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'IS-IS' ** Obsolete normative reference: RFC 5306 (Obsoleted by RFC 8706) -- Duplicate reference: RFC6325, mentioned in 'Err3002', was also mentioned in 'RFC6325'. -- Duplicate reference: RFC6325, mentioned in 'Err3003', was also mentioned in 'Err3002'. -- Duplicate reference: RFC6325, mentioned in 'Err3004', was also mentioned in 'Err3003'. -- Duplicate reference: RFC6325, mentioned in 'Err3052', was also mentioned in 'Err3004'. -- Duplicate reference: RFC6325, mentioned in 'Err3053', was also mentioned in 'Err3052'. -- Duplicate reference: RFC6325, mentioned in 'Err3508', was also mentioned in 'Err3053'. -- Obsolete informational reference (is this intentional?): RFC 6327 (Obsoleted by RFC 7177) -- Obsolete informational reference (is this intentional?): RFC 6439 (Obsoleted by RFC 8139) -- Obsolete informational reference (is this intentional?): RFC 7042 (Obsoleted by RFC 9542) -- Obsolete informational reference (is this intentional?): RFC 7180 (Obsoleted by RFC 7780) Summary: 1 error (**), 0 flaws (~~), 2 warnings (==), 14 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 TRILL Working Group Donald Eastlake 2 INTERNET-DRAFT Mingui Zhang 3 Intended status: Proposed Standard Huawei 4 Obsoletes: 7180 Radia Perlman 5 Updates: 6325, 7177, 7179 EMC 6 Ayan Banerjee 7 Cisco 8 Anoop Ghanwani 9 Dell 10 Sujay Gupta 11 IP Infusion 12 Expires: December 7, 2015 June 8, 2015 14 TRILL: Clarifications, Corrections, and Updates 15 17 Abstract 19 Since publication of the TRILL (Transparent Interconnection of Lots 20 of Links) base protocol in 2011, active development and deployment of 21 TRILL has revealed errata in RFC 6325 and areas that could use 22 clarifications or updates. RFCs 7177, 7357, and draft-eastlake-trill- 23 rfc6439bis provide clarifications and updates with respect to 24 Adjacency, the TRILL ESADI (End Station Address Distribution 25 Information) protocol, and Appointed Forwarders respectively. This 26 document provides other known clarifications, corrections, and 27 updates. It obsoletes RFC 7180 (the previous TRILL clarifications, 28 corrections, and updates RFC), updates RFC 7177, updates RFC 7179, 29 and updates RFC 6325. 31 Status of This Memo 33 This Internet-Draft is submitted to IETF in full conformance with the 34 provisions of BCP 78 and BCP 79. 36 Distribution of this document is unlimited. Comments should be sent 37 to the TRILL working group mailing list: . 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF), its areas, and its working groups. Note that 41 other groups may also distribute working documents as Internet- 42 Drafts. 44 Internet-Drafts are draft documents valid for a maximum of six months 45 and may be updated, replaced, or obsoleted by other documents at any 46 time. It is inappropriate to use Internet-Drafts as reference 47 material or to cite them other than as "work in progress." 48 The list of current Internet-Drafts can be accessed at 49 http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft 50 Shadow Directories can be accessed at 51 http://www.ietf.org/shadow.html. 53 Table of Contents 55 1. Introduction (Changed)..................................5 56 1.1 Precedence (Changed)...................................5 57 1.2 Changes That Are Not Backward Compatible (Unchanged)...5 58 1.3 Terminology and Acronyms (Changed).....................6 60 2. Overloaded and/or Unreachable RBridges (Unchanged)......7 61 2.1 Reachability...........................................7 62 2.2 Distribution Trees.....................................8 63 2.3 Overloaded Receipt of TRILL Data Packets...............8 64 2.3.1 Known Unicast Receipt................................9 65 2.3.2 Multi-Destination Receipt............................9 66 2.4 Overloaded Origination of TRILL Data Packets...........9 67 2.4.1 Known Unicast Origination............................9 68 2.4.2 Multi-Destination Origination.......................10 69 2.4.2.1 An Example Network................................10 70 2.4.2.2 Indicating OOMF Support...........................11 71 2.4.2.3 Using OOMF Service................................11 73 3. Distribution Trees and RPF Check (Changed).............13 74 3.1 Number of Distribution Trees (Unchanged)..............13 75 3.2 Distribution Tree Update Clarification (Unchanged)....13 76 3.3 Multicast Pruning Based on IP Address (Unchanged).....13 77 3.4 Numbering of Distribution Trees (Unchanged)...........14 78 3.5 Link Cost Directionality (Unchanged)..................14 79 3.6 Alternative RPF Check (New)...........................14 80 3.6.1 Example of the Potential Problem....................15 81 3.6.2 Solution and Discussion.............................16 83 4. Nicknames Selection (Unchanged)........................18 85 5. MTU (Maximum Transmission Unit) (Unchanged)............20 86 5.1 MTU-Related Errata in RFC 6325........................20 87 5.1.1 MTU PDU Addressing..................................20 88 5.1.2 MTU PDU Processing..................................21 89 5.1.3 MTU Testing.........................................21 90 5.2 Ethernet MTU Values...................................21 92 6. TRILL Port Modes (Unchanged)...........................23 93 7. The CFI/DEI Bit (Unchanged)............................24 95 8. Other IS-IS Considerations (Changed)...................25 96 8.1 E-L1FS Support (New)..................................25 97 8.1.1 Backward Compatibility..............................25 98 8.1.2 E-L1FS Use for Existing (sub)TLVs...................26 99 8.2 Control Packet Priorities (New).......................27 100 8.3 Unknown PDUs (New)....................................27 101 8.4 Nickname Flags APPsub-TLV (New).......................28 102 8.5 Graceful Restart (Unchanged)..........................30 103 8.6 Purge Originator Identification (New).................30 105 Table of Contents (continued) 107 9. Updates to [RFC7177] (Adjacency) (Changed).............31 109 10. TRILL Header Update (New).............................32 110 10.1 Color Bit............................................33 111 10.2 Flag Word Changes (update to [RFC7179])..............33 112 10.2.1 Extended Hop Count.................................33 113 10.2.1.1 Advertising Support..............................33 114 10.2.1.2 Ingress Behavior.................................34 115 10.2.1.3 Transit Behavior.................................34 116 10.2.1.4 Egress Behavior..................................35 117 10.2.2 Extended Color Field...............................35 118 10.3 Updated Flag Word Summary............................35 120 11. IANA Considerations (Changed).........................37 121 11.1 Previously Completed IANA Actions (Unchanged)........37 122 11.2 New IANA Actions (New)...............................37 123 11.2.1 Reference Updated..................................37 124 11.2.2 The 'E' Capability Bit.............................38 125 11.2.3 NickFlags APPsub-TLV Number and Registry...........38 126 11.2.4 Updated TRILL Extended Header Flags................38 127 11.2.5 TRILL-VER Sub-TLV Capability Flags.................39 128 11.2.6 Example Nicknames..................................39 130 12. Security Considerations (Changed).....................40 132 Normative References......................................41 133 Informative References....................................42 134 Acknowledgements..........................................44 136 Appendix A: Life Cycle of a TRILL Switch Port (New).......45 138 Appendix B: Example TRILL PDUs (New)......................48 139 B.1 LAN Hello over Ethernet...............................48 140 B.2 LSP Over PPP..........................................49 141 B.3 TRILL Data Over Ethernet..............................50 142 B.4 TRILL Data Over PPP...................................51 144 Appendix C: Appointed Forwarder Status Lost Counter (New).53 146 Appendix D: Changes to Previous RFCs (New)................54 147 D.1 Changes to Obsoleted [RFC7180]........................54 148 D.1.1 Changes.............................................54 149 D.1.2 Additions...........................................54 150 D.1.3 Deletions...........................................55 151 D.2 Changes to [RFC6325]..................................56 152 D.3 Changes to [RFC7177]..................................56 153 D.4 Changes to [RFC7179]..................................56 155 Appendix Z: Change History................................57 157 1. Introduction (Changed) 159 Since the TRILL base protocol [RFC6325] was published in 2011, active 160 development and deployment of TRILL has revealed errors in the 161 specification [RFC6325] and several areas that could use 162 clarifications or updates. 164 [RFC7177], [RFC7357], and [rfc6439bis] provide clarifications and 165 updates with respect to Adjacency, the TRILL ESADI (End Station 166 Address Distribution Information) protocol, and Appointed Forwarders 167 respectively. This document provides other known clarifications, 168 corrections, and updates to [RFC6325], [RFC7177], and [RFC7179]. This 169 document obsoletes [RFC7180], the previous TRILL clarifications, 170 corrections, and updates document, updates [RFC6325], updates 171 [RFC7177] as described in Section 9, and updates [rfc7179] as 172 described in Section 10.2 and 10.3. The charges to these RFCs are 173 summarized in Appendix D. 175 Sections of this document are annotated as to whether they are "New" 176 technical material, material that has been technically "Changed", or 177 material that is technically "Unchanged", by the appearance of one of 178 these three words in parenthesis at the end of the section header. A 179 section with only editorial changes is annotated as "(Unchanged)". If 180 no such notation appears, then the first notation encountered on 181 going to successively higher-level headers (those with shorter 182 numbers) applies. Appendix D describes changes, summarizes material 183 added, and lists material deleted. 185 1.1 Precedence (Changed) 187 In case of conflict between this document and [RFC6325], [RFC7177], 188 or [RFC7179] this document takes precedence. In addition, Section 189 1.2 (Normative Content and Precedence) of [RFC6325] is updated to 190 provide a more complete precedence ordering of the sections of 191 [RFC6325] as follows, where sections to the left take precedence over 192 sections to their right: 194 4 > 3 > 7 > 5 > 2 > 6 > 1 196 1.2 Changes That Are Not Backward Compatible (Unchanged) 198 The change made by Section 3.4 below, which was also present in 199 [RFC7180], is not backward compatible with [RFC6325] but has 200 nevertheless been adopted to reduce distribution tree changes 201 resulting from topology changes. 203 The several other changes herein that are fixes to errata for 204 [RFC6325] -- [Err3002] [Err3003] [Err3004] [Err3052] [Err3053] 205 [Err3508] -- may not be backward compatible with previous 206 implementations that conformed to errors in the specification. 208 1.3 Terminology and Acronyms (Changed) 210 This document uses the acronyms defined in [RFC6325], some of which 211 are repeated below for convenience, along with some additional 212 acronyms and terms as follows: 214 Campus - a TRILL network consisting of TRILL switches, links, and 215 possibly bridges bounded by end stations and IP routers. For 216 TRILL, there is no "academic" implication in the name "campus". 218 CFI - Canonical Format Indicator [802]. 220 DEI - Drop Eligibility Indicator [802.1Q-2014]. 222 FGL - Fine Grained Labeling [RFC7172] 224 OOMF - Overload Originated Multi-destination Frame. 226 RBridge - An alternative name for a TRILL Switch. 228 RPFC - Reverse Path Forwarding Check. 230 SNPA - SubNetwork Point of Attachment (for example, MAC address). 232 TRILL - Transparent Interconnection of Lots of Links or Tunneled 233 Routing in the Link Layer. 235 TRILL Switch - A device implementing the TRILL protocol. An 236 alternative name for an RBridge. 238 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 239 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 240 "OPTIONAL" in this document are to be interpreted as described in 241 [RFC2119]. 243 2. Overloaded and/or Unreachable RBridges (Unchanged) 245 In this Section 2, the term "neighbor" refers only to actual RBridges 246 and ignores pseudonodes. 248 RBridges may be in overload as indicated by the [IS-IS] overload flag 249 in their LSPs (Link State PDUs). This means that either (1) they are 250 incapable of holding the entire link-state database and thus do not 251 have a view of the entire topology or (2) they have been configured 252 to have the overload bit set. Although networks should be engineered 253 to avoid actual link-state overload, it might occur under various 254 circumstances. For example, if a very large campus included one or 255 more low-end TRILL Switches. 257 It is a common operational practice to set the overload bit in an 258 [IS-IS] router (such as a TRILL Switch) when performing maintenance 259 on that router that might affect its ability to correctly forward 260 packets; this will usually leave the router reachable for maintenance 261 traffic, but transit traffic will not be routed through it. (Also, 262 in some cases, TRILL provides for setting the overload bit in the 263 pseudonode of a link to stop TRILL Data traffic on an access link 264 (see Section 4.9.1 of [RFC6325]).) 