idnits 2.17.1 draft-ietf-trill-multilevel-single-nickname-11.txt: Checking boilerplate required by RFC 5378 and the IETF Trust (see https://trustee.ietf.org/license-info): ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/1id-guidelines.txt: ---------------------------------------------------------------------------- No issues found here. Checking nits according to https://www.ietf.org/id-info/checklist : ---------------------------------------------------------------------------- No issues found here. Miscellaneous warnings: ---------------------------------------------------------------------------- == The copyright year in the IETF Trust and authors Copyright Line does not match the current year -- The document date (June 26, 2020) is 1399 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '256' on line 514 -- Looks like a reference, but probably isn't: '257' on line 515 Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 3 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 1 INTERNET-DRAFT M. Zhang 2 Intended Status: Proposed Standard Huawei 3 D. Eastlake 4 Futurewei 5 R. Perlman 6 EMC 7 M. Cullen 8 Painless Security 9 H. Zhai 10 JIT 11 Expires: December 25, 2020 June 26, 2020 13 Transparent Interconnection of Lots of Links (TRILL) 14 Single Area Border RBridge Nickname for Multilevel 15 draft-ietf-trill-multilevel-single-nickname-11.txt 17 Abstract 18 A major issue in multilevel TRILL is how to manage RBridge nicknames. 19 In this document, area border RBridges use a single nickname in both 20 Level 1 and Level 2. RBridges in Level 2 must obtain unique nicknames 21 but RBridges in different Level 1 areas may have the same nicknames. 23 Status of This Memo 25 This Internet-Draft is submitted in full conformance with the 26 provisions of BCP 78 and BCP 79. 28 Distribution of this document is unlimited. Comments should be sent 29 to the authors or the IDR Working Group mailing list . 31 Internet-Drafts are working documents of the Internet Engineering 32 Task Force (IETF), its areas, and its working groups. Note that 33 other groups may also distribute working documents as Internet- 34 Drafts. 36 Internet-Drafts are draft documents valid for a maximum of six months 37 and may be updated, replaced, or obsoleted by other documents at any 38 time. It is inappropriate to use Internet-Drafts as reference 39 material or to cite them other than as "work in progress." 41 The list of current Internet-Drafts can be accessed at 42 http://www.ietf.org/1id-abstracts.html. The list of Internet-Draft 43 Shadow Directories can be accessed at 44 http://www.ietf.org/shadow.html. 46 Table of Contents 48 1. Introduction............................................3 49 2. Acronyms and Terminology................................4 51 3. Nickname Handling on Border RBridges....................5 52 3.1. Actions on Unicast Packets............................5 53 3.2. Actions on Multi-Destination Packets..................6 55 4. Per-flow Load Balancing.................................9 56 4.1. Ingress Nickname Replacement..........................9 57 4.2. Egress Nickname Replacement...........................9 59 5. Protocol Extensions for Discovery......................10 60 5.1. Discovery of Border RBridges in L1...................10 61 5.2. Discovery of Border RBridge Sets in L2...............10 63 6. One Border RBridge Connects Multiple Areas.............12 65 7. E-L1FS/E-L2FS Backwards Compatibility..................13 66 8. Manageability Considerations...........................13 68 9. Security Considerations................................14 69 10. IANA Considerations...................................14 71 11. References............................................15 72 11.1. Normative References................................15 73 11.2. Informative References..............................15 75 Appendix A. Level Transition Clarification................17 77 Authors' Addresses........................................18 79 1. Introduction 81 TRILL (Transparent Interconnection of Lots of Links [RFC6325] 82 [RFC7780]) multilevel techniques are designed to improve TRILL 83 scalability issues. 