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If you have contacted all the original authors and they are all willing to grant the BCP78 rights to the IETF Trust, then this is fine, and you can ignore this comment. If not, you may need to add the pre-RFC5378 disclaimer. (See the Legal Provisions document at https://trustee.ietf.org/license-info for more information.) -- The document date (January 21, 2015) is 3381 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) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group J. Uttaro 3 Internet-Draft ATT 4 Intended status: Standards Track P. Mohapatra 5 Expires: July 25, 2015 Sproute Networks 6 D. Smith 7 Cisco Systems 8 R. Raszuk 9 Mirantis Inc. 10 J. Scudder 11 Juniper Networks 12 January 21, 2015 14 BGP ACCEPT_OWN Community Attribute 15 draft-ietf-l3vpn-acceptown-community-09.txt 17 Abstract 19 Under certain conditions it is desirable for a BGP route reflector to 20 be able to modify the Route Target list of a VPN route that is 21 distributed by the route reflector, enabling the route reflector to 22 control how a route originated within one VRF is imported into other 23 VRFs. This technique works effectively as long as the VRF that 24 exports the route is not on the same PE as the VRF(s) that import the 25 route. However, due to the constraints of the BGP protocol, it does 26 not work if the two are on the same PE. This document describes a 27 modification to the BGP protocol allowing this technique to work when 28 the VRFs are on the same PE, allowing the technique to be used in a 29 standard manner throughout an autonomous system. 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 http://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 July 25, 2015. 48 Copyright Notice 50 Copyright (c) 2015 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 (http://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 1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3 67 2. ACCEPT_OWN Community . . . . . . . . . . . . . . . . . . . . 3 68 2.1. Route Acceptance . . . . . . . . . . . . . . . . . . . . 3 69 2.2. Propagating ACCEPT_OWN Between Address Families . . . . . 4 70 2.3. Configuration Control . . . . . . . . . . . . . . . . . . 4 71 3. Decision Process . . . . . . . . . . . . . . . . . . . . . . 4 72 4. Deployment Considerations . . . . . . . . . . . . . . . . . . 5 73 5. Other Applications . . . . . . . . . . . . . . . . . . . . . 5 74 6. Security Considerations . . . . . . . . . . . . . . . . . . . 5 75 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 76 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 77 9. Normative References . . . . . . . . . . . . . . . . . . . . 6 78 Appendix A. Local Extranet Application (non-informative) . . . . 6 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 81 1. Introduction 83 In certain scenarios, a BGP speaker may maintain multiple "VPN 84 Routing and Forwarding tables", or VRFs [RFC4364]. Under certain 85 conditions, it is desirable for a route reflector to be able to 86 modify the Route Target (RT) list of a VPN route that is distributed 87 by the route reflector, enabling the route reflector to control how a 88 route originated within one VRF is imported into other VRFs. Though 89 it is possible to perform such policy control directly on the 90 originator, it may be operationally cumbersome in an autonomous 91 system with a large number of border routers having complex BGP 92 policies. 94 The technique of the route reflector modifying the RT list works 95 effectively as long as the VRF that exports the route is not on the 96 same PE as the VRF(s) that import the route. However, due to the 97 constraints of the BGP protocol, it does not work if the two are on 98 the same PE. This is because per the BGP specification [RFC4271], a 99 BGP speaker rejects prefix advertisements received that were 100 originated by itself. In an autonomous system with route reflectors, 101 the route reflector attaches the ORIGINATOR_ID attribute to the 102 UPDATE messages so that if such prefix advertisements reach the 103 originator, the originator can reject them by simply checking the 104 ORIGINATOR_ID attribute. The BGP specification also mandates that a 105 route should not be accepted from a peer when the NEXT_HOP attribute 106 matches the receiver's own "IP address". 