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This draft specifies an 17 improvement to load balancing such links. 19 Status of This Memo 21 This Internet-Draft is submitted to IETF in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Distribution of this document is unlimited. Comments should be sent 25 to the BESS working group mailing list . 27 Internet-Drafts are working documents of the Internet Engineering 28 Task Force (IETF), its areas, and its working groups. Note that 29 other groups may also distribute working documents as Internet- 30 Drafts. 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 The list of current Internet-Drafts can be accessed at 38 http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft 39 Shadow Directories can be accessed at 40 http://www.ietf.org/shadow.html. 42 1. Introduction............................................3 43 1.1 Terminology and Acronyms...............................3 45 2. Improved Load Balancing.................................5 46 2.1 Problem 1: Traffic Bypassing...........................5 47 2.2 Problem 2: VID Encapsulation Confusion.................6 49 3. VLAN-Redirect-Extended Community Attribute..............7 51 4. Operation...............................................8 52 4.1 Establishment..........................................8 53 4.2 Handling Link Failure..................................8 55 5. IANA Considerations.....................................9 56 6. Security Considerations.................................9 58 Normative References......................................10 59 Informative References....................................10 61 Acknowledgements..........................................10 62 Authors' Addresses........................................11 64 1. Introduction 66 A principal feature of EVPN (Ethernet VPN [RFC7432]) is the ability 67 to support multihoming from a customer equipment (CE) to multiple 68 provider edge equipment (PE) with links used in an all-active 69 redundancy mode. That mode is where a device is multihomed to a group 70 of two or more PEs and where all PEs in such redundancy group can 71 forward traffic to/from the multihomed device or network for a given 72 VLAN [RFC7209]. This draft specifies an improvement in load balancing 73 such PE to CE all-active multi-homing links. 75 In the case where a CE is multihomed to multiple PE nodes, using a 76 Link Aggregation Group (LAG) with All-Active redundancy, it is 77 possible that only a single PE learns a set of the MAC addresses 78 associated with traffic transmitted by the CE. This leads to a 79 situation where remote PE nodes receive MAC/IP Advertisement routes 80 for these addresses from a single PE, even though multiple PEs are 81 connected to the multihomed segment. 83 To address this issue, EVPN introduces the concept of "aliasing", 84 which is the ability of a PE to signal that it has reachability to an 85 EVPN instance (EVI) on a given Ethernet segment (ES) even when it has 86 learned no MAC addresses from that EVI/ES. The Ethernet A-D per EVI 87 route is used for this purpose. A remote PE that receives a MAC/IP 88 Advertisement route with a non-reserved ESI SHOULD consider the 89 advertised MAC address to be reachable via all PEs that have 90 advertised reachability to that MAC address's EVI/ES via the 91 combination of an Ethernet A-D per EVI route for that EVI/ES (and 92 Ethernet tag, if applicable) AND Ethernet A-D per ES routes for that 93 ES with the "Single-Active" bit in the flags of the ESI Label 94 extended community set to 0. 96 1.1 Terminology and Acronyms 98 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 99 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 100 "OPTIONAL" in this document are to be interpreted as described in BCP 101 14 [RFC2119] [RFC8174] when, and only when, they appear in all 102 capitals, as shown here. 104 This document uses the following acronyms and terms: 106 A-D - Auto Discovery. 108 All-Active Redundancy Mode - When a device is multihomed to a group 109 of two or more PEs and when all PEs in such redundancy group can 110 forward traffic to/from the multihomed device or network for a 111 given VLAN. 113 CE - Customer Edge equipment. 115 ES - Ethernet Segment. 117 ESI - Ethernet Segment Identifier. 