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Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year == The document doesn't use any RFC 2119 keywords, yet seems to have RFC 2119 boilerplate text. -- The document date (February 22, 2021) is 1152 days in the past. Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 IDR Working Group A. Wang 3 Internet-Draft W. Wang 4 Intended status: Informational China Telecom 5 Expires: August 26, 2021 G. Mishra 6 Verizon Inc. 7 H. Wang 8 S. Zhuang 9 J. Dong 10 Huawei Technologies 11 February 22, 2021 13 Analysis of VPN Routes Control in Shared BGP Session 14 draft-wang-idr-vpn-routes-control-analysis-00 16 Abstract 18 This draft analyzes some scenarios and the necessaries for VPN routes 19 control in the shared BGP session, which can be the used as the base 20 for the design of related solutions. 22 Status of This Memo 24 This Internet-Draft is submitted in full conformance with the 25 provisions of BCP 78 and BCP 79. 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF). Note that other groups may also distribute 29 working documents as Internet-Drafts. The list of current Internet- 30 Drafts is at https://datatracker.ietf.org/drafts/current/. 32 Internet-Drafts are draft documents valid for a maximum of six months 33 and may be updated, replaced, or obsoleted by other documents at any 34 time. It is inappropriate to use Internet-Drafts as reference 35 material or to cite them other than as "work in progress." 37 This Internet-Draft will expire on August 26, 2021. 39 Copyright Notice 41 Copyright (c) 2021 IETF Trust and the persons identified as the 42 document authors. All rights reserved. 44 This document is subject to BCP 78 and the IETF Trust's Legal 45 Provisions Relating to IETF Documents 46 (https://trustee.ietf.org/license-info) in effect on the date of 47 publication of this document. Please review these documents 48 carefully, as they describe your rights and restrictions with respect 49 to this document. Code Components extracted from this document must 50 include Simplified BSD License text as described in Section 4.e of 51 the Trust Legal Provisions and are provided without warranty as 52 described in the Simplified BSD License. 54 Table of Contents 56 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 57 2. Conventions used in this document . . . . . . . . . . . . . . 2 58 3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 2 59 4. Inter-AS VPN Option B/AB Scenario . . . . . . . . . . . . . . 3 60 5. Inter-AS VPN Option C Scenario . . . . . . . . . . . . . . . 4 61 6. Intra-AS VPN RR Deployment Scenario . . . . . . . . . . . . . 5 62 7. VPN Routes Shared on one PE . . . . . . . . . . . . . . . . . 6 63 8. Requirements for the solutions . . . . . . . . . . . . . . . 7 64 9. Security Considerations . . . . . . . . . . . . . . . . . . . 8 65 10. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 66 11. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 8 67 12. Normative References . . . . . . . . . . . . . . . . . . . . 8 68 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 70 1. Introduction 72 BGP Maximum Prefix feature [RFC4486] is often used at the network 73 boundary to control the number of prefixes to be injected into the 74 network. But for some scenarios when the VPN routes from several 75 VRFs are advertised via one shared BGP session, there is lack of 76 appropriate methods to control the flooding of VPN routes within one 77 VRF to overwhelm the process of VPN routes in other VRFs. That is to 78 say, the excessive VPN routes advertisement should be controlled 79 individually for each VRF in such shared BGP session. 81 The following sections analyzes the scenarios that are necessary to 82 such mechanism. 84 2. Conventions used in this document 86 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 87 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 88 document are to be interpreted as described in [RFC2119] . 