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Checking references for intended status: Informational ---------------------------------------------------------------------------- == Outdated reference: A later version (-03) exists of draft-filsfils-spring-segment-routing-mpls-00 == Outdated reference: A later version (-07) exists of draft-ietf-mpls-seamless-mpls-06 == Outdated reference: A later version (-13) exists of draft-ietf-sfc-problem-statement-03 == Outdated reference: A later version (-02) exists of draft-kumar-sfc-dc-use-cases-01 == Outdated reference: A later version (-08) exists of draft-previdi-6man-segment-routing-header-00 == Outdated reference: A later version (-07) exists of draft-quinn-sfc-nsh-02 Summary: 0 errors (**), 0 flaws (~~), 7 warnings (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Spring J. Brzozowski 3 Internet-Draft J. Leddy 4 Intended status: Informational Comcast 5 Expires: October 6, 2014 I. Leung 6 Rogers Communications 7 S. Previdi 8 M. Townsley 9 C. Martin 10 C. Filsfils 11 R. Maglione, Ed. 12 Cisco Systems 13 April 4, 2014 15 IPv6 SPRING Use Cases 16 draft-martin-spring-segment-routing-ipv6-use-cases-01 18 Abstract 20 Source Packet Routing in Networking (SPRING) architecture leverages 21 the source routing paradigm. A node steers a packet through a 22 controlled set of instructions, called segments, by prepending the 23 packet with SPRING header. A segment can represent any instruction, 24 topological or service-based. A segment can have a local semantic to 25 the SPRING node or global within the SPRING domain. SPRING allows to 26 enforce a flow through any topological path and service chain while 27 maintaining per-flow state only at the ingress node to the SPRING 28 domain. 30 The objective of this document is to illustrate some use cases that 31 need to be taken into account by the Source Packet Routing in 32 Networking (SPRING) architecture. 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 October 6, 2014. 50 Copyright Notice 52 Copyright (c) 2014 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 . . . . . . . . . . . . . . . . . . . . . . . . 2 68 2. IPv6 SPRING use cases . . . . . . . . . . . . . . . . . . . . 3 69 2.1. SPRING in the Home Network . . . . . . . . . . . . . . . 4 70 2.2. SPRING in the Access Network . . . . . . . . . . . . . . 5 71 2.3. SPRING in the Data Center . . . . . . . . . . . . . . . . 6 72 2.4. SPRING in the Content Delivery Networks . . . . . . . . . 6 73 2.5. SPRING in the Core networks . . . . . . . . . . . . . . . 7 74 3. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9 75 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 76 5. Security Considerations . . . . . . . . . . . . . . . . . . . 9 77 6. Informative References . . . . . . . . . . . . . . . . . . . 9 78 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11 80 1. Introduction 82 Source Packet Routing in Networking (SPRING) architecture leverages 83 the source routing paradigm. An ingress node steers a packet through 84 a controlled set of instructions, called segments, by prepending the 85 packet with SPRING header. A segment can represent any instruction, 86 topological or service-based. A segment can represent a local 87 semantic on the SPRING node, or a global semantic within the SPRING 88 domain. SPRING allows one to enforce a flow through any topological 89 path and service chain while maintaining per-flow state only at the 90 ingress node to the SPRING domain. 92 The SPRING architecture is described in 93 [I-D.filsfils-rtgwg-segment-routing]. The SPRING control plane is 94 agnostic to the dataplane, thus it can be applied to both MPLS and 95 IPv6. In case of MPLS the (list of) segment identifiers are carried 96 in the MPLS label stack, while for the IPv6 dataplane, a new type of 97 routing extension header is required. 99 The details of the new routing extension header are described in 100 [I-D.previdi-6man-segment-routing-header] which also covers the 101 security considerations and the aspects related to the deprecation of 102 the IPv6 Type 0 Routing Header described in [RFC5095]. 104 2. IPv6 SPRING use cases 106 In today's networks, source routing is typically accomplished by 107 encapsulating IP packets in MPLS LSPs that are signaled via RSVP-TE. 108 Therefore, there are scenarios where it may be possible to run IPv6 109 on top of MPLS, and as such, the MPLS Segment Routing architecture 110 described in [I-D.filsfils-spring-segment-routing-mpls] could be 111 leveraged to provide SPRING capabilities in an IPv6/MPLS environment. 113 However, there are other cases and/or specific network segments (such 114 as for example the Home Network, the Data Center, etc.) where MPLS 115 may not be available or deployable for lack of support on network 116 elements or for an operator's design choice. In such scenarios a 117 non-MPLS based solution would be preferred by the network operators 118 of such infrastructures. 