266 [IS-IS] and TRILL make a reasonable effort to do what they can even 267 if some TRILL Switches/routers are in overload. They can do 268 reasonably well if a few scattered nodes are in overload. However, 269 actual least-cost paths are no longer assured if any TRILL Switches 270 are in overload. 272 For the effect of overload on the appointment of forwarders, see 273 [rfc6439bis]. 275 2.1 Reachability 277 Packets are not least-cost routed through an overloaded TRILL Switch, 278 although they may originate or terminate at an overloaded TRILL 279 Switch. In addition, packets will not be least-cost routed over 280 links with cost 2**24 - 1 [RFC5305]; such links are reserved for 281 traffic- engineered packets, the handling of which is beyond the 282 scope of this document. 284 As a result, a portion of the campus may be unreachable for least- 285 cost routed TRILL Data because all paths to it would be through 286 either a link with cost 2**24 - 1 or through an overloaded RBridge. 287 For example, an RBridge (TRILL Switch) RB1 is not reachable by TRILL 288 Data if all of its neighbors are connected to RB1 by links with cost 289 2**24 - 1. Such RBridges are called "data unreachable". 291 The link-state database at an RBridge, for example RB1, can also 292 contain information on TRILL Switches that are unreachable by IS-IS 293 link-state flooding due to link or RBridge failures. When such 294 failures partition the campus, the TRILL Switches adjacent to the 295 failure and on the same side of the failure as RB1 will update their 296 LSPs to show the lack of connectivity, and RB1 will receive those 297 updates. As a result, RB1 will be aware of the partition. Nodes on 298 the far side of the partition are both IS-IS unreachable and data 299 unreachable from RB1. However, LSPs held by RB1 for TRILL Switches 300 on the far side of the failure will not be updated and may stay 301 around until they time out, which could be tens of minutes or longer. 302 (The default in [IS-IS] is twenty minutes.) 304 2.2 Distribution Trees 306 An RBridge in overload cannot be trusted to correctly calculate 307 distribution trees or correctly perform the RPFC (Reverse-Path 308 Forwarding Check). Therefore, it cannot be trusted to forward multi- 309 destination TRILL Data packets. It can only appear as a leaf node in 310 a TRILL multi-destination distribution tree. Furthermore, if all the 311 immediate neighbors of an RBridge are overloaded, then it is omitted 312 from all trees in the campus and is unreachable by multi-destination 313 packets. 315 When an RBridge determines what nicknames to use as the roots of the 316 distribution trees it calculates, it MUST ignore all nicknames held 317 by TRILL Switches that are in overload or are data unreachable. When 318 calculating RPFCs for multi-destination packets, an RBridge, such as 319 RB1 MAY, to avoid calculating unnecessary RPFC state information, 320 ignore any trees that cannot reach to RB1 even if other RBridges list 321 those trees as trees that other TRILL Switches might use. (But see 322 Section 3.) 324 2.3 Overloaded Receipt of TRILL Data Packets 326 The receipt of TRILL Data packets by overloaded RBridge RB2 is 327 discussed in the subsections below. In all cases, the normal Hop 328 Count decrement is performed, and the TRILL Data packets are 329 discarded if the result is less than one or if the egress nickname is 330 illegal. 332 2.3.1 Known Unicast Receipt 334 RB2 will not usually receive unicast TRILL Data packets unless it is 335 the egress, in which case it egresses and delivers the data normally. 336 If RB2 receives a unicast TRILL Data packet for which it is not the 337 egress, perhaps because a neighbor does not yet know it is in 338 overload, RB2 MUST NOT discard the packet because the egress is an 339 unknown nickname as it might not know about all nicknames due to its 340 overloaded condition. If any neighbor, other than the neighbor from 341 which it received the packet, is not overloaded, it MUST attempt to 342 forward the packet to one of those neighbors selected at random 343 [RFC4086]. If there is no such neighbor, the packet is discarded. 345 2.3.2 Multi-Destination Receipt 347 If RB2 in overload receives a multi-destination TRILL Data packet, 348 RB2 MUST NOT apply an RPFC since, due to overload, it might not do so 349 correctly. RB2 egresses and delivers the frame locally where it is 350 Appointed Forwarder for the frame's VLAN (or, if the packet is FGL, 351 for the VLAN that FGL maps to at the port), subject to any multicast 352 pruning. But since, as stated above, RB2 can only be the leaf of a 353 distribution tree, it MUST NOT forward a multi-destination TRILL Data 354 packet (except as an egressed native frame where RB2 is Appointed 355 Forwarder). 357 2.4 Overloaded Origination of TRILL Data Packets 359 Overloaded origination of unicast TRILL Data packets with known 360 egress and of multi-destination packets is discussed in the 361 subsections below. 363 2.4.1 Known Unicast Origination 365 When RB2, an overloaded RBridge, ingresses or creates a known 366 destination unicast data packet, it delivers it locally if the 367 destination is local. Otherwise, RB2 unicasts it to any neighbor 368 TRILL Switch that is not overloaded. It MAY use what routing 369 information it has to help select the neighbor. 371 2.4.2 Multi-Destination Origination 373 Overloaded RBridge RB2 ingressing or creating a multi-destination 374 data packet is more complex than for the known unicast case as 375 discussed below. 377 2.4.2.1 An Example Network 379 For example, consider the network below in which, for simplicity, end 380 stations and any bridges are not shown. There is one distribution 381 tree of which RB4 is the root, as represented by double lines. Only 382 RBridge RB2 is overloaded. 384 +-----+ +-----+ +-----+ +-----+ 385 | RB7 +====+ RB5 +=====+ RB3 +=====+ RB1 | 386 +-----+ +--+--+ +-++--+ +--+--| 387 | || | 388 +---+---+ || | 389 +------+RB2(ov)|======++ | 390 | +-------+ || | 391 | || | 392 +--+--+ +-----+ ++==++=++ +--+--+ 393 | RB8 +====+ RB6 +===++ RB4 ++=====+ RB9 | 394 +-----+ +-----+ ++=====++ +-----+ 396 Since RB2 is overloaded, it does not know what the distribution tree 397 or trees are for the network. Thus, there is no way it can provide 398 normal TRILL Data service for multi-destination native frames. So 399 RB2 tunnels the frame to a neighbor that is not overloaded if it has 400 such a neighbor that has signaled that it is willing to offer this 401 service. RBridges indicate this in their Hellos as described below. 402 This service is called OOMF (Overload Originated Multi- destination 403 Frame) service. 405 - The multi-destination frame MUST NOT be locally distributed in 406 native form at RB2 before tunneling to a neighbor because this 407 would cause the frame to be delivered twice. For example, if RB2 408 locally distributed a multicast native frame and then tunneled it 409 to RB5, RB2 would get a copy of the frame when RB3 transmitted it 410 as a TRILL Data packet on the multi-access RB2-RB3-RB4 link. 411 Since RB2 would, in general, not be able to tell that this was a 412 frame it had tunneled for distribution, RB2 would decapsulate it 413 and locally distribute it a second time. 415 - On the other hand, if there is no neighbor of RB2 offering RB2 the 416 OOMF service, RB2 cannot tunnel the frame to a neighbor. In this 417 case, RB2 MUST locally distribute the frame where it is Appointed 418 Forwarder for the frame's VLAN and optionally subject to multicast 419 pruning. 421 2.4.2.2 Indicating OOMF Support 423 An RBridge RB3 indicates its willingness to offer the OOMF service to 424 RB2 in the TRILL Neighbor TLV in RB3's TRILL Hellos by setting a bit 425 associated with the SNPA (SubNetwork Point of Attachment, also known 426 as MAC address) of RB2 on the link (see IANA Considerations). 427 Overloaded RBridge RB2 can only distribute multi-destination TRILL 428 Data packets to the campus if a neighbor of RB2 not in overload 429 offers RB2 the OOMF service. If RB2 does not have OOMF service 430 available to it, RB2 can still receive multi-destination packets from 431 non-overloaded neighbors and, if RB2 should originate or ingress such 432 a frame, it distributes it locally in native form. 434 2.4.2.3 Using OOMF Service 436 If RB2 sees this OOMF (Overload Originated Multi-destination Frame) 437 service advertised for it by any of its neighbors on any link to 438 which RB2 connects, it selects one such neighbor by a means beyond 439 the scope of this document. Assuming RB2 selects RB3 to handle 440 multi-destination packets it originates, RB2 MUST advertise in its 441 LSP that it might use any of the distribution trees that RB3 442 advertises so that the RPFC will work in the rest of the campus. 443 Thus, notwithstanding its overloaded state, RB2 MUST retain this 444 information from RB3 LSPs, which it will receive as it is directly 445 connected to RB3. 447 RB2 then encapsulates such frames as TRILL Data packets to RB3 as 448 follows: M bit = 0, Hop Count = 2, ingress nickname = a nickname held 449 by RB2, and, since RB2 cannot tell what distribution tree RB3 will 450 use, egress nickname = a special nickname indicating an OOMF packet 451 (see IANA Considerations). RB2 then unicasts this TRILL Data packet 452 to RB3. (Implementation of Item 4 in Section 4 below provides 453 reasonable assurance that, notwithstanding its overloaded state, the 454 ingress nickname used by RB2 will be unique within at least the 455 portion of the campus that is IS-IS reachable from RB2.) 457 On receipt of such a packet, RB3 does the following: 459 - changes the Egress Nickname field to designate a distribution tree 460 that RB3 normally uses, 461 - sets the M bit to one, 462 - changes the Hop Count to the value it would normally use if it 463 were the ingress, and 464 - forwards the packet on that tree. 466 RB3 MAY rate limit the number of packets for which it is providing 467 this service by discarding some such packets from RB2. The provision 468 of even limited bandwidth for OOMFs by RB3, perhaps via the slow 469 path, may be important to the bootstrapping of services at RB2 or at 470 end stations connected to RB2, such as supporting DHCP and ARP/ND 471 (Address Resolution Protocol / Neighbor Discovery). (Everyone 472 sometimes needs a little OOMF (pronounced "oomph") to get off the 473 ground.) 475 3. Distribution Trees and RPF Check (Changed) 477 Two corrections, a clarification, and two updates related to 478 distribution trees appear in the subsections below along with an 479 alternative, stronger RPF (Reverse Path Forwarding) Check. See also 480 Section 2.2. 482 3.1 Number of Distribution Trees (Unchanged) 484 In [RFC6325], Section 4.5.2, page 56, Point 2, 4th paragraph, the 485 parenthetical "(up to the maximum of {j,k})" is incorrect [Err3052]. 486 It should read "(up to k if j is zero or the minimum of (j, k) if j 487 is non-zero)". 489 3.2 Distribution Tree Update Clarification (Unchanged) 491 When a link-state database change causes a change in the distribution 492 tree(s), there are several possibilities. If a tree root remains a 493 tree root but the tree changes, then local forwarding and RPFC 494 entries for that tree should be updated as soon as practical. 495 Similarly, if a new nickname becomes a tree root, forwarding and RPFC 496 entries for the new tree should be installed as soon as practical. 497 However, if a nickname ceases to be a tree root and there is 498 sufficient room in local tables, the forwarding and RPFC entries for 499 the former tree MAY be retained so that any multi-destination TRILL 500 Data packets already in flight on that tree have a higher probability 501 of being delivered. 503 3.3 Multicast Pruning Based on IP Address (Unchanged) 505 The TRILL base protocol specification [RFC6325] provides for and 506 recommends the pruning of multi-destination packet distribution trees 507 based on the location of IP multicast routers and listeners; however, 508 multicast listening is identified by derived MAC addresses as 509 communicated in the Group MAC Address sub-TLV [RFC7176]. 511 TRILL Switches MAY communicate multicast listeners and prune 512 distribution trees based on the actual IPv4 or IPv6 multicast 513 addresses involved. Additional Group Address sub-TLVs are provided 514 in [RFC7176] to carry this information. A TRILL Switch that is only 515 capable of pruning based on derived MAC address SHOULD calculate and 516 use such derived MAC addresses from the multicast listener IPv4/IPv6 517 address information it receives. 519 3.4 Numbering of Distribution Trees (Unchanged) 521 Section 4.5.1 of [RFC6325] specifies that, when building distribution 522 tree number j, node (RBridge) N that has multiple possible parents in 523 the tree is attached to possible parent number j mod p. Trees are 524 numbered starting with 1, but possible parents are numbered starting 525 with 0. As a result, if there are two trees and two possible 526 parents, in tree 1, parent 1 will be selected, and in tree 2, parent 527 0 will be selected. 