idnits 2.17.1 draft-ietf-trill-multilevel-single-nickname-14.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 (July 12, 2021) is 1016 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 525 -- Looks like a reference, but probably isn't: '257' on line 526 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: January 11, 2022 July 12, 2021 13 Transparent Interconnection of Lots of Links (TRILL) 14 Single Area Border RBridge Nickname for Multilevel 15 draft-ietf-trill-multilevel-single-nickname-14.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 https://www.ietf.org/1id-abstracts.html. The list of Internet-Draft 43 Shadow Directories can be accessed at 44 https://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 64 7. E-L1FS/E-L2FS Backwards Compatibility..................13 65 8. Manageability Considerations...........................13 67 9. Security Considerations................................15 68 10. IANA Considerations...................................15 70 11. References............................................16 71 11.1. Normative References................................16 72 11.2. Informative References..............................17 74 Appendix A. Level Transition Clarification................18 76 Authors' Addresses........................................19 78 1. Introduction 80 TRILL (Transparent Interconnection of Lots of Links [RFC6325] 81 [RFC7780]) multilevel techniques are designed to improve TRILL 82 scalability issues. 84 Informational [RFC8243] is an educational document to explain 85 multilevel TRILL and list possible concerns. It does not specify a 86 protocol. As described in [RFC8243], there have been two proposed 87 approaches. One approach, which is referred to as the "unique 88 nickname" approach, gives unique nicknames to all the TRILL switches 89 in the multilevel campus, either by having the Level 1/Level 2 border 90 TRILL switches advertise which nicknames are not available for 91 assignment in the area, or by partitioning the 16-bit nickname into 92 an "area" field and a "nickname inside the area" field. [RFC8397] is 93 the standards track document specifying a "unique nickname" flavor of 94 TRILL multilevel. The other approach, which is referred to in 95 [RFC8243] as the "aggregated nickname" approach, involves assigning 96 nicknames to the areas, and allowing nicknames to be reused inside 97 different areas, by having the border TRILL switches rewrite the 98 nickname fields when entering or leaving an area. [RFC8243] makes the 99 case that, while unique nickname multilevel solutions are simpler, 100 aggregated nickname solutions scale better. 102 The approach specified in this standards track document is somewhat 103 similar to the "aggregated nickname" approach in [RFC8243] but with a 104 very important difference. In this document, the nickname of an area 105 border RBridge is used in both Level 1 (L1) and Level 2 (L2). No 106 additional nicknames are assigned to represent L1 areas as such. 107 Instead, multiple border RBridges are allowed and each L1 area is 108 denoted by the set of all nicknames of those border RBridges of the 109 area. For this approach, nicknames in the L2 area MUST be unique but 110 nicknames inside an L1 area can be reused in other L1 areas that also 111 use this approach. The use of the approach specified in this document 112 in one L1 area does not prohibit the use of other approaches in other 113 L1 areas in the same TRILL campus, for example the use of the unique 114 nickname approach specified in [RFC8397]. The TRILL packet format is 115 unchanged by this document, but data plane processing is changed at 116 Border RBridges and efficient high volume data flow at Border 117 RBridges might require forwarding hardware change. 119 2. Acronyms and Terminology 121 Data Label: VLAN or FGL Fine-Grained Label (FGL). 123 DBRB: Designated Border RBridge. 125 IS-IS: Intermediate System to Intermediate System [IS-IS]. 127 Level: Similar to IS-IS, TRILL has Level 1 for intra-area and Level 2 128 for inter-area. Routing information is exchanged between Level 1 129 RBridges within the same Level 1 area, and Level 2 RBridges can only 130 form relationships and exchange information with other Level 2 131 RBridges. 