120 Specifically, there are a class of use cases that motivate an IPv6 121 data plane. We identify some fundamental scenarios that, when 122 recognized in conjunction, strongly indicate an IPv6 data plane: 124 1. There is a need or desire to impose source-routing semantics 125 within an application or at the edge of a network (for example, a 126 CPE or home gateway) 128 2. There is a strict lack of an MPLS dataplane 130 3. There is a need or desire to remove routing state from any node 131 other than the source, such that the source is the only node that 132 knows and will know the path a packet will take, a priori 134 4. There is a need to connect millions of addressable segment 135 endpoints, thus high routing scalability is a requirement. IPv6 136 addresses are inherently summarizable: a very large operator 137 could scale by summarizing IPv6 subnets at various internal 138 boundaries. This is very simple and is a basic property of IP 139 routing. MPLS node segments are not summarizable. To reach the 140 same scale, an operator would need to introduce additional 141 complexity, such as mechanisms described in 142 [I-D.ietf-mpls-seamless-mpls] 144 In any environment with requirements such as those listed above, an 145 IPv6 data plane provides a powerful combination of capabilities for a 146 network operator to realize benefits in explicit routing, protection 147 and restoration, high routing scalability, traffic engineering, 148 service chaining, service differentiation and application flexibility 149 via programmability. 151 This section will describe some scenarios where MPLS may not be 152 present and it will highlight how the SPRING architecture could be 153 used to address such use cases, particularly, when an MPLS data plane 154 is neither present nor desired. 156 The use cases described in the section do not constitute an 157 exhaustive list of all the possible scenarios; this section only 158 includes some of the most common envisioned deployment models for 159 IPv6 Segment Routing. 161 In addition to the use cases described in this document the SPRING 162 architecture can be applied to all the use cases described in 163 [I-D.filsfils-rtgwg-segment-routing-use-cases] for the SPRING MPLS 164 data plane, when an IPv6 data plane is present. 166 2.1. SPRING in the Home Network 168 An IPv6-enabled home network provides ample globally routed IP 169 addresses for all devices in the home. An IPv6 home network with 170 multiple egress points and associated provider-assigned prefixes 171 will, in turn, provide multiple IPv6 addresses to hosts. A homenet 172 performing Source and Destination Routing ([I-D.troan-homenet-sadr]) 173 will ensure that packets exit the home at the appropriate egress 174 based on the associated delegated prefix for that link. 176 A SPRING enabled home provides the possibility for imposition of a 177 Segment List by end-hosts in the home, or a customer edge router in 178 the home. If the Segment List is enabled at the customer edge 179 router, that router is responsible for classifying traffic and 180 inserting the appropriate Segment List. If hosts in the home have 181 explicit source selection rules (see 182 [I-D.lepape-6man-prefix-metadata]), classification can be based on 183 source address or associated network egress point, avoiding the need 184 for DPI-based implicit classification techniques. If the Segment 185 List is inserted by the host itself, it is important to know which 186 networks can interpret the SPRING header. This information can be 187 provided as part of host configuration as a property of the 188 configured IP address (see [I-D.bhandari-dhc-class-based-prefix]). 190 The ability to steer traffic to an appropriate egress or utilize a 191 specific type of media (e.g., low-power, WIFI, wired, femto-cell, 192 bluetooth, MOCA, HomePlug, etc.) within the home itself are obvious 193 cases which may be of interest to an application running within a 194 home network. 196 Steering to a specific egress point may be useful for a number of 197 reasons, including: 199 o Regulatory 201 o Performance of a particular service associated with a particular 202 link 204 o Cost imposed due to data-caps or per-byte charges 206 o Home vs. work traffic in homes with one or more teleworkers, etc. 208 o Specific services provided by one ISP vs. another 210 Information included in the Segment List, whether imposed by the end- 211 host itself, a customer edge router, or within the access network of 212 the ISP, may be of use at the far ends of the data communication as 213 well. For example, an application running on an end-host with 214 application-support in a data center can utilize the Segment List as 215 a channel to include information that affects its treatment within 216 the data center itself, allowing for application-level steering and 217 load-balancing without relying upon implicit application 218 classification techniques at the data-center edge. Further, as more 219 and more application traffic is encrypted, the ability to extract 220 (and include in the Segment List) just enough information to enable 221 the network and data center to load-balance and steer traffic 222 appropriately becomes more and more important. 224 2.2. SPRING in the Access Network 226 Access networks deliver a variety of types of traffic from the 227 service provider's network to the home environment and from the home 228 towards the service provider's network. 230 For bandwidth management or related purposes, the service provider 231 may want to associate certain types of traffic to specific physical 232 or logical downstream capacity pipes. 234 This mapping is not the same thing as classification and scheduling. 235 In the Cable access network, each of these pipes are represented at 236 the DOCCIS layer as different service flows, which are better 237 identified as differing data links. As such, creating this 238 separation allows an operator to differentiate between different 239 types of content and perform a variety of differing functions on 240 these pipes, such as egress vectoring, byte capping, regulatory 241 compliance functions, and billing. 