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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 1159 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-01 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 RD31 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, because the VPN prefix 122 limit is to prevent a flood from errors or other issues but does not 123 prevent the device from being overwhelmed and resources exhausted. 125 All it can do is to receive and process the excessive BGP updates 126 continuously, parse the excessive VPN routes for VPN1 and drop it, 127 extract the VPN routes for VPN2 and install it. 129 Doing so can certainly influence the performance of PE1 to serve the 130 other VPN services on it, considering that there are hundreds of VRFs 131 deployed on it. 133 PE1 should have the capability to control the advertisement of 134 specified excessive VPN routes from its BGP peer. The ASBR should 135 also have such capability. 137 +---------------------------+ +--------------------------+ 138 | | | | 139 | | | | 140 | +---------+ | | +---------+ | 141 | | PE1 | | | | PE3 | | 142 | +---------+ | | +---------+ | 143 |VPN1(RD11,RT1)\ | | /VPN1(RD31,RT1)| 144 | VPN2(RD2,RT2) \+---------+ MP-EBGP +---------+/ VPN2(RD2,RT2)| 145 | | | | | | 146 | | ASBR1 |-----------| ASBR2 | | 147 | | | | | | 148 | +---------+ +---------+ | 149 | / | | \ | 150 | +---------+/ | | \+---------+ | 151 | | PE2 | | | | PE4 | | 152 | +---------+ | | +---------+ | 153 |VPN1(RD21,RT1) | | VPN2(RD2,RT2) | 154 | AS1 | | AS2 | 155 +---------------------------+ +--------------------------+ 157 Figure 1: The Option B/Option AB cross-domain scenario 159 5. Inter-AS VPN Option C Scenario 161 For inter-AS VPN deployment option C scenario, as that described in 162 Figure 2, there is one BGP session between RR1 and RR2, which is used 163 to advertise the VPN routes from all the VRFs that located on the 164 edge routers(PE1 and PE2). The BGP maximum prefix bar can't also 165 prevent the excessive advertisement of VPN routes in one VRF, and 166 such abnormal behavior in one VRF can certainly influence the 167 performances of PEs to serve other normal VRFs. 169 PE and RR should all have some capabilities to control the specified 170 excessive VPN routes to be advertised from its upstream BGP peer. 172 MP-EBGP 173 +----------------------------------------+ 174 | | 175 +------------+------------+ +------------+------------+ 176 | +----+----+ | | +----+----+ | 177 | | | | | | | | 178 | +----+ RR1 +----+ | | +----+ RR2 +----+ | 179 | | | | | | | | | | | | 180 | | +---------+ | | | | +---------+ | | 181 | | | | | | | | 182 | |IBGP IBGP| | | |IBGP IBGP| | 183 | | | | | | | | 184 +-+--+----+ +----+--+-+ +-+--+----+ +----+--+-+ 185 | | | | | | | | 186 | PE1 | | ASBR1 |----------| ASBR2 | | PE2 | 187 | | | | | | | | 188 +-+-------+ AS1 +-------+-+ +-+-------+ AS2 +-------+-+ 189 +-------------------------+ +-------------------------+ 191 Figure 2: The Option C cross-domain scenario 193 6. Intra-AS VPN RR Deployment Scenario 195 For intra-AS VPN deployment, as depicted in Figure 3, if the RR is 196 present, the above excess VPN routes advertisement churn can also 197 occurs. For example, if PE3 receives excessive VPN routes for VPN1 198 VRF(there may be several reasons for this to occur, for example, 199 multiple CEs connect to PE3 advertising routes simultaneously causing 200 a wave of routes, redistribution from VRF to VRF, or from GRT to VRF 201 on PE3 etc.), it will advertise such excessive VPN routes to RR and 202 then to PE1. The BGP session between RR and PE3, and the BGP session 203 between RR and PE1 can't prevent this to occur. 205 When PE1 in this figure receives such excessive VPN routes, it can 206 only process them, among the other normal BGP updates. This can 207 certainly influence process of VPN routes for other normal services, 208 the consequences on the receiving PE1 may be the one or more of the 209 followings: 211 a) PE1 can't process a given number of routes in time period X 212 leading to dropping of routes 214 b) Delayed processing that may result in an incomplete number of 215 inputs to the BGP Best Path decision. 217 c) L3VPN customers experiencing an incorrect VPN specification for 218 some time period Y. 220 d) The convergence of control plane processing impacts the traffic 221 forwarding 223 PE and RR should all have some capabilities to control the specified 224 excessive VPN routes to be advertised from its upstream BGP peer. 226 +----------------------------------------------+ 227 | | 228 | | 229 | +---------+ +---------+ | 230 | | PE1 | | PE4 | | 231 | +---------+ +---------+ | 232 | VPN1(RD11,RT1) \ / VPN2(RD2,RT2)| 233 | VPN2(RD2,RT2) \+---------+ / | 234 | | | | 235 | | RR | | 236 | | | | 237 | +---------+ \ | 238 | / \ | 239 | +---------+/ +---------+ | 240 | | PE2 | | PE3 | | 241 | +---------+ +---------+ | 242 | VPN1(RD21,RT1) VPN1(RD31,RT1) | 243 | AS 100 VPN2(RD2,RT2) | 244 +----------------------------------------------+ 246 Figure 3: Intra-AS VPN RR deployment scenario 248 7. VPN Routes Shared on one PE 250 The scenarios described above are mainly in device level, that is to 251 say, if the receiving PE has some mechanism to control the excess VPN 252 routes advertisement from its BGP neighbor, the failure churn effect 253 can be controlled then. But there are also situations that the 254 granular control should be took place within the receiving PE itself. 256 Figure 4 below describes such scenario. There are four VRFs on PE, 257 and three of them import the same VPN routes that carry route target 258 RT3. Such deployment can occur in the inter-VRF communication 259 scenario. If the threshold of VPN route-limit for these VRFs is set 260 different, for example, are max-vpn-routes-vrf1, max-vpn-routes-vrf2, 261 max-vpn-routes-vrf3, max-vpn-routes-vrf4 respectively, and these 262 values have the following order, as max-vpn-routes-vrf1. 345 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 346 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 347 2006, . 349 [RFC4486] Chen, E. and V. Gillet, "Subcodes for BGP Cease 350 Notification Message", RFC 4486, DOI 10.17487/RFC4486, 351 April 2006, . 353 Authors' Addresses 355 Aijun Wang 356 China Telecom 357 Beiqijia Town, Changping District 358 Beijing, Beijing 102209 359 China 361 Email: wangaj3@chinatelecom.cn 362 Wei Wang 363 China Telecom 364 Beiqijia Town, Changping District 365 Beijing, Beijing 102209 366 China 368 Email: wangw36@chinatelecom.cn 370 Gyan S. Mishra 371 Verizon Inc. 372 13101 Columbia Pike 373 Silver Spring MD 20904 374 United States of America 376 Phone: 301 502-1347 377 Email: gyan.s.mishra@verizon.com 379 Haibo Wang 380 Huawei Technologies 381 Huawei Building, No.156 Beiqing Rd. 382 Beijing, Beijing 100095 383 China 385 Email: rainsword.wang@huawei.com 387 Shunwan Zhuang 388 Huawei Technologies 389 Huawei Building, No.156 Beiqing Rd. 390 Beijing, Beijing 100095 391 China 393 Email: zhuangshunwan@huawei.com 395 Jie Dong 396 Huawei Technologies 397 Huawei Building, No.156 Beiqing Rd. 398 Beijing, Beijing 100095 399 China 401 Email: jie.dong@huawei.com