529 This is changed so that the selected parent MUST be (j-1) mod p. As 530 a result, in the case above, tree 1 will select parent 0, and tree 2 531 will select parent 1. This change is not backward compatible with 532 [RFC6325]. If all RBridges in a campus do not determine distribution 533 trees in the same way, then for most topologies, the RPFC will drop 534 many multi-destination packets before they have been properly 535 delivered. 537 3.5 Link Cost Directionality (Unchanged) 539 Distribution tree construction, like other least-cost aspects of 540 TRILL, works even if link costs are asymmetric, so the cost of the 541 hop from RB1 to RB2 is different from the cost of the hop from RB2 to 542 RB1. However, it is essential that all RBridges calculate the same 543 distribution trees, and thus, all must either use the cost away from 544 the tree root or the cost towards the tree root. As corrected in 545 [Err3508], the text in Section 4.5.1 of [RFC6325] is incorrect. It 546 says: 548 In other words, the set of potential parents for N, for the tree 549 rooted at R, consists of those that give equally minimal cost 550 paths from N to R and ... 552 but the text should say "from R to N": 554 In other words, the set of potential parents for N, for the tree 555 rooted at R, consists of those that give equally minimal cost 556 paths from R to N and ... 558 3.6 Alternative RPF Check (New) 560 [RFC6325] mandates a Reverse Path Forwarding (RPF) Check on multi- 561 destination TRILL data packets to avoid possible multiplication 562 and/or looping of multi-destination traffic during TRILL campus 563 topology transients. This check is logically performed at each TRILL 564 switch input port and determines whether it is arriving on the 565 expected port based on where the packet started (the ingress 566 nickname) and the tree on which it is being distributed. If not, the 567 packet is silently discarded. This check is fine for point-to-point 568 links; however, there are rare circumstances involving multi-access 569 ("broadcast") links where a packet can be duplicated despite this RPF 570 Check and other checks performed by TRILL. 572 Section 3.6.1 gives an example of the potential problem and Section 573 3.6.2 specifies a solution. This solution is an alternative, stronger 574 RPF Check that TRILL Switches can implemented in place of the RFF 575 Check in [RFC6325]. 577 3.6.1 Example of the Potential Problem 579 Consider this network: 581 F--A--B--C--o--D 582 | 583 E 585 All the links except the link between C, D, and E are point-to-point 586 links. C, D, and E are connected over a broadcast link represented 587 by the pseudonode "o". For example, they could be connected by a 588 bridged LAN. (Bridged LANs are transparent to TRILL.) 590 Although the choice of root is unimportant here, assume that D or F 591 is chosen as the root of a distribution tree so it is obvious the 592 tree looks just like the diagram above. 594 Now assume a link comes up from A to the same bridged LAN. The 595 network then looks like this: 597 +--------+ 598 | | 599 F--A--B--C--o--D 600 | 601 E 603 Let's say the resulting tree in steady state includes all links 604 except the B-C link. After the network has converged, a packet that 605 starts from F will go F->A. Then A will send one copy on the A-B link 606 and another copy into the bridge LAN from which it will be received 607 by C and D. 609 Now consider a transition stage where A and D have acted on the new 610 LSPs and programmed their forwarding plane, while B and C have not 611 yet done so. This means that B and C both consider the link between 612 them to still be part of the tree. In this case, a packet that starts 613 out from F and reaches A will be copied by A into the A-B link and to 614 the bridge LAN. D's RPF check says to accept packets on this tree 615 coming from F over its port on the bridged LAN, so it gets accepted. 616 D is also adjacent to A on the tree, so the tree adjacency check, a 617 separate check mandated by [RFC6325] also passes. 619 However, the packet that gets to B gets sent out by B to C. C's RPF 620 check still has the old state, and it thinks the packet is OK. C 621 sends the packet along the old tree, which is into the bridge LAN. D 622 receives one more packet, but the tree adjacency check passes at D 623 because C is adjacent to D in the new tree as well. The RPF Check 624 also passes at D because D's port on the bridged LAN is OK for 625 receiving packets from F. 627 So, during this transient state, D gets duplicates of every multi- 628 destination packet ingressed at F (unless the packet gets pruned) 629 until B and C act on the new LSPs and program their hardware tables. 631 3.6.2 Solution and Discussion 633 The problem stems from the RPF Check in [RFC6325] depending only on 634 the port at which a TRILL data packet is received, the ingress 635 nickname, and the tree being used, that is, a check if {ingress 636 nickname, tree, input port} is a valid combination according to the 637 receiving TRILL switch's view of the campus topology. A multi-access 638 link actually has multiple adjacencies overlaid on one physical link 639 and to avoid the problem shown in Section 3.6.1, a stronger check is 640 needed that includes the Layer 2 source address of the TRILL Data 641 packet being received. (TRILL is a Layer 3 protocol and TRILL 642 switches are true routers that logically strip the Layer 2 header 643 from any arriving TRILL data packets and add the appropriate new 644 Layer 2 header to any outgoing TRILL Data packet to get it to the 645 next TRILL switch, so the Layer 2 source address in a TRILL Data 646 packet identifies the immediately previous TRILL Switch that 647 forwarded the packet.) 649 What is needed, instead of checking the validity of the triplet 650 {ingress nickname, tree, input port} is to check that the quadruplet 651 {ingress nickname, source SNPA, tree, input port} is valid (where 652 "source SNPA" (Sub-Network Point of Access) is the Outer.MacSA for an 653 Ethernet link). Although it is true that [RFC6325] also requires a 654 check that a multi-destination TRILL Data packet is from a TRILL 655 switch that is adjacent in the distribution tree being used, this is 656 a separate check from the RPF Check and these two independent checks 657 are not as powerful as the single unified check for a valid 658 quadruplet. 660 _______ 661 / \ 662 RB1 ------ o ----- RB2 663 \_______/ 665 However, this stronger RPF Check is not without cost. In the simple 666 case of a multi-access link where each TRILL switch has only one port 667 on the link, it merely increases the size of validity entries by 668 adding the source SNPA (Outer.MacSA). However, assume some TRILL 669 Switch RB1 has multiple ports attached to a multi-access link. In the 670 figure above, RB1 is show with three ports on the multi-access link. 671 RB1 is permitted to load split multi-destination traffic it is 672 sending into the multi-access link across those ports (Section 4.4.4 673 [RFC6325]). Assume RB2 is another TRILL Switch on the link and RB2 674 is distribution tree adjacent to RB1. The number of validity 675 quadruplets at RB2 for ingress nicknames whose multi-destination 676 traffic would arrive through RB1 is multiplied by the number of ports 677 RB1 has on the access-link because RB2 has to accept such traffic 678 from any of such ports. Although such instances seem to be very rare 679 in practice, the number of ports an RBridge has on a link could in 680 principle be tens or even a hundred or more ports, vastly increasing 681 the RPF check state at RB2 when this stronger RPF check is used. 683 Another potential cost of the stronger RPF Check is increased 684 transient loss of multi-destination TRILL data packets during a 685 topology change. For TRILL switch D, the new stronger RPF Check is 686 (tree->A, Outer.MacSA=A, ingress=A, arrival port=if1) while the old 687 one was ( tree->A, Outer.MacSA=C, ingress=A, arrival port=if1). 688 Suppose both A and B have switched to the new tree for multicast 689 forwarding while D has not updated its RPF Check yet, then the 690 multicast packet will be dropped at D's input port since D still 691 expects packet from "Outer.MacSA=C". But we do not have this packet 692 loss issue if the weaker triplet check (tree->A, ingress=A, arrival 693 port=if1) is used. Thus, the stronger check can increase the RPF 694 Check discard of multi-destination packets during topology 695 transients. 697 Because of these potential costs, implementation of this stronger RPF 698 Check is optional. The TRILL base protocol is updated to provide that 699 TRILL Switches MUST, for multi-destination packets, either implement 700 the RPF and other checks in [RFC6325] or implement this stronger RPF 701 Check as a substitute for the [RFC6325] RPF and tree adjacency 702 checks. There is no problem with a campus having a mixture of TRILL 703 switches some of which implement one of these RPF checks and some of 704 which implement the other. 706 4. Nicknames Selection (Unchanged) 708 Nickname selection is covered by Section 3.7.3 of [RFC6325]. 709 However, the following should be noted: 711 1. The second sentence in the second bullet item in Section 3.7.3 of 712 [RFC6325] on page 25 is erroneous [Err3002] and is corrected as 713 follows: 715 o The occurrence of "IS-IS ID (LAN ID)" is replaced with 716 "priority". 718 o The occurrence of "IS-IS System ID" is replaced with "seven- 719 byte IS-IS ID (LAN ID)". 721 The resulting corrected sentence in [RFC6325] reads as follows: 723 "If RB1 chooses nickname x, and RB1 discovers, through receipt 724 of an LSP for RB2 at any later time, that RB2 has also chosen 725 x, then the RBridge or pseudonode with the numerically higher 726 priority keeps the nickname, or if there is a tie in priority, 727 the RBridge with the numerically higher seven-byte IS-IS ID 728 (LAN ID) keeps the nickname, and the other RBridge MUST select 729 a new nickname." 731 2. In examining the link-state database for nickname conflicts, 732 nicknames held by IS-IS unreachable TRILL Switches MUST be 733 ignored, but nicknames held by IS-IS reachable TRILL Switches MUST 734 NOT be ignored even if they are data unreachable. 736 3. An RBridge may need to select a new nickname, either initially 737 because it has none or because of a conflict. When doing so, the 738 RBridge MUST consider as available all nicknames that do not 739 appear in its link-state database or that appear to be held by IS- 740 IS unreachable TRILL Switches; however, it SHOULD give preference 741 to selecting new nicknames that do not appear to be held by any 742 TRILL Switch in the campus, reachable or unreachable, so as to 743 minimize conflicts if IS-IS unreachable TRILL Switches later 744 become reachable. 746 4. An RBridge, even after it has acquired a nickname for which there 747 appears to be no conflicting claimant, MUST continue to monitor 748 for conflicts with the nickname or nicknames it holds. It does so 749 by checking in LSP PDUs it receives that should update its link- 750 state database for the following: any occurrence of any of its 751 nicknames held with higher priority by some other TRILL Switch 752 that is IS-IS reachable from it. If it finds such a conflict, it 753 MUST select a new nickname, even when in overloaded state. (It is 754 possible to receive an LSP that should update the link-state 755 database but does not do so due to overload.) 757 5. In the very unlikely case that an RBridge is unable to obtain a 758 nickname because all valid RBridge nicknames (0x0001 through 759 0xFFBF inclusive) are in use with higher priority by IS-IS 760 reachable TRILL Switches, it will be unable to act as an ingress, 761 egress, or tree root but will still be able to function as a 762 transit TRILL Switch. Although it cannot be a tree root, such an 763 RBridge is included in distribution trees computed for the campus 764 unless all its neighbors are overloaded. It would not be possible 765 to send a unicast RBridge Channel message specifically to such a 766 TRILL Switch [RFC7178]; however, it will receive unicast RBridge 767 Channel messages sent by a neighbor to the Any-RBridge egress 768 nickname and will receive appropriate multi-destination RBridge 769 Channel messages. 771 5. MTU (Maximum Transmission Unit) (Unchanged) 773 MTU values in TRILL key off the originatingL1LSPBufferSize value 774 communicated in the IS-IS originatingLSPBufferSize TLV [IS-IS]. The 775 campus-wide value Sz, as described in Section 4.3.1 of [RFC6325], is 776 the minimum value of originatingL1LSPBufferSize for the RBridges in a 777 campus, but not less than 1470. The MTU testing mechanism and 778 limiting LSPs to Sz assures that the LSPs can be flooded by IS-IS and 779 thus that IS-IS can operate properly. 