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Jounay 5 Expires: July 2, 2014 France Telecom 6 I. Wijnands 7 Cisco Systems, Inc 8 N. Leymann 9 Deutsche Telekom AG 10 December 29, 2013 12 LDP Extensions for Hub & Spoke Multipoint Label Switched Path 13 draft-ietf-mpls-mldp-hsmp-06.txt 15 Abstract 17 This draft introduces a hub & spoke multipoint (HSMP) Label Switched 18 Path (LSP), which allows traffic both from root to leaf through 19 point-to-multipoint (P2MP) LSP and also leaf to root along the 20 reverse path. That means traffic entering the HSMP LSP from 21 application/customer at the root node travels downstream to each leaf 22 node, exactly as if it is travelling downstream along a P2MP LSP to 23 each leaf node. Upstream traffic entering the HSMP LSP at any leaf 24 node travels upstream along the tree to the root, as if it is unicast 25 to the root. Direct communication among the leaf nodes is not 26 allowed. 28 Requirements Language 30 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 31 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 32 document are to be interpreted as described in RFC2119 [RFC2119]. 34 Status of this Memo 36 This Internet-Draft is submitted in full conformance with the 37 provisions of BCP 78 and BCP 79. 39 Internet-Drafts are working documents of the Internet Engineering 40 Task Force (IETF). Note that other groups may also distribute 41 working documents as Internet-Drafts. The list of current Internet- 42 Drafts is at http://datatracker.ietf.org/drafts/current/. 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 This Internet-Draft will expire on July 2, 2014. 50 Copyright Notice 52 Copyright (c) 2013 IETF Trust and the persons identified as the 53 document authors. All rights reserved. 55 This document is subject to BCP 78 and the IETF Trust's Legal 56 Provisions Relating to IETF Documents 57 (http://trustee.ietf.org/license-info) in effect on the date of 58 publication of this document. Please review these documents 59 carefully, as they describe your rights and restrictions with respect 60 to this document. Code Components extracted from this document must 61 include Simplified BSD License text as described in Section 4.e of 62 the Trust Legal Provisions and are provided without warranty as 63 described in the Simplified BSD License. 65 Table of Contents 67 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 68 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 69 3. Setting up HSMP LSP with LDP . . . . . . . . . . . . . . . . . 5 70 3.1. Support for HSMP LSP Setup with LDP . . . . . . . . . . . 5 71 3.2. HSMP FEC Elements . . . . . . . . . . . . . . . . . . . . 6 72 3.3. Using the HSMP FEC Elements . . . . . . . . . . . . . . . 6 73 3.4. HSMP LSP Label Map . . . . . . . . . . . . . . . . . . . . 7 74 3.4.1. HSMP LSP Leaf Node Operation . . . . . . . . . . . . . 8 75 3.4.2. HSMP LSP Transit Node Operation . . . . . . . . . . . 8 76 3.4.3. HSMP LSP Root Node Operation . . . . . . . . . . . . . 9 77 3.5. HSMP LSP Label Withdraw . . . . . . . . . . . . . . . . . 10 78 3.5.1. HSMP Leaf Operation . . . . . . . . . . . . . . . . . 10 79 3.5.2. HSMP Transit Node Operation . . . . . . . . . . . . . 10 80 3.5.3. HSMP Root Node Operation . . . . . . . . . . . . . . . 10 81 3.6. HSMP LSP Upstream LSR Change . . . . . . . . . . . . . . . 11 82 3.7. Determining Forwarding Interface . . . . . . . . . . . . . 11 83 4. HSMP LSP on a LAN . . . . . . . . . . . . . . . . . . . . . . 11 84 5. Redundancy Considerations . . . . . . . . . . . . . . . . . . 12 85 6. Failure Detection of HSMP LSP . . . . . . . . . . . . . . . . 12 86 7. Security Considerations . . . . . . . . . . . . . . . . . . . 13 87 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 13 88 8.1. New LDP FEC Element types . . . . . . . . . . . . . . . . 13 89 8.2. HSMP LSP capability TLV . . . . . . . . . . . . . . . . . 13 90 8.3. New sub-TLVs for the Target Stack TLV . . . . . . . . . . 14 91 9. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 14 92 10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 14 93 10.1. Normative references . . . . . . . . . . . . . . . . . . . 14 94 10.2. Informative References . . . . . . . . . . . . . . . . . . 