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If these are generic example addresses, they should be changed to use the 233.252.0.x range defined in RFC 5771 Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (March 12, 2017) is 2602 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(See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) == Outdated reference: A later version (-04) exists of draft-keyupate-idr-bgp-spf-02 Summary: 1 error (**), 0 flaws (~~), 3 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group X. Xu 3 Internet-Draft K. Bi 4 Intended status: Standards Track Huawei 5 Expires: September 13, 2017 J. Tantsura 6 Individual 7 March 12, 2017 9 BGP Neighbor Autodiscovery 10 draft-xu-idr-neighbor-autodiscovery-01 12 Abstract 14 BGP has been used as the routing protocol in many hyper-scale data 15 centers. This document proposes a BGP neighbor autodiscovery 16 mechanism which can be used to simplify the BGP deployment greatly. 17 This mechanism is very useful for those hyper-scale data centers 18 where BGP is used as the routing protocol. 20 Status of This Memo 22 This Internet-Draft is submitted in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Internet-Drafts are working documents of the Internet Engineering 26 Task Force (IETF). Note that other groups may also distribute 27 working documents as Internet-Drafts. The list of current Internet- 28 Drafts is at http://datatracker.ietf.org/drafts/current/. 30 Internet-Drafts are draft documents valid for a maximum of six months 31 and may be updated, replaced, or obsoleted by other documents at any 32 time. It is inappropriate to use Internet-Drafts as reference 33 material or to cite them other than as "work in progress." 35 This Internet-Draft will expire on September 13, 2017. 37 Copyright Notice 39 Copyright (c) 2017 IETF Trust and the persons identified as the 40 document authors. All rights reserved. 42 This document is subject to BCP 78 and the IETF Trust's Legal 43 Provisions Relating to IETF Documents 44 (http://trustee.ietf.org/license-info) in effect on the date of 45 publication of this document. Please review these documents 46 carefully, as they describe your rights and restrictions with respect 47 to this document. Code Components extracted from this document must 48 include Simplified BSD License text as described in Section 4.e of 49 the Trust Legal Provisions and are provided without warranty as 50 described in the Simplified BSD License. 52 Table of Contents 54 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 55 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 56 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 57 3. BGP Hello Message Format . . . . . . . . . . . . . . . . . . 3 58 4. Hello Message Procedure . . . . . . . . . . . . . . . . . . . 5 59 5. HELLO Message Error Handling . . . . . . . . . . . . . . . . 6 60 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 61 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 62 7.1. BGP Hello Message . . . . . . . . . . . . . . . . . . . . 6 63 7.2. TLVs of BGP Hello Message . . . . . . . . . . . . . . . . 7 64 8. Security Considerations . . . . . . . . . . . . . . . . . . . 7 65 9. References . . . . . . . . . . . . . . . . . . . . . . . . . 7 66 9.1. Normative References . . . . . . . . . . . . . . . . . . 7 67 9.2. Informative References . . . . . . . . . . . . . . . . . 8 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 70 1. Introduction 72 BGP has been used as the routing protocol instead of IGP in many 73 hyper-scale data centers [RFC7938]. Furthermore, there is an attempt 74 to leverages BGP Link-State distribution and the Shortest Path First 75 algorithm similar to Internal Gateway Protocols (IGPs) such as OSPF 76 [I-D.keyupate-idr-bgp-spf]. In a word, there is a strong motivation 77 to replace IGP by BGP in hyper-scale data centers. 79 However, BGP is not good as IGP from the perspective of deployment 80 automation and simplicity. For instance, the IP address and 81 Autonomous System Number (ASN) of each BGP neighbor have to be 82 manually configured on BGP routers although these BGP peers are 83 directly connected. In addition, for those directly connected BGP 84 routers, it's usually not ideal to establish BGP sessions over their 85 directly connected interface addresses due to the following reasons: 86 1) it's not convient to do trouble-shooting; 2) the BGP update volume 87 is unnecessarily increased when there are multiple physical links 88 between them and those links couldn't be configured as a Link 89 Aggregtion Group (LAG) due to whatever reason (e.g., diffferent link 90 type or speed). As a result, it's more common that loopback 91 interface addresses of those directly connected BGP peers are used 92 for BGP session establishment. To make those loopback addresses of 93 directly connected BGP peers reachable from one another, either 94 static routes have to be configured or some kind of IGP has to be 95 enabled. The former is not good from the automation perspective 96 while the latter is in conflict with the original intention of using 97 BGP as IGP. 99 This draft specifies a BGP neighbor