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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-03) exists of draft-tempia-ippm-p3m-01 Summary: 0 errors (**), 0 flaws (~~), 2 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 MPLS S. Bryant 3 Internet-Draft C. Pignataro 4 Intended status: Informational Cisco Systems 5 Expires: April 2, 2016 M. Chen 6 Z. Li 7 Huawei 8 G. Mirsky 9 Ericsson 10 September 30, 2015 12 MPLS Flow Identification 13 draft-bryant-mpls-flow-ident-02 15 Abstract 17 This memo discusses the desired capabilities for MPLS flow 18 identification. The key application that needs this is in-band 19 performance monitoring of user data packets. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on April 2, 2016. 38 Copyright Notice 40 Copyright (c) 2015 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Requirements Language . . . . . . . . . . . . . . . . . . . . 3 57 3. Loss Measurement Considerations . . . . . . . . . . . . . . . 3 58 4. Delay Measurement Considerations . . . . . . . . . . . . . . 4 59 5. Units of identification . . . . . . . . . . . . . . . . . . . 4 60 6. Types of LSP . . . . . . . . . . . . . . . . . . . . . . . . 5 61 7. Network Scope . . . . . . . . . . . . . . . . . . . . . . . . 6 62 8. Backwards Compatibility . . . . . . . . . . . . . . . . . . . 7 63 9. Dataplane . . . . . . . . . . . . . . . . . . . . . . . . . . 7 64 10. Control Plane . . . . . . . . . . . . . . . . . . . . . . . . 8 65 11. Privacy Considerations . . . . . . . . . . . . . . . . . . . 8 66 12. Security Considerations . . . . . . . . . . . . . . . . . . . 9 67 13. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 68 14. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 69 15. References . . . . . . . . . . . . . . . . . . . . . . . . . 9 70 15.1. Normative References . . . . . . . . . . . . . . . . . . 9 71 15.2. Informative References . . . . . . . . . . . . . . . . . 9 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10 74 1. Introduction 76 This memo discusses the desired capabilities for MPLS flow 77 identification. The key application that needs this is in-band 78 performance monitoring of user data packets. 80 There is a need to identify flows in MPLS networks for applications 81 such as packet loss and packet delay measurement. A method of loss 82 and delay measurement in MPLS networks was defined in [RFC6374]. 83 When used to measure packet loss [RFC6374] depends on the use of the 84 injected Operations, Administration, and Maintenance (OAM) packets to 85 designate the beginning and the end of the packet group over which 86 packet loss is being measured. Where the misordering of packets from 87 one group relative to the following group, or misordering of one of 88 the packets being counted relative to the [RFC6374] packet occurs, 89 then an error will occur in the packet loss measurement. In 90 addition, this packet performance measurement system needs to be 91 extended to deal with different granularities of flow and to address 92 a number of the multi-point cases in which to or more ingress Label 93 Switching Routers (LSRs) could send packets to one or more 94 destinations. 96 Improvements in link and transmission technologies mean that it may 97 be difficult to assess packet loss using active performance 98 measurement methods with synthetic traffic, due to the very low loss 99 rate in normal operation. That, together with more demanding service 100 level requirements, mean that network operators need to be able to 101 measure the loss of the actual user data traffic by using passive 102 performance measurement methods. Any technique deployed needs to be 103 transparent to the end user, and it needs to be assumed that they 104 will not take any active part in the measurement process. Indeed it 105 is important that any flow identification technique be invisible to 106 them and that no remnant of the identification of measurement process 107 leak into their network. 109 Additionally where there are multiple traffic sources, such as in 110 multi-point to point and multi-point to multi-point network 111 environments there needs to be a method whereby the sink can 112 distinguish between packets from the various sources, that is to say, 113 that a multi-point to multi-point measurement model needs to be 114 developed. 116 2. Requirements Language 118 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 119 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 120 document are to be interpreted as described in [RFC2119]. 122 3. Loss Measurement Considerations 124 Modern networks, if not oversubscribed, normally drop very few 125 packets, thus packet loss measurement is highly sensitive to counter 126 errors. Without some form of coloring or batch marking such as that 127 proposed in [I-D.tempia-ippm-p3m] it may not be possible to achieve 128 the required accuracy in the loss measurement of customer data 129 traffic. Where accuracy better than the data link loss performance 130 of a modern optical network is required, it may be economically 131 advantageous, or even a technical requirement, to include temporal 132 marking. 134 Where this level of accuracy is required and the traffic between a 135 source-destination pair is subject to Equal-Cost Multipath (ECMP) a 136 demarcation mechanism is needed to group the packets into batches. 