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Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Network Working Group Sami Boutros 3 INTERNET-DRAFT Siva Sivabalan 4 Intended Status: Standards Track George Swallow 5 Shaleen Saxena 6 Cisco Systems 8 Vishwas Manral 9 Hewlett Packard Co. 11 Sam Aldrin 12 Huawei Technologies, Inc. 14 Expires: April 19, 2014 October 16, 2013 16 Definition of Time-to-Live TLV for LSP-Ping Mechanisms 17 draft-ietf-mpls-lsp-ping-ttl-tlv-06.txt 19 Abstract 21 LSP-Ping is a widely deployed Operation, Administration, and 22 Maintenance (OAM) mechanism in MPLS networks. However, in the present 23 form, this mechanism is inadequate to verify connectivity of a 24 segment of a Multi-Segment PseudoWire (MS-PW) from any node on the 25 path of the MS-PW. This document defines a TLV to address this 26 shortcoming. 28 Status of this Memo 30 This Internet-Draft is submitted to IETF in full conformance with the 31 provisions of BCP 78 and BCP 79. 33 Internet-Drafts are working documents of the Internet Engineering 34 Task Force (IETF), its areas, and its working groups. Note that 35 other groups may also distribute working documents as 36 Internet-Drafts. 38 Internet-Drafts are draft documents valid for a maximum of six months 39 and may be updated, replaced, or obsoleted by other documents at any 40 time. It is inappropriate to use Internet-Drafts as reference 41 material or to cite them other than as "work in progress." 43 The list of current Internet-Drafts can be accessed at 44 http://www.ietf.org/1id-abstracts.html 46 The list of Internet-Draft Shadow Directories can be accessed at 47 http://www.ietf.org/shadow.html 49 Copyright and License Notice 51 Copyright (c) 2013 IETF Trust and the persons identified as the 52 document authors. All rights reserved. 54 This document is subject to BCP 78 and the IETF Trust's Legal 55 Provisions Relating to IETF Documents 56 (http://trustee.ietf.org/license-info) in effect on the date of 57 publication of this document. Please review these documents 58 carefully, as they describe your rights and restrictions with respect 59 to this document. Code Components extracted from this document must 60 include Simplified BSD License text as described in Section 4.e of 61 the Trust Legal Provisions and are provided without warranty as 62 described in the Simplified BSD License. 64 Table of Contents 66 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 67 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 68 3. Time To Live TLV . . . . . . . . . . . . . . . . . . . . . . . 4 69 3.1. TTL TLV Format . . . . . . . . . . . . . . . . . . . . . . 4 70 3.2. Usage . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 71 4. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 72 4.1. Traceroute mode . . . . . . . . . . . . . . . . . . . . . . 5 73 4.2. Error scenario . . . . . . . . . . . . . . . . . . . . . . 6 74 5. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 75 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 76 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 6 77 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 78 8.1 Normative References . . . . . . . . . . . . . . . . . . . 7 79 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 81 1. Introduction 83 A MS-PW may span across multiple service provider networks. In order 84 to allow Service Providers (SP) to verify segments of such MS-PW from 85 any node on the path of the MS-PW, any node along the path of the MS- 86 PW, should be able to originate an LSP-Ping echo request packet to 87 any another node along the path of the MS-PW and receive the 88 corresponding echo reply. If the originator of the echo request is at 89 the end of a MS-PW, the receiver of the request can send the reply 90 back to the sender without knowing the hop-count distance of the 91 originator. The reply will be intercepted by the originator 92 regardless of the TTL value on the reply packet. But, if the 93 originator is not at the end of the MS-PW, the receiver of the echo 94 request MAY need to know how many hops away the originator of the 95 echo request is so that it can set the TTL value on the MPLS