133 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 134 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 135 "OPTIONAL" in this document are to be interpreted as described in BCP 136 14 [RFC2119] [RFC8174] when, and only when, they appear in all 137 capitals, as shown here. 139 Familiarity with [RFC6325] is assumed in this document. 141 3. Nickname Handling on Border RBridges 143 This section provides an illustrative example and description of the 144 border learning border RBridge nicknames. 146 Area {2,20} level 2 Area {3,30} 147 +-------------------+ +-----------------+ +--------------+ 148 | | | | | | 149 | S--RB27---Rx--Rz----RB2---Rb---Rc--Rd---Re--RB3---Rk--RB44---D | 150 | 27 | | | | 44 | 151 | ----RB20--- ----RB30--- | 152 +-------------------+ +-----------------+ +--------------+ 154 Figure 1: An Example Topology for TRILL Multilevel 156 In Figure 1, RB2, RB20, RB3 and RB30 are area border TRILL switches 157 (RBridges). Their nicknames are 2, 20, 3 and 30 respectively and are 158 used as TRILL switch identifiers in their areas [RFC6325]. Area 159 border RBridges use the set of border nicknames to denote the L1 area 160 that they are attached to. For example, RB2 and RB20 use nicknames 161 {2,20} to denote the L1 area on the left. 163 A source S is attached to RB27 and a destination D is attached to 164 RB44. RB27 has a nickname, say 27, and RB44 has a nickname, say 44 165 (and in fact, they could even have the same nickname, since the TRILL 166 switch nickname will not be visible outside these Level 1 areas). 168 3.1. Actions on Unicast Packets 170 Let's say that S transmits a frame to destination D and let's say 171 that D's location has been learned by the relevant TRILL switches 172 already. These relevant switches have learned the following: 174 1) RB27 has learned that D is connected to nickname 3. 175 2) RB3 has learned that D is attached to nickname 44. 177 The following sequence of events will occur: 179 - S transmits an Ethernet frame with source MAC = S and destination 180 MAC = D. 182 - RB27 encapsulates with a TRILL header with ingress RBridge = 27, 183 and egress RBridge = 3 producing a TRILL Data packet. 185 - RB2 and RB20 have announced in the Level 1 IS-IS instance in area 186 {2,20}, that they are attached to all those area nicknames, 187 including {3,30}. Therefore, IS-IS routes the packet to RB2 (or 188 RB20, if RB20 on the least-cost route from RB27 to RB3). 190 - RB2, when transitioning the packet from Level 1 to Level 2, 191 replaces the ingress TRILL switch nickname with its own nickname, 192 replacing 27 with 2. Within Level 2, the ingress RBridge field in 193 the TRILL header will therefore be 2, and the egress RBridge field 194 will be 3. (The egress nickname MAY be replaced with an area 195 nickname selected from {3,30}. See Section 4 for the detail of the 196 selection method. Here, suppose nickname 3 is used.) Also RB2 197 learns that S is attached to nickname 27 in area {2,20} to 198 accommodate return traffic. RB2 SHOULD synchronize with RB20 using 199 ESADI protocol [RFC7357] that MAC = S is attached to nickname 27. 201 - The packet is forwarded through Level 2, to RB3, which has 202 advertised, in Level 2, its L2 nickname as 3. 204 - RB3, when forwarding into area {3,30}, replaces the egress 205 nickname in the TRILL header with RB44's nickname (44). (The 206 ingress nickname MAY be replaced with an area nickname selected 207 from {2,20}. See Section 4 for the detail of the selection method. 208 Here, suppose nickname 2 is selected.) So, within the destination 209 area, the ingress nickname will be 2 and the egress nickname will 210 be 44. 212 - RB44, when decapsulating, learns that S is attached to nickname 2, 213 which is one of the area nicknames of the ingress. 