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Cui 3 Internet-Draft R. Winter 4 Updates: 5654 (if approved) NEC 5 Intended status: Informational H. Shah 6 Expires: August 25, 2017 Ciena 7 S. Aldrin 8 Huawei Technologies 9 M. Daikoku 10 KDDI 11 February 21, 2017 13 Use Cases and Requirements for MPLS-TP multi-failure protection 14 draft-ietf-mpls-tp-mfp-use-case-and-requirements-03 16 Abstract 18 For the Multiprotocol Label Switching Transport Profile (MPLS-TP) 19 linear protection capable of 1+1 and 1:1 protection has already been 20 defined. That linear protection mechanism has not been designed for 21 handling multiple, simultaneously occuring failures, i.e. multiple 22 failures that affect the working and the protection entity during the 23 same time period. In these situations currently defined protection 24 mechanisms would fail. 26 This document introduces use cases and requirements for mechanisms 27 that are capable of protecting against such failures. It does not 28 specify a multi-failure protection mechanism itself. 30 Status of This Memo 32 This Internet-Draft is submitted in full conformance with the 33 provisions of BCP 78 and BCP 79. 35 Internet-Drafts are working documents of the Internet Engineering 36 Task Force (IETF). Note that other groups may also distribute 37 working documents as Internet-Drafts. The list of current Internet- 38 Drafts is at http://datatracker.ietf.org/drafts/current/. 40 Internet-Drafts are draft documents valid for a maximum of six months 41 and may be updated, replaced, or obsoleted by other documents at any 42 time. It is inappropriate to use Internet-Drafts as reference 43 material or to cite them other than as "work in progress." 45 This Internet-Draft will expire on August 25, 2017. 47 Copyright Notice 49 Copyright (c) 2017 IETF Trust and the persons identified as the 50 document authors. All rights reserved. 52 This document is subject to BCP 78 and the IETF Trust's Legal 53 Provisions Relating to IETF Documents 54 (http://trustee.ietf.org/license-info) in effect on the date of 55 publication of this document. Please review these documents 56 carefully, as they describe your rights and restrictions with respect 57 to this document. Code Components extracted from this document must 58 include Simplified BSD License text as described in Section 4.e of 59 the Trust Legal Provisions and are provided without warranty as 60 described in the Simplified BSD License. 62 Table of Contents 64 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 65 1.1. Document scope . . . . . . . . . . . . . . . . . . . . . 3 66 1.2. Requirements notation . . . . . . . . . . . . . . . . . . 3 67 1.3. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3 68 2. General m:n protection scenario . . . . . . . . . . . . . . . 4 69 3. Use cases . . . . . . . . . . . . . . . . . . . . . . . . . . 5 70 3.1. m:1 (m > 1) protection . . . . . . . . . . . . . . . . . 5 71 3.1.1. Pre-configuration . . . . . . . . . . . . . . . . . . 5 72 3.1.2. On-demand configuration . . . . . . . . . . . . . . . 6 73 3.2. m:n (m, n > 1, n >= m > 1) protection . . . . . . . . . . 6 74 4. Requirements . . . . . . . . . . . . . . . . . . . . . . . . 6 75 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 76 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 7 77 7. Normative References . . . . . . . . . . . . . . . . . . . . 7 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 8 80 1. Introduction 82 Today's packet optical transport networks concentrate large volumes 83 of traffic onto a relatively small number of nodes and links. As a 84 result, the failure of a single network element can potentially 85 interrupt a large amount of traffic. For this reason, ensuring 86 survivability through careful network design and appropriate 87 technical means is important. 89 In MPLS-TP networks, a basic end-to-end linear protection 90 survivability technique is available as specified in [RFC6378], 91 [RFC7271] and [RFC7324]. That protocol however is limited to 1+1 and 92 1:1 protection and not designed to handle multiple failures that 93 affect both the working and protection entity at the same time. 95 There are various scenarios where multi-failure protection is an 96 important requirement for network survivability. E.g. for disaster 97 recovery, after catastrophic events such as earthquakes or tsunamis. 98 During the period after such events, network availability is crucial, 99 in particular for high-priority services such as emergency telephone 100 calls. Existing 1+1 or 1:n protection however is limited to cover 101 single failures which has proven as not sufficient during past 102 events. 104 Beyond the natural disaster use case above, multi-failure protection 105 is also beneficial in situations where the network is particularly 106 vulnerable, e.g., when a working entity or protection entity was 107 closed for maintenance or construction work. During this time, the 108 network service becomes vulnerable to single failures since one 109 entity is already down. If a failure occurs during this time, an 110 operator might not be able to meet service level agreements (SLA). 