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'IS-IS' -- Obsolete informational reference (is this intentional?): RFC 6439 (Obsoleted by RFC 8139) Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 4 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT Donald Eastlake 2 Intended status: Proposed Standard Mingui Zhang 3 Updates: 6325, 7177 Huawei 4 Ayan Banerjee 5 Cisco 6 Vishwas Manral 7 Ionos 8 Expires: December 31, 2015 July 1, 2015 10 TRILL: Multi-Topology 11 13 Abstract 14 This document specifies extensions to the IETF TRILL (Transparent 15 Interconnection of Lots of Links) protocol to support multi-topology 16 routing of unicast and multi-destination traffic based on IS-IS 17 (Intermediate System to Intermediate System) multi-topology specified 18 in RFC 5120. It updates RFC 6325 and RFC 7177. 20 Status of This Memo 22 This Internet-Draft is submitted to IETF in full conformance with the 23 provisions of BCP 78 and BCP 79. 25 Distribution of this document is unlimited. Comments should be sent 26 to the TRILL working group mailing list. 28 Internet-Drafts are working documents of the Internet Engineering 29 Task Force (IETF), its areas, and its working groups. Note that 30 other groups may also distribute working documents as Internet- 31 Drafts. 33 Internet-Drafts are draft documents valid for a maximum of six months 34 and may be updated, replaced, or obsoleted by other documents at any 35 time. It is inappropriate to use Internet-Drafts as reference 36 material or to cite them other than as "work in progress." 38 The list of current Internet-Drafts can be accessed at 39 http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft 40 Shadow Directories can be accessed at 41 http://www.ietf.org/shadow.html. 43 Table of Contents 45 1. Introduction............................................3 46 1.1 Terminology............................................4 48 2. Topologies..............................................5 49 2.1 Special Topology Zero..................................5 50 2.2 Links and Multi-Topology...............................5 51 2.3 TRILL Switches and Multi-Topology......................5 52 2.4 TRILL Data Packets and Multi-Topology..................6 53 2.4.1 Explicit Topology Labeling Support...................6 54 2.4.2 Explicit Topology Labels.............................7 56 3. TRILL Multi-Topology Adjacency and Routing..............9 57 3.1 Adjacency (Updates to RFC 7177)........................9 58 3.2 TRILL Switch Nicknames.................................9 59 3.3 TRILL Unicast Routing.................................10 60 3.4 TRILL Multi-Destination Routing.......................10 61 3.4.1 Distribution Trees..................................10 62 3.4.2 Multi-Access Links..................................12 64 4. Mixed Links............................................13 66 5. Other Multi-Topology Considerations....................14 67 5.1 Address Learning......................................14 68 5.1.1 Data Plane Learning.................................14 69 5.1.2 Multi-Topology ESADI................................14 70 5.2 Legacy Stubs..........................................14 71 5.3 RBridge Channel Messages..............................14 72 5.4 Implementations Considerations........................15 74 6. Allocation Considerations..............................16 75 6.1 IEEE Registration Authority Considerations............16 76 6.2 IANA Considerations...................................16 78 7. Security Considerations................................17 80 Normative References......................................18 81 Informative References....................................19 82 Acknowledgements..........................................20 84 Appendix A: Differences from RFC 5120.....................21 86 Authors' Addresses........................................22 88 1. Introduction 90 This document specifies extensions to the IETF TRILL (Transparent 91 Interconnection of Lots of Links) protocol [RFC6325] [RFC7176] 92 [RFC7177] to support multi-topology routing for both unicast and 93 multi-destination traffic based on IS-IS (Intermediate System to 94 Intermediate System, [IS-IS]) multi-topology [RFC5120]. 95 Implementation and use of multi-topology are optional and use 96 requires configuration. It is anticipated that not all TRILL campuses 97 will need or use multi-topology. 