215 3.2. Actions on Multi-Destination Packets 217 Distribution trees for flooding of multi-destination packets are 218 calculated separately within each L1 area and in L2. When a multi- 219 destination packet arrives at the border, it needs to be transitioned 220 either from L1 to L2, or from L2 to L1. All border RBridges are 221 eligible for Level transition. However, for each multi-destination 222 packet, only one of them acts as the Designated Border RBridge (DBRB) 223 to do the transition while other non-DBRBs MUST drop the received 224 copies. All border RBridges of an area MUST agree on a pseudorandom 225 algorithm as the tie-breaker to locally determine the DBRB. The same 226 pseudorandom algorithm will be reused in Section 4 for the purpose of 227 load balancing. It's also possible to implement a certain election 228 protocol to elect the DBRB. However, such kind of implementations are 229 out the scope of this document. By default, the border RBridge with 230 the smallest nickname, considered as an unsigned integer, is elected 231 DBRB. 233 As per [RFC6325], multi-destination packets can be classified into 234 three types: unicast packet with unknown destination MAC address 235 (unknown-unicast packet), multicast packet and broadcast packet. Now 236 suppose that D's location has not been learned by RB27 or the frame 237 received by RB27 is recognized as broadcast or multicast. What will 238 happen within a Level 1 area (as it would in TRILL today) is that 239 RB27 will forward the packet as multi-destination, setting its M bit 240 to 1 and choosing an L1 tree, flooding the packet on the distribution 241 tree, subject to possible pruning. 243 When the copies of the multi-destination packet arrive at area border 244 RBridges, non-DBRBs MUST drop the packet while the DBRB, say RB2, 245 needs to do the Level transition for the multi-destination packet. 246 For a unknown-unicast packet, if the DBRB has learnt the destination 247 MAC address, it SHOULD convert the packet to unicast and set its M 248 bit to 0. Otherwise, the multi-destination packet will continue to be 249 flooded as multicast packet on the distribution tree. The DBRB 250 chooses the new distribution tree by replacing the egress nickname 251 with the new tree root RBridge nickname. The following sequence of 252 events will occur: 254 - RB2, when transitioning the packet from Level 1 to Level 2, 255 replaces the ingress TRILL switch nickname with its own nickname, 256 replacing 27 with 2. RB2 also needs to replace the egress RBridge 257 nickname with an L2 tree root RBridge nickname (say 2). In order 258 to accommodate return traffic, RB2 records that S is attached to 259 nickname 27 and SHOULD use the ESADI protocol [RFC7357] to 260 synchronize this attachment information with other border RBridges 261 (say RB20) in the area. 263 - RB20, will receive the packet flooded on the L2 tree by RB2. It is 264 important that RB20 does not transition this packet back to L1 as 265 it does for a multicast packet normally received from another 266 remote L1 area. RB20 should examine the ingress nickname of this 267 packet. If this nickname is found to be a border RBridge nickname 268 of the area {2,20}, RB2 must not forwarded the packet into this 269 area. 271 - The packet is flooded on the Level 2 tree to reach both RB3 and 272 RB30. Suppose RB3 is the selected DBRB. The non-DBRB RB30 will 273 drop the packet. 275 - RB3, when forwarding into area {3,30}, replaces the egress 276 nickname in the TRILL header with a root RBridge nickname (say 3) 277 of the distribution tree of L1 area {3,30}. [Here, the ingress 278 nickname MAY be replaced with a different area nickname selected 279 from {2,20}, the set of border RBridges to the ingress area, as 280 specified in Section 4.] Now suppose that RB27 has learned the 281 location of D (attached to nickname 3), but RB3 does not know 282 where D is. In that case, RB3 must turn the packet into a multi- 283 destination packet and floods it on the distribution tree of L1 284 area {3,30}. 286 - RB30, will receive the packet flooded on the L1 tree by RB3. It is 287 important that RB30 does not transition this packet back to L2. 289 RB30 should also examine the ingress nickname of this packet. If 290 this nickname is found to be an L2 border RBridge nickname, RB30 291 must not transition the packet back to L2. 