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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 INTERNET-DRAFT Patrice Brissette 3 Intended Status: Proposed Standard Samir Thoria 4 Ali Sajassi 5 Cisco Systems 7 Expires: September 12, 2019 March 11, 2019 9 EVPN multi-homing port-active load-balancing 10 draft-brissette-bess-evpn-mh-pa-03 12 Abstract 14 The Multi-Chassis Link Aggregation Group (MC-LAG) technology enables 15 the establishment of a logical port-channel connection with a 16 redundant group of independent nodes. The purpose of multi-chassis 17 LAG is to provide a solution to achieve higher network availability, 18 while providing different modes of sharing/balancing of traffic. EVPN 19 standard defines EVPN based MC-LAG with single-active and all-active 20 multi-homing load-balancing mode. The current draft expands on 21 existing redundancy mechanisms supported by EVPN and introduces 22 support of port-active load-balancing mode. In the current draft, 23 port-active load-balancing mode is also referred to as per interface 24 active/standby. 26 Status of this Memo 28 This Internet-Draft is submitted to IETF in full conformance with the 29 provisions of BCP 78 and BCP 79. 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF), its areas, and its working groups. Note that 33 other groups may also distribute working documents as 34 Internet-Drafts. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 The list of current Internet-Drafts can be accessed at 42 http://www.ietf.org/1id-abstracts.html 44 The list of Internet-Draft Shadow Directories can be accessed at 45 http://www.ietf.org/shadow.html 47 Copyright and License Notice 49 Copyright (c) 2019 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 65 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4 66 2. Multi-Chassis Ethernet Bundles . . . . . . . . . . . . . . . . 4 67 3. Port-active load-balancing procedure . . . . . . . . . . . . . 4 68 4. Algorithm to elect per port-active PE . . . . . . . . . . . . . 5 69 5. Convergence considerations . . . . . . . . . . . . . . . . . . 5 70 6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 6 71 7. Overall Advantages . . . . . . . . . . . . . . . . . . . . . . 6 72 8 Security Considerations . . . . . . . . . . . . . . . . . . . . 8 73 9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8 74 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 8 75 11 References . . . . . . . . . . . . . . . . . . . . . . . . . . 8 76 11.1 Normative References . . . . . . . . . . . . . . . . . . . 8 77 11.2 Informative References . . . . . . . . . . . . . . . . . . 8 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9 80 1 Introduction 82 EVPN, as per [RFC7432], provides all-active per flow load balancing 83 for multi-homing. It also defines single-active with service carving 84 mode, where one of the PEs, in redundancy relationship, is active per 85 service. 87 While these two multi-homing scenarios are most widely utilized in 88 data center and service provider access networks, there are scenarios 89 where active-standby per interface multi-homing redundancy is useful 90 and required. Main consideration for this mode of redundancy is the 91 determinism of traffic forwarding through specific interface rather 92 than statistical per flow load balancing across multiple PEs 93 providing multi-homing. The determinism provided by active-standby 94 per interface is also required for certain QOS features to work. 95 While using this mode, customers also expect minimized convergence 96 during failures. A new term of load-balancing mode "port-active load- 97 balancing" is then defined. 99 This draft describes how that new redundancy mode can be supported 100 via EVPN. 102 +-----+ 103 | PE3 | 104 +-----+ 105 +-----------+ 106 | MPLS/IP | 107 | CORE | 108 +-----------+ 109 +-----+ +-----+ 110 | PE1 | | PE2 | 111 +-----+ +-----+ 112 | | 113 I1 I2 114 \ / 115 \ / 116 +---+ 117 |CE1| 118 +---+ 120 Figure 1. MC-LAG topology 122 Figure 1 shows a MC-LAG multi-homing topology where PE1 and PE2 are 123 part of the same redundancy group providing multi-homing to CE1 via 124 interfaces I1 and I2. Interfaces I1 and I2 are Bundle-Ethernet 125 interfaces running LACP protocol. The core, shown as IP or MPLS 126 enabled, provides wide range of L2 and L3 services. MC-LAG multi- 127 homing functionality is decoupled from those services in the core and 128 it focuses on providing multi-homing to CE. With per-port 129 active/standby redundancy, only one of the two interface I1 or I2 130 would be in forwarding, the other interface will be in standby. This 131 also implies that all services on the active interface are in active 132 mode and all services on the standby interface operate in standby 133 mode. When EVPN is used to provide MC-LAG functionality, we refer to 134 it as EVLAG in this draft. 