15 95 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15 97 1. Introduction 99 The point-to-multipoint (P2MP) Label Switched Path (LSP) defined in 100 [RFC6388] allows traffic to transmit from root to several leaf nodes, 101 and multipoint-to-multipoint (MP2MP) LSP allows traffic from every 102 node to transmit to every other node. This draft introduces a hub & 103 spoke multipoint (HSMP) LSP, which has one root node and one or more 104 leaf nodes. HSMP LSP allows traffic both from root to leaf through 105 downstream LSP and also leaf to root along the upstream LSP. That 106 means traffic entering the HSMP LSP at the root node travels along 107 downstream LSP, exactly as if it is travelling along a P2MP LSP, and 108 traffic entering the HSMP LSP at any other leaf nodes travels along 109 upstream LSP toward only the root node. The upstream LSP should be 110 thought of unicast LSP to the root node, except that it follows the 111 reverse direction of the downstream LSP, rather than routing protocol 112 based unicast path. The combination of upstream LSPs initiated from 113 all leaf nodes forms a multipoint-to-point LSP. 115 2. Terminology 117 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 118 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 119 document are to be interpreted as described in [RFC2119]. 121 This document uses some terms and acronyms as follows: 123 mLDP: Multipoint extensions for Label Distribution Protocol (LDP) 124 defined in [RFC6388]. 126 P2MP LSP: point-to-multipoint Label Switched Path. An LSP that 127 has one Ingress Label Switching Router (LSR) and one or more 128 Egress LSRs. 130 MP2MP LSP: multipoint-to-multipoint Label Switched Path. An LSP 131 that connects a set of nodes, such that traffic sent by any node 132 in the LSP is delivered to all others. 134 HSMP LSP: hub & spoke multipoint Label Switched Path. An LSP that 135 has one root node and one or more leaf nodes, allows traffic from 136 root to all leaf nodes along downstream P2MP LSP and also leaf to 137 root node along the upstream unicast LSP. 139 FEC: Forwarding Equivalence Class 141 3. Setting up HSMP LSP with LDP 143 HSMP LSP is similar to MP2MP LSP described in [RFC6388], with the 144 difference that, when the leaf LSRs send traffic on the LSP, the 145 traffic is first delivered only to the root node and follows the 146 upstream path from the leaf node to the root node. The root node 147 then distributes the traffic on the P2MP tree to all of the leaf 148 nodes. 150 HSMP LSP consists of a downstream path and upstream path. The 151 downstream path is same as P2MP LSP, while the upstream path is only 152 from leaf to root node, without communication between leaf and leaf 153 nodes. The transmission of packets from the root node of an HSMP LSP 154 to the receivers (the leaf nodes) is identical to that of a P2MP LSP. 155 Traffic from a leaf node to the root follows the upstream path that 156 is the reverse of the path from the root to the leaf. Unlike an 157 MP2MP LSP, traffic from a leaf node does not branch toward other leaf 158 nodes, but is sent direct to the root where it is placed on the P2MP 159 path and distributed to all leaf nodes including the original sender. 161 To set up the upstream path of an HSMP LSP, ordered mode MUST be 162 used. Ordered mode can guarantee a leaf to start sending packets to 163 root immediately after the upstream path is installed, without being 164 dropped due to an incomplete LSP. 166 3.1. Support for HSMP LSP Setup with LDP 168 HSMP LSP requires the LDP capabilities [RFC5561] for nodes to 169 indicate that they support setup of HSMP LSPs. An implementation 170 supporting the HSMP LSP procedures specified in this document MUST 171 implement the procedures for Capability Parameters in Initialization 172 Messages. Advertisement of the HSMP LSP Capability indicates support 173 of the procedures for HSMP LSP setup. 175 A new Capability Parameter TLV is defined, the HSMP LSP Capability 176 Parameter. Following is the format of the HSMP LSP Capability 177 Parameter. 