781 If an RBridge knows nothing about the MTU of the links or the 782 originatingL1LSPBufferSize of other RBridges in a campus, the 783 originatingL1LSPBufferSize for that RBridge should default to the 784 minimum of the LSP size that its TRILL IS-IS software can handle and 785 the minimum MTU of the ports that it might use to receive or transmit 786 LSPs. If an RBridge does have knowledge of link MTUs or other 787 RBridge originatingL1LSPBufferSize, then, to avoid the necessity to 788 regenerate the local LSPs using a different maximum size, the 789 RBridge's originatingL1LSPBufferSize SHOULD be configured to the 790 minimum of (1) the smallest value that other RBridges are or will be 791 announcing as their originatingL1LSPBufferSize and (2) a value small 792 enough that the campus will not partition due to a significant number 793 of links with limited MTU. However, as provided in [RFC6325], in no 794 case can originatingL1LSPBufferSize be less than 1470. In a well- 795 configured campus, to minimize any LSP regeneration due to re-sizing, 796 all RBridges will be configured with the same 797 originatingL1LSPBufferSize. 799 Section 5.1 below corrects errata in [RFC6325], and Section 5.2 800 clarifies the meaning of various MTU limits for TRILL Ethernet links. 802 5.1 MTU-Related Errata in RFC 6325 804 Three MTU-related errata in [RFC6325] are corrected in the 805 subsections below. 807 5.1.1 MTU PDU Addressing 809 Section 4.3.2 of [RFC6325] incorrectly states that multi-destination 810 MTU-probe and MTU-ack TRILL IS-IS PDUs are sent on Ethernet links 811 with the All-RBridges multicast address as the Outer.MacDA [Err3004]. 812 As TRILL IS-IS PDUs, when multicast on an Ethernet link, these multi- 813 destination MTU-probe and MTU-ack PDUs MUST be sent to the All-IS-IS- 814 RBridges multicast address. 816 5.1.2 MTU PDU Processing 818 As discussed in [RFC6325] and, in more detail, in [RFC7177], MTU- 819 probe and MTU-ack PDUs MAY be unicast; however, Section 4.6 of 820 [RFC6325] erroneously does not allow for this possibility [Err3003]. 821 It is corrected by replacing Item numbered "1" in Section 4.6.2 of 822 [RFC6325] with the following quoted text to which TRILL Switches MUST 823 conform: 825 "1. If the Ethertype is L2-IS-IS and the Outer.MacDA is either All- 826 IS-IS-RBridges or the unicast MAC address of the receiving 827 RBridge port, the frame is handled as described in Section 828 4.6.2.1" 830 The reference to "Section 4.6.2.1" in the above quoted text is to 831 that section in [RFC6325]. 833 5.1.3 MTU Testing 835 The last two sentences of Section 4.3.2 of [RFC6325] have errors 836 [Err3053]. They currently read: 838 "If X is not greater than Sz, then RB1 sets the "failed minimum 839 MTU test" flag for RB2 in RB1's Hello. If size X succeeds, and X 840 > Sz, then RB1 advertises the largest tested X for each adjacency 841 in the TRILL Hellos RB1 sends on that link, and RB1 MAY advertise 842 X as an attribute of the link to RB2 in RB1's LSP." 844 They should read: 846 "If X is not greater than or equal to Sz, then RB1 sets the 847 "failed minimum MTU test" flag for RB2 in RB1's Hello. If size X 848 succeeds, and X >= Sz, then RB1 advertises the largest tested X 849 for each adjacency in the TRILL Hellos RB1 sends on that link, and 850 RB1 MAY advertise X as an attribute of the link to RB2 in RB1's 851 LSP." 853 5.2 Ethernet MTU Values 855 originatingL1LSPBufferSize is the maximum permitted size of LSPs 856 starting with and including the 0x83 Intradomain Routeing Protocol 857 Discriminator byte. In Layer 3 IS-IS, originatingL1LSPBufferSize 858 defaults to 1492 bytes. (This is because, in its previous life as 859 DECnet Phase V, IS-IS was encoded using the SNAP SAP (Sub-Network 860 Access Protocol Service Access Point) [RFC7042] format, which takes 8 861 bytes of overhead and 1492 + 8 = 1500, the classic Ethernet maximum. 863 When standardized by ISO/IEC [IS-IS] to use Logical Link Control 864 (LLC) encoding, this default could have been increased by a few bytes 865 but was not.) 867 In TRILL, originatingL1LSPBufferSize defaults to 1470 bytes. This 868 allows 27 bytes of headroom or safety margin to accommodate legacy 869 devices with the classic Ethernet maximum MTU despite headers such as 870 an Outer.VLAN. 872 Assuming the campus-wide minimum link MTU is Sz, RBridges on Ethernet 873 links MUST limit most TRILL IS-IS PDUs so that PDUz (the length of 874 the PDU starting just after the L2-IS-IS Ethertype and ending just 875 before the Ethernet Frame Check Sequence (FCS)) does not to exceed 876 Sz. The PDU exceptions are TRILL Hello PDUs, which MUST NOT exceed 877 1470 bytes, and MTU-probe and MTU-ack PDUs that are padded by an 878 amount that depends on the size being tested (which may exceed Sz). 880 Sz does not limit TRILL Data packets. They are only limited by the 881 MTU of the devices and links that they actually pass through; 882 however, links that can accommodate IS-IS PDUs up to Sz would 883 accommodate, with a generous safety margin, TRILL Data packet 884 payloads of (Sz - 24) bytes, starting after the Inner.VLAN and ending 885 just before the FCS. 887 Most modern Ethernet equipment has ample headroom for frames with 888 extensive headers and is sometimes engineered to accommodate 9K byte 889 jumbo frames. 891 6. TRILL Port Modes (Unchanged) 893 Section 4.9.1 of [RFC6325] specifies four mode bits for RBridge ports 894 but may not be completely clear on the effects of all combinations of 895 bits in terms of allowed frame types. 897 The table below explicitly indicates the effect of all possible 898 combinations of the TRILL port mode bits. "*" in one of the first 899 four columns indicates that the bit can be either zero or one. The 900 following columns indicate allowed frame types. The Disable bit 901 normally disables all frames, but, as an implementation choice, some 902 or all low-level Layer 2 control message can still be sent or 903 received. Examples of Layer 2 control messages are those control 904 frames for Ethernet identified in Section 1.4 of [RFC6325] or PPP 905 link negotiation messages [RFC6361]. 907 +-+-+-+-+--------+-------+-------+-------+-------+ 908 |D| | | | | | | | | 909 |i| |A| | | | TRILL | | | 910 |s| |c|T| |native | Data | | | 911 |a| |c|r| |ingress| | | | 912 |b|P|e|u| | | LSP | | | 913 |l|2|s|n|Layer 2 |native | SNP | TRILL | P2P | 914 |e|P|s|k|Control |egress | MTU | Hello | Hello | 915 +-+-+-+-+--------+-------+-------+-------+-------+ 916 |0|0|0|0| Yes | Yes | Yes | Yes | No | 917 +-+-+-+-+--------+-------+-------+-------+-------+ 918 |0|0|0|1| Yes | No | Yes | Yes | No | 919 +-+-+-+-+--------+-------+-------+-------+-------+ 920 |0|0|1|0| Yes | Yes | No | Yes | No | 921 +-+-+-+-+--------+-------+-------+-------+-------+ 922 |0|0|1|1| Yes | No | No | Yes | No | 923 +-+-+-+-+--------+-------+-------+-------+-------+ 924 |0|1|0|*| Yes | No | Yes | No | Yes | 925 +-+-+-+-+--------+-------+-------+-------+-------+ 926 |0|1|1|*| Yes | No | No | No | Yes | 927 +-+-+-+-+--------+-------+-------+-------+-------+ 928 |1|*|*|*|Optional| No | No | No | No | 929 +-+-+-+-+--------+-------+-------+-------+-------+ 931 The formal name of the "access bit" above is the "TRILL traffic 932 disable bit". The formal name of the "trunk bit" is the "end-station 933 service disable bit" [RFC6325]. 935 7. The CFI/DEI Bit (Unchanged) 937 In May 2011, the IEEE promulgated IEEE Std 802.1Q-2011, which changed 938 the meaning of the bit between the priority and VLAN ID bits in the 939 payload of C-VLAN tags. Previously, this bit was called the CFI 940 (Canonical Format Indicator) bit [802] and had a special meaning in 941 connection with IEEE 802.5 (Token Ring) frames. Now, after 942 802.1Q-2011 and in subsequent versions the current of which is 943 [802.1Q-2014], it is a DEI (Drop Eligibility Indicator) bit, similar 944 to that bit in S-VLAN/B-VLAN tags where this bit has always been a 945 DEI bit. 947 The TRILL base protocol specification [RFC6325] assumed, in effect, 948 that the link by which end stations are connected to TRILL Switches 949 and the restricted virtual link provided by the TRILL Data packet are 950 IEEE 802.3 Ethernet links on which the CFI bit is always zero. 951 Should an end station be attached by some other type of link, such as 952 a Token Ring link, [RFC6325] implicitly assumed that such frames 953 would be canonicalized to 802.3 frames before being ingressed, and 954 similarly, on egress, such frames would be converted from 802.3 to 955 the appropriate frame type for the link. Thus, [RFC6325] required 956 that the CFI bit in the Inner.VLAN, which is shown as the "C" bit in 957 Section 4.1.1 of [RFC6325], always be zero. 959 However, for TRILL Switches with ports conforming to the change 960 incorporated in the IEEE 802.1Q-2011 standard, the bit in the 961 Inner.VLAN, now a DEI bit, MUST be set to the DEI value provided by 962 the port interface on ingressing a native frame. Similarly, this bit 963 MUST be provided to the port when transiting or egressing a TRILL 964 Data packet. As with the 3-bit Priority field, the DEI bit to use in 965 forwarding a transit packet MUST be taken from the Inner.VLAN. The 966 exact effect on the Outer.VLAN DEI and priority bits and whether or 967 not an Outer.VLAN appears at all on the wire for output frames may 968 depend on output port configuration. 970 TRILL campuses with a mixture of ports, some compliant with versions 971 of 802.1Q from IEEE Std 802.1Q-2011 onward and some compliant with 972 pre-802.1Q-2011 standards, especially if they have actual Token Ring 973 links, may operate incorrectly and may corrupt data, just as a 974 bridged LAN with such mixed ports and links would. 976 8. Other IS-IS Considerations (Changed) 978 This section covers E-L1FS Support, Control Packet Priorities, 979 Unknown PDUs, the Nickname Flags APPsub-TLV, Graceful Restart, and 980 Purge Originator Identification. 982 8.1 E-L1FS Support (New) 984 TRILL switches MUST support Extended Level 1 Flooding Scope PDUs (E- 985 L1FS) [RFC7356] and MUST include a Scoped Flooding Support TLV 986 [RFC7356] in all TRILL Hellos they send indicating support for this 987 scope and any other FS-LSP scopes that they support. This support 988 increases the number of fragments available for link state 989 information by over two orders of magnitude. (See Section 9 for 990 further information on support of the Scoped Flooding Support TLV.) 992 In addition, TRILL switches MUST advertise their support of E-L1FS 993 flooding in a TRILL Version sub-TLV capability bit (see [RFC7176] and 994 Section 11.2). This bit is used by a TRILL switch, say RB1, to 995 determine support for E-L1FS by some remote RBx. The alternative of 996 simply looking for an E-L1FS FS-LSP originated by RBx fails because 997 (1) RBx might support E-L1FS flooding but not be originating any E- 998 L1FS FS-LSPs and (2) even if RBx is originating E-L1FS FS-LSPs there 999 might, due to legacy TRILL switches in the campus, be no path between 1000 RBx and RB1 through TRILL switches supporting E-L1FS flooding. If 1001 that were the case, no E-L1FS FS-LSP originated by RBx could get to 1002 RB1. 1004 E-L1FS will commonly be used to flood TRILL GENINFO TLVs and enclosed 1005 TRILL APPsub-TLVs [RFC7357]. For robustness, E-L1FS fragment zero 1006 MUST NOT exceed 1470 bytes in length; however, if such a fragment is 1007 received that is larger, it is processed normally. It is anticipated 1008 that in the future, some particularly important TRILL APPsub-TLVs 1009 will be specified as being flooded in E-L1FS fragment zero. TRILL 1010 GENINFO TLVs MUST NOT be sent in LSPs; however, if one is received in 1011 an LSP, it is processed normally. 1013 8.1.1 Backward Compatibility 1015 A TRILL campus might contain TRILL switches supporting E-L1FS 1016 flooding and legacy TRILL switches that do not support E-L1FS or 1017 perhaps do not support any [RFC7356] scopes. 1019 A TRILL switch conformant to this document can always tell which 1020 adjacent TRILL switches support E-L1FS flooding from the adjacency 1021 table entries on its ports (see Section 9). In addition, such a TRILL 1022 switch can tell which remote TRILL switches in a campus support E- 1023 L1FS by the presence of a TRILL Version sub-TLV in that TRILL 1024 switch's LSP with the E-L1FS support bit set in the Capabilities 1025 field; this capability bit is ignored for adjacent TRILL switches for 1026 which only the adjacency table entry is consulted to determine E-L1FS 1027 support. 1029 TRILL specifications making use of E-L1FS MUST specify how situations 1030 involving mixed TRILL campus of TRILL switches will be handled. 