136 1.1 Terminology 138 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 139 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 140 document are to be interpreted as described in RFC 2119 [RFC2119]. 142 2. Multi-Chassis Ethernet Bundles 144 When a CE is multi-homed to a set of PE nodes using the [802.1AX] 145 Link Aggregation Control Protocol (LACP), the PEs must act as if they 146 were a single LACP speaker for the Ethernet links to form a bundle, 147 and operate as a Link Aggregation Group (LAG). To achieve this, the 148 PEs connected to the same multi-homed CE must synchronize LACP 149 configuration and operational data among them. ICCP-based protocol 150 has been used for that purpose. EVPN LAG simplifies greatly that 151 solution. Along with the simplification comes few assumptions: 153 - Links in the Ethernet Bundle MUST operate in all-active load- 154 balancing mode 156 - Same LACP parameters MUST be configured on peering PEs such as 157 system id, port priority, etc. 159 Any discrepancies from this list is left for future study. 160 Furthermore, mis-configuration and mis-wiring detection across 161 peering PEs are also left for further study. 163 3. Port-active load-balancing procedure 165 Following steps describe the proposed procedure with EVPN LAG to 166 support port-active load-balancing mode: 168 1- ESI MUST be assigned per access interface as described in 169 [RFC7432], which may be auto derived or manually assigned. Access 170 interface MAY be a Layer-2 or Layer3 interface. 172 2- Ethernet-Segment MUST be configured in port-active load-balancing 173 mode on peering PEs for specific interface 174 3- Peering PEs MAY exchange only Ethernet-Segment route (Route Type- 175 4) 177 4- PEs in the redundancy group leverages DF election defined in 178 [EVPN-DF] to determine which PE keeps the port in active mode and 179 which one(s) keep it in standby mode. While the DF election defined 180 in [EVPN-DF] is per granularity, for port-active mode of 181 multi-homing, the DF election is done per . The details of this 182 algorithm are described in Section 4. 184 5- DF router MUST keep corresponding access interface in up and 185 forwarding active state for that Ethernet-Segment 187 6- Non-DF routers MAY bring and keep peering access interface 188 attached to it in operational down state. If the interface is running 189 LACP protocol, then the non-DF PE MAY also set the LACP state to OOS 190 (Out of Sync) as opposed to interface state down. This allows for 191 better convergence on standby to active transition. 193 7- For EVPN-VPWS service, the usage of primary/backup bits of EVPN 194 Layer2 attributes extended community [RFC8214] is highly recommended 195 to achieve better convergence. 197 4. Algorithm to elect per port-active PE 199 The default DF Election algorithm, or modulus-based algorithm as in 200 [RFC7432], is used here also, at the granularity of only. For 201 Modulo calculation, byte 10 of the ESI is used. 203 Highest Random Weight (HRW) algorithm defined in [EVPN-DF] MAY also 204 be used and signaled, and modified to operate at the granularity of 205 rather than per . 207 Let Active(ESI) denote the PE that will be the active PE for port 208 with Ethernet segment identifier - ESI. The other PEs in the 209 redundancy group will be standby PE(s) for the same port (ES). Ai is 210 the address of the PEi and weight() is a pseudorandom function of ESi 211 and Ai, Wrand() function defined in [EVPN-DF] is used as the Weight() 212 function. 214 Active(ESI) = PEi: if Weight(ESI, Ai) >= Weight(ESI, Aj), for all j, 215 0 <= I,j <= Number of PEs in the redundancy group. In case of a tie, 216 choose the PE whose IP address is numerically the least. 