119 EVI - EVPN Instance. 121 EVPN - Ethernet VPN [RFC7432]. 123 FRR - Fast ReRoute. 125 MAC - Media Access Control. 127 PE - Provider Edge equipment. 129 Single-Active Redundancy Mode - When a device or a network is 130 multihomed to a group of two or more PEs and when only a single PE 131 in such a redundancy group can forward traffic to/from the 132 multihomed device or network for a given VLAN. 134 VPN - Virtual Private Network. 136 2. Improved Load Balancing 138 Consider the example in Figure 1. CE1 is multihomed to PE1 and PE2. 139 CE1 typically uses a hash algorithm to determine whether to send a 140 particular traffic to PE1 or to PE2. Thus, if such traffic from CE1 141 is only sent to PE1, then PE1 will learn CE1's MAC address(es) and 142 that PE2 will not. 144 PE3 and PE4 can do aliasing [RFC7432] because PE1 and PE2 will be 145 advertising the same ESI. Thus PE3 and PE4 will expect that a MAC 146 address reachable from PE1 will also be reachable from PE2. This 147 aliasing will cause PE3 and PE4 to load balance to CE1's MAC(s), 148 sending some traffic to PE1 and some to PE2. 150 ......... 151 +----------+ . . +----------+ 152 | PE1 MAC +------+ +------+ PE3 | 153 | Learning | . . | | 154 +----------+ . . +----------+ 155 / ^ . . | \ 156 +---+ | . EVPN . | +---+ 157 |CE1| | . MPLS . | |CE2| 158 +---+ | . . | +---+ 159 \ | . . | / 160 +----------+ . . +----------+ 161 | PE2 | . . | PE4 | 162 | +------+ +------+ | 163 +----------+ . . +----------+ 164 ......... 166 Figure 1. Current Situation 168 There are two problems associated with this situation that are 169 described in the subsections below. Section 3 describes the 170 mechanism to address these problems. 172 2.1 Problem 1: Traffic Bypassing 174 Since PE2 has not learning CE1's MAC(s), the MAC lookup at PE2 will 175 find that MAC address associated with PE1. PE2 will then tunnel the 176 traffic to PE1. 178 As an enhancement that solves this problem, PE1 can send MAC 179 address(es) with VLAN and ESI information. PE2 will then receive the 180 MAC address(es) and VLAN that PE1 associates with the ESI and PE2 can 181 use this to update its forwarding tables (see Figure 2). As a result, 182 when traffic addressed to a CE1 MAC arrives at PE2, it can send it on 183 the appropriate local interface and VLAN. This avoids the unnecessary 184 extra hop through PE1 for such traffic arriving at PE2. 186 ......... 187 +----------+ . . +----------+ 188 | PE1 MAC +------+ +------+ PE3 | 189 | Learning | . . | | 190 +----------+ . . +----------+ 191 / ^ . . | \ 192 +---+ | . EVPN . | +---+ 193 |CE1| Sy|nc . MPLS . | |CE2| 194 +---+ | . . | +---+ 195 \ v . . | / 196 +----------+ . . +----------+ 197 | PE2 | . . | PE4 | 198 | +------+ +------+ | 199 +----------+ . . +----------+ 200 ......... 202 Figure 2. With Enhancement 204 2.2 Problem 2: VID Encapsulation Confusion 206 If CE1 is connected through a VLAN and has only one VLAN under the 207 EVPN instance of PE2, the unicast traffic can be directly sent to the 208 appropriate interface and encapsulated with the appropriate VID and 209 forwarded to CE1. 211 However, there may be multiple ways for CE1 to connect to PE1 and 212 PE2, including Ethernet Tag, Ethernet Tag termination, and Q-in-Q. 213 PE2 cannot always obtain the appropriate VLANs and in such cases PE2 214 is missing the information needed to forward the unicast traffic to 215 CE1 directly. 217 3. VLAN-Redirect-Extended Community Attribute 219 This document defines a new BGP extended community attribute called 220 the VLAN-Redirect-Extended Community attribute as shown in Figure 3. 222 0 1 2 3 223 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 1 224 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 225 | 0x06 | Sub-Type=TBA | Flags | Reserved | 226 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 227 | S-VLAN | C-VLAN | 228 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 230 Figure 3. VLAN-Redirect-Extended Community Attribute 232 Where: 234 0x06: EVPN Extended Community Type field. 236 Sub-Type: Sub-Type field indicating that the extended community 237 attribute is a VLAN-Redirect-Extended Community attribute, and 238 the value is TBA as assigned by the IANA. 240 Flags: 8 bits of identification information. Bit 0 set to 0 241 indicates that the action is redirected to the VLANs in this 242 community 244 Reserved: Not used. MUST be sent as zero and ignored on receipt. 