85 Informational [RFC8243] is an educational document to explain 86 multilevel TRILL and list possible concerns. It does not specify a 87 protocol. As described in [RFC8243], there have been two proposed 88 approaches. One approach, which is referred to as the "unique 89 nickname" approach, gives unique nicknames to all the TRILL switches 90 in the multilevel campus, either by having the Level 1/Level 2 border 91 TRILL switches advertise which nicknames are not available for 92 assignment in the area, or by partitioning the 16-bit nickname into 93 an "area" field and a "nickname inside the area" field. [RFC8397] is 94 the standards track document specifying a "unique nickname" flavor of 95 TRILL multilevel. The other approach, which is referred to in 96 [RFC8243] as the "aggregated nickname" approach, involves assigning 97 nicknames to the areas, and allowing nicknames to be reused inside 98 different areas, by having the border TRILL switches rewrite the 99 nickname fields when entering or leaving an area. [RFC8243] makes the 100 case that, while unique nickname multilevel solutions are simpler, 101 aggregated nickname solutions scale better. 103 The approach specified in this standards track document is somewhat 104 similar to the "aggregated nickname" approach in [RFC8243] but with a 105 very important difference. In this document, the nickname of an area 106 border RBridge is used in both Level 1 (L1) and Level 2 (L2). No 107 additional nicknames are assigned to represent L1 areas as such. 108 Instead, multiple border RBridges are allowed and each L1 area is 109 denoted by the set of all nicknames of those border RBridges of the 110 area. For this approach, nicknames in the L2 area MUST be unique but 111 nicknames inside an L1 area can be reused in other L1 areas that also 112 use this approach. The use of the approach specified in this document 113 in one L1 area does not prohibit the use of other approaches in other 114 L1 areas in the same TRILL campus, for example the use of the unique 115 nickname approach specified in [RFC8397]. The TRILL packet format is 116 unchanged by this document, but data plane processing is changed at 117 Border RBridges and efficient high volume data flow at Border 118 RBridges might require forwarding hardware change. 120 2. Acronyms and Terminology 122 Data Label: VLAN or FGL Fine-Grained Label (FGL). 124 DBRB: Designated Border RBridge. 126 IS-IS: Intermediate System to Intermediate System [IS-IS]. 128 Level: Similar to IS-IS, TRILL has Level 1 for intra-area and Level 2 129 for inter-area. Routing information is exchanged between Level 1 130 RBridges within the same Level 1 area, and Level 2 RBridges can only 131 form relationships and exchange information with other Level 2 132 RBridges. 134 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 135 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 136 "OPTIONAL" in this document are to be interpreted as described in BCP 137 14 [RFC2119] [RFC8174] when, and only when, they appear in all 138 capitals, as shown here. 140 Familiarity with [RFC6325] is assumed in this document. 142 3. Nickname Handling on Border RBridges 144 This section provides an illustrative example and description of the 145 border learning border RBridge nicknames. 147 Area {2,20} level 2 Area {3,30} 148 +-------------------+ +-----------------+ +--------------+ 149 | | | | | | 150 | S--RB27---Rx--Rz----RB2---Rb---Rc--Rd---Re--RB3---Rk--RB44---D | 151 | 27 | | | | 44 | 152 | ----RB20--- ----RB30--- | 153 +-------------------+ +-----------------+ +--------------+ 155 Figure 1: An Example Topology for TRILL Multilevel 157 In Figure 1, RB2, RB20, RB3 and RB30 are area border TRILL switches 158 (RBridges). Their nicknames are 2, 20, 3 and 30 respectively and are 159 used as TRILL switch identifiers in their areas [RFC6325]. Area 160 border RBridges use the set of border nicknames to denote the L1 area 161 that they are attached to. For example, RB2 and RB20 use nicknames 162 {2,20} to denote the L1 area on the left. 164 A source S is attached to RB27 and a destination D is attached to 165 RB44. RB27 has a nickname, say 27, and RB44 has a nickname, say 44 166 (and in fact, they could even have the same nickname, since the TRILL 167 switch nickname will not be visible outside these Level 1 areas). 169 3.1. Actions on Unicast Packets 171 Let's say that S transmits a frame to destination D and let's say 172 that D's location has been learned by the relevant TRILL switches 173 already. These relevant switches have learned the following: 175 1) RB27 has learned that D is connected to nickname 3. 176 2) RB3 has learned that D is attached to nickname 44. 