autodiscovery mechanism by 100 borrowing some ideas from the Label Distribution Protocol (LDP) 101 [RFC5036] . More specifically, directly connected BGP routers could 102 automatically discovery the loopback address and the ASN of one other 103 through the exchange of the to-be-defined BGP HELLO messages. The 104 BGP session establishment process as defined in [RFC4271] is 105 triggered once directly connected BGP neighbors are discovered from 106 one another. Note that the BGP session should be established over 107 the discovered loopback address of the BGP neighbor. In addition, to 108 elimnate the need of configing static routes or enabling IGP for the 109 loopback addresses, a certain type of routes towards the BGP 110 neighbor's loopback addresses are dymatically created once the BGP 111 neighbor has been discovered. The administritive distance of such 112 type of routes MUST be smaller than their equivalents which are 113 learnt via the normal BGP update messages . Otherwise, circular 114 dependency problem would occur once these loopback addresses are 115 advertised via the normal BGP update messages as well. 117 1.1. Requirements Language 119 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 120 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 121 document are to be interpreted as described in RFC 2119 [RFC2119]. 123 2. Terminology 125 This memo makes use of the terms defined in [RFC4271]. 127 3. BGP Hello Message Format 129 To automatically discover directly connected BGP neighbors, a BGP 130 router periodically sends BGP HELLO messages out those interfaces on 131 which BGP neighbor autodiscovery are enabled. The BGP HELLO message 132 is a new BGP message which has the same fixed-size BGP header as the 133 exiting BGP messages. However, the HELLO message MUST sent as UDP 134 packets addressed to the to-be-assigned BGP discovery port (179 is 135 the suggested port value) for the "all routers on this subnet" group 136 multicast address (i.e., 224.0.0.2 in the IPv4 case and FF02::2 in 137 the IPv6 case). The IP source address is set to the address of the 138 interface over which the message is sent out. 140 In addition to the fixed-size BGP header, the HELLO message contains 141 the following fields: 143 0 1 2 3 144 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 1 145 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 146 | Version | Hold Time | Message Length | 147 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 148 | TLVs | 149 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 150 Figure 1: BGP Hello Message 152 Version: This 1-octet unsigned integer indicates the protocol 153 version number of the message. The current BGP version number is 154 4. 156 Hold Time: Hello hold timer in seconds. Hello Hold Time specifies 157 the time the sending BGP peer will maintain its record of Hellos 158 from the receiving BGP peer without receipt of another Hello. A 159 pair of BGP peers negotiates the hold times they use for Hellos 160 from each other. Each proposes a hold time. The hold time used 161 is the minimum of the hold times proposed in their Hellos. A 162 value of 0 means use the default 15 seconds. 164 Message Length: This 2-octet unsigned integer specifies the length 165 in octects of the ASN TLV, Connection Address TLV and other TLVs. 167 TLVs: This field contains ASN TLV, Connection Address TLV and 168 other TLVs. 170 The ASN TLV format is show as follows: 172 0 1 2 3 173 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 1 174 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 175 | Type=TBD2 | Length | 176 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 177 | AS Number (2-octet or 4-octet) | 178 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 179 Figure 2: ASN TLV 181 Type: TBD2. 183 Length: Specifies the length of the Value field in octets. 185 AS Number: This variable-length field indicates the 2-octet or 186 4-octet ASN of the sender. 188 The Connection Address TLV format is shown as follows: 190 0 1 2 3 191 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 1 192 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 193 | Type=TBD3 | Length | 194 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 195 | Connection Address (4-octet or 16-octet) | 196 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 197 Figure 3: Connection Address TLV 199 Type: TBD3 201 Length:Specifies the length of the Value field in octets. 203 Connection Address: This variable-length field indicates the IPv4 204 or IPv6 loopback address which is used for establishing BGP 205 sessions. 207 The Router ID TLV format is shown as follows: 209 0 1 2 3 210 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 1 211 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 212 | Type=TBD4 | Length | 213 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 214 | Router ID (4-octet or 16-octet) | 215 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 216 Figure 4: Router ID TLV 218 Type: TBD3 220 Length:Specifies the length of the Value field in octets and it's 221 set to 4 for the IPv4-address-formatted BGP Router ID. 223 Router ID: This variable-length field indicates the BGP router ID 224 which is used for performing the BGP-SPF algorithm as described in 225 [I-D.keyupate-idr-bgp-spf]. 