1032 8.1.2 E-L1FS Use for Existing (sub)TLVs 1034 In a campus where all TRILL switches support E-L1FS, all TRILL sub- 1035 TLVs listed in Section 2.3 of [RFC7176], except the TRILL Version 1036 sub-TLV, MAY be advertised by inclusion in Router Capability or MT- 1037 Capability TLVs in E-L1FS FS-LSPs [RFC7356]. (The TRILL Version sub- 1038 TLV still MUST appear in an LSP fragment zero.) 1040 In a mixed campus where some TRILL switches support E-L1FS and some 1041 do not, then only the following four sub-TLVs of those listed in 1042 Section 2.3 of [RFC7176] can appear in E-L1FS and then only under the 1043 conditions discussed below. In the following list, each sub-TLV is 1044 preceded by an abbreviated acronym used only in this Section 8.1.2: 1046 IV: Interested VLANs and Spanning Tree Roots sub-TLV 1047 VG: VLAN Groups sub-TLV 1048 IL: Interested Labels and Spanning Tree Roots sub-TLV 1049 LG: Label Groups sub-TLV 1051 An IV or VG sub-TLV MUST NOT be advertised by TRILL switch RB1 in an 1052 E-L1FS FS-LSP (instead being advertised in an LSP) unless the 1053 following conditions are met: 1054 - E-L1FS is supported by all of the TRILL switches that are data 1055 reachable from RB1 and are interested in the VLANs mentioned in 1056 the IV or VG sub-TLV, and 1057 - there is E-L1FS connectivity between all such TRILL switches in 1058 the campus interested in the VLANs mentioned in the IV or VG sub- 1059 TLV (connectivity involving only intermediate TRILL switches that 1060 also support E-L1FS). 1062 Any IV and VG sub-TLVs MAY still be advertised via core TRILL IS-IS 1063 LSP by any TRILL switch that has enough room in its LSPs. 1065 The conditions for using E-L1FS for the IL and LG sub-TLVs are the 1066 same as for IV and VG but with Fine Grained Labels [RFC7172] 1067 substituted for VLANs. 1069 Note, for example, that the above would permit a contiguous subset 1070 of the campus that supported Fine Grained Labels and E-L1FS to use 1071 E-L1FS to advertise IL and LG sub-TLVs even if the remainder of 1072 the campus did not support Fine Grained Labels or E-L1FS. 1074 8.2 Control Packet Priorities (New) 1076 When deciding what packet to send out a port, control packets used to 1077 establish and maintain adjacency between TRILL switches SHOULD be 1078 treated as being in the highest priority category. This includes 1079 TRILL IS-IS Hello and MTU PDUs and possibly other adjacency [RFC7177] 1080 or link technology specific packets. Other control and data packets 1081 SHOULD be given lower priority so that a flood of such other packets 1082 cannot lead to loss of or inability to establish adjacency. Loss of 1083 adjacency causes a topology transient that can result in reduced 1084 throughput, re-ordering, increased probability of loss of data, and, 1085 in the worst case, if the adjacency is a cut point, network 1086 partition. 1088 Other important control packets should be given second highest 1089 priority. Lower priorities should be given to data or less important 1090 control packets. 1092 Control packets can be ordered into priority classes as shown below. 1093 Although few implementations will actually treat all of these classes 1094 differently, lower numbered classes SHOULD NOT be treated as lower 1095 priority than higher numbered class. There may be additional control 1096 packets, not specifically listed in any category below, that SHOULD 1097 be handled as being in the most nearly analogous category. 1099 1. Hello, MTU-probe, MTU-ack, and other packets critical to 1100 establishing and maintaining adjacency. 1102 2. LSPs, CSNP/PSNPs, and other important control packets, 1104 3. Circuit scoped FS-LSP, FS-CSNP, and FS-PSNPs. 1106 4. Non-circuit scoped FS-LSP, FS-CSNP, and FS-PSNPs. 1108 8.3 Unknown PDUs (New) 1110 TRILL switches MUST silently discard [IS-IS] PDUs they receive with 1111 PDU numbers they do not understand, just as they ignore TLVs and sub- 1112 TLVs they receive that have unknown Types and sub-Types; however, 1113 they SHOULD maintain a counter of how many such PDUs have been 1114 received, on a per PDU number basis. (This is not burdensome as the 1115 PDU number is only a 5-bit field.) 1116 Note: The set of valid [IS-IS] PDUs was stable for so long that 1117 some IS-IS implementations may treat PDUs with unknown PDU 1118 numbers as a serious error and, for example, an indication that 1119 other valid PDUs from the sender are not to be trusted or that 1120 they should drop adjacency to the sender if it was adjacent. 1121 However, the MTU-probe and MTU-ack PDUs were added by [RFC7176] 1122 and now [RFC7356] has added three more new PDUs. While the 1123 authors of this document are not aware of any Internet drafts 1124 calling for further PDUs, the eventual addition of further new 1125 PDUs should not be surprising. 1127 8.4 Nickname Flags APPsub-TLV (New) 1129 An optional Nickname Flags APPsub-TLV within the TRILL GENINFO TLV 1130 [RFC7357] is specified below. 1132 1 1 1 1 1 1 1133 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 1134 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1135 | Type = NickFlags (#tbd2) | (2 bytes) 1136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1137 | Length = 4*K | (2 bytes) 1138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1139 | NICKFLAG RECORD 1 (4 bytes) | 1140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1141 ... 1142 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1143 | NICKFLAG RECORD K (4 bytes) | 1144 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1146 Where each NICKFLAG RECORD has the following format: 1148 0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 1149 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 1150 | Nickname | 1151 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 1152 |IN| RESV | 1153 +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ 1155 o Type: NickFlags TRILL APPsub-TLV, set to tbd2 (NICKFLAGS) 1157 o Length: 4 times the number of NICKFLAG RECORDS present. 1159 o Nickname: A 16-bit TRILL nickname held by the advertising TRILL 1160 switch ([RFC6325] and Section 4). 1162 o IN: Ingress. If this flag is one, it indicates the advertising 1163 TRILL switch may use the nickname in the NICKFLAG RECORD as the 1164 ingress nickname of TRILL Headers it creates. If the flag is 1165 zero, that nickname will not be used for that purpose. 1167 o RESV: Reserved for additional flags to be specified in the 1168 future. MUST be sent as zero and ignored on receipt. 1170 The entire NickFlags APPsub-TLV is ignored if the Length is not a 1171 multiple of 4. A NICKFLAG RECORD is ignored if the nickname it lists 1172 is not a nickname owned by the TRILL switch advertising the enclosing 1173 NickFlags APPsub-TLV. 1175 If a TRILL switch intends to use a nickname in the ingress nickname 1176 field of TRILL Headers it constructs, it can advertise this through 1177 E-L1FS FS-LSPs (see Section 8.1) using a NickFlags APPsub-TLV entry 1178 with the IN flag set. If it owns only one nickname, there is no 1179 reason to do this because, if a TRILL switch advertises no NickFlags 1180 APPsub-TLVs with the IN flag set for nicknames it owns, it is assumed 1181 that the TRILL switch might use any or all nicknames it owns as the 1182 ingress nickname in TRILL Headers it constructs. If a TRILL switch 1183 advertises any NickFlags APPsub-TLV entries with the IN flag set, 1184 then it MUST NOT use any other nickname(s) it owns as the ingress 1185 nickname in TRILL Headers it constructs. 1187 Every reasonable effort should be made to be sure that Nickname sub- 1188 TLVs [RFC7176] and NickFlags APPsub-TLVs remain in sync. If all TRILL 1189 switches in a campus support E-L1FS, so that Nickname sub-TLVs can be 1190 advertised in E-L1FS FS-LSPs, then the Nickname sub-TLV and any 1191 NickFlags APPsub-TLVs for any particular nickname SHOULD be 1192 advertised in the same fragment. If they are not in the same fragment 1193 then, to the extent practical, all fragments involving those sub-TLVs 1194 for the same nickname should be propagated as an atomic action. If a 1195 TRILL switch sees multiple NickFlags APPsub-TLV entries for the same 1196 nickname, it assumes that nickname might be used as the ingress in a 1197 TRILL Header if any of the NickFlags APPsub-TLV entries have the IN 1198 bit set. 1200 It is possible that a NickFlags APPsub-TLV would not be propagated 1201 throughout the TRILL campus due to legacy TRILL switches not 1202 supporting E-L1FS. In that case, Nickname sub-TLVs MUST be advertised 1203 in LSPs and TRILL switches not receiving NickFlags APPsub-TLVs having 1204 entries with the IN flag set will simply assume that the source TRILL 1205 switch might use any of its nicknames as ingress in constructing 1206 TRILL Headers. Thus the use of this optional APPsub-TLV is backwards 1207 compatible with legacy lack of E-L1FS support. 1209 Additional flags may be assigned for other purposes out of the RESV 1210 field in the future. 1212 8.5 Graceful Restart (Unchanged) 1214 TRILL Switches SHOULD support the features specified in [RFC5306], 1215 which describes a mechanism for a restarting IS-IS router to signal 1216 to its neighbors that it is restarting, allowing them to reestablish 1217 their adjacencies without cycling through the down state, while still 1218 correctly initiating link-state database synchronization. If this 1219 feature is not supported, it may increase the number of topology 1220 transients cause by a TRILL switch rebooting due to errors or 1221 maintenance. 1223 8.6 Purge Originator Identification (New) 1225 To ease debugging of any purge related problems, TRILL switches 1226 SHOULD include the Purge Originator Identification TLV [RFC6232] in 1227 all purge PDUs in TRILL IS-IS including Flooding Scoped purges 1228 [RFC7356] and in ESADI [RFC7357]. 1230 9. Updates to [RFC7177] (Adjacency) (Changed) 1232 To support the E-L1FS flooding scope [RFC7356] mandated by Section 1233 8.1 and backwards compatibility with legacy RBridges not supporting 1234 E-L1FS flooding, the following changes are made to [RFC7177]: 1236 1. The list in the second paragraph of [RFC7177] Section 3.1 has the 1237 following item added: 1239 - The Scoped Flooding Support TLV. 1241 In addition, the sentence immediately after that list is modified to 1242 read as follows: 1244 Of course, the priority, Desired Designated VLAN, Scoped Flooding 1245 Support TLV, and possibly the inclusion or value of the PORT- 1246 TRILL-VER sub-TLV, and/or BFD-Enabled TLV could change on 1247 occasion, but then the new value(s) must similarly be used in all 1248 TRILL Hellos on the LAN port, regardless of VLAN. 1250 2. An additional bullet item is added to the end of Section 3.2 of 1251 [RFC7177] as follows: 1253 o The value from the Scoped Flooding Support TLV or a null string 1254 if none was included. 1256 3. Near the bottom of Section 3.3 of [RFC7177] a bullet item as 1257 follows is added: 1259 o The variable length value part of the Scoped Flooding Support 1260 TLV in the Hello or a null string if that TLV does not occur in 1261 the Hello. 1263 4. At the beginning of Section 4 of [RFC7177], a bullet item is added 1264 to the list as follows: 1266 o The variable length value part of the Scoped Flooding Support 1267 TLV used in TRILL Hellos sent on the port. 1269 5. Add a line to Table 4: TRILL Hello Contents in Section 9.1 of 1270 [RFC7177] as follows: 1272 LAN P2P Number Content Item 1273 --- --- ------ ----------------------------- 1275 M M 1 Scoped Flooding Support TLV 1277 10. TRILL Header Update (New) 1279 The TRILL header has been updated from its original specification in 1280 [RFC6325] by [RFC7455] and [RFC7179] and is further updated by this 1281 document. The TRILL header is now as shown in the figure below which 1282 is followed by references for all of the fields. Those fields for 1283 which the reference is only to [RFC6325] are unchanged from that RFC. 1285 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1286 | V |A|C|M| RESV |F| Hop Count | 1287 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1288 | Egress Nickname | Ingress Nickname | 1289 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1290 : Optional Flag Word : 1291 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1293 In calculating a TRILL data packet hash as part of equal-cost multi- 1294 path selection, a TRILL switch MUST ignore the value of the "A" and 1295 "C" bits. 1297 In [RFC6325] and [RFC7179] there is an "Ex-Length" or TRILL Header 1298 Extensions Length field which is hereby changed to consist of the 1299 RESV and F fields above. 1301 o V (Version): 2-bit unsigned integer. See Section 3.2 of [RFC6325]. 1303 o A (Alert): 1 bit. See [RFC7455]. 1305 o C (Color): 1 bit. See Section 10.1. 1307 o M (Multi-destination): 1 bit. See Section 3.4 of [RFC6325]. 1309 o RESV: 4 bits. These bits are reserved and MUST be sent as zero. 1310 Due to the previous use of these bits specified in [RFC6325], most 1311 TRILL fast path hardware implementations trap and do not forward 1312 TRILL Data packets with these bits non-zero. A TRILL switch 1313 receiving a TRILL Data packet with any of these bits non-zero MUST 1314 discard the packet unless the non-zero bit or bits have some 1315 future use specified that the TRILL switch understands. 1317 o F: 1 bit. If this field is non-zero, then the optional Flag Word 1318 described in Section 10.2 is present. If it is zero, the Flag Word 1319 is not present. 1321 o Hop Count: 6 bits. See Section 3.6 of [RFC6325] and Section 10.2.1 1322 below. 1324 o Egress Nickname. See Section 3.7.1 of [RFC6325]. 1326 o Ingress Nickname. See Section 3.7.2 of [RFC6325]. 1328 o Optional Flag Word: See [RFC7179] and Section 10.2. 1330 10.1 Color Bit 1332 The Color bit provides an optional way ingress TRILL switches MAY 1333 mark TRILL Data packets for implementation specific purposes. 