178 The following sequence of events will occur: 180 - S transmits an Ethernet frame with source MAC = S and destination 181 MAC = D. 183 - RB27 encapsulates with a TRILL header with ingress RBridge = 27, 184 and egress RBridge = 3 producing a TRILL Data packet. 186 - RB2 and RB20 have announced in the Level 1 IS-IS instance in area 187 {2,20}, that they are attached to all those area nicknames, 188 including {3,30}. Therefore, IS-IS routes the packet to RB2 (or 189 RB20, if RB20 on the least-cost route from RB27 to RB3). 191 - RB2, when transitioning the packet from Level 1 to Level 2, 192 replaces the ingress TRILL switch nickname with its own nickname, 193 so replaces 27 with 2. Within Level 2, the ingress RBridge field 194 in the TRILL header will therefore be 2, and the egress RBridge 195 field will be 3. (The egress nickname MAY be replaced with an area 196 nickname selected from {3,30}. See Section 4 for the detail of the 197 selection method. Here, suppose nickname 3 is used.) Also RB2 198 learns that S is attached to nickname 27 in area {2,20} to 199 accommodate return traffic. RB2 SHOULD synchronize with RB20 using 200 ESADI protocol [RFC7357] that MAC = S is attached to nickname 27. 202 - The packet is forwarded through Level 2, to RB3, which has 203 advertised, in Level 2, its L2 nickname as 3. 205 - RB3, when forwarding into area {3,30}, replaces the egress 206 nickname in the TRILL header with RB44's nickname (44). (The 207 ingress nickname MAY be replaced with an area nickname selected 208 from {2,20}. See Section 4 for the detail of the selection method. 209 Here, suppose nickname 2 is selected.) So, within the destination 210 area, the ingress nickname will be 2 and the egress nickname will 211 be 44. 213 - RB44, when decapsulating, learns that S is attached to nickname 2, 214 which is one of the area nicknames of the ingress. 216 3.2. Actions on Multi-Destination Packets 218 Distribution trees for flooding of multi-destination packets are 219 calculated separately within each L1 area and in L2. When a multi- 220 destination packet arrives at the border, it needs to be transitioned 221 either from L1 to L2, or from L2 to L1. All border RBridges are 222 eligible for Level transition. However, for each multi-destination 223 packet, only one of them acts as the Designated Border RBridge (DBRB) 224 to do the transition while other non-DBRBs MUST drop the received 225 copies. All border RBridges of an area MUST agree on a pseudorandom 226 algorithm as the tie-breaker to locally determine the DBRB. The same 227 pseudorandom algorithm will be reused in Section 4 for the purpose of 228 load balancing. It's also possible to implement a certain election 229 protocol to elect the DBRB. However, such kind of implementations are 230 out the scope of this document. By default, the border RBridge with 231 the smallest nickname, considered as an unsigned integer, is elected 232 DBRB. 234 As per [RFC6325], multi-destination packets can be classified into 235 three types: unicast packet with unknown destination MAC address 236 (unknown-unicast packet), multicast packet and broadcast packet. Now 237 suppose that D's location has not been learned by RB27 or the frame 238 received by RB27 is recognized as broadcast or multicast. What will 239 happen within a Level 1 area, as it would in TRILL today, is that 240 RB27 will forward the packet as multi-destination, setting its M bit 241 to 1 and choosing an L1 tree, flooding the packet on the distribution 242 tree, subject to possible pruning. 244 When the copies of the multi-destination packet arrive at area border 245 RBridges, non-DBRBs MUST drop the packet while the DBRB, say RB2, 246 needs to do the Level transition for the multi-destination packet. 247 For a unknown-unicast packet, if the DBRB has learnt the destination 248 MAC address, it SHOULD convert the packet to unicast and set its M 249 bit to 0. Otherwise, the multi-destination packet will continue to be 250 flooded as multicast packet on the distribution tree. The DBRB 251 chooses the new distribution tree by replacing the egress nickname 252 with the new tree root RBridge nickname. The following sequence of 253 events will occur: 255 - RB2, when transitioning the packet from Level 1 to Level 2, 256 replaces the ingress TRILL switch nickname with its own nickname, 257 so replaces 27 with 2. RB2 also needs to replace the egress 258 RBridge nickname with an L2 tree root RBridge nickname, say 2. In 259 order to accommodate return traffic, RB2 records that S is 260 attached