90 3. Terminology 92 The following terms are defined in this draft: 94 o RD: Route Distinguisher, defined in [RFC4364] 95 o RR: Router Reflector, provides a simple solution to the problem of 96 IBGP full mesh connection in large-scale IBGP implementation. 98 o VRF: Virtual Routing Forwarding, a virtual routing table based on 99 VPN instance. 101 4. Inter-AS VPN Option B/AB Scenario 103 For inter-AS VPN deployment option B/AB scenario, as described in 104 Figure 1, there is one BGP session between ASBR1 and ASBR2, which is 105 used to advertise the VPN routes from VPN1 and VPN2 VRF. Normally 106 the operator will deploy the BGP maximum prefixes feature under 107 different address families between the ASBR1 and ASBR2, but the 108 threshold must be set very high to cope with the situation when all 109 the VRFs in each family reach their VPN routes limit simultaneously. 110 In case VPN routes in only one of VRF, for example VPN1 in PE3, 111 advertises excess VPN routes(with RD set to RD1 and RT import/export 112 set to RT1. Configurations on other PEs are similar) into the 113 network, but VPN routes advertisement in other VRFs are in normal, 114 the prefix bar set between the ASBRs will not take effect. Such 115 excessive VPN routes will be advertised into the AS1, to PE1 and PE2 116 respectively. 118 PE1 in this example, provides the services for VPN2 at the same time. 119 If it receives the excessive VPN routes for VPN1 from ASBR1, although 120 such VPN routes have exceeded the limit within the VRF VPN1, it can't 121 break the BGP session with ASBR1 directly. All it can do is to 122 receive and process the excessive BGP updates continuously, parse the 123 excessive VPN routes for VPN1 and drop it, extract the VPN routes for 124 VPN2 and install it. 126 Doing so can certainly influence the performance of PE1 to serve the 127 other VPN services on it, considering that there are hundreds of VRFs 128 deployed on it. 130 PE1 should have the capability to control the advertisement of 131 specified excessive VPN routes from its BGP peer. The ASBR should 132 also have such capability. 134 +---------------------------+ +--------------------------+ 135 | | | | 136 | | | | 137 | +---------+ | | +---------+ | 138 | | PE1 | | | | PE3 | | 139 | +---------+ | | +---------+ | 140 | VPN1(RD1,RT1)\ | | / VPN1(RD1,RT1)| 141 | VPN2(RD2,RT2) \+---------+ MP-EBGP +---------+/ VPN2(RD2,RT2)| 142 | | | | | | 143 | | ASBR1 |-----------| ASBR2 | | 144 | | | | | | 145 | +---------+ +---------+ | 146 | / | | \ | 147 | +---------+/ | | \+---------+ | 148 | | PE2 | | | | PE4 | | 149 | +---------+ | | +---------+ | 150 | VPN1(RD1,RT1) | | VPN2(RD2,RT2) | 151 | AS1 | | AS2 | 152 +---------------------------+ +--------------------------+ 154 Figure 1: The Option B/Option AB cross-domain scenario 156 5. Inter-AS VPN Option C Scenario 158 For inter-AS VPN deployment option C scenario, as that described in 159 Figure 2, there is one BGP session between RR1 and RR2, which is used 160 to advertise the VPN routes from all the VRFs that located on the 161 edge routers(PE1 and PE2). The BGP maximum prefix bar can't also 162 prevent the excessive advertisement of VPN routes in one VRF, and 163 such abnormal behavior in one VRF can certainly influence the 164 performances of PEs to serve other normal VRFs. 166 PE and RR should all have some capabilities to control the specified 167 excessive VPN routes to be advertised from its upstream BGP peer. 169 MP-EBGP 170 +----------------------------------------+ 171 | | 172 +------------+------------+ +------------+------------+ 173 | +----+----+ | | +----+----+ | 174 | | | | | | | | 175 | +----+ RR1 +----+ | | +----+ RR2 +----+ | 176 | | | | | | | | | | | | 177 | | +---------+ | | | | +---------+ | | 178 | | | | | | | | 179 | |IBGP IBGP| | | |IBGP IBGP| | 180 | | | | | | | | 181 +-+--+----+ +----+--+-+ +-+--+----+ +----+--+-+ 182 | | | | | | | | 183 | PE1 | | ASBR1 |----------| ASBR2 | | PE2 | 184 | | | | | | | | 185 +-+-------+ AS1 +-------+-+ +-+-------+ AS2 +-------+-+ 186 +-------------------------+ +-------------------------+ 188 Figure 2: The Option C cross-domain scenario 190 6. Intra-AS VPN RR Deployment Scenario 192 For intra-AS VPN deployment, as depicted in Figure 3, if the RR is 193 present, the above excess VPN routes advertisement churn can also 194 occurs. For example, if PE3 receives excessive VPN routes for VPN1 195 VRF(there may be several reasons for this to occur, for example, 196 multiple CEs connect to PE3 advertising routes simultaneously causing 197 a wave of routes, redistribution from VRF to VRF, or from GRT to VRF 198 on PE3 etc.), it will advertise such excessive VPN routes to RR and 199 then to PE1. The BGP session between RR and PE3, and the BGP session 200 between RR and PE1 can't prevent this to occur. 