137 Once a batch is correlated at both ingress and egress, the packet 138 accounting mechanism is then able to operate on the batch of packets 139 which can be accounted for at both the packet ingress and the packet 140 egress. Errors in the accounting are particularly acute in Label 141 Switched Paths (LSPs) subjected to ECMP because the network transit 142 time will be different for the various ECMP paths since: 144 a. The packets may traverse different sets of LSRs. 146 b. The packets may depart from different interfaces on different 147 line cards on LSRs 149 c. The packets may arrive at different interfaces on different line 150 cards on LSRs. 152 A consideration in modifying the identity label (the MPLS label 153 ordinarily used to identify the LSP, Virtual Private Network, 154 Pseudowire etc) to indicate the batch is the impact that this has on 155 the path chosen by the ECMP mechanism. When the member of the ECMP 156 path set is chosen by deep packet inspection a change of batch 157 represented by a change of identity label will have no impact on the 158 ECMP path. Where the path member is chosen by reference to an 159 entropy label [RFC6790] then changing the batch identifier will not 160 result in a change to the chosen ECMP path. ECMP is so pervasive in 161 multi-point to (multi-) point networks that some method of avoiding 162 accounting errors introduced by ECMP needs to be supported. 164 4. Delay Measurement Considerations 166 Most of the existing delay measurement methods are active measurement 167 that depend on the extra injected test packet to evaluate the delay 168 of a path. With the active measurement method, the rate, numbers and 169 interval between the injected packets may affect the accuracy of the 170 results. Also, for injected test packets, these may not be co-routed 171 with the data traffic due to ECMP. Thus there exists a requirements 172 to measure the delay of the real traffic. For combined loss-delay 173 measurements, the identity considerations described in Section 3 also 174 apply. 176 5. Units of identification 178 The most basic unit of identification is the identity of the node 179 that processed the packet on its entry to the MPLS network. However, 180 the required unit of identification may vary depending on the use 181 case for accounting, performance measurement or other types of packet 182 observations. In particular note that there may be a need to impose 183 identify at several different layers of the MPLS label stack. 185 This document considers following units of identifications: 187 o Per source LSR - everything from one source is aggregated. 189 o Per group of LSPs chosen by an ingress LSR - an ingress LSP 190 aggregates group of LSPs (ex: all LSPs of a tunnel). 192 o Per LSP - the basic form. 194 o Per flow [RFC6790] within an LSP - fine graining method. 196 Note that a finer grained identity resolution is needed when there is 197 a need to perform these operations on a flow not readily identified 198 by some other element in the label stack. Such fine grained 199 resolution may be possible by deep packet inspection, but this may 200 not always be possible, or it may be desired to minimise processing 201 costs by doing this only in entry to the network, and adding a 202 suitable identifier to the packet for reference by other network 203 elements. An example of such a fine grained case might be traffic 204 from a specific application, or from a specific application from a 205 specific source, particularly if matters related to service level 206 agreement or application performance were being investigated. 208 We can thus characterize the identification requirement in the 209 following broad terms: 211 o There needs to be some way for an egress LSR to identify the 212 ingress LSR with an appropriate degree of scope. This concept is 213 discussed further in Section 7. 215 o There needs to be a way to identify a specific LSP at the egress 216 node. This allows for the case of instrumenting multiple LSPs 217 operate between the same pair of nodes. In such cases the 218 identity of the ingress LSR is insufficient. 220 o In order to conserve resources such as labels, counters and/or 221 compute cycles it may be desirable to identify an LSP group so 222 that a operation can be performed on the group as an aggregate. 224 o There needs to be a way to identify a flow within an LSP. This is 225 necessary when investigating a specific flow that has been 226 aggregated into an LSP. 228 The unit of identification and the method of determining which 229 packets constitute a flow will be application or use-case specific 230 and is out of scope of this memo. 232 6. Types of LSP 234 We need to consider a number of types of LSP. The two simplest types 235 to monitor are point to point LSPs and point to multi-point LSPs. 236 The ingress LSR for a point to point LSP, such as those created using 237 the Resource Reservation Protocol - Traffic Engineering (RSVP-TE) 238 [RFC5420] signalling protocol, or those that conform to the MPLS 239 Transport Profile (MPLS-TP) [RFC5654] may be identified by inspection 240 of the top label in the stack, since at any provider-edge (PE) or 241 provider (P) router on the path this is unique to the ingress-egress 242 pair at every hop at a given layer in the LSP hierarchy. Provided 243 that penultimate hop popping is disabled, the identity of the ingress 244 LSR of a point to point LSP is available at the egress LSR and thus 245 determining the identity of the ingress LSR must be regarded as a 246 solved problem. Note however that the identity of a flow cannot to 247 be determined without further information being carried in the 248 packet, or gleaned from some aspect of the packet payload. 