ 102 | Action (1 bit) | 103 +------------------------------+ 104 | Sequence Number (4 octets) | 105 +------------------------------+ 106 | Capability Code (1 octet) | 107 +------------------------------+ 108 | Capability Length (2 octets) | 109 +------------------------------+ 110 | Capability Value (variable) | 111 +------------------------------+ 113 The Init/Ack bit indicates whether a capability revision is being 114 initiated (when set to 0), or being acknowledged (when set to 1). 116 The Ack Request bit indicates whether an acknowledgment is requested 117 (when set to 1), or not (when set to 0) for a capability revision 118 being initiated. 120 The Reserved bits should be set to zero by the sender and ignored by 121 the receiver. 123 The Action bit is 0 for advertising a capability, and 1 for removing 124 a capability. 126 The Sequence Number field can be used by a BGP speaker to match an 127 acknowledgment with a capability revision that the speaker initiated 128 previously. 130 Conceptually the triple is the same as the one defined in [RFC5492], and it 132 specifies a capability for which the "Action" shall be applied. 134 4. Operation 136 A BGP speaker that is willing to receive the CAPABILITY message (for 137 one or more capability codes) from its peer SHOULD use the BGP 138 Capabilities Advertisement [RFC5492] to advertise the Dynamic 139 Capability for these capability codes. 141 A BGP speaker MAY send to its peer a CAPABILITY message to initiate 142 revisions for one or more capability codes only if these capability 143 codes are listed in the Dynamic Capability of the OPEN message 144 received from its peer. 146 A CAPABILITY message MAY be received only in the Established state. 147 Receiving a CAPABILITY message in any other state is a Finite State 148 Machine Error as defined in [RFC4271]. A BGP speaker SHOULD reset the 149 HoldTimer upon receiving a CAPABILITY message from its peer. 151 When a BGP speaker sends a CAPABILITY message to its peer to initiate 152 a capability revision, the Init/Ack bit for the capability revision 153 in the message MUST be set to 0. The setting of the Ack Request bit 154 is capability specific. The assignment of the Sequence Number is a 155 local matter, but MUST allow the BGP speaker to unambiguously 156 identify a capability revision it initiated previously based on the 157 Sequence Number carried in the acknowledgment from the peer. 159 If the Init/Ack bit is set to 1 for a capability revision in a 160 CAPABILITY message received by a BGP speaker, then the BGP speaker 161 SHALL treat the capability revision as an acknowledgment of the 162 receipt of a capability revision initiated by the BGP speaker. The 163 BGP speaker MUST ignore the Ack Request bit, and SHALL use the 164 Sequence Number carried in the capability revision to match with the 165 capability revision previously initiated. The BGP speaker SHALL 166 ignore an acknowledgment for a capability revision in which an 167 acknowledgment was not requested by the BGP speaker. If the Sequence 168 Number carried in the capability revision does not match any of the 169 the Sequence Numbers used in the capability revisions initiated by 170 the BGP speaker, then the BGP speaker SHOULD send a NOTIFICATION 171 message as specified in the Error Handling section. 173 If the Init/Ack bit is set to 0 for a capability revision in a 174 CAPABILITY message received by a BGP speaker, then the BGP speaker 175 SHOULD first validate the capability code in the message. If the 176 capability code is not listed in the Dynamic Capability advertised by 177 the speaker to the peer, the BGP speaker SHOULD send a NOTIFICATION 178 message as specified in the Error Handling section. For a valid 179 capability code, if the Ack Request bit is set to 1, the BGP speaker 180 MUST first send a CAPABILITY message to acknowledge the receipt of 181 the capability revision. The Init/Ack bit in the acknowledgment MUST 182 be set to 1, and all the other fields in the capability revision MUST 183 be kept unchanged. 185 After receiving a capability revision initiated by a peer, the BGP 186 speaker SHALL update the capability previously received from that 187 peer based on the Action bit in the message, and then function in 188 accordance with the revised capability for the peer. The BGP speaker 189 SHALL ignore such a capbility revision that either results in no 190 change to an existing capability, or removes a capability that was 191 not advertised previously. The procedures specified in the "Error 192 Handling" section SHOULD be followed when an error is detected in 193 processing the CAPABILITY message. 