202 When PE1 in this figure receives such excessive VPN routes, it can 203 only process them, among the other normal BGP updates. This can 204 certainly influence process of VPN routes for other normal services, 205 the consequences on the receiving PE1 may be the one or more of the 206 followings: 208 a) PE1 can't process a given number of routes in time period X 209 leading to dropping of routes 211 b) Delayed processing that may result in an incomplete number of 212 inputs to the BGP Best Path decision. 214 c) L3VPN customers experiencing an incorrect VPN specification for 215 some time period Y. 217 d) The convergence of control plane processing impacts the traffic 218 forwarding 220 PE and RR should all have some capabilities to control the specified 221 excessive VPN routes to be advertised from its upstream BGP peer. 223 +----------------------------------------------+ 224 | | 225 | | 226 | +---------+ +---------+ | 227 | | PE1 | | PE4 | | 228 | +---------+ +---------+ | 229 | VPN1(RD1,RT1) \ / VPN2(RD2,RT2)| 230 | VPN2(RD2,RT2) \+---------+ / | 231 | | | | 232 | | RR | | 233 | | | | 234 | +---------+ \ | 235 | / \ | 236 | +---------+/ +---------+ | 237 | | PE2 | | PE3 | | 238 | +---------+ +---------+ | 239 | VPN1(RD1,RT1) VPN1(RD1,RT1) | 240 | AS 100 VPN2(RD2,RT2) | 241 +----------------------------------------------+ 243 Figure 3: Intra-AS VPN RR deployment scenario 245 7. VPN Routes Shared on one PE 247 The scenarios described above are mainly in device level, that is to 248 say, if the receiving PE has some mechanism to control the excess VPN 249 routes advertisement from its BGP neighbor, the failure churn effect 250 can be controlled then. But there are also situations that the 251 granular control should be took place within the receiving PE itself. 253 Figure 4 below describes such scenario. There are four VRFs on PE, 254 and three of them import the same VPN routes that carry route target 255 RT3. Such deployment can occur in the inter-VRF communication 256 scenario. If the threshold of VPN route-limit for these VRFs is set 257 different, for example, are max-vpn-routes-vrf1, max-vpn-routes-vrf2, 258 max-vpn-routes-vrf3, max-vpn-routes-vrf4 respectively, and these 259 values have the following order, as max-vpn-routes-vrf1. 342 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 343 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 344 2006, . 346 [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease 347 Notification Message", RFC 4486, DOI 10.17487/RFC4486, 348 April 2006, . 350 Authors' Addresses 352 Aijun Wang 353 China Telecom 354 Beiqijia Town, Changping District 355 Beijing, Beijing 102209 356 China 358 Email: wangaj3@chinatelecom.cn 359 Wei Wang 360 China Telecom 361 Beiqijia Town, Changping District 362 Beijing, Beijing 102209 363 China 365 Email: wangw36@chinatelecom.cn 367 Gyan S. Mishra 368 Verizon Inc. 369 13101 Columbia Pike 370 Silver Spring MD 20904 371 United States of America 373 Phone: 301 502-1347 374 Email: gyan.s.mishra@verizon.com 376 Haibo Wang 377 Huawei Technologies 378 Huawei Building, No.156 Beiqing Rd. 379 Beijing, Beijing 100095 380 China 382 Email: rainsword.wang@huawei.com 384 Shunwan Zhuang 385 Huawei Technologies 386 Huawei Building, No.156 Beiqing Rd. 387 Beijing, Beijing 100095 388 China 390 Email: zhuangshunwan@huawei.com 392 Jie Dong 393 Huawei Technologies 394 Huawei Building, No.156 Beiqing Rd. 395 Beijing, Beijing 100095 396 China 398 Email: jie.dong@huawei.com