111 Thus, a technical means for multi-failure protection could take 112 pressure off network operations. 114 1.1. Document scope 116 This document describes use cases and requirements for m:1 and m:n 117 protection in MPLS-TP networks without the use of control plane 118 protocols. Existing solutions based on a control plane such as GMPLS 119 may be able to restore user traffic when multiple failures occur. 120 Some networks however do not use full control plane operation for 121 reasons such as service provider preferences, certain limitations or 122 the requirement for fast service restoration (faster than achievable 123 with control plane mechanisms). These networks are the focus of this 124 document which defines a set of requirements for m:1 and m:n 125 protection not based on control plane support. This document imposes 126 no formal time constraints on detection times. 128 1.2. Requirements notation 130 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 131 "SHOULD","SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 132 document are to be interpreted as described in [RFC2119]. 134 1.3. Terminology 136 The terminology used in this document is based on the terminology 137 defined in the MPLS-TP Survivability Framework document [RFC6372], 138 which in turn is based on [RFC4427]. 140 In particular, the following protection schemes are defined in 141 [RFC4427] and used as terms in this document: 143 o 1+1 protection 145 o 1:n (n >= 1) protection 147 o m:n (m, n > 1, n >= m > 1) protection 149 o Further, the following additional terminology is from [RFC4427] is 150 used: 152 o "broadcast bridge" 154 o "selector bridge" 156 o "working entity" 158 o "protection entity" 160 This document defines a new protection type: 162 o m:1 (m > 1) protection: A set of m protection entities protecting 163 a single working entity 165 2. General m:n protection scenario 167 The general underlying assumption of this work is that an m:n 168 relationship between protection entity and working entity exists, 169 i.e. there is no artificial limitation on the ratio between 170 protection and working entities. 172 This general scenario is illustrated in Figure 1 which shows a 173 protection domain with n working entities and m protection entities 174 between Node A and Node Z. 176 At Node A, traffic is transported over its respective working entity 177 and may be simultaneously transported over one of its protection 178 entities (in case of a broadcast bridge), or it is transported over 179 its working entity and only in case of failure over one of the 180 protection entities (in case of a selector bridge). At Node Z, the 181 traffic is selected from either its working entity or one of the 182 protection entities. Note that any of the n working entities and m 183 protection entities should follow a disjoint path through the network 184 from Node A to Node Z. 186 +------+ +------+ 187 |Node A| working entity #1 |Node Z| 188 | |=============================| | 189 | | .... | | 190 | | working entity #n | | 191 | |=============================| | 192 | | | | 193 | | | | 194 | | protection entity #1 | | 195 | |*****************************| | 196 | | .... | | 197 | | protection entity #m | | 198 | |*****************************| | 199 +------+ +------+ 200 |--------Protection Domain--------| 202 Figure 1: m:n protection domain 204 3. Use cases 206 3.1. m:1 (m > 1) protection 208 With MPLS-TP linear protection such as 1+1/1:1 protection, when a 209 single failure is detected on the working entity, the service can be 210 restored using the protection entity. However, during the time the 211 protection is active the traffic is unprotected until the working 212 entity is restored. 214 m:1 protection can increase service availability and reduce 215 operational pressure since multiple protection entities are 216 available. For any m > 1, m - 1 protection entities may fail and the 217 service still would have a protection entity available. 219 There are different ways to provision these alternative protection 220 entities which are outlined in the following sub-sections. 222 3.1.1. Pre-configuration 224 The relationship between the working entity and the protection 225 entities is part of the system configuration and needs to be 226 configured before the working entity is being used. The same applies 227 to additional protection entities. 229 Unprotected traffic can be transported over the m protection entities 230 as long as these entities do not carry protected traffic. 232 3.1.2. On-demand configuration 234 The protection relationship between a working entity and a protection 235 entity is configured while the system is in operation. 237 Additional protection entities are configured by either a control 238 plane protocol or static configuration using a management system 239 directly after failure detection and/or notification of either the 240 working entity or the protection entities. In case a management 241 system is used, there is no need for a standardized solution. 