1334 Transit TRILL switches MUST NOT change this bit. Transit and egress 1335 TRILL switches MAY use the Color bit for implementation dependent 1336 traffic labeling or statistical or other traffic study or analysis. 1338 10.2 Flag Word Changes (update to [RFC7179]) 1340 When the F bit in the TRILL Header is non-zero, the first 32 bits 1341 after the Ingress nickname field provides additional flags. These 1342 bits are as specified in [RFC7179] except as changed by the 1343 subsections below that provide extended Hop Count and extended Color 1344 fields. See Section 10.3 for a diagram and summary of these fields. 1346 10.2.1 Extended Hop Count 1348 The TRILL base protocol [RFC6325] specifies the Hop Count field in 1349 the header, to avoid packets persisting in the network due to looping 1350 or the like. However, the Hop Count field size (6 bits) limits the 1351 maximum hops a TRILL data packet can traverse to 64. Optionally, 1352 TRILL switches can use a field composed of bits 14 through 16 in the 1353 Flag Word, as specified below, to extend this field to 9 bits. This 1354 increases the maximum Hop Count to 512. Except in rare circumstances, 1355 reliable use of Hop Counts in excess of 64 requires support of this 1356 optional capability at all TRILL switches along the path of a TRILL 1357 Data packet. 1359 10.2.1.1 Advertising Support 1361 In case of a TRILL campus such that the unicast calculated path, plus 1362 a reasonable allowance for alternate pathing, or the distribution 1363 tree calculated path, traverse more than 64 hops, it may be that not 1364 all the TRILL switches support the extended Hop Count mechanism. As 1365 such it is required that TRILL switches advertise their support by 1366 setting bit 14 in the TRILL Version Sub-TLV Capabilities and Header 1367 Flags Supported field [RFC7176]; bits 15 and 16 of that field are now 1368 specified as Unassigned (see Section 11.2.5). 1370 10.2.1.2 Ingress Behavior 1372 If an ingress TRILL switch determines it should set the hop count for 1373 a TRILL Data packet to 63 or less, then behavior is as specified in 1374 the TRILL base protocol [RFC6325]. If the optional TRILL Header Flag 1375 Word is present, bits 14, 15, and 16 and the Critical Reserved bit of 1376 the Critical Summary Bits are zero. 1378 If the hop count for a TRILL Data packet should be set to some value 1379 greater than 63 but less than 512 and all TRILL switches that the 1380 packet is reasonably likely to encounter support extended Hop Count, 1381 then the resulting TRILL Header has the Flag Word extension present, 1382 the high order three bits of the desired hop count are stored in the 1383 extended Hop Count field in the Flag Word, the five low order bits 1384 are stored in the Hop Count field in the first word of the TRILL 1385 Header, and bit two (the Critical Reserved bit of the Critical 1386 Summary Bits) in the Flag Word is set to one. 1388 For known unicast traffic (TRILL Header M bit zero), an ingress TRILL 1389 switch discards the frame if it determines that the least cost path 1390 to the egress is (1) more than 64 hops and not all TRILL switches on 1391 that path support the extended Hop Count feature or (2) more than 512 1392 hops. 1394 For multi-destination traffic, when a TRILL switch determines that 1395 one or more tree paths from the ingress are more than 64 hops and not 1396 all TRILL switches in the campus support the extended Hop Count 1397 feature, the encapsulation uses a total Hop Count of 63 to obtain at 1398 least partial distribution of the traffic. 1400 10.2.1.3 Transit Behavior 1402 A transit TRILL switch supporting extended Hop Count behaves like a 1403 base protocol [RFC6325] TRILL switch in decrementing the hop count 1404 except that it considers the hop count to be a 9 bit field where the 1405 extended Hop Count field constitutes the high order three bits. 1407 To be more precise: a TRILL switch supporting extended Hop Count 1408 takes the first of the following actions that is applicable: 1410 1. If both the Hop Count and extended Hop Count fields are zero, the 1411 packet is discarded. 1413 2. If the Hop Count is non-zero, it is decremented. As long as the 1414 extended Hop Count is non-zero, no special action is taken. If the 1415 result of this decrement is zero, the packet is processed 1416 normally. 1418 3. If the Hop Count is zero, it is set to the maximum value of 63 and 1419 the extended Hop Count is decremented. 1421 10.2.1.4 Egress Behavior 1423 No special behavior is required when egressing a TRILL Data packet 1424 that uses the extended Hop Count. The Flag Word, if present, is 1425 removed along with the rest of the TRILL Header during decapsulation. 1427 10.2.2 Extended Color Field 1429 Flag Word bits 27 and 28 are specified to be a two-bit Extended Color 1430 field (see Section 10.3). These bits are in the non-critical ingress- 1431 to-egress region of the Flag Word. 1433 The Extended Color field provides an optional way by which ingress 1434 TRILL switches MAY mark TRILL Data packets for implementation 1435 specific purposes. Transit TRILL switches MUST NOT change this bit. 1436 Transit and egress TRILL switches MAY use the Color bit for 1437 implementation dependent traffic labeling or statistical or other 1438 traffic study or analysis. 1440 As provided in Section 2.3.1 of [RFC7176], support for these bits is 1441 indicated by the same bits (27 and 28) in the Capabilities and Header 1442 Flags Supported field of the TRILL Version Sub-TLV. In the spirit of 1443 indicating support, a TRILL switch that sets or senses the Extended 1444 Color field SHOULD set the corresponding 2-bit field in the TRILL 1445 Version Sub-TLV non-zero. The meaning of the possible non-zero values 1446 of this 2-bit field (1, 2 or 3) is implementation dependent. 1448 10.3 Updated Flag Word Summary 1450 With the changes above, the 32-bit Flag Word extension to the TRILL 1451 Header [RFC7179], appearing as the "TRILL Extended Header Flags" 1452 registry on the TRILL Parameters IANA web page, is now as follows: 1454 0 1 2 3 1455 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 1456 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1457 |Crit.| CHbH | NCHbH |CRSV | NCRSV | CItE | NCItE | 1458 |.....|.........|...........|.....|.......|...........|.........| 1459 |C|C|C| |C|N| | Ext | | |Ext| | 1460 |R|R|R| |R|C| | Hop | | |Clr| | 1461 |H|I|R| |C|C| | Cnt | | | | | 1462 |b|t|s| |A|A| | | | | | | 1463 |H|E|v| |F|F| | | | | | | 1464 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 1466 Bit 0 to 2 are the Critical Summary bits as specified in [RFC7179] 1467 consisting of the Critical Hop-by-Hop, Critical Ingres-to-Egress, and 1468 Critical Reserved bits, respectively. The next two fields are 1469 specific Critical and Non-Critical Hop-by-Hop bits, CHbH and NCHbH, 1470 respectively, containing the Critical and Non-Critical Channel Alert 1471 flags as specified in [RFC7179]. The next field is the Critical 1472 Reserved bits (CRSV) that are specified herein to be the Extended Hop 1473 Count. Then the Non-Critical Reserved Bits (NCRSV) and the Critical 1474 Ingress-to-Egress bits (CITE) as specified in [RFC7179]. Finally, 1475 there is the Non-Critical Ingress-to-Egress field, the top two bits 1476 of which are specified herein as the Extended Color field. 1478 11. IANA Considerations (Changed) 1480 This section gives IANA actions previously completed and new IANA 1481 actions. 1483 11.1 Previously Completed IANA Actions (Unchanged) 1485 The following IANA actions were completed as part of [RFC7180] and 1486 are included here for completeness, since this document obsoletes 1487 [RFC7180]. 1489 1. The nickname 0xFFC1, which was reserved by [RFC6325], is allocated 1490 for use in the TRILL Header Egress Nickname field to indicate an 1491 OOMF (Overload Originated Multi-destination Frame). 1493 2. Bit 1 from the seven previously reserved (RESV) bits in the per- 1494 neighbor "Neighbor RECORD" in the TRILL Neighbor TLV [RFC7176] is 1495 allocated to indicate that the RBridge sending the TRILL Hello 1496 volunteers to provide the OOMF forwarding service described in 1497 Section 2.4.2 to such frames originated by the TRILL Switch whose 1498 SNPA (MAC address) appears in that Neighbor RECORD. The 1499 description of this bit is "Offering OOMF service". 1501 3. Bit 0 is allocated from the Capability bits in the PORT-TRILL-VER 1502 sub-TLV [RFC7176] to indicate support of the VLANs Appointed sub- 1503 TLV [RFC7176] and the VLAN inhibition setting mechanisms specified 1504 in [rfc6439bis]. The description of this bit is "Hello reduction 1505 support". 1507 11.2 New IANA Actions (New) 1509 The following are new IANA actions for this document: 1511 11.2.1 Reference Updated 1513 All references to [RFC7180] in the TRILL Parameters Registry are 1514 replaced with references to this document except that the Reference 1515 for bit 0 in the PORT-TRILL-VER Sub-TLV Capability Flags is changed 1516 to [rfc6439bis]. 1518 11.2.2 The 'E' Capability Bit 1520 IANA has allocate tbd1 from the previous reserved bits in the TRILL 1521 Version sub-TLV carried in the Router Capability and MT Capability 1522 TLVs (#242, #144) to indicate support of the E-L1FS flooding scope as 1523 specified in Section 8.1. This capability bit is referred to as the 1524 "E" bit. The following is the addition to the registry: 1526 Bit Description References 1527 ---- --------------------- --------------- 1528 tbd1 E-L1FS FS-LSP support [this document][RFC7356] 1530 11.2.3 NickFlags APPsub-TLV Number and Registry 1532 IANA has assigned tbd2 APPsub-TLV number under the TRILL GENINFO TLV 1533 from the range less than 255. 1535 Type Name References 1536 ---- --------- ----------- 1537 tbd2 NICKFLAGS [this document] 1539 In addition, IANA has created a registry on the TRILL Parameters web 1540 page for NickFlags bit assignments as follows: 1542 Name: NickFlags Bits 1543 Registration Procedure: IETF Review 1544 Reference: [this document] 1546 Bit Mnemonic Description Reference 1547 ----- -------- ----------- --------- 1548 0 IN Used as ingress [this document] 1549 1-15 - Unassigned [this document] 1551 11.2.4 Updated TRILL Extended Header Flags 1553 Update the "TRILL Extended Header Flags" registry as follows: 1555 Bits Purpose References 1556 ----- ------------------------------------------ ------------ 1558 14-16 Extended Hop Count [this document] 1560 27-28 Extended Color [this document] 1562 29-31 Available non-critical ingress-to-egress flags 1563 [RFC7179] [this document] 1565 11.2.5 TRILL-VER Sub-TLV Capability Flags 1567 Update the "TRILL-VER Sub-TLV Capability Flags" registry as follows: 1569 Bit Description Reference 1570 ----- -------------------------- ---------------- 1572 14 Extended Hop Count support [this document] 1574 15-16 Unassigned [this document] 1576 27-28 Extended Color support [this document] 1578 29-31 Extended header flag support [RFC7179] [this document] 1580 11.2.6 Example Nicknames 1582 IANA has assigned a block of four nicknames for use as examples in 1583 documentation such as in Appendix B below. TRILL Nicknames registry 1584 has been updated by changing the previous "0xFFC2-0xFFFE Unassigned" 1585 line to the following: 1587 Name Description Reference 1588 ------------- -------------- ----------- 1589 0xFFC2-0xFFD7 Unassigned 1590 0xFFD8-0xFFDF For use in documentation examples [this document] 1591 0xFFE0-0xFFFE Unassigned 1593 12. Security Considerations (Changed) 1595 See [RFC6325] for general TRILL security considerations. 1597 This memo improves the documentation of the TRILL protocol, corrects 1598 five errata in [RFC6325], updates [RFC6325], [RFC7177], and [RFC7179] 1599 and obsoletes [RFC7180]. In most cases, it does not change the 1600 security considerations of those RFCs. 1602 E-L1FS FS-LSPs can be authenticated with IS-IS security [RFC5310]. 1604 Normative References 1606 [802.1Q-2014] - IEEE, "IEEE Standard for Local and metropolitan area 1607 networks -- Media Access Control (MAC) Bridges and Virtual 1608 Bridged Local Area Networks", IEEE Std 802.1Q-2014, 19 December 1609 2014. 1611 [IS-IS] - International Organization for Standardization, 1612 "Intermediate System to Intermediate System intra-domain 1613 routeing information exchange protocol for use in conjunction 1614 with the protocol for providing the connectionless-mode network 1615 service (ISO 8473)", Second Edition, November 2002. 1617 [RFC2119] - Bradner, S., "Key words for use in RFCs to Indicate 1618 Requirement Levels", BCP 14, RFC 2119, March 1997. 1620 [RFC5305] - Li, T. and H. Smit, "IS-IS Extensions for Traffic 1621 Engineering", RFC 5305, October 2008. 1623 [RFC5306] - Shand, M. and L. Ginsberg, "Restart Signaling for IS-IS", 1624 RFC 5306, October 2008. 1626 [RFC5310] - Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 1627 and M. Fanto, "IS-IS Generic Cryptographic Authentication", RFC 1628 5310, February 2009, . 1630 [RFC6232] - Wei, F., Qin, Y., Li, Z., Li, T., and J. Dong, "Purge 1631 Originator Identification TLV for IS-IS", RFC 6232, May 2011, 1632 . 1634 [RFC6325] - Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. 1635 Ghanwani, "Routing Bridges (RBridges): Base Protocol 1636 Specification", RFC 6325, July 2011. 