250 In the case of a point to multi-point LSP, and in the absence of 251 Penultimate Hop Popping (PHP) the identity of the ingress LSR may 252 also be inferred from the top label. However, it may not possible to 253 adequately identify the flow from the top label alone. In designing 254 any solution it is desirable that a common flow identity solution be 255 used for both point to point and point to multi-point LSP types. 256 Similarly it is desirable that a common method of LSP group 257 identification be used. In the above cases, a context label needs to 258 be used to provide the required identity information. This is widely 259 supported MPLS feature. 261 A more interesting case is the case of a multi-point to point LSP. 262 In this case the same label is normally used by multiple ingress or 263 upstream LSRs and hence source identification is not possible by 264 inspection of the top label by the egress LSRs. It is therefore 265 necessary for a packet to be able to explicitly convey any of the 266 identity types described in Section 5. 268 Similarly, in the case of a multi-point to multi-point LSP the same 269 label is normally used by multiple ingress or upstream LSRs and hence 270 source identification is not possible by inspection of the top label 271 by egress LSRs. The various types of identity described in Section 5 272 are again needed. Note however, that the scope of the identity may 273 be constrained to be unique within the set of multi-point to multi- 274 point LSPs terminating on any common node. 276 7. Network Scope 278 The scope of identification can be constrained to the set of flows 279 that are uniquely identifiable at an ingress LSR, or some aggregation 280 thereof. There is no question of an ingress LSR seeking assistance 281 from outside the MPLS protocol domain. 283 In any solution that constrains itself to carrying the required 284 identity in the MPLS label stack rather than in some different 285 associated data structure, constraints on the label stack size imply 286 that the scope of identity reside within that MPLS domain. For 287 similar reasons the identity scope of a component of an LSP should be 288 constrained to the scope of that LSP. 290 8. Backwards Compatibility 292 In any network it is unlikely that all LSRs will have the same 293 capability to support the methods of identification discussed in this 294 memo. It is therefore an important constraint on any flow identity 295 solution that it is backwards compatible with deployed MPLS equipment 296 to the extent that deploying the new feature will not disable 297 anything that currently works on a legacy equipment. 299 This is particularly the case when the deployment is incremental or 300 when the feature is not required for all LSRs or all LSPs. Thus in 301 broad the flow identification design MUST support the co-existence of 302 both LSRs that can, and cannot, identify the traffic components 303 described in Section 5. In addition the identification of the 304 traffic components described in Section 5 MUST be an optional feature 305 that is disabled by default. As a design simplification, a solution 306 MAY require that all egress LSRs of a point to multipoint or a multi- 307 point to multipoint LSP support the identification type in use so 308 that a single packet can be correctly processed by all egress 309 devices. The corollary of this last point is that either all egress 310 LSRs are enabled to support the required identity type, or none of 311 them are. 313 9. Dataplane 315 There is a huge installed base of MPLS equipment, typically this type 316 of equipment remains in service for an extended period of time, and 317 in many cases hardware constraints mean that it is not possible to 318 upgrade its dataplane functionality. Changes to the MPLS data plane 319 are therefore expensive to implement, add complexity to the network, 320 and may significantly impact the deployability of a solution that 321 requires such changes. For these reasons, the MPLS designers have 322 set a very high bar to changes to the MPLS data plane, and only a 323 very small number have been adopted. Hence, it is important that the 324 method of identification must minimize changes to the MPLS data 325 plane. Ideally method(s) of identification that require no changes 326 to the MPLS data plane should be given preferential consideration. 327 If a method of identification makes a change to the data plane is 328 chosen it will need to have a significant advantage over any method 329 that makes no change, and the advantage of the approach will need to 330 be carefully evaluated and documented. If a change is necessary to 331 the MPLS data plane proves necessary, it should be (a) be as small a 332 change as possible and (b) be a general purpose method so as to 333 maximise its use for future applications. It is imperative that, as 334 far as can be foreseen, any necessary change made to the MPLS data 335 plane does not impose any foreseeable future limitation on the MPLS 336 data plane. 