108 This document proposes a modification to BGP's behavior by defining a 109 new community [RFC1997] value, in order to allow the technique of RT 110 list modification by the route reflector to be used in a standard 111 manner throughout an autonomous system, irrespective of whether the 112 VRFs are on the same, or different PEs. 114 1.1. Requirements Language 116 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 117 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 118 document are to be interpreted as described in RFC 2119 [RFC2119]. 120 2. ACCEPT_OWN Community 122 This memo defines a new BGP community from the First Come First 123 Served range, ACCEPT_OWN, whose value as assigned by IANA is 124 0xFFFF0001. Processing of the ACCEPT_OWN community SHOULD be 125 controlled by configuration. The functionality SHOULD default to 126 being disabled, as further specified in Section 2.3. 128 2.1. Route Acceptance 130 A router MAY accept a route whose ORIGINATOR_ID or NEXT_HOP value 131 matches that of the receiving speaker if all of the following are 132 true: 134 o Processing of the ACCEPT_OWN community is enabled by 135 configuration. 137 o The route in question carries the ACCEPT_OWN community. 139 o The route in question was originated from a source VRF on the 140 router. The source VRF is a VRF on the router whose configured 141 Route Distinguisher is equal to the Route Distinguisher carried in 142 the route. 144 o The route in question is targeted to one or more destination VRFs 145 on the router (as determined by inspecting the Route Target(s)). 147 o At least one destination VRF is different from the source VRF. 149 A route MUST never be accepted back into its source VRF, even if it 150 carries one or more Route Targets (RTs) which match that VRF. 152 2.2. Propagating ACCEPT_OWN Between Address Families 154 The ACCEPT_OWN community controls propagation of routes which can be 155 associated with a source VRF by inspection of their Route 156 Distinguisher and with a target VRF by inspection of their Route 157 Target list (for example VPN routes with a SAFI of 128). As such, it 158 SHOULD NOT be attached to any routes which cannot be associated with 159 a source VRF. This implies that when propagating routes into a VRF, 160 the ACCEPT_OWN community should not be propagated. Likewise, if a 161 route carrying the ACCEPT_OWN community is received in an address 162 family which does not allow the source VRF to be looked up, the 163 ACCEPT_OWN community MUST be discarded. An OPTIONAL message may be 164 logged in this case. 166 2.3. Configuration Control 168 ACCEPT_OWN handling SHOULD be controlled by configuration, and SHOULD 169 default to being disabled. When ACCEPT_OWN is disabled by 170 configuration (either explicitly or by default), the router MUST NOT 171 apply the special route acceptance rules detailed in Section 2.1. 172 The router SHOULD still apply the propagation rules detailed in 173 Section 2.2. 175 3. Decision Process 177 If a BGP speaker supports ACCEPT_OWN and is configured for the 178 extensions defined in this document, the following step is inserted 179 after the LOCAL_PREF comparison step in BGP decision process: 181 When comparing a pair of routes for a BGP destination, the route 182 attached with ACCEPT_OWN community is preferred over the route 183 that does not have the community. 185 In all other respects, the decision process remains unchanged. This 186 extra step MUST only be invoked during the best path selection 187 process of VPN-IP routes [RFC4364] (i.e. it MUST NOT be invoked for 188 the best path selection of "imported" IP routes in a VRF). The 189 purpose of the extra step is to allow the paths advertised by the 190 route reflector with ACCEPT_OWN community to be selected as best over 191 other paths that the BGP speaker may have received, hence enabling 192 the applications ACCEPT_OWN is designed for. 194 4. Deployment Considerations 196 The ACCEPT_OWN community as described in this document is useful 197 within a single autonomous system which uses a single layer of route 198 reflectors. Its use with hierarchical route reflectors would require 199 further specification and is out of scope for this document. 200 Likewise, its use across multiple autonomous systems is out of scope 201 for this document. 203 5. Other Applications 205 This approach may also be relevant to other scenarios where a BGP 206 speaker maintains multiple routing contexts using an approach 207 different from that of [RFC4364], as long as the specific approach in 208 use has the property that the BGP speaker originates and receives 209 routes within a particular context. In such a case, "VRF" in this 210 document should be understood to mean whatever construct provides a 211 routing context in the specific technology under consideration. 