to nickname 27 and SHOULD use ESADI protocol [RFC7357] to 261 synchronize this attachment information with other border RBridges 262 (say RB20) in the area. 264 - RB20, will receive the packet flooded on the L2 tree by RB2. It is 265 important that RB20 does not transition this packet back to L1 as 266 it does for a multicast packet normally received from another 267 remote L1 area. RB20 should examine the ingress nickname of this 268 packet. If this nickname is found to be a border RBridge nickname 269 of the area {2,20}, RB2 must not forwarded the packet into this 270 area. 272 - The packet is flooded on the Level 2 tree to reach both RB3 and 273 RB30. Suppose RB3 is the selected DBRB. The non-DBRB RB30 will 274 drop the packet. 276 - RB3, when forwarding into area {3,30}, replaces the egress 277 nickname in the TRILL header with a root RBridge nickname, say 3, 278 of the distribution tree of L1 area {3,30}. (Here, the ingress 279 nickname MAY be replaced with a different area nickname selected 280 from {2,20}, the set of border RBridges to the ingress area, as 281 specified in Section 4.) Now suppose that RB27 has learned the 282 location of D (attached to nickname 3), but RB3 does not know 283 where D is. In that case, RB3 must turn the packet into a multi- 284 destination packet and floods it on the distribution tree of L1 285 area {3,30}. 287 - RB30, will receive the packet flooded on the L1 tree by RB3. It is 288 important that RB30 does not transition this packet back to L2. 290 RB30 should also examine the ingress nickname of this packet. If 291 this nickname is found to be an L2 border RBridge nickname, RB30 292 must not transition the packet back to L2. 294 - The multicast listener RB44, when decapsulating the received 295 packet, learns that S is attached to nickname 2, which is one of 296 the area nicknames of the ingress. 298 4. Per-flow Load Balancing 300 Area border RBridges perform ingress/egress nickname replacement when 301 they transition TRILL data packets between Level 1 and Level 2. The 302 egress nickname will again be replaced when the packet transitions 303 from Level 2 to Level 1. This nickname replacement enables the per- 304 flow load balance which is specified as follows. 306 4.1. Ingress Nickname Replacement 308 When a TRILL data packet from other areas arrives at an area border 309 RBridge, this RBridge MAY select one area nickname of the ingress 310 area to replace the ingress nickname of the packet so that the 311 returning TRILL data packet can be forwarded to this selected 312 nickname. The selection is simply based on a pseudorandom algorithm 313 as defined in Section 5.3 of [RFC7357]. With the random ingress 314 nickname replacement, the border RBridge actually achieves a per-flow 315 load balance for returning traffic. 317 All area border RBridges in an L1 area MUST agree on the same 318 pseudorandom algorithm. The source MAC address, ingress area 319 nicknames, egress area nicknames and the Data Label of the received 320 TRILL data packet are candidate factors of the input of this 321 pseudorandom algorithm. Note that the value of the destination MAC 322 address SHOULD be excluded from the input of this pseudorandom 323 algorithm, otherwise the egress RBridge will see one source MAC 324 address flip flopping among multiple ingress RBridges. 326 4.2. Egress Nickname Replacement 328 When a TRILL data packet originated from an L1 area arrives at an 329 area border RBridge of that area, that RBridge MAY select one area 330 nickname of the egress area to replace the egress nickname of the 331 packet. By default, it SHOULD choose the egress area border RBridge 332 with the least cost route to reach or, if there are multiple equal 333 cost egress area border RBridges, use the pseudorandom algorithm as 334 defined in Section 5.3 of [RFC7357] to select one. The use of that 335 algorithm MAY be extended to selection among some stable set of 336 egress area border RBridges that include non-least-cost alternatives 337 if it is desired to obtain more load spreading at the cost of 338 sometimes using a non-least-cost Level 2 route to forward the TRILL 339 data packet to the egress area. 341 5. Protocol Extensions for Discovery 343 The following topology change scenarios will trigger the discover 344 processes as defined in Sections 5.1 and Section 5.2: 345 - A new node comes up or recovers from a previous failure. 