179 0 1 2 3 180 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 1 181 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 182 |U|F| HSMP LSP Cap(TBD IANA) | Length | 183 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 184 |S| Reserved | 185 +-+-+-+-+-+-+-+-+ 186 Figure 1. HSMP LSP Capability Parameter encoding 188 U-bit: Unknown TLV bit, as described in [RFC5036]. The value MUST be 189 1. The unknown TLV MUST be silently ignored and the rest of the 190 message processed as if the unknown TLV did not exist. 192 F-bit: Forward unknown TLV bit, as described in [RFC5036]. The value 193 of this bit MUST be 0 since a Capability Parameter TLV is sent only 194 in Initialization and Capability messages, which are not forwarded. 196 The length SHOULD be 1, and the S bit and reserved bits are defined 197 in [RFC5561] section 3. 199 The HSMP LSP Capability Parameter type is to be assigned by IANA. 201 If the peer has not advertised the corresponding capability, then 202 label messages using the HSMP Forwarding Equivalence Class (FEC) 203 Element SHOULD NOT (as described in [RFC6388] section 2.1) be sent to 204 the peer. Since ordered mode is applied for HSMP LSP signalling, the 205 label message break would ensure that the initiating leaf node is 206 unable to establish the upstream path to root node. 208 3.2. HSMP FEC Elements 210 Similar as MP2MP LSP, we define two new protocol entities, the HSMP 211 Downstream FEC Element and Upstream FEC Element. If a FEC TLV 212 contains one of the HSMP FEC Elements, the HSMP FEC Element MUST be 213 the only FEC Element in the FEC TLV. The structure, encoding and 214 error handling for the HSMP Downstream FEC Element and Upstream FEC 215 Element are the same as for the P2MP FEC Element described in 216 [RFC6388] Section 2.2. The difference is that two additional new FEC 217 types are defined: HSMP Downstream FEC (to be assigned by IANA) and 218 HSMP Upstream FEC (to be assigned by IANA). 220 3.3. Using the HSMP FEC Elements 222 In order to describe the message processing clearly, the entries in 223 the list below define the processing of the HSMP FEC Elements. 224 Additionally, the entries defined in [RFC6388] section 3.3 are also 225 reused in the following sections. 227 1. HSMP downstream LSP (or simply downstream ): an HSMP 228 LSP downstream path with root node address X and opaque value Y. 230 2. HSMP upstream LSP (or simply upstream ): an HSMP LSP 231 upstream path for root node address X and opaque value Y which will 232 be used by any of downstream node to send traffic upstream to root 233 node. 235 3. HSMP downstream FEC Element : a FEC Element with root node 236 address X and opaque value Y used for a downstream HSMP LSP. 238 4. HSMP upstream FEC Element : a FEC Element with root node 239 address X and opaque value Y used for an upstream HSMP LSP. 241 5. HSMP-D Label Mapping : A Label Mapping message with a 242 single HSMP downstream FEC Element and label TLV with label L. 243 Label L MUST be allocated from the per-platform label space of the 244 LSR sending the Label Mapping Message. 246 6. HSMP-U Label Mapping : A Label Mapping message with a 247 single HSMP upstream FEC Element and label TLV with label Lu. 248 Label Lu MUST be allocated from the per-platform label space of the 249 LSR sending the Label Mapping Message. 251 7. HSMP-D Label Withdraw : a Label Withdraw message with a 252 FEC TLV with a single HSMP downstream FEC Element and label 253 TLV with label L. 255 8. HSMP-U Label Withdraw : a Label Withdraw message with a 256 FEC TLV with a single HSMP upstream FEC Element and label TLV 257 with label Lu. 259 9. HSMP-D Label Release : a Label Release message with a 260 FEC TLV with a single HSMP downstream FEC Element and Label 261 TLV with label L. 263 10. HSMP-U Label Release : a Label Release message with a 264 FEC TLV with a single HSMP upstream FEC Element and label TLV 265 with label Lu. 267 3.4. HSMP LSP Label Map 269 This section specifies the procedures for originating HSMP Label 270 Mapping messages and processing received HSMP Label Mapping messages 271 for a particular HSMP LSP. The procedure of downstream HSMP LSP is 272 similar as that of downstream MP2MP LSP described in [RFC6388]. When 273 LDP operates in Ordered Label Distribution Control mode [RFC5036], 274 the upstream LSP will be set up by sending HSMP LSP LDP Label Mapping 275 message with a label which is allocated by upstream LSR to its 276 downstream LSR hop by hop from root to leaf node, installing the 277 upstream forwarding table by every node along the LSP. The detail 278 procedure of setting up upstream HSMP LSP is different with that of 279 upstream MP2MP LSP, and is specified in below section. 