99 Multi-topology creates different topologies or subsets from a single 100 physical TRILL campus topology. This is different from Data Labels 101 (VLANs and Fine Grained Labels [RFC7172]). Data Labels specify 102 communities of end stations and can be viewed as creating virtual 103 topologies of end station connectivity. However, in a single topology 104 TRILL campus, TRILL Data packets can use any part of the physical 105 topology of TRILL switches and links between TRILL switches, 106 regardless of the Data Label of that packet's payload. In a multi- 107 topology TRILL campus, TRILL data packets in a topology are 108 restricted to the physical TRILL switches and links that are in their 109 topology but may still use any of the TRILL switches and links in 110 their topology regardless of the Data Label of their payload. 112 The essence of multi-topology behavior is that a multi-topology 113 router classifies packets as to the topology within which they should 114 be routed and uses logically different routing tables for different 115 topologies. If routers in the network do not agree on the topology 116 classification of packets or links, persistent routing loops can 117 occur. 119 The multi-topology TRILL extensions can be used for a wide variety of 120 purposes, such as maintaining separate routing domains for isolated 121 multicast or IPv6 islands, routing a class of traffic so that it 122 avoids certain TRILL switches that lack some characteristic needed by 123 that traffic, or making a class of traffic avoid certain links due to 124 security, reliability, or other concerns. 126 It is possible for a particular topology to not be fully connected 127 resulting in two or more islands of that topology. In that case, end 128 station connected in that topology to different islands will be 129 unable to communicate with each other. 131 Multi-topology TRILL supports regions of topology ignorant TRILL 132 switches as part of an multi-topology campus; however, such regions 133 can only ingress, egress, or transit TRILL Data frames in the special 134 base topology zero. 136 1.1 Terminology 138 The terminology and acronyms of [RFC6325] are used in this document 139 along with the following: 141 campus - The name for a TRILL network, like "bridged LAN" is a 142 name for a bridged network. It does not have any academic 143 implication. 145 FGL - Fine-Grained Labeling or Fine-Grained Labeled or Fine- 146 Grained Label [RFC7176]. 148 LSP - [IS-IS] Link State PDU (Protocol Data Unit). For TRILL this 149 include L1-LSPs and E-L1FS-LSPs [rfc7180bis]. 151 MT - Multi-Topology, this document and [RFC5120]. 153 MT TRILL Switch - A FGL TRILL switch supporting the multi-topology 154 feature specified in this document. 156 RBridge - "Routing Bridge", an alternative name for a TRILL 157 switch. 159 TRILL - Transparent Interconnecton of Lots of Links or Tunneled 160 Routing in the Link Layer [RFC6325]. 162 TRILL Switch - A switch implementing the TRILL protocol. 164 VL - VLAN Labeling or VLAN Labeled or VLAN Label [RFC7172]. 166 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 167 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 168 document are to be interpreted as described in [RFC2119]. 170 2. Topologies 172 In TRILL multi-topology, a topology is a subset of the TRILL switches 173 and of the links between TRILL switches in a TRILL campus. TRILL Data 174 packets are constrained to the subset of switches and links 175 corresponding to the packet's topology. TRILL multi-topology is based 176 on [RFC5120] IS-IS multi-topology. See Appendix A for differences 177 between TRILL multi-topology and [RFC5120]. 179 The zero topology is special as described in Section 2.1. Sections 180 2.2, 2.3, and 2.4 discuss the topology of links, TRILL switches, and 181 TRILL Data packets respectively. 183 2.1 Special Topology Zero 185 The zero topology is special as the default base topology. All TRILL 186 switches and links are considered to be in and MUST support topology 187 zero. Thus, for example, topology zero can be used for general TRILL 188 switch access within a campus for management messages, BFD messages 189 [RFC7175], RBridge Channel messages [RFC7178], and the like. 191 2.2 Links and Multi-Topology 193 Multi-topology TRILL switches advertise the topologies for which they 194 are willing to send and received TRILL Data packets on a port by 195 listing those topologies in one or more MT TLVs [RFC5120] appearing 196 in every TRILL Hello [RFC7177] they send out that port except that 197 they MUST handle topology zero, which it is optional to list. 199 A link is only usable for TRILL Data packets in non-zero topology T 200 if (1) all TRILL switch ports on the link advertise topology T 201 support in their Hellos and (2) if any TRILL switch port on the link 202 requires explicit TRILL Data packet topology labeling (see Section 203 2.4) every other TRILL switch port on the link is capable of 204 generating explicit packet topology labeling. 