293 - The multicast listener RB44, when decapsulating the received 294 packet, learns that S is attached to nickname 2, which is one of 295 the area nicknames of the ingress. 297 4. Per-flow Load Balancing 299 Area border RBridges perform ingress/egress nickname replacement when 300 they transition TRILL data packets between Level 1 and Level 2. The 301 egress nickname will again be replaced when the packet transitions 302 from Level 2 to Level 1. This nickname replacement enables the per- 303 flow load balance which is specified as follows. 305 4.1. Ingress Nickname Replacement 307 When a TRILL data packet from other areas arrives at an area border 308 RBridge, this RBridge MAY select one area nickname of the ingress 309 area to replace the ingress nickname of the packet so that the 310 returning TRILL data packet can be forwarded to this selected 311 nickname. The selection is simply based on a pseudorandom algorithm 312 as defined in Section 5.3 of [RFC7357]. With the random ingress 313 nickname replacement, the border RBridge actually achieves a per-flow 314 load balance for returning traffic. 316 All area border RBridges in an L1 area MUST agree on the same 317 pseudorandom algorithm. The source MAC address, ingress area 318 nicknames, egress area nicknames and the Data Label of the received 319 TRILL data packet are candidate factors of the input of this 320 pseudorandom algorithm. Note that the value of the destination MAC 321 address SHOULD be excluded from the input of this pseudorandom 322 algorithm, otherwise the egress RBridge will see one source MAC 323 address flip flopping among multiple ingress RBridges. 325 4.2. Egress Nickname Replacement 327 When a TRILL data packet originated from an L1 area arrives at an 328 area border RBridge of that area, that RBridge MAY select one area 329 nickname of the egress area to replace the egress nickname of the 330 packet. By default, it SHOULD choose the egress area border RBridge 331 with the least cost route to reach or, if there are multiple equal 332 cost egress area border RBridges, use the pseudorandom algorithm as 333 defined in Section 5.3 of [RFC7357] to select one. The use of that 334 algorithm MAY be extended to selection among some stable set of 335 egress area border RBridges that include non-least-cost alternatives 336 if it is desired to obtain more load spreading at the cost of 337 sometimes using a non-least-cost Level 2 route to forward the TRILL 338 data packet to the egress area. 340 5. Protocol Extensions for Discovery 342 The following topology change scenarios will trigger the discovery 343 processes as defined in Sections 5.1 and 5.2: 344 - A new node comes up or recovers from a previous failure. 345 - A node goes down. 346 - A link or node fails and causes partition of an L1/L2 area. 347 - A link or node whose failure have caused partitioning of an L1/L2 348 area is repaired. 350 5.1. Discovery of Border RBridges in L1 352 The following Level 1 Border RBridge APPsub-TLV will be included in 353 an E-L1FS FS-LSP fragment zero [RFC7780] as an APPsub-TLV of the 354 TRILL GENINFO-TLV. Through listening for this APPsub-TLV, an area 355 border RBridge discovers all other area border RBridges in this area. 357 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 358 | Type = L1-BORDER-RBRIDGE | (2 bytes) 359 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 360 | Length | (2 bytes) 361 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 362 | Sender Nickname | (2 bytes) 363 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 365 o Type: Level 1 Border RBridge (TRILL APPsub-TLV type tbd1) 367 o Length: 2 369 o Sender Nickname: The nickname the originating IS will use as the 370 L1 Border RBridge nickname. This field is useful because the 371 originating IS might own multiple nicknames. 