195 In order to avoid ambiguities in sending and processing UPDATE 196 messages, certain capability revisions may require close coordination 197 between the BGP speaker (the Initiator) that initiates the capability 198 revisions and another BGP speaker (the Receiver) that receives the 199 capability revisions. The mechanism of acknowledgment defined in 200 this document SHALL be used for the revision of such a capability. 201 For the Initiator, the capability revision SHALL take effect (for the 202 purpose of sending updates) immediately after the capability revision 203 is sent, and the capability revision SHALL take effect (for the 204 purpose of receiving updates) immediately after an acknowledgment is 205 received from the Receiver. For the Receiver, the capability 206 revision SHALL take effect (for the purpose of receiving updates) 207 immediately after the capability revision is received from the 208 Initiator, and the capability revision SHALL take effect (for the 209 purpose of sending updates) immediately after an acknowledgment is 210 sent. 212 5. Error Handling 214 This document defines a new NOTIFICATION error code: 216 Error Code Symbolic Name 218 7 CAPABILITY Message Error 220 The following error subcodes are defined as well: 222 Subcode Symbolic Name 224 1 Unknown Sequence Number 225 2 Invalid Capability Length 226 3 Malformed Capability Value 227 4 Unsupported Capability Code 229 If a BGP speaker detects an error while processing a CAPABILITY 230 message, it MUST send a NOTIFICATION message with Error Code 231 CAPABILITY Message Error. If any of the defined error subcode is 232 applicable, the Data field of the NOTIFICATION message MUST contain 233 the tuple for the capability revision that causes the speaker to send 234 the message. 236 If the Sequence Number carried in a capability revision marked as 237 acknowledgment does not match any of the the Sequence Numbers used in 238 the capability revisions initiated by the BGP speaker, then the error 239 subcode is set to Unknown Sequence Number. 241 If the Capability Length field in the CAPABILITY message is incorrect 242 for a Capability Code, then the error subcode is set to Invalid 243 Capability Length. 245 If the Capability Value field in the CAPABILITY message is malformed 246 (the definition of "malformed" depends on the Capability Code), then 247 the error subcode is set to Malformed Capability Value. 249 If the Capability Code in the CAPABILITY message is not any of the 250 capability codes advertised in the Dynamic Capability by the speaker, 251 then the error subcode is set to Unsupported Capability Code. 253 6. IANA Considerations 255 This document defines the CAPABILITY message type for BGP with type 256 code 6, and a NOTIFICATION error code and subcodes for the errors in 257 a CAPABILITY message. 259 This document uses a BGP capability code to indicate that a BGP 260 speaker supports the Dynamic Capability. The capability code 67 has 261 been assigned by IANA. 263 7. Security Considerations 265 This extension to BGP does not change the underlying security issues. 267 8. Acknowledgments 269 The authors would like to thank Yakov Rekhter, Ravi Chandra, Dino 270 Farinacci, Pedro Marques, Chandrashekhar Appanna, Derek Yeung, Bruno 271 Rijsman, John Scudder and Jeffrey Haas for their review and comments. 273 9. Normative References 275 [RFC4271] Rekhter, Y., T. Li, and S. Hares, "A Border Gateway 276 Protocol 4 (BGP-4)," RFC 4271, January 2006. 278 [RFC4760] Bates, T., Chandra, R., Rekhter, Y., and D. Katz, 279 "Multiprotocol Extensions for BGP-4", RFC 4760, January 2007. 281 [RFC5492] Scudder, J. and R. Chandra, "Capabilities Advertisement 282 with BGP-4", RFC 5492, February 2009. 284 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 285 Requirement Levels", BCP 14, RFC 2119, March 1997. 287 10. Authors' Addresses 289 Enke Chen 290 Cisco Systems, Inc. 291 170 W. Tasman Dr. 292 San Jose, CA 95134 294 Email: enkechen@cisco.com 296 Srihari R. Sangli 297 Cisco Systems, Inc. 298 170 W. Tasman Dr. 299 San Jose, CA 95134 301 Email: rsrihari@cisco.com