206 2.3 TRILL Switches and Multi-Topology 208 A TRILL switch advertises the topologies that it supports by listing 209 them in one or more MT TLVs [RFC5120] in its LSP except that it MUST 210 support topology zero which is optional to list. 212 There is no general "MT capability bit". A TRILL switch advertises 213 that it is MT capable by advertising in its LSP support for any 214 topology or topologies with the MT TLV, even if it just explicitly 215 advertises support for topology zero. 217 2.4 TRILL Data Packets and Multi-Topology 219 Commonly, the topology of a TRILL Data packet is determined from 220 either (1) some field or fields present in the packet itself or (2) 221 the port on which the packet was received; however optional explicit 222 topology labeling of TRILL Data packets is also proved. This can be 223 included in the data labeling area of TRILL Data packets as specified 224 below. 226 Examples of fields that may sometimes used to determine topology are 227 values or ranges of values of the payload VLAN or Fine Grained Label 228 [RFC7172], packet priority, IP version (IPv6 versus IPv4) or IP 229 protocol, Ethertype, unicast versus multi-destination payload, IP 230 Differentiated Services Code Point (DSCP) bits, or the like. 232 "Multi-topology" does not apply to TRILL IS-IS packets or to link 233 level control frames. Those message are link local and can be thought 234 of as being outside all topologies. "Multi-topology" only applies to 235 TRILL Data packets. 237 2.4.1 Explicit Topology Labeling Support 239 Support of the explicit topology label is optional even for MT TRILL 240 switches. Support could depend on port hardware and is indicated by 241 a two-bit capability field in the Port TRILL Version sub-TLV 242 [RFC7176] appearing in the Port Capabilities TLV in Hellos. If there 243 is no Port TRILL Capabilities sub-TLV in a Hello, then it is assumed 244 that explicit topology labeling is not supported on that port. See 245 the table below for the meaning of values of the Explicit Topology 246 capability field: 248 Value Meaning 249 ----- ------- 250 0 No support. Cannot send TRILL Data packets with an explicit 251 topology label and should treat as erroneous and discard any 252 data packet received with a topology label. 253 1 Capable of inserting an explicit topology label in data 254 packets sent and tolerant of such labels in received data 255 packets. Such a port is capable of determining TRILL Data 256 packet topology without an explicit lable for all of the 257 topologies it supports and thus does not require such a label 258 in received TRILL Data packets. On receiving a packet whose 259 explicit topology label differs from the ports topology 260 determination for that packet, the TRILL switch MUST discard 261 the packet. 262 2/3 Requires an explicit topology label in received TRILL Data packets 263 except for topology zero. Any TRILL Data packets received 264 without such a label is classified as being in topology zero. 265 Also capable of inserting an explicit topology label in TRILL 266 Data packets sent. (Values 2 and 3 are treated the same, 267 which is the same as saying that if the 2 bit is on, the 1 268 bit is ignored.) 270 A TRILL switch advertising in a Hello on Port P support for topology 271 T but not advertising in those Hellos that it requires explicit 272 topology labeling is assumed to have the ability and configuration to 273 correctly classify TRILL Data packets into topology T by examination 274 of those TRILL Data packets or by using the fact that they are 275 arriving at port P. 277 When a TRILL switch transmits a TRILL Data packet onto a link, if any 278 other TRILL switch on that link requires explicit topology labeling, 279 an explicit topology label MUST be included. If a label is not so 280 required but all other TRILL switches on that link support explicit 281 topology labeling, then such a label MAY be included. 283 2.4.2 Explicit Topology Labels 285 The TRILL MT label is structured as follows: 287 0 1 2 3 288 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 1 289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 290 | TRILL-MT Ethertype TBD | RESV | MT-ID | 291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 293 Figure 1. TRILL MT Label 295 where RESV is a 4-bit reserved field that MUST be sent as zero and 296 ignored on receipt and MT-ID is the 12-bit topology of the TRILL Data 297 packet using the topology number space of the MT TLV [RFC5120]. With 298 the addition of the TRILL MT label, the four standardized content 299 varieties for the TRILL Data packet data labeling area (the area 300 after the Inner.MacSA and before the payload) are as show below. 