373 5.2. Discovery of Border RBridge Sets in L2 375 The following APPsub-TLV will be included in an E-L2FS FS-LSP 376 fragment zero [RFC7780] as an APPsub-TLV of the TRILL GENINFO-TLV. 377 Through listening to this APPsub-TLV in L2, an area border RBridge 378 discovers all groups of L1 border RBridges and each such group 379 identifies an area. 381 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 382 | Type = L1-BORDER-RB-GROUP | (2 bytes) 383 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 384 | Length | (2 bytes) 385 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 386 | L1 Border RBridge Nickname 1 | (2 bytes) 387 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 388 | ... | 389 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 390 | L1 Border RBridge Nickname k | (2 bytes) 391 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 393 o Type: Level 1 Border RBridge Group (TRILL APPsub-TLV type tbd2) 395 o Length: 2 * k. If length is not a multiple of 2, the APPsub-TLV is 396 corrupt and MUST be ignored. 398 o L1 Border RBridge Nickname: The nickname that an area border 399 RBridge uses as the L1 Border RBridge nickname. The L1-BORDER-RB- 400 GROUP TLV generated by an area border RBridge MUST include all L1 401 Border RBridge nicknames of the area. It's RECOMMENDED that these 402 k nicknames are ordered in ascending order according to the 403 2-octet nickname considered as an unsigned integer. 405 When an L1 area is partitioned [RFC8243], border RBridges will re- 406 discover each other in both L1 and L2 through exchanging LSPs. In L2, 407 the set of border RBridge nicknames for this splitting area will 408 change. Border RBridges that detect such a change MUST flush the 409 reachability information associated to any RBridge nickname from this 410 changing set. 412 6. One Border RBridge Connects Multiple Areas 414 It's possible that one border RBridge (say RB1) connects multiple L1 415 areas. RB1 SHOULD use a single area nickname for all these areas. 417 Nicknames used within one of these L1 areas can be reused within 418 other areas. It's important that packets destined to those duplicated 419 nicknames are sent to the right area. Since these areas are connected 420 to form a layer 2 network, duplicated {MAC, Data Label} across these 421 areas SHOULD NOT occur (see Section 4.2.6 of [RFC6325] for tie 422 breaking rules). Now suppose a TRILL data packet arrives at the area 423 border nickname of RB1. For a unicast packet, RB1 can look up the 424 {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: either RB1 is not the 427 DBRB and RB1 will not transition the packet oe RB1 is the DBRB. If 428 RB1 is the DBRB, RB1 follows the following rules: 430 - if this packet originated from an area out of the connected areas, 431 RB1 replicates this packet and floods it on the proper Level 1 432 trees of all the areas in which it acts as the DBRB. 434 - if the packet originated from one of the connected areas, RB1 435 replicates the packet it receives from the Level 1 tree and floods 436 it on other proper Level 1 trees of all the areas in which it acts 437 as the DBRB except the originating area (i.e., the area connected 438 to the incoming interface). RB1 might also receive the replication 439 of the packet from the Level 2 tree. This replication MUST be 440 dropped by RB1. It recognizes such packets by their ingress 441 nickname being the nickname of one of the border RBridges of an L1 442 area to which the receiving border RBridge is attached. 444 7. E-L1FS/E-L2FS Backwards Compatibility 446 All Level 2 RBridges MUST support E-L2FS [RFC7356] [RFC7780]. The 447 Extended TLVs defined in Section 5 are to be used in Extended Level 448 1/2 Flooding Scope (E-L1FS/E-L2FS) PDUs. Area border RBridges MUST 449 support both E-L1FS and E-L2FS. RBridges that do not support both 450 E-L1FS or E-L2FS cannot serve as area border RBridges but they can 451 appear in an L1 area acting as non-area-border RBridges. 453 8. Manageability Considerations 455 If an L1 Border RBridge Nickname is configured at an RBridge and that 456 RBridge has both L1 and L2 adjacencies, the multilevel feature as 457 specified in this document is turned on for that RBridge. In 458 contrast, unique nickname multilevel as specified in [RFC8397] is 459 enabled by the presence of L1 and L2 adjacencies without an L1 Border 460 RBridge Nickname being configured. RBridges supporting only unique 461 nickname multilevel do not support the configuration of an L2 Border 462 RBridge Nickname. RBridges supporting only the single level TRILL 463 base protocol specified in [RFC6325] do not support L2 adjacencies. 