281 All labels discussed here are downstream-assigned [RFC5332] except 282 those which are assigned using the procedures described in Section 4. 284 Determining the upstream LSR for the HSMP LSP follows the 285 procedure for a P2MP LSP described in [RFC6388] Section 2.4.1.1. 286 That is, a node Z that wants to join an HSMP LSP determines 287 the LDP peer U that is Z's next-hop on the best path from Z to the 288 root node X. If there are multiple upstream LSRs, local algorithm 289 should be applied to ensure that there is a single upstream LSRs for 290 a particular LSP. 292 To determining one's HSMP downstream LSR, an upstream LDP peer which 293 receives a Label Mapping with HSMP downstream FEC Element from an LDP 294 peer D will treat D as HSMP downstream LDP peer. 296 3.4.1. HSMP LSP Leaf Node Operation 298 The leaf node operation is much the same as the operation of MP2MP 299 LSP defined in [RFC6388] Section 3.3.1.4. The only difference is the 300 FEC elements as specified below. 302 A leaf node Z of an HSMP LSP determines its upstream LSR U for 303 as per Section 3.3, allocates a label L, and sends an HSMP-D 304 Label Mapping to U. Leaf node Z expects an HSMP-U Label 305 Mapping from node U and checks whether it already has 306 forwarding state for upstream . If not, Z creates forwarding 307 state to push label Lu onto the traffic that Z wants to forward over 308 the HSMP LSP. How it determines what traffic to forward on this HSMP 309 LSP is outside the scope of this document. 311 3.4.2. HSMP LSP Transit Node Operation 313 The procedure of HSMP-D Label Mapping message is much the same as 314 processing MP2MP-D Label Mapping message defined in [RFC6388] Section 315 3.3.1.5. The processing of HSMP-U Label Mapping message is different 316 with that of MP2MP-U Label Mapping message as specified below. 318 Suppose node Z receives an HSMP-D Label Mapping from LSR D. 319 Z checks whether it has forwarding state for downstream . If 320 not, Z determines its upstream LSR U for as per Section 3.3. 321 Using this Label Mapping to update the label forwarding table MUST 322 NOT be done as long as LSR D is equal to LSR U. If LSR U is different 323 from LSR D, Z will allocate a label L' and install downstream 324 forwarding state to swap label L' with label L over interface I 325 associated with LSR D and send an HSMP-D Label Mapping to 326 U. Interface I is determined via the procedures in Section 3.7. 328 If Z already has forwarding state for downstream , all that Z 329 needs to do in this case is check that LSR D is not equal to the 330 upstream LSR of and update its forwarding state. Assuming its 331 old forwarding state was L'-> { ..., }, its 332 new forwarding state becomes L'-> { ..., , 333 }. If the LSR D is equal to the installed upstream LSR, the 334 Label Mapping from LSR D MUST be retained and MUST NOT update the 335 label forwarding table. 337 Node Z checks if upstream LSR U already has assigned a label Lu to 338 upstream . If not, transit node Z waits until it receives an 339 HSMP-U Label Mapping from LSR U. Once the HSMP-U Label 340 Mapping is received from LSR U, node Z checks whether it already has 341 forwarding state upstream with incoming label Lu' and outgoing 342 label Lu. If it does not, it allocates a label Lu' and creates a new 343 label swap for Lu' with Label Lu over interface Iu. Interface Iu is 344 determined via the procedures in Section 3.7. Node Z determines the 345 downstream HSMP LSR as per Section 4.3.1, and sends an HSMP-U Label 346 Mapping to node D. 348 Since a packet from any downstream node is forwarded only to the 349 upstream node, the same label (representing the upstream path) SHOULD 350 be distributed to all downstream nodes. This differs from the 351 procedures for MP2MP LSPs [RFC6388], where a distinct label must be 352 distributed to each downstream node. The forwarding state upstream 353 on node Z will be like this {, }. Iu means the 354 upstream interface over which Z receives HSMP-U Label Map 355 from LSR U. Packets from any downstream interface over which Z sends 356 HSMP-U Label Map with label Lu' will be forwarded to Iu 357 with label Lu' swap to Lu. 359 3.4.3. HSMP LSP Root Node Operation 361 The procedure of HSMP-D Label Mapping message is much the same as 362 processing MP2MP-D Label Mapping message defined in [RFC6388] Section 363 3.3.1.6. The processing of HSMP-U Label Mapping message is different 364 with that of MP2MP-U Label Mapping message as specified below. 