346 - A node goes down. 347 - A link or node fails and causes partition of an L1/L2 area. 348 - A link or node whose failure have caused partitioning of an L1/L2 349 area is repaired. 351 5.1. Discovery of Border RBridges in L1 353 The following Level 1 Border RBridge APPsub-TLV will be included in 354 an E-L1FS FS-LSP fragment zero [RFC7780] as an APPsub-TLV of the 355 TRILL GENINFO-TLV. Through listening for this APPsub-TLV, an area 356 border RBridge discovers all other area border RBridges in this area. 358 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 359 | Type = L1-BORDER-RBRIDGE | (2 bytes) 360 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 361 | Length | (2 bytes) 362 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 363 | Sender Nickname | (2 bytes) 364 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 366 o Type: Level 1 Border RBridge (TRILL APPsub-TLV type tbd1) 368 o Length: 2 370 o Sender Nickname: The nickname the originating IS will use as the 371 L1 Border RBridge nickname. This field is useful because the 372 originating IS might own multiple nicknames. 374 5.2. Discovery of Border RBridge Sets in L2 376 The following APPsub-TLV will be included in an E-L2FS FS-LSP 377 fragment zero [RFC7780] as an APPsub-TLV of the TRILL GENINFO-TLV. 378 Through listening to this APPsub-TLV in L2, an area border RBridge 379 discovers all groups of L1 border RBridges and each such group 380 identifies an area. 382 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 383 | Type = L1-BORDER-RB-GROUP | (2 bytes) 384 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 385 | Length | (2 bytes) 386 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 387 | L1 Border RBridge Nickname 1 | (2 bytes) 388 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 389 | ... | 390 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 391 | L1 Border RBridge Nickname k | (2 bytes) 392 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 394 o Type: Level 1 Border RBridge Group (TRILL APPsub-TLV type tbd2) 396 o Length: 2 * k. If length is not a multiple of 2, the APPsub-TLV is 397 corrupt and MUST be ignored. 399 o L1 Border RBridge Nickname: The nickname that an area border 400 RBridge uses as the L1 Border RBridge nickname. The L1-BORDER-RB- 401 GROUP TLV generated by an area border RBridge MUST include all L1 402 Border RBridge nicknames of the area. It's RECOMMENDED that these 403 k nicknames are ordered in ascending order according to the 404 2-octet nickname considered as an unsigned integer. 406 When an L1 area is partitioned [RFC8243], border RBridges will re- 407 discover each other in both L1 and L2 through exchanging LSPs. In L2, 408 the set of border RBridge nicknames for this splitting area will 409 change. Border RBridges that detect such a change MUST flush the 410 reachability information associated to any RBridge nickname from this 411 changing set. 413 6. One Border RBridge Connects Multiple Areas 415 It's possible that one border RBridge (say RB1) connects multiple L1 416 areas. RB1 SHOULD use a single area nickname for all these areas. 418 Nicknames used within one of these L1 areas can be reused within 419 other areas. It's important that packets destined to those duplicated 420 nicknames are sent to the right area. Since these areas are connected 421 to form a layer 2 network, duplicated {MAC, Data Label} across these 422 areas ought not occur. Now suppose a TRILL data packet arrives at the 423 area border nickname of RB1. For a unicast packet, RB1 can look up 424 the {MAC, Data Label} entry in its MAC table to identify the right 425 destination area (i.e., the outgoing interface) and the egress 426 RBridge's nickname. For a multicast packet: suppose RB1 is not the 427 DBRB, RB1 will not transition the packet; otherwise, RB1 is the DBRB, 429 - if this packet originated from an area out of the connected areas, 430 RB1 replicates this packet and floods it on the proper Level 1 431 trees of all the areas in which it acts as the DBRB. 433 - if the packet originated from one of the connected areas, RB1 434 replicates the packet it receives from the Level 1 tree and floods 435 it on other proper Level 1 trees of all the areas in which it acts 436 as the DBRB except the originating area (i.e., the area connected 437 to the incoming interface). RB1 might also receive the replication 438 of the packet from the Level 2 tree. This replication MUST be 439 dropped by RB1. It recognizes such packets by their ingress 440 nickname being the nickname of one of the border RBridges of an L1 441 area to which the receiving border RBridge is attached. 