465 If there are multiple border RBridges between an L1 area and L2 and 466 one or more of them only support or are only configured for unique 467 nickname multilevel ([RFC8397]), any of these border RBridges that 468 are configured to used single nickname multilevel as specified in 469 this document MUST support [RFC8397] and fall back to behaving as a 470 unique nickname border RBridge for that L1 area. Because overlapping 471 sets of RBridges may be the border RBridges for different L1 areas, 472 an RBridge supporting single nickname MUST be able to simultaneously 473 support single nickname for some of its L1 areas and unique nickname 474 for others. For example, RB1 and RB2 might be border RBridges for L1 475 area A1 using single nickname while RB2 and RB3 are border RBridges 476 for area A2. If RB3 only supports unique nicknames then RB2 must fall 477 back to unique nickname for area A2 but continue to support single 478 nickname for area A1. Operators SHOULD be notified when this fall 479 back occurs. 481 In both the unique nickname approach specified in [RFC8397] and the 482 single nickname aggregated approach specified in this document, an 483 RBridge that has L1 and L2 adjacencies uses the same nickname in L1 484 and L2. If an RBridge is configured with an L1 Border RBridge 485 Nickname for any a Level 1 area, it uses this nickname across the 486 Level 2 area. This L1 Border RBridge Nickname cannot be used in any 487 other Level 1 area except other Level 1 areas for which the same 488 RBridge is a border RBridge with this L1 Border RBridge Nickname 489 configured. 491 Other than the manageability considerations specified above, the 492 manageability specifications in [RFC6325] still apply. 494 Border RBridges replace ingress and/or egress nickname when a TRILL 495 data packet traverses TRILL L2 area. A TRILL OAM message will be 496 forwarded through the multilevel single nickname TRILL campus using a 497 MAC address belonging to the destination RBridge [RFC7455]. 499 9. Security Considerations 501 For general TRILL Security Considerations, see [RFC6325]. 503 The newly defined TRILL APPsub-TLVs in Section 5 are transported in 504 IS-IS PDUs whose authenticity can be enforced using regular IS-IS 505 security mechanism [IS-IS] [RFC5310]. This document raises no new 506 security issues for IS-IS. 508 Using a variation of aggregated nicknames, and the resulting possible 509 duplication of nicknames between areas, increases the possibility of 510 a TRILL Data packet being delivered to the wrong egress RBridge if 511 areas are unexpectedly merged. However, in many cases the data would 512 be discarded at that egress RBridge because it would not match a 513 known end station data label/MAC address. 515 10. IANA Considerations 517 IANA is requested to allocate two new types under the TRILL GENINFO 518 TLV [RFC7357] from the range allocated by standards action for the 519 TRILL APPsub-TLVs defined in Section 5. The following entries are 520 added to the "TRILL APPsub-TLV Types under IS-IS TLV 251 Application 521 Identifier 1" Registry on the TRILL Parameters IANA web page. 523 Type Name Reference 524 --------- ---- --------- 525 tbd1[256] L1-BORDER-RBRIDGE [This document] 526 tbd2[257] L1-BORDER-RB-GROUP [This document] 528 11. References 530 11.1. Normative References 532 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 533 Requirement Levels", BCP 14, RFC 2119, DOI 534 10.17487/RFC2119, March 1997, . 537 [RFC6325] Perlman, R., Eastlake 3rd, D., Dutt, D., Gai, S., and A. 538 Ghanwani, "Routing Bridges (RBridges): Base Protocol 539 Specification", RFC 6325, DOI 10.17487/RFC6325, July 2011, 540 . 542 [RFC7356] Ginsberg, L., Previdi, S., and Y. Yang, "IS-IS Flooding 543 Scope Link State PDUs (LSPs)", RFC 7356, DOI 544 10.17487/RFC7356, September 2014, . 