366 Suppose the root node Z receives an HSMP-D Label Mapping 367 from node D. Z checks whether it already has forwarding state for 368 downstream . If not, Z creates downstream forwarding state and 369 installs a outgoing label L over interface I. Interface I is 370 determined via the procedures in Section 3.7. If Z already has 371 forwarding state for downstream , then Z will add label L over 372 interface I to the existing state. 374 Node Z checks if it has forwarding state for upstream . If 375 not, Z creates a forwarding state for incoming label Lu' that 376 indicates that Z is the HSMP LSP egress LER. E.g., the forwarding 377 state might specify that the label stack is popped and the packet 378 passed to some specific application. Node Z determines the 379 downstream HSMP LSR as per Section 3.3, and sends an HSMP-U Label Map 380 to node D. 382 Since Z is the root of the tree, Z will not send an HSMP-D Label Map 383 and will not receive an HSMP-U Label Mapping. 385 Root node could also be a leaf node, and it is able to determine what 386 traffic to forward on this HSMP LSP which is outside the scope of 387 this document. 389 3.5. HSMP LSP Label Withdraw 391 3.5.1. HSMP Leaf Operation 393 If a leaf node Z discovers that it has no need to be an Egress LSR 394 for that LSP (by means outside the scope of this document), then it 395 SHOULD send an HSMP-D Label Withdraw to its upstream LSR U 396 for , where L is the label it had previously advertised to U 397 for . Leaf node Z will also send an unsolicited HSMP-U Label 398 Release to U to indicate that the upstream path is no 399 longer used and that label Lu can be removed. 401 Leaf node Z expects the upstream router U to respond by sending a 402 downstream Label Release for L. 404 3.5.2. HSMP Transit Node Operation 406 If a transit node Z receives an HSMP-D Label Withdraw message from node D, it deletes label L from its forwarding state 408 downstream . Node Z sends an HSMP-D Label Release message with 409 label L to D. There is no need to send an HSMP-U Label Withdraw to D because node D already removed Lu and sent a label 411 release for Lu to Z. 413 If deleting L from Z's forwarding state for downstream results 414 in no state remaining for , then Z propagates the HSMP-D Label 415 Withdraw to its upstream node U for . Z should also 416 check if there are any incoming interface in forwarding state 417 upstream . If all downstream nodes are released and there is 418 no incoming interface, Z should delete the forwarding state upstream 419 and send HSMP-U Label Release message to its upstream node. 420 Otherwise, no HSMP-U Label Release message will be sent to the 421 upstream node. 423 3.5.3. HSMP Root Node Operation 425 When the root node of an HSMP LSP receives an HSMP-D Label Withdraw 426 and HSMP-U Label Release message, the procedure is the same as that 427 for transit nodes, except that the root node will not propagate the 428 Label Withdraw and Label Release upstream (as it has no upstream). 430 3.6. HSMP LSP Upstream LSR Change 432 The procedure for changing the upstream LSR is the same as defined in 433 [RFC6388] Section 2.4.3, only with different processing FEC Element. 435 When the upstream LSR changes from U to U', node Z should set up the 436 HSMP LSP to U' by applying procedures in Section 3.4. Z will 437 also remove HSMP LSP to U by applying procedure in Section 438 3.5. 440 To set up HSMP LSP to U' before/after removing HSMP LSP to U is a 441 local matter, and the recommended default behavior is to remove 442 before adding. 