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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 (==), 1 comment (--). 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 1, 2018 February 28, 2018 9 EVPN multi-homing port-active load-balancing 10 draft-brissette-bess-evpn-mh-pa-01 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) 2018 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. Port-active over Integrated Routing-Bridging Interface . . . . 6 70 6. Convergence considerations . . . . . . . . . . . . . . . . . . 7 71 6. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 7 72 7. Overall Advantages . . . . . . . . . . . . . . . . . . . . . . 8 73 8 Security Considerations . . . . . . . . . . . . . . . . . . . . 9 74 9 IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 9 75 10 References . . . . . . . . . . . . . . . . . . . . . . . . . . 9 76 10.1 Normative References . . . . . . . . . . . . . . . . . . . 9 77 10.2 Informative References . . . . . . . . . . . . . . . . . . 9 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 since a long while. EVLAG simplifies 151 greatly that solution. Along with the simplification comes few 152 assumptions: 154 - Links in the Ethernet Bundle MUST operate in all-active load- 155 balancing mode 157 - Same LACP parameters MUST be configured on peering PEs such as 158 system id, port priority, etc. 160 Any discrepancies from this list is left for future study. 161 Furthermore, mis-configuration and mis-wiring detection across 162 peering PEs are also left for further study. 164 3. Port-active load-balancing procedure 166 Following steps describe the proposed procedure with EVLAG to support 167 port-active load-balancing mode: 169 1- ESI MUST be assigned per access interface as described in 170 [RFC7432], which may be auto derived or manually assigned. Access 171 interface MAY be a Layer-2 or Layer3 interface. 173 2- Ethernet-Segment MUST be configured in port-active load-balancing 174 mode on peering PEs for specific interface 175 3- Peering PEs MAY exchange only Ethernet-Segment route (Route Type- 176 4) 178 4- PEs in the redundancy group leverages DF election defined in 179 [draft-ietf-bess-evpn-df-election] to determine which PE keeps the 180 port in active mode and which one(s) keep it in standby mode. While 181 the DF election defined in [draft-ietf-bess-evpn-df-election] is per 182 granularity, for port-active mode of multi-homing, the DF 183 election is done per . The details of this algorithm are 184 described in Section 4. 186 5- DF router MUST keep corresponding access interface in up and 187 forwarding active state for that Ethernet-Segment 189 6- Non-DF routers MUST bring and keep peering access interface 190 attached to it in operational down state. If the interface is running 191 LACP protocol, then the non-DF PE MAY also set the LACP state to OOS 192 (Out of Sync) as opposed to interface state down. This allows for 193 better convergence on standby to active transition. 195 4. Algorithm to elect per port-active PE 197 The default mode of Designated Forwarder Election algorithm remains 198 as per [RFC7432] at the granularity of . 200 However, Highest Random Weight (HRW) algorithm defined in [draft- 201 ietf-bess-evpn-df-election] is leveraged, and modified to operate at 202 the granularity of rather than per . 204 Let Active(ESI) denote the PE that will be the active PE for port 205 with Ethernet segment identifier - ESI. The other PEs in the 206 redundancy group will be standby PE(s) for the same port (ES). Ai is 207 the address of the PEi and weight() is a pseudorandom function of ESi 208 and Ai, Wrand() function defined in [draft-ietf-bess-evpn-df- 209 election] is used as the Weight() function. 211 Active(ESI) = PEi: if Weight(ESI, Ai) >= Weight(ESI, Aj), for all j, 212 0 <= I,j <= Number of PEs in the redundancy group. In case of a tie, 213 choose the PE whose IP address is numerically the least. 215 5. Port-active over Integrated Routing-Bridging Interface 216 +-----+ 217 | PE3 | 218 |(IRB)| 219 | GW3 | 220 +-----+ 221 +-----------+ 222 | MPLS/IP | 223 | CORE | 224 +-----------+ 225 +-----+ +-----+ 226 | GW1 | | GW2 | 227 |(IRB)| |(IRB)| 228 | PE1 | | PE2 | 229 +-----+ +-----+ 230 | | | 231 I1 I2 I3 232 \ / | 233 \ / \ 234 +---+ +---+ 235 |CE1| |CE2| 236 +---+ +---+ 238 Figure 2. EVPN-IRB Port-active load-balancing 240 Figure 2 shows a simple network where EVPN-IRB is used for inter- 241 subnet connectivity. IRB interfaces on PE1 and PE2 are configured in 242 anycast gateway (same MAC, same IP). CE1 device is multi-homed to 243 both PE1 and PE2. The Ethernet-segment load-balancing mode, of the 244 connected CE1 to peering PEs, can be of any type e.g. all-active, 245 single-active or port-active. CE2 device is connected to a single PE 246 (PE2). It operates as single-homed device via an orphan port I3. 247 Finally, port-active load-balancing is apply to IRB interface on 248 peering PEs (PE1 and PE2). Manual Ethernet-Segment Identifier is 249 assigned per IRB interface. ESI auto-generation is also possible 250 based on the IRB anycast IP address. 252 DF election is performed between peering PE over IRB interface (per 253 ESI/EVI). Designed forwarder (DF) IRB interface remains in up state. 