301 {PRI, D} is a 3-bit priority and a drop eligibility indicator bit 302 [rfc7180bis]. All MT TRILL switches MUST support FGL and thus MUST 303 support all four data labeling area contents shown below. 305 1. C-VLAN [RFC6325] 307 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 308 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 1 309 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 310 | 0x8100 | PRI |D| VLAN ID | 311 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 313 2. FGL [RFC7172] 315 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 316 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 1 317 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 318 | 0x893B | PRI |D| FGL High Part | 319 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 320 | 0x893B | PRI |D| FGL Low Part | 321 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 323 3. MT C-VLAN [this document] 325 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 326 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 1 327 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 328 | TRILL-MT Ethertype TBD | RESV | MT-ID | 329 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 330 | 0x8100 | PRI |D| VLAN ID | 331 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 333 4. MT FGL [this document] [RFC7172] 335 1 1 1 1 1 1 1 1 1 1 2 2 2 2 2 2 2 2 2 2 3 3 336 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 1 337 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 338 | TRILL-MT Ethertype TBD | RESV | MT-ID | 339 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 340 | 0x893B | PRI |D| FGL High Part | 341 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 342 | 0x893B | PRI |D| FGL Low Part | 343 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 345 Inclusion of S-VLAN or other stacked tags is beyond the scope of this 346 document but, as stated in [RFC6325], is an obvious extension. 348 3. TRILL Multi-Topology Adjacency and Routing 350 Routing calculations in IS-IS are based on adjacency. Section 3.1 351 specifies multi-topology updates to the TRILL adjacency 352 specification. Section 3.2 describes the handling of nicknames. 353 Sections 3.3 and 3.4 specify how unicast and multi-destination TRILL 354 multi-topology routing differ from the TRILL base protocol. 356 3.1 Adjacency (Updates to RFC 7177) 358 There is no change in the determination or announement of adjacency 359 for topology zero as specified in [RFC7177]. When an adjacency 360 reaches the Report state as specified in [RFC7177], the adjacency is 361 announced for topology zero in LSPs using the Extended Intermediate 362 System Reachability TLV (#22). 364 Adjacency is announced for non-zero topologies in LSPs using the MT 365 Reachable Intermediate Systems TLV as specified in [RFC5120]. The 366 ports on a TRILL link are reported as adjacent for non-zero topology 367 T if and only if that adjacency is in the Report state [RFC7177] and 368 the two conditions listed in Section 2.2 are true, namely: 370 1. All the ports on the link are announcing support of topology T. 372 2. If any port announces that it requires explicit topology labeling 373 (Explicit Topology capability field value 2 or 3), all other ports 374 advertise that they are capable of producing such labeling 375 (Explicit Topology capability field value of 1, 2, or 3). 377 3.2 TRILL Switch Nicknames 379 TRILL switches are usually identified within the TRILL protocol (for 380 example in the TRILL Header) by nicknames [RFC6325] [rfc7180bis]. 381 Such nicknames can be viewed as simply 16-bit abbreviation for a 382 TRILL switch's (or pseudo-node's) 7-byte IS-IS ID. A TRILL switch or 383 pseudo-node can have more than one nickname, each of which identifies 384 it. 386 Nicknames are common across all topologies, just as IS-IS IDs are. 387 Nicknames are determined as specified in [RFC6325] and [rfc7180bis] 388 using only the Nickname sub-TLVs appearing in Router Capabilities 389 TLVs (#242) advertised by TRILL switches. In particular, the nickname 390 allocation algorithm ignores Nickname sub-TLVs that appear in MT 391 Router Capability TLVs (#144). (However, nickname sub-TLVs that 392 appear in MT Router Capability TLVs with a non-zero topology do 393 affect the choice of distribution tree roots as described in Section 394 3.4.1.) 