1638 [RFC6361] - Carlson, J. and D. Eastlake 3rd, "PPP Transparent 1639 Interconnection of Lots of Links (TRILL) Protocol Control 1640 Protocol", RFC 6361, August 2011. 1642 [RFC7172] - Eastlake 3rd, D., Zhang, M., Agarwal, P., Perlman, R., 1643 and D. Dutt, "Transparent Interconnection of Lots of Links 1644 (TRILL): Fine-Grained Labeling", RFC 7172, May 2014. 1646 [RFC7176] - Eastlake 3rd, D., Senevirathne, T., Ghanwani, A., Dutt, 1647 D., and A. Banerjee, "Transparent Interconnection of Lots of 1648 Links (TRILL) Use of IS-IS", RFC 7176, May 2014. 1650 [RFC7177] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Yang, H., 1651 and V. Manral, "Transparent Interconnection of Lots of Links 1652 (TRILL): Adjacency", RFC 7177, May 2014. 1654 [RFC7179] - Eastlake 3rd, D., Ghanwani, A., Manral, V., Li, Y., and 1655 C. Bestler, "Transparent Interconnection of Lots of Links 1656 (TRILL): Header Extension", RFC 7179, May 2014, 1657 . 1659 [RFC7356] - Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 1660 Scope Link State PDUs (LSPs)", RFC 7356, September 2014, 1661 . 1663 [RFC7455] - Senevirathne, T., Finn, N., Salam, S., Kumar, D., 1664 Eastlake 3rd, D., Aldrin, S., and Y. Li, "Transparent 1665 Interconnection of Lots of Links (TRILL): Fault Management", 1666 RFC 7455, March 2015, . 1668 Informative References 1670 [802] - IEEE 802, "IEEE Standard for Local and metropolitan area 1671 networks: Overview and Architecture", IEEE Std 802.1-2014, 12 1672 June 2014. 1674 [Err3002] - RFC Errata, Errata ID 3002, RFC 6325, . 1677 [Err3003] - RFC Errata, Errata ID 3003, RFC 6325, . 1680 [Err3004] - RFC Errata, Errata ID 3004, RFC 6325, . 1683 [Err3052] - RFC Errata, Errata ID 3052, RFC 6325, . 1686 [Err3053] - RFC Errata, Errata ID 3053, RFC 6325, . 1689 [Err3508] - RFC Errata, Errata ID 3508, RFC 6325, . 1692 [RFC826] - Plummer, D., "Ethernet Address Resolution Protocol: Or 1693 Converting Network Protocol Addresses to 48.bit Ethernet 1694 Address for Transmission on Ethernet Hardware", STD 37, RFC 1695 826, November 1982, . 1697 [RFC792] - Postel, J., "Internet Control Message Protocol", STD 5, 1698 RFC 792, September 1981, . 1701 [RFC4086] - Eastlake 3rd, D., Schiller, J., and S. Crocker, 1702 "Randomness Requirements for Security", BCP 106, RFC 4086, June 1703 2005, . 1705 [RFC6327] - Eastlake 3rd, D., Perlman, R., Ghanwani, A., Dutt, D., 1706 and V. Manral, "Routing Bridges (RBridges): Adjacency", RFC 1707 6327, July 2011, . 1709 [RFC6439] - Perlman, R., Eastlake, D., Li, Y., Banerjee, A., and F. 1710 Hu, "Routing Bridges (RBridges): Appointed Forwarders", RFC 1711 6439, November 2011, . 1713 [RFC7042] - Eastlake 3rd, D. and J. Abley, "IANA Considerations and 1714 IETF Protocol and Documentation Usage for IEEE 802 Parameters", 1715 BCP 141, RFC 7042, October 2013. 1717 [RFC7175] - Manral, V., Eastlake 3rd, D., Ward, D., and A. Banerjee, 1718 "Transparent Interconnection of Lots of Links (TRILL): 1719 Bidirectional Forwarding Detection (BFD) Support", RFC 7175, 1720 May 2014. 1722 [RFC7178] - Eastlake 3rd, D., Manral, V., Li, Y., Aldrin, S., and D. 1723 Ward, "Transparent Interconnection of Lots of Links (TRILL): 1724 RBridge Channel Support", RFC 7178, May 2014. 1726 [RFC7180] - Eastlake 3rd, D., Zhang, M., Ghanwani, A., Manral, V., 1727 and A. Banerjee, "Transparent Interconnection of Lots of Links 1728 (TRILL): Clarifications, Corrections, and Updates", RFC 7180, 1729 May 2014. 1731 [RFC7357] - Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O. 1732 Stokes, "Transparent Interconnection of Lots of Links (TRILL): 1733 End Station Address Distribution Information (ESADI) Protocol", 1734 RFC 7357, September 2014, . 1737 [RFC7379] - Li, Y., Hao, W., Perlman, R., Hudson, J., and H. Zhai, 1738 "Problem Statement and Goals for Active-Active Connection at 1739 the Transparent Interconnection of Lots of Links (TRILL) Edge", 1740 RFC 7379, October 2014, . 1743 [rfc6439bis] - Eastlake, D., et al., "TRILL: Appointed Forwarders", 1744 draft-eastlake-trill-rfc6439bis, work in progress. 1746 Acknowledgements 1748 The contributions of the following individuals to this document are 1749 gratefully acknowledged: 1751 Santosh Rajagopalan, Gayle Noble 1753 The contributions of the following, listed in alphabetic order, to 1754 the preceding version of this document, [RFC7180], are gratefully 1755 acknowledged: 1757 Somnath Chatterjee, Weiguo Hao, Rakesh Kumar, Yizhou Li, Radia 1758 Perlman, Mike Shand, Meral Shirazipour, and Varun Shah. 1760 The document was prepared in raw nroff. All macros used were defined 1761 within the source file. 1763 Appendix A: Life Cycle of a TRILL Switch Port (New) 1765 The contents of this informational Appendix originated in 1766 http://www.ietf.org/mail-archive/web/trill/current/msg06355.html 1768 Question: Suppose we are developing a TRILL implementation to run on 1769 different machines. Then what happens first? Is LSP flooding or 1770 ESADI started first? -> Link state database creation -> Designated 1771 RBridge election (How to set priority? any fixed process that 1772 depends on user settings? ) -> etc. ? 1774 Answer: 1776 The first thing that happens on a port/link is any link set-up 1777 that is needed. For example, on a PPP link [RFC6361], you need to 1778 negotiate that you will be using TRILL. However, if you have 1779 Ethernet links [RFC6325], which are probably the most common type, 1780 there isn't any link set-up needed. 1782 As soon as the port is set-up, it can ingress or egress native 1783 frames if end-station service is being offered on that port. 1784 Offering end-station service is the default; however, if the port 1785 trunk bit (end-station service disable) is set or the port is 1786 configured as an IS-IS point-to-point link port, then end-station 1787 service is not offered so native frames received are ignored and 1788 native frames are not egressed. 1790 Then TRILL IS-IS Hellos get sent out the port to be exchanged with 1791 any other TRILL switches on the link [RFC7177]. Optionally, you 1792 might also exchange MTU-probe/ack PDUs [RFC7177], BFD PDUs 1793 [RFC7175], or other link test packets. But all these other things 1794 are optional. Only Hellos are required. 1796 TRILL doesn't send any TRILL Data or TRILL IS-IS packets out the 1797 port to the link except Hellos until the link gets to the Two Way 1798 or Report state [RFC7177]. 1800 If a link is configured as a point-to-point link, there is no 1801 Designated RBridge (DRB) election. By default, an Ethernet link is 1802 considered a LAN link and the DRB election occurs when the link is 1803 in any state other than Down. You don't have to configure 1804 priorities for each TRILL switch (RBridge) to be Designated 1805 RBridge (DRB). Things will work fine with all the RBridges on a 1806 link using default priority. But if the network manager wants to 1807 control this, there should be a way for them to configure the 1808 priority to be DRB of the TRILL switch ports on the link. 1810 (To avoid complexity, this appendix generally describes things for 1811 a link that only has two TRILL switches on it. But TRILL works 1812 fine as currently specified on a broadcast link with multiple 1813 TRILL switches on it, actually multiple TRILL switch ports, since 1814 a TRILL switch can have multiple ports connected to the same link. 1815 The most likely way to get such a multi-access link with current 1816 technology and the existing TRILL standards is to have more than 2 1817 TRILL switch Ethernet ports connected to a bridged LAN. Since the 1818 TRILL protocol operates above all bridging, to the first 1819 approximation the bridge LAN looks like a transparent broadcast 1820 link to TRILL.) 1822 When a link gets to the 2-Way or Report state, then LSP, CSNP, and 1823 PSNP PDUs start to flow on the link (as well as FS-LSPs, FS-CSNPs, 1824 and FS-PSNPs for E-L1FS (see Section 8.1)). 1826 When a link gets to the Report state, then there is adjacency. The 1827 existence of that adjacency is flooded (reported) to the campus in 1828 LSPs. TRILL data packets can then start to flow on the link as 1829 TRILL switches recalculate the least cost paths and distribution 1830 trees to take the new adjacency into account. Until it gets to the 1831 Report state, there is no adjacency and no TRILL Data packets can 1832 flow over that link (with the minor corner case exception that an 1833 RBridge Channel message can, for its first hop only, be sent on a 1834 port where there is no adjacency (Section 2.4 of [RFC7178]). 1835 (Although this paragraph seems to be talking about link state, it 1836 is actually port state. It is possible for different TRILL switch 1837 ports on the same link to temporarily be in different states. The 1838 adjacency state machinery runs independently on each port.) 1840 ESADI [RFC7357] is built on top of the regular TRILL Data routing. 1841 Since ESADI PDUs look, to transit TRILL switches, like regular 1842 TRILL Data packets, no ESADI PDUs can flow until adjacencies are 1843 established and TRILL data is flowing. Of course, ESADI is 1844 optional and is not used unless configured... 1846 Question: Does it require TRILL Full headers at the time TRILL-LSPs 1847 start being broadcast on a link? Because at that time it's not 1848 defined Egress and Ingress nicknames. 1850 Answer: 1852 TRILL Headers are only for TRILL Data packets. TRILL IS-IS 1853 packets, such as TRILL-LSPs, are sent in a different way that does 1854 not use a TRILL Header and does not depend on nicknames. 1856 Probably, in most implementations, a TRILL switch will start up 1857 using the same nickname it had when it shut down or last got 1858 disconnected from a campus. If you want, you can implement TRILL 1859 to come up initially not reporting any nickname (by not including 1860 an Nickname sub-TLV in its LSPs) until you get the link state 1861 database or most of the link state database, and then choose a 1862 nickname no other TRILL switch in the campus is using. Of course, 1863 if a TRILL switch does not have a nickname, then it cannot ingress 1864 data, cannot egress known unicast data, and cannot be a tree root. 1866 TRILL IS-IS PDUs such as LSPs, and the link state database, all 1867 work based on the 7-byte IS-IS System-ID (sometimes called the LAN 1868 ID [IS-IS]). System-IDs always have to be unique across the campus 1869 so there is no problem determining topology regardless of nickname 1870 state. The Nickname system is built on top of that. 1872 Appendix B: Example TRILL PDUs (New) 1874 This appendix gives example TRILL IS-IS PDUs. The primary purpose of 1875 these examples is to clarify bit ordering issues. 1877 B.1 LAN Hello over Ethernet 1879 A TRILL Hello sent from a TRILL switch (RBridge) with 7-byte System 1880 ID 0x30033003300300 holding nickname 0xFFDE over Ethernet from a port 1881 with MAC address 0x00005E0053DE on VLAN 1 at priority 7. There is one 1882 neighbor that is DRB. The neighbor's port MAC is 0x00005E0053E3 and 1883 the neighbor's System ID is 0x44444444444400. 1885 Ethernet Header 1886 Outer.MacDA, Outer.MacSA 1887 0x0180C2000041 All-IS-IS-RBridges Dest. MAC Addr. 1888 0x00005E0053DE Source MAC Address 1889 Outer VLAN Tsg (optional) 1890 0x8100 C-VLAN Ethertype [802.1Q] 1891 0xE001 Priority 7, Outer.VLAN 1892 IS-IS 1893 0x22F4 L2-IS-IS Ethertype 1894 IS-IS Payload 1895 Common Header 1896 0x83 Interdomain Routeing Discriminator 1897 0x08 Header Length 1898 0x01 IS-IS Version Number 1899 0x06 ID Length of 6 Octets 1900 0x0F PDU Type (Level 1 LAN Hello) 1901 0x01 Version 1902 0x00 Reserved 1903 0x01 Maximum Area Addresses 1904 Hello PDU Specific Fields 1905 0x01 Circuit Type (Level 1) 1906 0x30033003300300 Source System ID 1907 0x0009 Holding Time 1908 0xXXXX PDU Length 1909 0x40 Priority to be DRB 1910 0x44444444444400 LAN ID 1911 TLVs (the below order of TLVs or of sub-TLVs in a TLV 1912 is not significant. 1913 Area Addresses TLV 1914 0x01 Area Addresses Type 1915 0x02 Length of Value 1916 0x01 Length of Address 1917 0x00 The fixed TRILL Area Address 1919 MT Port Capabilities TLV 1920 0x8F MT Port Capabilities Type 1921 0x0011 Length of Value 1922 0x0000 Topology 1923 Special VLANs and Flags Sub-TLV 1924 0x01 Sub-TLV Type 1925 0x08 Length 1926 0x0123 Port ID 1927 0xFFDE Sender Nickname 1928 0x0001 Outer.VLAN 1929 0x0001 Designated VLAN 1930 Enabled VLANs sub-TLV (optional) 1931 0x02 Sub-TLV Type 1932 0x03 Length 1933 0x0001 Start VLAN 1 1934 0x80 VLAN 1 1935 TRILL Neighbor TLV 1936 0x91 Neighbor Type 1937 0x0A Length of Value 1938 0xC0 S & L Flags = 1, SIZE field 0 1939 NEIGHBOR RECORD 1940 0x00 Flags 1941 0x2328 MTU = 9K bytes 1942 0x00005E0053E3 Neighbor MAC Address 1943 Scoped Flooding Support TLV 1944 0xF3 Scoped Flooding Support Type 1945 0x01 Length of Value 1946 0x40 E-L1FS Flooding Scope 1947 More TLVs (optional) 1948 ... 1949 Ethernet Trailer 1950 0xXXXXXXXX Ethernet Frame Check Sequence 1952 B.2 LSP Over PPP 1954 Here is an example of a TRILL LSP PDU sent over a PPP link by the 1955 same source TRILL switch as the example in B.1. 