547 [RFC7357] Zhai, H., Hu, F., Perlman, R., Eastlake 3rd, D., and O. 548 Stokes, "Transparent Interconnection of Lots of Links 549 (TRILL): End Station Address Distribution Information 550 (ESADI) Protocol", RFC 7357, DOI 10.17487/RFC7357, 551 September 2014, . 553 [RFC7455] Senevirathne, T., Finn, N., Salam, S., Kumar, D., Eastlake 554 3rd, D., Aldrin, S., and Y. Li, "Transparent 555 Interconnection of Lots of Links (TRILL): Fault 556 Management", RFC 7455, DOI 10.17487/RFC7455, March 2015, 557 . 559 [RFC7780] Eastlake 3rd, D., Zhang, M., Perlman, R., Banerjee, A., 560 Ghanwani, A., and S. Gupta, "Transparent Interconnection of 561 Lots of Links (TRILL): Clarifications, Corrections, and 562 Updates", RFC 7780, DOI 10.17487/RFC7780, February 2016, 563 . 565 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 2119 566 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, May 567 2017, . 569 [RFC8397] Zhang, M., Eastlake 3rd, D., Perlman, R., Zhai, H., and D. 570 Liu, "Transparent Interconnection of Lots of Links (TRILL) 571 Multilevel Using Unique Nicknames", RFC 8397, DOI 572 10.17487/RFC8397, May 2018, . 575 11.2. Informative References 577 [IS-IS] International Organization for Standardization, ISO/IEC 578 10589:2002, "Information technology -- Telecommunications 579 and information exchange between systems -- Intermediate 580 System to Intermediate System intra-domain routeing 581 information exchange protocol for use in conjunction with 582 the protocol for providing the connectionless-mode network 583 service", ISO 8473, Second Edition, November 2002. 585 [RFC5310] Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R., 586 and M. Fanto, "IS-IS Generic Cryptographic Authentication", 587 RFC 5310, DOI 10.17487/RFC5310, February 2009, 588 . 590 [RFC8243] Perlman, R., Eastlake 3rd, D., Zhang, M., Ghanwani, A., and 591 H. Zhai, "Alternatives for Multilevel Transparent 592 Interconnection of Lots of Links (TRILL)", RFC 8243, DOI 593 10.17487/RFC8243, September 2017, . 596 Appendix A. Level Transition Clarification 598 It's possible that an L1 RBridge is only reachable from a non-DBRB 599 border RBridge. If this non-DBRB RBridge refrains from Level 600 transition, the question is, how can a multicast packet reach this L1 601 RBridge? The answer is, it will be reached after the DBRB performs 602 the Level transition and floods the packet using an L1 distribution 603 tree. 605 Take the following figure as an example. RB77 is reachable from the 606 border RBridge RB30 while RB3 is the DBRB. RB3 transitions the 607 multicast packet into L1 and floods the packet on the distribution 608 tree rooted from RB3. This packet is finally flooded to RB77 via 609 RB30. 611 Area{3,30} 612 +--------------+ (root) RB3 o 613 | | \ 614 -RB3 | | o RB30 615 | | | / 616 -RB30-RB77 | RB77 o 617 +--------------+ 619 Example Topology L1 Tree 621 In the above example, the multicast packet is forwarded along a non- 622 optimal path. A possible improvement is to have RB3 configured not to 623 belong to this area. In this way, RB30 will surely act as the DBRB to 624 do the Level transition. 626 Authors' Addresses 628 Mingui Zhang 629 Huawei Technologies 630 No. 156 Beiqing Rd. Haidian District 631 Beijing 100095 632 China 634 Email: zhangmingui@huawei.com 636 Donald E. Eastlake, 3rd 637 Futurewei Technologies 638 2386 Panoramic Circle 639 Apopka, FL 32703 640 United States 642 Phone: +1-508-333-2270 643 Email: d3e3e3@gmail.com 645 Radia Perlman 646 EMC 647 2010 256th Avenue NE, #200 648 Bellevue, WA 98007 649 United States 651 Email: radia@alum.mit.edu 653 Margaret Cullen 654 Painless Security 655 356 Abbott Street 656 North Andover, MA 01845 657 United States 659 Phone: +1-781-405-7464 660 Email: margaret@painless-security.com 661 URI: http://www.painless-security.com 663 Hongjun Zhai 664 Jinling Institute of Technology 665 99 Hongjing Avenue, Jiangning District 666 Nanjing, Jiangsu 211169 667 China 669 Email: honjun.zhai@tom.com 671 Copyright, Disclaimer, and Additional IPR Provisions 673 Copyright (c) 2021 IETF Trust and the persons identified as the 674 document authors. 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