396 To minimize transient inconsistencies, all Nickname sub-TLVs 397 advertised by a TRILL switch for a particular nickname, whether in 398 Router Capability or MT Router Capability TLVs, SHOULD appear in the 399 same LSP. If that is not the case, then all LSPs in which they do 400 occur should be flooded as an atomic action. 402 3.3 TRILL Unicast Routing 404 TRILL Data packets being TRILL unicast (those with TRILL Header M bit 405 = 0) are routed based on the egress nickname using logically separate 406 forwarding tables per topology where each such table has been 407 calculated based on least cost routing within the particular 408 topology. Thus, the next hop when forwarding TRILL Data packets is 409 determined by a lookup logically based on {topology, egress 410 nickname}. 412 3.4 TRILL Multi-Destination Routing 414 TRILL sends multi-destination data packets (those packets with TRILL 415 Header M bit = 1) over a distribution tree. Trees are designated by 416 nicknames that appear in the "egress nickname" field of multi- 417 destination TRILL Data packets. To constrain multi-destination 418 packets to a topology and still distribute them properly requires the 419 use of a distribution tree constrained to that topology. Handling 420 such TRILL Data packets and distribution trees in MT is as described 421 in the subsections below. 423 3.4.1 Distribution Trees 425 General provisions for distribution trees and how those trees are 426 determined are as specified in [RFC6325], [rfc7180bis], and 427 [RFC7172]. The distribution trees for topology zero are determined as 428 specified in those references and are the same as they would be with 429 topology-ignorant TRILL switches. 431 The TRILL distribution tree construction and packet handling for some 432 non-zero topology T are determine as specified in [RFC6325], 433 [rfc7180bis], and [RFC7172] with the following changes: 435 o As specified in [RFC5120], only links usable with topology T 436 TRILL Data frames are considered when building a distribution 437 tree for topology T. As a result, such trees are automatically 438 limited to and separately span every internally connected 439 island of topology T. In other words, if non-zero topology T 440 consists of disjoint islands, distribution tree construction 441 for topology T is local to each such island. 443 o Only the Nickname sub-TLV, Trees sub-TLV, Tree Identifiers sub- 444 TLV, and Trees Used sub-TLV occurring in an MT Router 445 Capabilities TLV (#144) specifying topology T are used in 446 determining the tree root(s), if any, for topology T. 448 + There may be non-zero topologies with no multi-destination 449 traffic. For example, if only known destination unicast IPv6 450 TRILL Data packets were in topology T and all multi- 451 destination IPv6 TRILL Data packets were in some other 452 topology, there would be no need for a distribution tree for 453 topology T. For this reasons, a Number of Trees to Compute 454 of zero in the Trees sub-TLV for the TRILL switch holding 455 the highest priority to be a tree root for a non-zero 456 topology T is honored and causes no distribution trees to be 457 calculated for non-zero topology T. This is different from 458 the base topology zero where, as specified in [RFC6325], a 459 zero Number of Trees to Compute causes one tree to be 460 computed. 462 o Nicknames are allocated as described in Section 3.2. If a 463 TRILL switch advertising that it provides topology T service 464 holds nickname N, the priority of N to be a tree root is given 465 by the tree root priority field of the Nickname sub-TLV that 466 has N in its nickname field and occurs in a topology T MT 467 Router Capabilities TLV advertised by that TRILL switch. If no 468 such Nickname sub-TLV can be found, the priority of N to be a 469 tree root is the default for an FGL TRILL switch as specified 470 in [RFC7172]. 472 + There could be multiple topology T Nickname sub-TLVs for N 473 being advertised for a particular RBridge or pseudo-node, 474 due to transient conditions or errors. In that case, the one 475 in the lowest numbered LSP fragment is used and if there are 476 multiple in that fragment, the one with the smallest offset 477 from the beginning of the LSP is used. 479 o Tree pruning for topology T uses only the Interested VLANs and 480 Interested Labels sub-TLVs [RFC7176] advertised in MT Router 481 Capabilities TLVs for topology T. 483 An MT TRILL switch MUST have logically separate routing tables per 484 topology for the forwarding of multi-destination traffic. 486 3.4.2 Multi-Access Links 488 Multi-destination TRILL Data packets are forwarded on broadcast 489 (multi-access) links in such a way as to be received by all other 490 TRILL switch ports on the link. For example, on Ethernet links they 491 are sent with a multicast Outer.MacDA [RFC6325]. Care must be taken 492 that a TRILL Data packet in a non-zero topology is only forwarded by 493 an MT TRILL switch. 