1957 PPP Header 1958 0x405D PPP TRILL Link State Protocol 1960 IS-IS Payload 1961 Common Header 1962 0x83 Interdomain Routeing Discriminator 1963 0x08 Header Length 1964 0x01 IS-IS Version Number 1965 0x06 ID Length of 6 Octets 1966 0x12 PDU Type (Level 1 LSP) 1967 0x01 Version 1968 0x00 Reserved 1969 0x01 Maximum Area Addresses 1970 LSP Specific Fields 1971 0xXXXX PDU Length 1972 0x0123 Remaining Lifetime 1973 0x3003300330030009 LSP ID (fragment 9) 1974 0x00001234 Sequence Number 1975 0xXXXX Checksum 1976 0x01 Flags = Level 1 1977 TLVs (the below order of TLVs or of sub-TLVs in a TLV 1978 is not significant. 1979 Router Capability TLV 1980 0xF2 Router Capability Type 1981 0x0F Length of Value 1982 0x00 Flags 1983 Nickname Sub-TLV 1984 0x06 Sub-TLV Type 1985 0x05 Length of Value 1986 NICKNAME RECORD 1987 0x33 Nickname Priority 1988 0x1234 Tree Root Priority 1989 0xFFDE Nickname 1990 TRILL Version Sub-TLV 1991 0x0D Sub-TLV Type 1992 0x05 1993 0x00 Max Version 1994 0x40000000 Flags = FGL Support 1995 More TLVs (optional 1996 ... 1997 PPP Trailer 1998 0xXXXXXX PPP Frame Check Sequence 2000 B.3 TRILL Data Over Ethernet 2002 Below is an IPv4 ICMP Echo [RFC792] sent in a TRILL Data packet from 2003 the TRILL switch that sent the Hello in B.1 to the neighbor TRILL 2004 switch on the link used in B.1. 2006 Ethernet Header 2007 Outer.MacDA, Outer.MacSA 2008 0x00005E0053E3 Destination MAC Address 2009 0x00005E0053DE Source MAC Address 2010 Outer VLAN Tsg (optional) 2011 0x8100 C-VLAN Ethertype [802.1Q] 2012 0x0001 Priority 0, Outer.VLAN 1 2013 TRILL 2014 0x22F3 TRILL Ethertype 2015 TRILL Header 2016 0X000E Flags, Hop Count 14 2017 0xFFDF Egress Nickname 2018 0xFFDC Igress Nickname 2019 Inner Ethernet Header 2020 Inner.MacDA, Inner.MacSA 2021 0x00005E005322 Destination Mac Address 2022 0x00005E005344 Source Mac Address 2023 Inner VLAN Tag 2024 0x8100 C-VLAN Ethertype 2025 0x0022 Priority 0, Inner.VLAN 34 2026 Ethertype 2027 0x0800 IPv4 Ethertype 2028 IP Header 2029 0x4500 Version 4, Header Length 5, ToS 0 2030 0xXXXX Total Length 2031 0x3579 Identification 2032 0x0000 Flags, Fragment Offset 2033 0x1101 TTL 17, ICMP = Protocol 1 2034 0xXXXX Header Checksum 2035 0xC0000207 Source IP 192.0.2.7 2036 0xC000020D Destination IP 192.0.2.13 2037 0x00000000 Options, Padding 2038 ICMP 2039 0x0800 ICMP Echo 2040 0xXXXX Checksum 2041 0x87654321 Identifier, Sequence Number 2042 ... Echo Data 2043 Ethernet Trailer 2044 0xXXXXXXXX Ethernet Frame Check Sequence 2046 B.4 TRILL Data Over PPP 2048 Below is an ARP [RFC826] sent in a TRILL Data packet from the TRILL 2049 switch that sent the Hello in B.1 over a PPP link. 2051 PPP Header 2052 0x005D PPP TRILL Network Protocol 2054 TRILL Header 2055 0X080D Flags (M=1), Hop Count 13 2056 0xFFDD Distribution Tree Root Nickname 2057 0xFFDC Igress Nickname 2058 Inner Ethernet Header 2059 Inner.MacDA, Inner.MacSA 2060 0xFFFFFFFFFFFF Destination Mac Address 2061 0x00005E005344 Source Mac Address 2062 Inner VLAN Tag 2063 0x8100 C-VLAN Ethertype 2064 0x0022 Priority 0, Inner.VLAN 34 2065 Ethertype 2066 0x0806 ARP Ethertype 2067 ARP 2068 0x0001 Hardware Address Space = Ethernet 2069 0x0001 Protocol Address Space = IPv4 2070 0x06 Size of Hardware Address 2071 0x04 Size of Protocol Address 2072 0x0001 OpCode = Request 2073 0x00005E005344 Sender Hardware Address 2074 0xC0000207 Sender Protocol Address 192.0.2.7 2075 0x000000000000 Target Hardware Address 2076 0xC000020D Target Protocol Address 192.0.2.13 2077 PPP Trailer 2078 0xXXXXXX PPP Frame Check Sequence 2080 Appendix C: Appointed Forwarder Status Lost Counter (New) 2082 This appendix is derived from http://www.ietf.org/mail- 2083 archive/web/trill/current/msg05279.html. 2085 Strict conformance to the provisions of Section 4.8.3 of [RFC6325] on 2086 the value of the Appointed Forwarder Status Lost Counter can result 2087 in splitting of Interested VLANs and Spanning Tree Roots sub-TLVs 2088 [RFC7176], or the corresponding Interested Labels sub-TLVs, due to 2089 minor/accidental differences in the counter value for different VLANs 2090 or FGLs. 2092 This counter is a mechanism to optimize data plane learning by 2093 trimming the expiration timer for learned addresses on a per VLAN/FGL 2094 basis under some circumstances. Note the following: 2096 (1) If you, the implementer don't care about that optimization and 2097 don't mind some time outs being longer than they otherwise would 2098 be, you can just not bother changing the counter, even if you are 2099 using data plane learning. On the other hand, if you don't care 2100 about some time outs being shortened when they otherwise 2101 wouldn't, you could increment the counter for multiple VLANs even 2102 if you don't lose AF status on a port for all those VLANs but, 2103 for example, only one of them. 2105 (2) If you are relying on ESADI [RFC7357] or Directory Assist 2106 [RFC7379] and not learning from the data plane, the counter 2107 doesn't matter and there really isn't any need to increment it. 2109 (3) If an RBridge port has been configured with the "disable end 2110 station traffic" bit on (also known as the trunk bit), then it 2111 makes no difference if that port is appointed forwarder or not 2112 even though, according to the standard, the Appointed Forwarder 2113 selection mechanism continues to operate. So, under such 2114 circumstances, there is no reason to increment the counter if 2115 such a port loses Appointed Forwarder status. 2117 (4) If you are updating the counter, incrementing it by more than one 2118 (even up to incrementing it by a couple of hundred), so that it 2119 matches the counter for some adjacent VLAN for the same RBridge 2120 would have an extremely small probability of causing any sub- 2121 optimization and, if it did, that sub-optimization would just be 2122 to occasionally fail to specially decrease the time out for some 2123 learned addresses. 2125 Appendix D: Changes to Previous RFCs (New) 2127 D.1 Changes to Obsoleted [RFC7180] 2129 This section summarizes the changes, augmentations, and excisions 2130 this document makes to [RFC7180] which it obsoletes and replaces. 2132 D.1.1 Changes 2134 For each heading in this document ending with "(Changed)", this 2135 section summarizes how it was changed: 2137 Section 1, Introduction: numerous changes to reflect the overall 2138 changes in contents. 2140 Section 1.1, Precedence: changed to add mention of [RFC7179]. 2142 Section 1.3, Terminology and Acronyms: numerous terms added. 2144 Section 3, Distribution Trees and RPF Check: changed by the addition 2145 of the new material in Section 3.6. See C.1.2 item 1. 2147 Section 8, Other IS-IS Considerations: Changed by the addition of 2148 Sections 8.1, 8.2, 8.3, and 8.4. See Appendix C.1.2 items 2, 3, 4, 2149 and 5 respectively. 2151 Section 9, Updates to [RFC7177] (Adjacency): Changes and additions to 2152 [RFC7177] to support E-L1FS. See Appendix C.1.2, item 2. 2154 Section 11, IANA Considerations: changed by the addition of material 2155 in Section 11.2. See Appendix C.1.2, item 7. 2157 Section 12, Security Considerations: minor changes in the RFCs 2158 listed. 2160 D.1.2 Additions 2162 The following material was added to [RFC7180] in producing this 2163 document: 2165 1. Addition of support for an alternative Reverse Path Forwarding 2166 Check (RPFC) along with considerations for deciding between the 2167 original [RFC6325] RPFC and this alternative RPFC. This 2168 alternative RPFC was originally discussed on the TRILL WG mailing 2169 list in http://www.ietf.org/mail- 2170 archive/web/trill/current/msg01852.html and subsequent messages. 2171 (Section 3.6) 2173 2. Addition of mandatory E-L1FS [RFC7356] support (Section 8.1, 2174 Section 9). 2176 3. Recommendations concerning control packet priorities. (Section 2177 8.2) 2179 4. Implementation requirements concerning unknown IS-IS PDU types 2180 (Section 8.3). 2182 5. Specification of an optional Nickname Flags APPsub-TLV and an 2183 ingress flag within that APPsub-TLV. (Section 8.4) 2185 6. Update TRILL Header to allocate a Color bit (Section 10.1) and 2186 update the optional TRILL Header Extension Flag Word to allocate 2187 a two-bit Extended Color field (Section 10.2). 2189 7. Some new IANA Considerations in Section 11.2 including 2190 reservation of nicknames for use as examples in documentation. 2192 8. Informative Appendix A and C on the Lifecycle of a TRILL Port and 2193 the Appointed Forwarder Status Lost Counter, respectively. 2195 9. Add Appendix B with example TRILL PDUs. 2197 10. Add recommendation to use Purge Originator Identification TLV. 2198 (Section 8.6) 2200 D.1.3 Deletions 2202 The following material was deleted from [RFC7180] in producing this 2203 document: 2205 1. Removal of all updates to [RFC6327] that occurred in [RFC7180]. 2206 These have been rolled into [RFC7177] that obsoletes [RFC6327]. 2207 However, new updates to [RFC7177] are included (see Item 1 in 2208 Section A.1). 2210 2. Removal of all updates to [RFC6439]. These have been rolled into 2211 [rfc6439bis] that obsoletes [RFC6439]. 2213 D.2 Changes to [RFC6325] 2215 This document contains many normative changes to [RFC6325], some of 2216 which were in [RFC7180] that it replaces, including the following: 2218 1. Change nickname allocation to ignore conflicts with data- 2219 unreachable RBridges. 2221 2. Fix errors: [Err3002] [Err3003] [Err3004] [Err3052] [Err3053] 2222 [Err3508]. 2224 3. Change for the requirement to use the RPF check in [RFC6325] for 2225 multi-destination TRILL Data packets by providing an alternative 2226 stronger RPF check. 2228 4. Adoption of the change of the CFI bit, which was required to be 2229 zero in the inner frame, to the DEI bit which is obtained from 2230 inner frame ingress or creation. 2232 5. Require all RBridge to support E-L1FS FS-LSPs flooding. 2234 6. The variable length TRILL Header extensions area is reduced to one 2235 optional flags word and the extensions length field reduced to one 2236 bit indicated that the flag word is present with the rest of the 2237 length field now reserved. 2239 D.3 Changes to [RFC7177] 2241 All of the updates to [RFC7177] herein are in Section 9. Basically, 2242 this document requires a Scoped Flooding Support TLV [RFC7356] to 2243 appear in all Hellos and that TRILL switches retain in their 2244 adjacency state the information received in that TLV. 2246 D.4 Changes to [RFC7179] 2248 The updates to [RFC7179] herein are in Sections 10.2 and 10.3. 2250 Appendix Z: Change History 2252 This appendix lists version changes in this document. 2254 From -00 to -01: 2256 1. Expand Appendix D to cover changes to RFC 6325, RFC 7177, and RFC 2257 7179 as well as 7180 and add material to the Introduction on 2258 changes or previous RFCs. 2260 2. Add a paragraph just before the Section 8.1.1 header about the 2261 uses of E-L1FS FS-LSPs, the size limit on E-L1FS fragment zero, 2262 and handling of TRILL GENINFO TLVs. 2264 3. At the end of Section 9, add item 5 updating Table 4 in [RFC7177]. 2266 4. In Section 11.2.3, add a Registry for NickFlags bits. 2268 5. Add Section 11.2.6 assigning nicknames for use as examples in 2269 documentation. 2271 6. Small improvements to the Security Considerations section. 2273 7. Augment and update references. 2275 8. Add a bit to Appendix A and add a lot to Appendix B. 2277 9. Minor editorial changes. 2279 From -01 to -02 2281 1. Add Section 8.6 on Purge Originator Identification TLV. 2283 2. Update reference to IEEE Std 802. 2285 3. Move Acknowledgements after References as this is now the RFC 2286 Editor preference. 2288 4. Numerous editorial fixes. 2290 From -02 to -03 2292 Updated for Shepherd comments. No technical change. 2294 From -03 to -04 2296 Update reference to draft-ietf-trill-oam-fm to be to [RFC7455]. 2298 From -04 to -05 2299 Fix typo at the beginning of Section 10 based on RTG Directorate 2300 review. 2302 Authors' Addresses 2304 Donald Eastlake 3rd 2305 Huawei Technology 2306 155 Beaver Street 2307 Milford, MA 01757 USA 2309 Phone: +1-508-333-2270 2310 EMail: d3e3e3@gmail.com 2312 Mingui Zhang 2313 Huawei Technologies 2314 No. 156 Beiqing Rd. Haidian District, 2315 Beijing 100095 2316 P.R. China 2318 EMail: zhangmingui@huawei.com 2320 Radia Perlman 2321 EMC 2322 2010 256th Avenue NE, #200 2323 Bellevue, WA 98007 USA 2325 EMail: radia@alum.mit.edu 2327 Ayan Banerjee 2328 Cisco 2330 EMail: ayabaner@cisco.com 2332 Anoop Ghanwani 2333 Dell 2334 5450 Great America Parkway 2335 Santa Clara, CA 95054 USA 2337 EMail: anoop@alumni.duke.edu 2339 Sujay Gupta 2340 IP Infusion, 2341 RMZ Centennial 2342 Mahadevapura Post 2343 Bangalore - 560048 India 2345 EMail: sujay.gupta@ipinfusion.com 2347 Copyright and IPR Provisions 2349 Copyright (c) 2015 IETF Trust and the persons identified as the 2350 document authors. All rights reserved. 2352 This document is subject to BCP 78 and the IETF Trust's Legal 2353 Provisions Relating to IETF Documents 2354 (http://trustee.ietf.org/license-info) in effect on the date of 2355 publication of this document. Please review these documents 2356 carefully, as they describe your rights and restrictions with respect 2357 to this document. Code Components extracted from this document must 2358 include Simplified BSD License text as described in Section 4.e of 2359 the Trust Legal Provisions and are provided without warranty as 2360 described in the Simplified BSD License.