218 5. Convergence considerations 220 To improve the convergence, upon failure and recovery, when port- 221 active load-balancing mode is used, some advanced synchronization 222 between peering PEs may be required. Port-active is challenging in a 223 sense that the "standby" port is in down state. It takes some time to 224 bring a "standby" port in up-state and settle the network. For IRB 225 and L3 services, ARP / MLD cache may be synchronized. Moreover, 226 associated VRF tables may also be synchronized. For L2 services, MAC 227 table synchronization may be considered. Finally, using bundle- 228 Ethernet interface, where LACP is running, is usually a smart thing 229 since it provides the ability to set the "standby" port in "out-of- 230 sync" state aka "warm-standby". 232 6. Applicability 234 A common deployment is to provide L2 or L3 service on the PEs 235 providing multi-homing. The services could be any L2 EVPN such as 236 EVPN VPWS, EVPN [RFC7432], etc. L3 service could be in VPN context 237 [RFC4364] or in global routing context. When a PE provides first hop 238 routing, EVPN IRB could also be deployed on the PEs. The mechanism 239 defined in this draft is used between the PEs providing the L2 and/or 240 L3 service, when the requirement is to use per port active. 242 A possible alternate solution is the one described in this draft is 243 MC-LAG with ICCP [RFC7275] active-standby redundancy. However, ICCP 244 requires LDP to be enabled as a transport of ICCP messages. There are 245 many scenarios where LDP is not required e.g. deployments with VXLAN 246 or SRv6. The solution defined in this draft with EVPN does not 247 mandate the need to use LDP or ICCP and is independent of the 248 underlay encapsulation. 250 7. Overall Advantages 252 There are many advantages in EVPN LAG to support port-active load- 253 balancing mode. Here is a non-exhaustive list: 255 - Open standards based per interface single-active redundancy 256 mechanism that eliminates the need to run ICCP and LDP. 258 - Agnostic of underlay technology (MPLS, VXLAN, SRv6) and associated 259 services (L2, L3, Bridging, E-LINE, etc). 261 - Provides a way to enable deterministic QOS over MC-LAG attachment 262 circuits 264 - Fully compliant with RFC-7432, does not require any new protocol 265 enhancement to existing EVPN RFCs. 267 - Can leverage various DF election algorithms e.g. modulo, HRW, etc. 269 - Replaces legacy MC-LAG ICCP-based solution, and offers following 270 additional benefits: 272 - Efficiently supports 1+N redundancy mode (with EVPN using BGP 273 RR) where as ICCP requires full mesh of LDP sessions among PEs in 274 redundancy group 276 - Fast convergence with mass-withdraw is possible with EVPN, no 277 equivalent in ICCP 279 - Customers want per interface single-active redundancy, but don't 280 want to enable LDP (e.g. they may be running VXLAN or SRv6 in the 281 network). Currently there is no alternative to this. 283 8 Security Considerations 285 The same Security Considerations described in [RFC7432] are valid for 286 this document. 288 9 IANA Considerations 290 There are no new IANA considerations in this document. 292 10. Acknowledgements 294 Authors would like to thank Luc Andre Burdet for valuable reviews and 295 inputs. 297 11 References 299 11.1 Normative References 301 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 302 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 303 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 304 2015, . 306 [RFC7275] Martini, L., Salam, S., Sajassi, A., Bocci, M., 307 Matsushima, S., and T. Nadeau, "Inter-Chassis 308 Communication Protocol for Layer 2 Virtual Private Network 309 (L2VPN) Provider Edge (PE) Redundancy", RFC 7275, DOI 310 10.17487/RFC7275, June 2014, . 313 [RFC8214] Boutros, S., Sajassi, A., Salam, S., Drake, J., and J. 314 Rabadan, "Virtual Private Wire Service Support in Ethernet 315 VPN", RFC 8214, DOI 10.17487/RFC8214, August 2017, 316 . 318 [EVPN-DF] Rabadan J., Mohanty S. et al. "Framework for EVPN 319 Designated Forwarder Election Extensibility", draft- 320 ietf-bess-evpn-df-election- framework-07, work-in- 321 progress, December, 2018. 323 11.2 Informative References 325 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 326 Requirement Levels", BCP 14, RFC 2119, DOI 327 10.17487/RFC2119, March 1997, . 330 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 331 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 332 2006, . 334 Authors' Addresses 336 Patrice Brissette 337 Cisco Systems 338 EMail: pbrisset@cisco.com 340 Samir Thoria 341 Cisco Systems 342 EMail: sthoria@cisco.com 344 Ali Sajassi 345 Cisco Systems 346 EMail: sajassi@cisco.com