header 96 for the echo reply to be intercepted at the originator node. 98 In MPLS networks, for bidirectional co-routed LSPs, if it is desired 99 to verify connectivity from any intermediate node (LSR) on the LSP to 100 the any other LSR on the LSP the receiver may need to know the TTL to 101 send the Echo reply with, so as the packet is intercepted by the 102 originator node. 104 A new optional TTL TLV is being proposed in this document this TLV 105 will be added by the originator of the echo request to inform the 106 receiver how many hops away the originator is on the path of the MS- 107 PW or Bidirectional LSP. 109 The scope of this TTL TLV is currently limited to MS-PW or 110 Bidirectional co-routed MPLS LSPs. 112 2. Terminology 114 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 115 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 116 document are to be interpreted as described in RFC 2119 [RFC2119]. 118 LSR: Label Switching Router 120 MPLS-TP: MPLS Transport Profile 122 MS-PW: Multi-Segment Pseudowire 124 PW: Pseudowire 126 TLV: Type Length Value 128 TTL: Time To Live 130 3. Time To Live TLV 132 3.1. TTL TLV Format 134 0 1 2 3 135 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 1 136 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 137 | Type = TBD | Length = 8 | 138 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 139 | Value | Reserved | Flags | 140 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 141 Figure 1: Time To Live TLV format 143 The TTL TLV has the format shown in Figure 1. 145 Value 147 The value of the TTL as specified by this TLV 149 Flags 151 The Flags field is a bit vector with the following format: 153 0 1 154 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 155 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 156 | MBZ |R| 157 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ 159 One flag is defined for now, the R flag; the rest of the 160 flags are currently undefined and must be zero (MBZ) when 161 sending and ignored on receipt. 163 The R flag (Reply TTL) is set signify that the value is 164 meant to be used as the TTL for the reply packet. Other bits 165 may be defined later to enhance the scope of this TLV. 167 3.2. Usage 169 This TLV shall be included in the echo request by the originator of 170 request. The use of this TLV is optional. If a receiver does not 171 understand the TTL TLV, it will simply ignore the TLV (Type value of 172 TLV is assumed to be in the range of optional TLV's which SHOULD be 173 ignored if an implementation does not support or understand them). In 174 the absence of TTL TLV or if TTL TLV is ignored by a receiver, the 175 determination of the TTL value used in the MPLS label on the echo 176 reply is beyond the scope of this document. 178 If a receiver understands the TTL TLV, and the TTL TLV is present in 179 the echo request, and if the value field is zero, the LSP Ping Echo 180 request packet SHOULD be dropped. 182 If a receiver understands the TTL TLV, and the TTL TLV is present in 183 the echo request, the receiver MUST use the TTL value specified in 184 TLV in the MPLS header of the echo reply. In other words, if the 185 value of the TTL provided by this TLV does not match the TTL 186 determined by other means, such as Switching Point TLV in MS-PW, then 187 TTL TLV must be used. This will aid the originator of the echo 188 request in analyzing the return path. 190 4. Operation 192 In this section, we explain a use case for the TTL TLV with an MPLS 193 MS-PW. 194 <------------------MS-PW ---------------------> 196 A B C D E 197 o -------- o -------- o --------- o --------- o 198 ------Echo Request-----> 199 <-----Echo Reply-------- 201 Figure 2: Use-case with MS-PWs 203 Let us assume a MS-PW going through LSRs A, B, C, D, and E. 204 Furthermore, assume that an operator wants to perform a connectivity 205 check between B and D from B. Thus, an LSP-Ping request with the TTL 206 TLV is originated from B and sent towards D. The echo request packet 207 contains the FEC of the PW Segment between C and D. The value field 208 of the TTL TLV and the TTL field of the MPLS label are set to 2, the 209 choice of the value 2 will be based on the operator input requesting 210 the echo request or from the optional LDP switching point TLV. The 211 echo request is intercepted at D because of TTL expiry. D detects the 212 TTL TLV in the request, and use the TTL value (i.e., 2) specified in 213 the TLV on the MPLS label of the echo reply. The echo reply will be 214 intercepted by B because of TTL expiry. 