212 Likewise, "Route Distinguisher" should be understood to mean whatever 213 construct allows a route's originator to associate that route with 214 its source context, and "Route Target" should be understood to mean 215 whatever construct allows a route to be targeted for import into a 216 context other than its source. 218 6. Security Considerations 220 ACCEPT_OWN as described above permits a router's own route prefix to 221 be advertised to a different VRF on that router. In this respect, 222 such a route is similar to any other BGP route and shares the same 223 set of security vulnerabilities and concerns. No new fundamental 224 security issues are introduced by ACCEPT_OWN. 226 7. IANA Considerations 228 IANA has assigned the value 0xFFFF0001 from BGP well-known 229 communities registry for ACCEPT_OWN community. No additional IANA 230 action is required. 232 8. Acknowledgments 234 The authors would like to thank Yakov Rekhter, Jim Guichard, Clarence 235 Filsfils, John Mullooly, Jeff Haas, Pranav Mehta, and Tamas Mondal 236 for their valuable comments and suggestions. The decision process 237 changes were suggested by Pranav Mehta to solve the remote extranet 238 problem. 240 9. Normative References 242 [RFC1997] Chandrasekeran, R., Traina, P., and T. Li, "BGP 243 Communities Attribute", RFC 1997, August 1996. 245 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 246 Requirement Levels", BCP 14, RFC 2119, March 1997. 248 [RFC4271] Rekhter, Y., Li, T., and S. Hares, "A Border Gateway 249 Protocol 4 (BGP-4)", RFC 4271, January 2006. 251 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 252 Networks (VPNs)", RFC 4364, February 2006. 254 Appendix A. Local Extranet Application (non-informative) 256 One of the applications for this behavior is auto-configuration of 257 extranets within MPLS VPN networks. Consider the following topology: 259 CE1 --------+ 260 | 261 (VRF 1, RD 1, RT 1) 262 PE1 ................... RR 263 (VRF 2, RD 2, RT 2) 264 | 265 CE2 --------+ 267 Figure 1: Extranet Application 269 Within the above topology, PE1 receives a prefix X from CE1. Prefix 270 X is installed in VRF 1 and is advertised to the route reflector with 271 route distinguisher (RD) 1 and route target (RT) 1 as configured on 272 PE1. The requirement is to import prefix X into VRF 2 and advertise 273 it to CE2 in support of extranet VPN connectivity between CE1/VRF1 274 and CE2/VRF2. Current BGP mechanisms for MPLS VPNs[RFC4364] require 275 changing the import RT value and/or import policy for VRF 2 on PE1. 276 This is operationally cumbersome in a network with a large number of 277 border routers having complex BGP policies. 279 Alternatively, using the new ACCEPT_OWN community value, the route 280 reflector can simply re-advertise prefix X back to PE1 with RT 2 281 appended. In this way, PE1 will accept prefix X despite its 282 ORIGINATOR_ID or NEXT_HOP value, import it into VRF 2 as a result of 283 RT 2, and will then determine the correct adjacency rewrite within 284 VRF 1 based on the RD value (1) and the prefix. Note that the RT 1 285 value originally attached to the route will simply be ignored since 286 associated with the source VRF 1. The same operation needs also to 287 happen in the reverse direction (VRF 1 learning a route from VRF 2) 288 to achieve establishment of an extranet VPN strictly via the route 289 reflector without changing the BGP policy of PE1 in any way. 291 A router performing such an extranet application can accept a route 292 with its own ORIGINATOR_ID or NEXT_HOP value only if the VRF in which 293 the router originated the route is different than the VRF in which 294 the router accepts the re-advertised route. 296 Authors' Addresses 298 James Uttaro 299 ATT 300 200 S. Laurel Avenue 301 Middletown, NJ 07748 302 USA 304 Email: uttaro@att.com 306 Pradosh Mohapatra 307 Sproute Networks 309 Email: mpradosh@yahoo.com 311 David J. Smith 312 Cisco Systems 313 111 Wood Avenue South 314 Iselin, NJ 08830 315 USA 317 Email: djsmith@cisco.com 319 Robert Raszuk 320 Mirantis Inc. 321 615 National Ave. #100 322 Mt View, CA 94043 323 USA 325 Email: robert@raszuk.net 326 John Scudder 327 Juniper Networks 328 1194 N. Mathilda Ave 329 Sunnyvale, CA 94089 330 USA 332 Email: jgs@juniper.net