227 4. Hello Message Procedure 229 A BGP peer receiving Hellos from another peer maintains a Hello 230 adjacency corresponding to the Hellos. The peer maintains a hold 231 timer with the Hello adjacency, which it restarts whenever it 232 receives a Hello that matches the Hello adjacency. If the hold timer 233 for a Hello adjacency expires the peer discards the Hello adjacency. 235 We recommend that the interval between Hello transmissions be at most 236 one third of the Hello hold time. 238 A BGP session with a peer has one or more Hello adjacencies. 240 A BGP session has multiple Hello adjacencies when a pair of BGP peers 241 is connected by multiple links that have the same connection address; 242 for example, multiple PPP links between a pair of routers. In this 243 situation, the Hellos a BGP peer sends on each such link carry the 244 same Connection Address. In addition, to elimnate the need of 245 configing static routes or enabling IGP for the loopback addresses, a 246 certain type of routes towards the BGP neighbor's loopback addresses 247 (e.g., carried in the Connection Address TLV) are dymatically created 248 once the BGP neighbor has been discovered. The administritive 249 distance of such type of routes MUST be smaller than their 250 equivalents which are learnt via the normal BGP update messages. 251 Otherwise, circular dependency problem would occur once these 252 loopback addresses are advertised via the normal BGP update messages 253 as well. 255 BGP uses the regular receipt of BGP Discovery Hellos to indicate a 256 peer's intent to keep BGP session identified by the Hello. A BGP 257 peer maintains a hold timer with each Hello adjacency that it 258 restarts when it receives a Hello that matches the adjacency. If the 259 timer expires without receipt of a matching Hello from the peer, BGP 260 concludes that the peer no longer wishes to keep BGP session for that 261 link or that the peer has failed. The BGP peer then deletes the 262 Hello adjacency. When the last Hello adjacency for an BGP session is 263 deleted, the BGP peer terminates the BGP session by sending a 264 Notification message and closing the transport connection. 266 5. HELLO Message Error Handling 268 TBD 270 6. Acknowledgements 272 The authors would like to thank 274 7. IANA Considerations 276 7.1. BGP Hello Message 278 This document requests IANA to allocate a new UDP port for BGP Hello 279 message. 281 Value TLV Name Reference 282 ----- ------------------------------------ ------------- 283 Service Name: BGP-HELLO 284 Transport Protocol(s): UDP 285 Assignee: IESG 286 Contact: IETF Chair . 287 Description: BGP Hello Message. 288 Reference: This document -- draft-xu-idr-neighbor-autodiscovery. 289 Port Number: TBD1 (179 is the suggested value) -- To be assigned by IANA. 291 7.2. TLVs of BGP Hello Message 293 This document requests IANA to create a new registry "TLVs of BGP 294 Hello Message" with the following registration procedure: 296 Registry Name: TLVs of BGP Hello Message. 298 Value TLV Name Reference 299 ------- ------------------------------------------ ------------- 300 0 Reserved This document 301 1 ASN This document 302 2 Connection Address This document 303 3 Router ID This document 304 4-65500 Unassigned 305 65501-65534 Experimental This document 306 65535 Reserved This document 308 8. Security Considerations 310 For security purposes, BGP speakers usually only accept TCP 311 connection attempts to port 179 from the specified BGP peers or those 312 within the configured address range. With the BGP auto-discovery 313 mechanism, it's configurable to enable or disable sending/receiving 314 BGP hello messages on the per-interface basis and BGP hello messages 315 are only exchanged between physically connected peers that are 316 trustworthy. Therefore, the BGP auto-discovery mechanism doesn't 317 introduce additional security risks associated with BGP. 319 9. References 321 9.1. Normative References 323 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 324 Requirement Levels", BCP 14, RFC 2119, 325 DOI 10.17487/RFC2119, March 1997, 326 . 328 [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A 329 Border Gateway Protocol 4 (BGP-4)", RFC 4271, 330 DOI 10.17487/RFC4271, January 2006, 331 . 333 9.2. Informative References 335 [I-D.keyupate-idr-bgp-spf] 336 Patel, K., Lindem, A., Zandi, S., and G. Velde, "Shortest 337 Path Routing Extensions for BGP Protocol", draft-keyupate- 338 idr-bgp-spf-02 (work in progress), December 2016. 340 [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., 341 "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, 342 October 2007, . 344 [RFC7938] Lapukhov, P., Premji, A., and J. Mitchell, Ed., "Use of 345 BGP for Routing in Large-Scale Data Centers", RFC 7938, 346 DOI 10.17487/RFC7938, August 2016, 347 . 349 Authors' Addresses 351 Xiaohu Xu 352 Huawei 354 Email: xuxiaohu@huawei.com 356 Kunyang Bi 357 Huawei 359 Email: bikunyang@huawei.com 361 Jeff Tantsura 362 Individual 364 Email: jefftant@gmail.com