444 3.7. Determining Forwarding Interface 446 The co-routed path between upstream and downstream LSP would be 447 achieved for HSMP LSP. Both LSR U and LSR D would ensure the same 448 interface to send traffic by applying some procedures. For a network 449 with symmetric IGP cost configuration, the following procedure MAY be 450 used. To determine the downstream interface, LSR U MUST do a lookup 451 in the unicast routing table to find the best interface and next-hop 452 to reach LSR D. If the next-hop and interface are also advertised by 453 LSR D via the LDP session, it should be used to transmit the packet 454 to LSR D. Determine the upstream interface mechanism is same as 455 determining the downstream interface by exchanging the role of LSR U 456 and LSR D. If symmetric IGP cost could not be ensured, static route 457 configuration on LSR U and D could also be a possible way to ensure 458 co-routed path. 460 If co-routed is not required for HSMP LSP, the procedure defined in 461 [RFC6388] Section 2.4.1.2 could be applied. LSR U is free to 462 transmit the packet on any of the interfaces to LSR D. The algorithm 463 it uses to choose a particular interface is a local matter. 464 Determine the upstream interface mechanism is the same as determining 465 the downstream interface. 467 4. HSMP LSP on a LAN 469 The procedure to process the downstream HSMP LSP on a LAN is much the 470 same as downstream MP2MP LSP described in [RFC6388] section 6.1.1. 472 When establishing the downstream path of an HSMP LSP, as defined in 473 [RFC6389], a Label Request message for an LSP label is sent to the 474 upstream LSR. The upstream LSR should send Label Mapping message 475 that contains the LSP label for the downstream HSMP FEC and the 476 upstream LSR context label defined in [RFC5331]. When the LSR 477 forwards a packet downstream on one of those LSPs, the packet's top 478 label must be the "upstream LSR context label", and the packet's 479 second label is "LSP label". The HSMP downstream path will be 480 installed in the context-specific forwarding table corresponding to 481 the upstream LSR label. Packets sent by the upstream LSR can be 482 forwarded downstream using this forwarding state based on a two-label 483 lookup. 485 The upstream path of an HSMP LSP on a LAN is the same as the one on 486 other kind of links. That is, the upstream LSR must send Label 487 Mapping message that contains the LSP label for upstream HSMP FEC to 488 downstream node. Packets travelling upstream need to be forwarded in 489 the direction of the root by using the label allocated for upstream 490 HSMP FEC. 492 5. Redundancy Considerations 494 In some scenarios, it is necessary to provide two root nodes for 495 redundancy purpose. One way to implement this is to use two 496 independent HSMP LSPs acting as active/standby. At one time, only 497 one HSMP LSP will be active, and the other will be standby. After 498 detecting the failure of active HSMP LSP, the root and leaf nodes 499 will switch the traffic to the standby HSMP LSP which takes on the 500 role as active HSMP LSP. The detail of redundancy mechanism is out 501 of the scope. 503 6. Failure Detection of HSMP LSP 505 The idea of LSP ping for HSMP LSPs could be expressed as an intention 506 to test the LSP Ping Echo Request packets that enter at the root 507 along a particular downstream path of HSMP LSP, and end their MPLS 508 path on the leaf. The leaf node then sends the LSP Ping Echo Reply 509 along the upstream path of HSMP LSP, and end on the root that are the 510 (intended) root node. 512 New sub-TLVs are required to be assigned by IANA in Target FEC Stack 513 TLV and Reverse-path Target FEC Stack TLV to define the corresponding 514 HSMP-downstream FEC type and HSMP-upstream FEC type. In order to 515 ensure the leaf node to send the LSP Ping Echo Reply along the HSMP 516 upstream path, the R bit (Validate Reverse Path) in Global Flags 517 Field defined in [RFC6426] is reused here. 519 The node processing mechanism of LSP Ping Echo Request and Echo Reply 520 for HSMP LSP is inherited from [RFC6425] and [RFC6426] Section 3.4, 521 except the following: 523 1. The root node sending LSP Ping Echo Request message for HSMP LSP 524 MUST attach Target FEC Stack with HSMP downstream FEC, and set R bit 525 to '1' in Global Flags Field. 