338 Stack size is an issue with many MPLS implementations both as a 339 result of hardware limitations, and due to the impact on networks and 340 applications where a large number of small payloads need to be 341 transported In particular one MPLS payload may be carried inside 342 another. For example one LSP may be carried over another LSP, or a 343 PW or similar multiplexing construct may be carried over an LSP and 344 identification may be required at both layers. Of particular concern 345 is the implementation of low cost edge LSRs that for cost reasons 346 have a significant limit on the number of Label Stack Elements (LSEs) 347 that they can impose or dispose. Therefore, any method of identity 348 MUST NOT consume an excessive number of unique labels, and MUST NOT 349 result in an excessive increase in the size of the label stack. 351 The MPLS data plane design provides two types of special purpose 352 labels: the original 16 reserved labels and the much larger set of 353 special purpose labels defined in [RFC7274]. The original reserved 354 labels need one LSE, and the newer [RFC7274] special purpose labels 355 need two LSEs. Given the tiny number of original reserved labels, it 356 is core to the MPLS design philosophy that this scarce resource is 357 only used when it is absolutely necessary. Using a single LSE 358 reserved or special purpose label to encode flow identity thus 359 requires two stack entries, one for the reserved label and one for 360 the flow identity. The larger set of [RFC7274] labels requires two 361 labels stack entries for the special purpose label itself and hence a 362 total of three label stack entries to encode the flow identity. 364 The use of special purpose labels (SPL) [RFC7274]as part of a method 365 to encode the identity information therefore has a number of 366 undesirable implications for the data plane and hence whilst a 367 solution may use SPL(s), methods that do not require SPLs need to be 368 carefully considered. 370 10. Control Plane 372 Any flow identity design should both seek to minimise the complexity 373 of the control plane and should minimise the amount of label co- 374 ordination needed amongst LSRs. 376 11. Privacy Considerations 378 The inclusion of originating and/or flow information in a packet 379 provides more identity information and hence potentially degrades the 380 privacy of the communication. Recent IETF concerns on pervasive 381 monitoring [RFC7258] would lead it to prefer a solution that does not 382 degrade the privacy of user traffic below that of an MPLS network not 383 implementing the flow identification feature. The minimizing the 384 scope of the identity indication can be useful in minimizing the 385 observability of the flow characteristics. 387 12. Security Considerations 389 Any solution to the flow identification needs must not degrade the 390 security of the MPLS network below that of an equivalent network not 391 deploying the specified identity solution. Propagation of 392 identification information outside the MPLS network imposing it must 393 be disabled by default. Any solution should provide for the 394 restriction of the identity information to those components of the 395 network that need to know it. It is thus desirable to limit the 396 knowledge of the identify of an endpoint to only those LSRs that need 397 to participate in traffic flow. 399 13. IANA Considerations 401 This memo has no IANA considerations. 403 14. Acknowledgements 405 The authors thank Nobo Akiya (nobo@cisco.com), Nagendra Kumar Nainar 406 (naikumar@cisco.com) and George Swallow (swallow@cisco.com) for their 407 comments. 409 15. References 411 15.1. Normative References 413 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 414 Requirement Levels", BCP 14, RFC 2119, 415 DOI 10.17487/RFC2119, March 1997, 416 . 418 15.2. Informative References 420 [I-D.tempia-ippm-p3m] 421 Capello, A., Cociglio, M., Fioccola, G., Castaldelli, L., 422 and A. Bonda, "A packet based method for passive 423 performance monitoring", draft-tempia-ippm-p3m-01 (work in 424 progress), September 2015. 426 [RFC5420] Farrel, A., Ed., Papadimitriou, D., Vasseur, JP., and A. 427 Ayyangarps, "Encoding of Attributes for MPLS LSP 428 Establishment Using Resource Reservation Protocol Traffic 429 Engineering (RSVP-TE)", RFC 5420, DOI 10.17487/RFC5420, 430 February 2009, . 432 [RFC5654] Niven-Jenkins, B., Ed., Brungard, D., Ed., Betts, M., Ed., 433 Sprecher, N., and S. Ueno, "Requirements of an MPLS 434 Transport Profile", RFC 5654, DOI 10.17487/RFC5654, 435 September 2009, . 437 [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay 438 Measurement for MPLS Networks", RFC 6374, 439 DOI 10.17487/RFC6374, September 2011, 440 . 442 [RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and 443 L. Yong, "The Use of Entropy Labels in MPLS Forwarding", 444 RFC 6790, DOI 10.17487/RFC6790, November 2012, 445 . 447 [RFC7258] Farrell, S. and H. Tschofenig, "Pervasive Monitoring Is an 448 Attack", BCP 188, RFC 7258, DOI 10.17487/RFC7258, May 449 2014, . 451 [RFC7274] Kompella, K., Andersson, L., and A. Farrel, "Allocating 452 and Retiring Special-Purpose MPLS Labels", RFC 7274, 453 DOI 10.17487/RFC7274, June 2014, 454 . 456 Authors' Addresses 458 Stewart Bryant 459 Cisco Systems 461 Email: stbryant@cisco.com 463 Carlos Pignataro 464 Cisco Systems 466 Email: cpignata@cisco.com 468 Mach Chen 469 Huawei 471 Email: mach.chen@huawei.com 473 Zhenbin Li 474 Huawei 476 Email: lizhenbin@huawei.com 477 Gregory Mirsky 478 Ericsson 480 Email: gregory.mirsky@ericsson.com