216 The same operation will apply in the case a co-routed bidirectional 217 LSP and we want to check connectivity from an intermediate LSR B to 218 another LSR D, from B. 220 4.1. Traceroute mode 222 In the traceroute mode TTL value in the TLV is successively set to 1, 223 2, and so on. This is similar to the TTL values used for the label 224 set on the packet. 226 4.2. Error scenario 228 It is possible that the echo request packet was intercepted before 229 the intended destination for reason other than label TTL expiry. This 230 could be due network faults, misconfiguration or other reasons. In 231 such cases, if the return TTL is set to the value specified in the 232 TTL TLV then the echo response packet will continue beyond the 233 originating node. This becomes a security issue. 235 To prevent this, the label TTL value used in the Echo Reply packet 236 must be modified by deducting the incoming label TTL on the received 237 packet from TTL TLV value. If the echo request packet is punted to 238 the CPU before the incoming label TTL is deducted, then another 1 239 must be deducted. In other words: 241 Return TTL Value on the Echo Reply packet = (TTL TLV Value)-(Incoming 242 Label TTL) + 1 244 5. Security Considerations 246 This draft allows the setting of the TTL value in the MPLS Label of 247 an echo reply, so that it can be intercepted by an intermediate 248 device. This can cause a device to get a lot of LSP Ping packets 249 which get redirected to the CPU. 251 However the same is possible even without the changes mentioned in 252 this document. A device should rate limit the LSP ping packets 253 redirected to the CPU so that the CPU is not overwhelmed. 255 6. IANA Considerations 257 IANA is requested to assign TLV type value to the following TLV from 258 the "Multiprotocol Label Switching Architecture (MPLS) Label Switched 259 Paths (LSPs) Parameters - TLVs" registry, "TLVs and sub-TLVs" sub- 260 registry. 262 Time To Live TLV (See Section 3). The value should be assigned from 263 the range (32768-49161) of optional TLV's which SHOULD be ignored if 264 an implementation does not support or understand them as defined in 265 section 3 of RFC 4379 [RFC4379]. 267 7. Acknowledgements 268 The authors would like to thank Greg Mirsky for his comments. 270 8. References 272 8.1 Normative References 274 [1] K. Kompella, G. Swallow, "Detecting Multi-Protocol Label Switched 275 (MPLS) Data Plane Failures", RFC 4379, February 2006. 277 [2] T. Nadeau, et. al, "Pseudowire Virtual Circuit Connectivity 278 Verification (VCCV): A Control Channel for Pseudowires ", RFC 5085, 279 December 2007. 281 [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement 282 Levels", BCP 14, RFC 2119, March 1997. 284 Authors' Addresses 286 Siva Sivabalan 287 Cisco Systems, Inc. 288 2000 Innovation Drive 289 Kanata, Ontario, K2K 3E8 290 Canada 291 Email: msiva@cisco.com 293 Sami Boutros 294 Cisco Systems, Inc. 295 3750 Cisco Way 296 San Jose, California 95134 297 USA 298 Email: sboutros@cisco.com 300 George Swallow 301 Cisco Systems, Inc. 302 300 Beaver Brook Road 303 Boxborough , MASSACHUSETTS 01719 304 United States 305 Email: swallow@cisco.com 307 Shaleen Saxena 308 Cisco Systems, Inc. 309 1414 Massachusetts Avenue 310 Boxborough , MASSACHUSETTS 01719 311 United States 312 Email: ssaxena@cisco.com 314 Vishwas Manral 315 Hewlett Packard Co. 316 19111 Pruneridge Ave, 317 Cupertino, CA 95014 USA 318 United States 319 EMail: vishwas.manral@hp.com 321 Michael Wildt 322 Cisco Systems, Inc. 323 1414 Massachusetts Avenue 324 Boxborough , MASSACHUSETTS 01719 325 United States 326 Email: mwildt@cisco.com 328 Sam Aldrin 329 Huawei Technologies, Inc. 330 1188 Central Express Way, 331 Santa Clara, CA 95051 332 United States 333 Email: aldrin.ietf@gmail.com