527 2. When the leaf node receiving the LSP Ping Echo Request, it MUST 528 send the LSP Ping Echo Reply to the associated HSMP upstream path. 529 The Reverse-path Target FEC Stack TLV attached by leaf node in Echo 530 Reply message SHOULD contain the sub-TLV of associated HSMP upstream 531 FEC. 533 7. Security Considerations 535 The same security considerations apply as for the MP2MP LSP described 536 in [RFC6388] and [RFC6425]. 538 Although this document introduces new FEC Elements and corresponding 539 procedures, the protocol does not bring any new security issues 540 compared to [RFC6388] and [RFC6425]. 542 8. IANA Considerations 544 8.1. New LDP FEC Element types 546 This document requires allocation of two new LDP FEC Element types 547 from the "Label Distribution Protocol (LDP) Parameters registry" the 548 "Forwarding Equivalence Class (FEC) Type Name Space": 550 1. the HSMP-upstream FEC type - requested value TBD 552 2. the HSMP-downstream FEC type - requested value TBD 554 The values should be allocated using the lowest free values from the 555 "IETF Consensus"-range (0-127). 557 8.2. HSMP LSP capability TLV 559 This document requires allocation of one new code points for the HSMP 560 LSP capability TLV from "Label Distribution Protocol (LDP) Parameters 561 registry" the "TLV Type Name Space": 563 HSMP LSP Capability Parameter - requested value TBD 565 The value should be allocated from the range 0x0901-0x3DFF (IETF 566 Consensus) using the first free value within this range. 568 8.3. New sub-TLVs for the Target Stack TLV 570 This document requires allocation of two new sub-TLV types for 571 inclusion within the LSP ping [RFC4379] Target FEC Stack TLV (TLV 572 type 1) and Reverse-path Target FEC Stack TLV (TLV type 16). 574 1. the HSMP-upstream LDP FEC Stack - requested value TBD 576 2. the HSMP-downstream LDP FEC Stack - requested value TBD 578 The value should be allocated from the IETF Standards Action range 579 (0-16383) that is used for mandatory and optional sub-TLVs that 580 requires a response if not understood. The value should be allocated 581 using the lowest free value within this range. 583 9. Acknowledgement 585 The author would like to thank Eric Rosen, Sebastien Jobert, Fei Su, 586 Edward, Mach Chen, Thomas Morin, Loa Andersson for their valuable 587 comments. 589 10. References 591 10.1. Normative references 593 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 594 Requirement Levels", BCP 14, RFC 2119, March 1997. 596 [RFC5331] Aggarwal, R., Rekhter, Y., and E. Rosen, "MPLS Upstream 597 Label Assignment and Context-Specific Label Space", 598 RFC 5331, August 2008. 600 [RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS 601 Multicast Encapsulations", RFC 5332, August 2008. 603 [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. 604 Le Roux, "LDP Capabilities", RFC 5561, July 2009. 606 [RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas, 607 "Label Distribution Protocol Extensions for Point-to- 608 Multipoint and Multipoint-to-Multipoint Label Switched 609 Paths", RFC 6388, November 2011. 611 [RFC6389] Aggarwal, R. and JL. Le Roux, "MPLS Upstream Label 612 Assignment for LDP", RFC 6389, November 2011. 614 [RFC6425] Saxena, S., Swallow, G., Ali, Z., Farrel, A., Yasukawa, 615 S., and T. Nadeau, "Detecting Data-Plane Failures in 616 Point-to-Multipoint MPLS - Extensions to LSP Ping", 617 RFC 6425, November 2011. 619 [RFC6426] Gray, E., Bahadur, N., Boutros, S., and R. Aggarwal, "MPLS 620 On-Demand Connectivity Verification and Route Tracing", 621 RFC 6426, November 2011. 623 10.2. Informative References 625 [RFC4379] Kompella, K. and G. Swallow, "Detecting Multi-Protocol 626 Label Switched (MPLS) Data Plane Failures", RFC 4379, 627 February 2006. 629 [RFC5036] Andersson, L., Minei, I., and B. Thomas, "LDP 630 Specification", RFC 5036, October 2007. 632 Authors' Addresses 634 Lizhong Jin 635 Shanghai, China 637 Email: lizho.jin@gmail.com 639 Frederic Jounay 640 France Telecom 641 2, avenue Pierre-Marzin 642 22307 Lannion Cedex, FRANCE 644 Email: frederic.jounay@orange.ch 646 IJsbrand Wijnands 647 Cisco Systems, Inc 648 De kleetlaan 6a 649 Diegem 1831, Belgium 651 Email: ice@cisco.com 652 Nicolai Leymann 653 Deutsche Telekom AG 654 Winterfeldtstrasse 21 655 Berlin 10781 657 Email: N.Leymann@telekom.de