495 For this reason, a non-zero topology TRILL Data packet MUST NOT be 496 forwarded onto a link unless the link meets the requirements 497 specified in Section 2.2 for use in that topology even if there are 498 one or more MT TRILL switch ports on the link. 500 4. Mixed Links 502 A link might have any combination of MT, FGL, or even VL TRILL 503 switches on it [RFC7172]. DRB (Designated RBridge) election and 504 Forwarder appointment on the link work as previously specified in 505 [RFC6439] and [RFC7177]. It is up to the network manager to configure 506 and manage the TRILL switches on a link so that the desired switch is 507 DRB and the desired switch is the Appointed Forwarder for the 508 appropriate VLANs. 510 Frames ingressed by MT TRILL switches can potentially be in any 511 topology recognized by the switch and permitted on the ingress port. 512 Frames ingressed by VL or FGL TRILL switches can only be in the base 513 zero topology. Because FGL and VL TRILL switches do not understand 514 topologies, all occurrences of the following sub-TLVs MUST occur only 515 in MT Port Capability TLVs with a zero MT-ID. Any occurrence of these 516 sub-TVLs in an MT Port Capability TLV with a nonzero MT-ID is 517 ignored. 519 Special VLANs and Flags Sub-TLV 520 Enabled-VLANs Sub-TLV 521 Appointed Forwarders Sub-TLV 522 VLANs Appointed Sub-TLV 524 Native frames cannot be explicitly labeled (see Section 2.4) as to 525 their topology. 527 5. Other Multi-Topology Considerations 529 5.1 Address Learning 531 The learning of end station MAC addresses is per topology as well as 532 per label (VLAN or FGL). The same MAC address can occur for different 533 end stations that differ only in topology. 535 5.1.1 Data Plane Learning 537 End station MAC addresses learned from ingressing native frames or 538 egressing TRILL Data packets are, for MT TRILL switches, qualified by 539 topology, that is, either the topology into which that TRILL switch 540 classified the ingressed native frame or the topology that the 541 egressed TRILL Data frame was in. 543 5.1.2 Multi-Topology ESADI 545 In an MT TRILL switch, ESADI [RFC7357] operates per label (VLAN or 546 FGL) per topology. Since ESADI messages appear, to transit TRILL 547 switches, like normal multi-destination TRILL Data packets, ESADI 548 link state databases are per topology as well as per label and local 549 to each area of multi-destination TRILL data connectivity for that 550 topology. 552 5.2 Legacy Stubs 554 Areas of topology ignorant TRILL switches can be connected to and 555 become part of an MT TRILL campus but will only be able to ingress, 556 transit, or egress topology zero TRILL Data packets. 558 5.3 RBridge Channel Messages 560 RBridge Channel messages [RFC7178], such as BFD over TRILL [RFC7175] 561 appear, to transit TRILL switches, like normal multi-destination 562 TRILL Data packets. Thus, they have a topology and are constrained by 563 topology like other TRILL Data packets. In general, when sent for 564 network management purposes, they are sent in topology zero. 566 5.4 Implementations Considerations 568 MT is an optional TRILL switch capability. 570 Experience with the actual deployment of Layer 3 IS-IS MT [RFC5120] 571 indicates that a single router handling more than eight topologies is 572 rare. There may be many more than eight distinct topologies in a 573 routed area, such as a TRILL campus, but in that case many of these 574 topologies will be handled by disjoint sets of routers and/or links. 576 Based on this deployment experience, a TRILL switch capable of 577 handling 8 or more topologies can be considered a full implementation 578 while a TRILL switch capable of handling 4 topologies can be 579 considered a minimal implementation but still useful under some 580 circumstances. 582 6. Allocation Considerations 584 IEEE Registration Authority and IANA considerations are given below. 586 6.1 IEEE Registration Authority Considerations 588 The IEEE Registration Authority will be requested to allocate a new 589 Ethertype for TRILL-MT (see Section 2.4). 591 6.2 IANA Considerations 593 IANA will allocate a field of two adjacent bits TBD from bits 14 594 through 31 of the Capabilities bits of the Port TRILL Version Sub-TLV 595 for the Explicit Topology capability field. 597 7. Security Considerations 599 Multiple topologies are sometimes used for the isolation or security 600 of traffic. For example, if some links was more likely than others to 601 be subject to adversarial observation it might be desirable to 602 classify certain sensitive traffic in a topology that excluded those 603 links. 