254 Non-designated forwarder (NDF) IRB interface goes down. Furthermore, 255 if all access interfaces connected to an IRB interface are down state 256 (failure or admin) OR in blocked forward state(NDF), IRB interface is 257 brought down. For example, interface I3 fails at the same time than 258 interface I2 (in single-active load-balancing mode) is in blocked 259 forwarding state. 261 In the example where IRB on PE2 is NDF, all L3 traffic coming from 262 PE3 is going via PE1. An IRB interface in down state doesn't attract 263 traffic from core side. CE2 device reachability is done via an L2 264 subnet stretch between PE1 and PE2. Therefore L3 traffic coming from 265 PE3 destinated to CE2 goes via GW1 first, then via an L2 connection 266 to PE2 and finally via interface I3 to CE2 device. 268 There are many reasons of configuring port-active load-balancing mode 269 over IRB interface: 270 - Ease replacement of legacy technology such VRRP / HSRP 272 - Better scalability than legacy protocols 274 - Traffic predictability 276 - Optimal routing and entirely independent of load-balancing mode 277 configured on any access interfaces 279 6. Convergence considerations 281 To improve the convergence, upon failure and recovery, when port- 282 active load-balancing mode is used, some advanced synchronization 283 between peering PEs may be required. Port-active is challenging in a 284 sense that the "standby" port is in down state. It takes some time to 285 bring a "standby" port in up-state and settle the network. For IRB 286 and L3 services, ARP / MLD cache may be synchronized. Moreover, 287 associated VRF tables may also be synchronized. For L2 services, MAC 288 table synchronization may be considered. Finally, using bundle- 289 Ethernet interface, where LACP is running, is usually a smart thing 290 since it provides the ability to set the "standby" port in "out-of- 291 sync" state aka "warm-standby". 293 6. Applicability 295 A common deployment is to provide L2 or L3 service on the PEs 296 providing multi-homing. The services could be any L2 EVPN such as 297 EVPN VPWS, EVPN [RFC7432], etc. L3 service could be in VPN context 298 [RFC4364] or in global routing context. When a PE provides first hop 299 routing, EVPN IRB could also be deployed on the PEs. The mechanism 300 defined in this draft is used between the PEs providing the L2 or L3 301 service, when the requirement is to use per port active. 303 A possible alternate solution is the one described in this draft is 304 MC-LAG with ICCP [RFC7275] active-standby redundancy. However, ICCP 305 requires LDP to be enabled as a transport of ICCP messages. There are 306 many scenarios where LDP is not required e.g. deployments with VXLAN 307 or SRv6. The solution defined in this draft with EVPN does not 308 mandate the need to use LDP or ICCP and is independent of the overlay 309 encapsulation. 311 7. Overall Advantages 313 There are many advantages in EVLAG to support port-active load- 314 balancing mode. Here is a non-exhaustive list: 316 - Open standards based per interface single-active redundancy 317 mechanism that eliminates the need to run ICCP and LDP. 319 - Agnostic of underlay technology (MPLS, VXLAN, SRv6) and associated 320 services (L2, L3, Bridging, E-LINE, etc). 322 - Provides a way to enable deterministic QOS over MC-LAG attachment 323 circuits 325 - Fully compliant with RFC-7432, does not require any new protocol 326 enhancement to existing EVPN RFCs. 328 - Can leverage various DF election algorithms e.g. modulo, HRW, etc. 330 - Replaces legacy MC-LAG ICCP-based solution, and offers following 331 additional benefits: 333 - Efficiently supports 1+N redundancy mode (with EVPN using BGP 334 RR) where as ICCP requires full mesh of LDP sessions among PEs in 335 redundancy group 337 - Fast convergence with mass-withdraw is possible with EVPN, no 338 equivalent in ICCP 340 - Customers want per interface single-active redundancy, but don't 341 want to enable LDP (e.g. they may be running VXLAN or SRv6 in the 342 network). Currently there is no alternative to this. 344 8 Security Considerations 346 The same Security Considerations described in [RFC7432] are valid for 347 this document. 349 9 IANA Considerations 351 There are no new IANA considerations in this document. 353 10 References 355 10.1 Normative References 357 [RFC7432] Sajassi, A., Ed., Aggarwal, R., Bitar, N., Isaac, A., 358 Uttaro, J., Drake, J., and W. Henderickx, "BGP MPLS-Based 359 Ethernet VPN", RFC 7432, DOI 10.17487/RFC7432, February 360 2015, . 362 [RFC7275] Martini, L., Salam, S., Sajassi, A., Bocci, M., 363 Matsushima, S., and T. Nadeau, "Inter-Chassis 364 Communication Protocol for Layer 2 Virtual Private Network 365 (L2VPN) Provider Edge (PE) Redundancy", RFC 7275, DOI 366 10.17487/RFC7275, June 2014, . 369 10.2 Informative References 371 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 372 Requirement Levels", BCP 14, RFC 2119, DOI 373 10.17487/RFC2119, March 1997, . 376 [RFC4364] Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private 377 Networks (VPNs)", RFC 4364, DOI 10.17487/RFC4364, February 378 2006, . 380 Authors' Addresses 382 Patrice Brissette 383 Cisco Systems 384 EMail: pbrisset@cisco.com 386 Samir Thoria 387 Cisco Systems 388 EMail: sthoria@cisco.com 390 Ali Sajassi 391 Cisco Systems 392 EMail: sajassi@cisco.com