246 S-VLAN: Outer VLAN information, can not be 0, 0 is illegal value 248 C-VLAN: Inner VLAN information. When 0, it means there is no C- 249 VLAN. 251 4. Operation 253 Operation with the solution specified in Section 3 and the topology 254 shown in Figure 2 is described below. 256 4.1 Establishment 258 1. PE1 learns MAC addresses from CE1, advertises them to PE2, carries 259 the ESI value as ES1 and the next hop as PE1, and carries the 260 VLAN- Redirect-Extended Community attributes. 262 2. PE2 receives the MAC route advertised by PE1 and finds the 263 interface that connects to CE1 locally according to the ESI value. 264 At the same time, PE2 fills in the VLAN information according to 265 the VLAN-Redirect-Extended Community attributes 267 3. At the same time, PE2 generates a fast reroute (FRR) entry 268 according to the next hop information (PE1) of the MAC route, that 269 is, a MAC address entry on PE2, where the primary path points to 270 the CE1 link and the standby path points to PE1 272 4. PE2 also sends the MAC as a local MAC route to PE1 274 5. PE1 receives the MAC route advertised by PE2 and generates the FRR 275 entry with the MAC route learned by CE1, that is, the MAC address 276 entry on PE1, with the primary path pointing to the CE1 link and 277 the secondary path pointing to PE2 279 4.2 Handling Link Failure 281 1. When the link between PE1 and CE1 fails, PE1 withdraws the MAC 282 address that advertised to PE2 284 2. PE2 receives the MAC withdrawal from PE1, does not delete the MAC 285 immediately, but starts an aging timer, and does not withdraw the 286 MAC address that PE1 advertised to PE2. 288 3. When the aging timer expires, if PE2 cannot receive the traffic 289 from CE1, then PE2 withdraws the MAC address that was advertised 290 to PE2 by PE1 and deletes the MAC entry. If PE2 can communicate 291 directly with CE1, it just eliminates the FRR standby path to PE1. 293 5. IANA Considerations 295 IANA is requested to assign a new EVPN Extended Community SubType as 296 follows: 298 Sub-Type Value Name Reference 299 -------------- -------------------------------- ---------- 300 TBA VLAN-Redirect Extended Community [this doc] 302 6. Security Considerations 304 TBD 306 For general EVPN Security Considerations, see [RFC7432]. 308 Normative References 310 [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate 311 Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/RFC2119, 312 March 1997, . 314 [RFC7432] - Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 315 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 316 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 2015, 317 . 319 [RFC8174] - Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 320 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 321 2017, . 323 Informative References 325 [RFC7209] - Sajassi, A., Aggarwal, R., Uttaro, J., Bitar, N., 326 Henderickx, W., and A. Isaac, "Requirements for Ethernet VPN 327 (EVPN)", RFC 7209, DOI 10.17487/RFC7209, May 2014, 328 . 330 Acknowledgements 332 The authors of this document would like to thank the following for 333 their comments and review of this document: 335 TBD 337 Authors' Addresses 339 Donald E. Eastlake, 3rd 340 Huawei Technologies 341 1424 Pro Shop Court 342 Davenport, FL USA 344 Phone: +1-508-333-2270 345 Email: d3e3e3@gmail.com 347 Zhenbin Li 348 Huawei Technologies 349 Huawei Bldg., No. 156 Beiqing Road 350 Beijing 100095 China 352 Email: lizhenbin@huawei.com 354 Shunwan Zhang 355 Huawei Technologies 356 Huawei Bldg., No. 156 Beiqing Road 357 Beijing 100095 China 359 Email: zhuangshunwan@huawei.com 361 Haibo Wang 362 Huawei Technologies 363 Huawei Bldg., No. 156 Beiqing Road 364 Beijing 100095 China 366 Email: rainsword.wang@huawei.com 368 Copyright, Disclaimer, and Additional IPR Provisions 370 Copyright (c) 2018 IETF Trust and the persons identified as the 371 document authors. All rights reserved. 373 This document is subject to BCP 78 and the IETF Trust's Legal 374 Provisions Relating to IETF Documents 375 (http://trustee.ietf.org/license-info) in effect on the date of 376 publication of this document. 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