443 7. E-L1FS/E-L2FS Backwards Compatibility 445 All Level 2 RBridges MUST support E-L2FS [RFC7356] [RFC7780]. The 446 Extended TLVs defined in Section 5 are to be used in Extended Level 447 1/2 Flooding Scope (E-L1FS/E-L2FS) PDUs. Area border RBridges MUST 448 support both E-L1FS and E-L2FS. RBridges that do not support both 449 E-L1FS or E-L2FS cannot serve as area border RBridges but they can 450 appear in an L1 area acting as non-area-border RBridges. 452 8. Manageability Considerations 454 If an L1 Border RBridge Nickname is configured at an RBridge and that 455 RBridge has both L1 and L2 adjacencies, the multilevel feature as 456 specified in this document is turned on for that RBridge. In 457 contrast, unique nickname multilevel as specified in [RFC8397] is 458 enabled by the presence of L1 and L2 adjacencies without an L1 Border 459 RBridge Nickname being configured. RBridges supporting only unique 460 nickname multilevel do not support the configuration of an L2 Border 461 RBridge Nickname. RBridges supporting only the single level TRILL 462 base protocol specified in [RFC6325] do not support L2 adjacencies. 464 If there are multiple border RBridges between an L1 area and L2 and 465 one or more of them only support or are only configured for unique 466 nickname multilevel ([RFC8397]), any of these border RBridges that 467 are configured to used single nickname multilevel as specified in 468 this document MUST fall back to behaving as a unique nickname border 469 RBridge for that L1 area. Because overlapping sets of RBridges may be 470 the border RBridges for different L1 areas, an RBridge supporting 471 single nickname MUST be able to simultaneously support single 472 nickname for some of its L1 areas and unique nickname for others. For 473 example, RB1 and RB2 might be border RBridges for L1 area A1 using 474 single nickname while RB2 and RB3 are border RBridges for area A2. If 475 RB3 only supports unique nicknames then RB2 must fall back to unique 476 nickname for area A2 but continue to support single nickname for area 477 A1. 479 If an RBridge is configured with an L1 Border RBridge Nickname for 480 any a Level 1 area, it uses this nickname across the Level 2 area. 481 This L1 Border RBridge Nickname cannot be used in any other Level 1 482 area except other Level 1 areas for which the same RBridge is a 483 border RBridge with this L1 Border RBridge Nickname configured. 485 Other than the manageability considerations specified above, the 486 manageability specifications in [RFC6325] still apply. 488 9. Security Considerations 490 For general TRILL Security Considerations, see [RFC6325]. 492 The newly defined TRILL APPsub-TLVs in Section 5 are transported in 493 IS-IS PDUs whose authenticity can be enforced using regular IS-IS 494 security mechanism [IS-IS] [RFC5310]. This document raises no new 495 security issues for IS-IS. 497 Using a variation of aggregated nicknames, and the resulting possible 498 duplication of nicknames between areas, increases the possibility of 499 a TRILL Data packet being delivered to the wrong egress RBridge if 500 areas are unexpectedly merged. However, in many cases the data would 501 be discarded at that egress RBridge because it would not match a 502 known end station data label/MAC address. 504 10. IANA Considerations 506 IANA is requested to allocate two new types under the TRILL GENINFO 507 TLV [RFC7357] from the range allocated by standards action for the 508 TRILL APPsub-TLVs defined in Section 5. The following entries are 509 added to the "TRILL APPsub-TLV Types under IS-IS TLV 251 Application 510 Identifier 1" Registry on the TRILL Parameters IANA web page. 512 Type Name Reference 513 --------- ---- --------- 514 tbd1[256] L1-BORDER-RBRIDGE [This document] 515 tbd2[257] L1-BORDER-RB-GROUP [This document] 517 11. References 519 11.1. Normative References 521 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 522 Requirement Levels", BCP 14, RFC 2119, DOI 523 10.17487/RFC2119, March 1997, . 526 [RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. 527 Ghanwani, "Routing Bridges (RBridges): Base Protocol 528 Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011, 529 . 531 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 532 Scope Link State PDUs (LSPs)", RFC 7356, DOI 533 10.17487/RFC7356, September 2014, . 