243 3.2. m:n (m, n > 1, n >= m > 1) protection 245 Because m:1 protecion introduces additional protection entities 246 compared to 1:1 protection, an additional cost has to be paid. In 247 order to reduce the cost of these additional protection entities, in 248 the m:n scenario, m dedicated protection transport entities are 249 sharing protection resources for n working transport entities. 251 The bandwidth of each protection entity should be allocated in such a 252 way that it may be possible to protect any of the n working entities 253 in case at least one of the m protection entities is available. When 254 a working entity is determined to be impaired, its traffic first must 255 be assigned to an available protection transport entity followed by a 256 transition from the working to the assigned protection entity at both 257 Node A and Node Z of the protected domain. It is noted that when 258 more than m working entities are impaired, only m working entities 259 can be protected. 261 4. Requirements 263 Recovery requirements are defined in section 2.5 of RFC 5654 264 [RFC5654]. More specifically, RFC 5654 outlines protection 265 requirements in subsections 2.5.1.1. and 2.5.1.2. These however are 266 limited to cover single failure cases and not multiple, 267 simultaneously occuring failures. This section extends the list of 268 requirements to support multiple failures scenarios. 270 R1. MPLS-TP SHOULD support m:1 (m > 1) protection. 272 1. An m:1 protection mechanism MUST protect against multiple 273 failures that are detected on both the working entity and one or 274 more protection entities. 276 2. Pre-configuration of protection entities SHOULD be supported. 278 3. On-demand protection entity configuration MAY be supported. 280 4. On-demand protection resource activation MAY be supported. 282 5. A priority scheme MUST be provided, since a protection entity has 283 to be chosen out of two or more protection entities. 285 R2. MPLS-TP SHOULD support m:n (m, n > 1, n >= m > 1) protection. 287 1. An m:n protection mechanism MUST protect against multiple 288 failures that are simultaneously detected on both a working 289 entity and a protection entity or multiple working entities. 291 2. A priority scheme MUST be provided, since protection resources 292 are shared by multiple working entities dynamically. 294 If a solution is designed based on an existing mechanism such as PSC, 295 then this solution MUST be backward compatible and not break such 296 mechanisms. 298 5. Security Considerations 300 General security considerations for MPLS-TP are covered in [RFC5921]. 301 The security considerations for the generic associated control 302 channel are described in [RFC5586]. The requirements described in 303 this document are extensions to the requirements presented in 304 [RFC5654] and does not introduce any new security risks. 306 6. IANA Considerations 308 This document makes no request of IANA. 310 Note to RFC Editor: this section may be removed on publication as an 311 RFC. 313 7. Normative References 315 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 316 Requirement Levels", BCP 14, RFC 2119, March 1997. 318 [RFC4427] Mannie, E. and D. Papadimitriou, "Recovery (Protection and 319 Restoration) Terminology for Generalized Multi-Protocol 320 Label Switching (GMPLS)", RFC 4427, March 2006. 322 [RFC5586] Bocci, M., Vigoureux, M., and S. Bryant, "MPLS Generic 323 Associated Channel", RFC 5586, June 2009. 325 [RFC5654] Niven-Jenkins, B., Brungard, D., Betts, M., Sprecher, N., 326 and S. Ueno, "Requirements of an MPLS Transport Profile", 327 RFC 5654, September 2009. 329 [RFC5921] Bocci, M., Bryant, S., Frost, D., Levrau, L., and L. 330 Berger, "A Framework for MPLS in Transport Networks", RFC 331 5921, July 2010. 333 [RFC6372] Sprecher, N. and A. Farrel, "MPLS Transport Profile (MPLS- 334 TP) Survivability Framework", RFC 6372, September 2011. 336 [RFC6378] Weingarten, Y., Bryant, S., Osborne, E., Sprecher, N., and 337 A. Fulignoli, "MPLS Transport Profile (MPLS-TP) Linear 338 Protection", RFC 6378, October 2011. 340 [RFC7271] Ryoo, J., Gray, E., van Helvoort, H., D'Alessandro, A., 341 Cheung, T., and E. Osborne, "MPLS Transport Profile (MPLS- 342 TP) Linear Protection to Match the Operational 343 Expectations of Synchronous Digital Hierarchy, Optical 344 Transport Network, and Ethernet Transport Network 345 Operators", RFC 7271, June 2014. 347 [RFC7324] Osborne, E., "Updates to MPLS Transport Profile Linear 348 Protection", RFC 7324, July 2014. 350 Authors' Addresses 352 Zhenlong Cui 353 NEC 355 Email: c-sai@bx.jp.nec.com 357 Rolf Winter 358 NEC 360 Email: Rolf.Winter@neclab.eu 362 Himanshu Shah 363 Ciena 365 Email: hshah@ciena.com 367 Sam Aldrin 368 Huawei Technologies 370 Email: aldrin.ietf@gmail.com 371 Masahiro Daikoku 372 KDDI 374 Email: ms-daikoku@kddi.com