605 Delivery of data originating in one topology outside of that topology 606 is generally a security policy violation to be avoided at all 607 reasonable costs. 609 For general TRILL security considerations, see [RFC6325]. 611 Normative References 613 [IS-IS] - ISO/IEC 10589:2002, Second Edition, "Intermediate System to 614 Intermediate System Intra-Domain Routeing Exchange Protocol for 615 use in Conjunction with the Protocol for Providing the 616 Connectionless-mode Network Service (ISO 8473)", 2002. 618 [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate 619 Requirement Levels", BCP 14, RFC 2119, March 1997. 621 [RFC5120] - Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi 622 Topology (MT) Routing in Intermediate System to Intermediate 623 Systems (IS-ISs)", RFC 5120, February 2008. 625 [RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. 626 Ghanwani, "Routing Bridges (RBridges): Base Protocol 627 Specification", RFC 6325, July 2011. 629 [RFC7172] - Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., 630 and D. Dutt, "Transparent Interconnection of Lots of Links 631 (TRILL): Fine-Grained Labeling", RFC 7172, May 2014. 633 [RFC7176] - Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt, 634 D., and A. Banerjee, "Transparent Interconnection of Lots of 635 Links (TRILL) Use of IS-IS", RFC 7176, May 2014. 637 [RFC7177] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H., 638 and V. Manral, "Transparent Interconnection of Lots of Links 639 (TRILL): Adjacency", RFC 7177, May 2014. 641 [RFC7178] - Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D. 642 Ward, "Transparent Interconnection of Lots of Links (TRILL): 643 RBridge Channel Support", RFC 7178, May 2014. 645 [RFC7357] - Hhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O. 646 Stokes, "Transparent Interconnection of Lots of Links (TRILL): 647 End Station Address Distribution Information (ESADI) Protocol", 648 RFC 7357, DOI 10.17487/RFC7357, September 2014, 649 . 651 [rfc7180bis] - Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, 652 A., Ghanwani, A., and S. Gupta, "Transparent Interconnection of 653 Lots of Links (TRILL): Clarifications, Corrections, and 654 Updates", draft-ietf-trill-rfc7180bis, work in progress. 656 Informative References 658 [RFC6439] - Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F. 659 Hu, "Routing Bridges (RBridges): Appointed Forwarders", RFC 660 6439, November 2011. 662 [RFC7175] - Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee, 663 "Transparent Interconnection of Lots of Links (TRILL): 664 Bidirectional Forwarding Detection (BFD) Support", RFC 7175, 665 May 2014. 667 Acknowledgements 669 The comments and suggestions of the following are gratefully 670 acknowledged: 672 TBD 674 The document was prepared in raw nroff. All macros used were defined 675 within the source file. 677 Appendix A: Differences from RFC 5120 679 This document differs from RFC 5120 as follows: 681 1. [RFC5120] provides for unicast multi-topology. This document 682 extends that to cover multi-destination TRILL data distribution 683 (see Section 3.4). 685 2. [RFC5120] assumes the topology of data packets is always 686 determined implicitly, that is, based on the port over which the 687 packets are received or pre-existing fields within the packet. 688 This document supports implicit determination but extends this for 689 TRILL by providing for optional explicit topology labeling of 690 TRILL Data packets (see Section 2.4). 692 3. [RFC5120] makes support of the default topology zero optional for 693 MT routers and links. For simplicity and ease in network 694 management, this document requires all TRILL switches and links 695 between TRILL switches to support topology zero (see Section 2.1). 697 Authors' Addresses 699 Donald Eastlake 3rd 700 Huawei Technologies 701 155 Beaver Street 702 Milford, MA 01757 USA 704 Phone: +1-508-333-2270 705 Email: d3e3e3@gmail.com 707 Mingui Zhang 708 Huawei Technologies Co., Ltd 709 HuaWei Building, No.3 Xinxi Rd., Shang-Di 710 Information Industry Base, Hai-Dian District, 711 Beijing, 100085 P.R. China 713 Email: zhangmingui@huawei.com 715 Ayan Banerjee 716 Cisco 718 Email: ayabaner@cisco.com 720 Vishwas Manral 721 Ionos Corp. 722 4100 Moorpark Ave. 723 San Jose, CA 95117 USA 725 EMail: vishwas@ionosnetworks.com 727 Copyright, Disclaimer, and Additional IPR Provisions 729 Copyright (c) 2015 IETF Trust and the persons identified as the 730 document authors. 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