536 [RFC7357] Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O. 537 Stokes, "Transparent Interconnection of Lots of Links 538 (TRILL): End Station Address Distribution Information 539 (ESADI) Protocol", RFC 7357, DOI 10.17487/RFC7357, 540 September 2014, . 542 [RFC7780] Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A., 543 Ghanwani, A., and S. Gupta, "Transparent Interconnection of 544 Lots of Links (TRILL): Clarifications, Corrections, and 545 Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016, 546 . 548 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 549 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 550 2017, . 552 11.2. Informative References 554 [IS-IS] International Organization for Standardization, ISO/IEC 555 10589:2002, "Information technology -- Telecommunications 556 and information exchange between systems -- Intermediate 557 System to Intermediate System intra-domain routeing 558 information exchange protocol for use in conjunction with 559 the protocol for providing the connectionless-mode network 560 service", ISO 8473, Second Edition, November 2002. 562 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 563 and M. Fanto, "IS-IS Generic Cryptographic Authentication", 564 RFC 5310, DOI 10.17487/RFC5310, February 2009, 565 . 567 [RFC8243] Perlman, R., Eastlake 3rd, D., Zhang, M., Ghanwani, A., and 568 H. Zhai, "Alternatives for Multilevel Transparent 569 Interconnection of Lots of Links (TRILL)", RFC 8243, DOI 570 10.17487/RFC8243, September 2017, . 573 [RFC8397] Zhang, M., Eastlake 3rd, D., Perlman, R., Zhai, H., and D. 574 Liu, "Transparent Interconnection of Lots of Links (TRILL) 575 Multilevel Using Unique Nicknames", RFC 8397, DOI 576 10.17487/RFC8397, May 2018, . 579 Appendix A. Level Transition Clarification 581 It's possible that an L1 RBridge is only reachable from a non-DBRB 582 border RBridge. If this non-DBRB RBridge refrains from Level 583 transition, the question is, how can a multicast packet reach this L1 584 RBridge? The answer is, it will be reached after the DBRB performs 585 the Level transition and floods the packet using an L1 distribution 586 tree. 588 Take the following figure as an example. RB77 is reachable from the 589 border RBridge RB30 while RB3 is the DBRB. RB3 transitions the 590 multicast packet into L1 and floods the packet on the distribution 591 tree rooted from RB3. This packet is finally flooded to RB77 via 592 RB30. 594 Area{3,30} 595 +--------------+ (root) RB3 o 596 | | \ 597 -RB3 | | o RB30 598 | | | / 599 -RB30-RB77 | RB77 o 600 +--------------+ 602 Example Topology L1 Tree 604 In the above example, the multicast packet is forwarded along a non- 605 optimal path. A possible improvement is to have RB3 configured not to 606 belong to this area. In this way, RB30 will surely act as the DBRB to 607 do the Level transition. 609 Authors' Addresses 611 Mingui Zhang 612 Huawei Technologies 613 No. 156 Beiqing Rd. Haidian District 614 Beijing 100095 615 China 617 Email: zhangmingui@huawei.com 619 Donald E. Eastlake, 3rd 620 Futurewei Technologies 621 2386 Panoramic Circle 622 Apopka, FL 32703 623 United States 625 Phone: +1-508-333-2270 626 Email: d3e3e3@gmail.com 628 Radia Perlman 629 EMC 630 2010 256th Avenue NE, #200 631 Bellevue, WA 98007 632 United States 634 Email: radia@alum.mit.edu 636 Margaret Cullen 637 Painless Security 638 356 Abbott Street 639 North Andover, MA 01845 640 United States 642 Phone: +1-781-405-7464 643 Email: margaret@painless-security.com 644 URI: http://www.painless-security.com 646 Hongjun Zhai 647 Jinling Institute of Technology 648 99 Hongjing Avenue, Jiangning District 649 Nanjing, Jiangsu 211169 650 China 652 Email: honjun.zhai@tom.com 654 Copyright, Disclaimer, and Additional IPR Provisions 656 Copyright (c) 2020 IETF Trust and the persons identified as the 657 document authors. All rights reserved. 659 This document is subject to BCP 78 and the IETF Trust's Legal 660 Provisions Relating to IETF Documents 661 (http://trustee.ietf.org/license-info) in effect on the date of 662 publication of this document. Please review these documents 663 carefully, as they describe your rights and restrictions with respect 664 to this document. Code Components extracted from this document must 665 include Simplified BSD License text as described in Section 4.e of 666 the Trust Legal Provisions and are provided without warranty as 667 described in the Simplified BSD License.