243 In a cable operator's environment, these downstream pipes could be a 244 specific QAM, a DOCSIS service flow or a service group. 246 Similarly, the operator may want to map traffic from the home sent 247 towards the service provider's network to specific upstream capacity 248 pipes. Information carried in a packet's SPRING header could provide 249 the target pipe for this specific packet. The access device would 250 not need to know specific details about the packet to perform this 251 mapping; instead the access device would only need to know how to map 252 the SR SID value to the target pipe. 254 2.3. SPRING in the Data Center 256 A key use case for SPRING is to cause a packet to follow a specific 257 path through the network. One can think of the service function 258 performed at each SPRING node to be forwarding. More complex service 259 functions could be applied to the packet by a SPRING node including 260 accounting, IDS, load balancing, and fire walling. 262 The term "Service Function Chain", as defined in 263 [I-D.ietf-sfc-problem-statement], it is used to describe an ordered 264 set of service functions that must be applied to packets. 266 A service provider may choose to have these service functions 267 performed external to the routing infrastructure, specifically on 268 either dedicated physical servers or within VMs running on a 269 virtualization platform. 271 [I-D.kumar-sfc-dc-use-cases] describes use cases that demonstrate the 272 applicability of Service Function Chaining (SFC) within a data center 273 environment and provides SFC requirements for data center centric use 274 cases. 276 2.4. SPRING in the Content Delivery Networks 278 The rise of online video applications and new, video-capable IP 279 devices has led to an explosion of video traffic traversing network 280 operator infrastructures. In the drive to reduce the capital and 281 operational impact of the massive influx of online video traffic, as 282 well as to extend traditional TV services to new devices and screens, 283 network operators are increasingly turning to Content Delivery 284 Networks (CDNs). 286 Several studies showed the benefits of connecting caches in a 287 hierarchical structure following the hierarchical nature of the 288 Internet. In a cache hierarchy one cache establishes peering 289 relationships with its neighbor caches. There are two types of 290 relationship: parent and sibling. A parent cache is essentially one 291 level up in a cache hierarchy. A sibling cache is on the same level. 292 Multiple levels of hierarchy are commonly used in order to build 293 efficient caches architecture. 295 In an environment, where each single cache system can be uniquely 296 identified by its own IPv6 address, a Segment List containing a 297 sequence of the caches in a hierarchy can be built. At each node 298 (cache) present in the Segment List a TCP session to port 80 is 299 established and if the requested content is found at the cache (cache 300 hits scenario) the sequence ends, even if there are more nodes in the 301 list. 303 To achieve the behavior described above, in addition to the Segment 304 List, which specifies the path to be followed to explore the 305 hierarchic architecture, a way to instruct the node to take a 306 specific action is required. The function to be performed by a 307 service node can be carried into a new header called Network Service 308 Header (NSH) defined in [I-D.quinn-sfc-nsh]. A Network Service 309 Header (NSH) is metadata added to a packet that is used to create a 310 service plane. The service header is added by a service 311 classification function that determines which packets require 312 servicing, and correspondingly which service path to follow to apply 313 the appropriate service. 315 In the above example the service to be performed by the service node 316 was to establish a TCP session to port 80, but in other scenarios 317 different functions may be required. Another example of action to be 318 taken by the service node is the capability to perform 319 transformations on payload data, like real-time video transcode 320 option (for rate and/or resolution). 322 The use of SPRING together with the NSH allows building flexible 323 service chains where the topological information related to the path 324 to be followed is carried into the Segment List while the "service 325 plane related information" (function/action to be performed) is 326 encoded in the metadata, carried into the NSH. The details about 327 using SPRING together with NSH will be described in a separate 328 document. 330 2.5. SPRING in the Core networks 332 MPLS is a well-known technology widely deployed in many IP core 333 networks. However there are some operators that do not run MPLS 334 everywhere in their core network today, thus moving forward they 335 would prefer to have an IPv6 native infrastructure for the core 336 network. 338 While the overall amount of traffic offered to the network continues 339 to grow and considering that multiple types of traffic with different 340 characteristics and requirements are quickly converging over single 341 network architecture, the network operators are starting to face new 342 challenges. 344 Some operators are looking at the possibility to setup an explicit 345 path based on the IPv6 source address for specific types of traffic 346 in order to efficiently use their network infrastructure. In case of 347 IPv6 some operators are currently assigning or plan to assign IPv6 348 prefix(es) to their IPv6 customers based on regions/geography, thus 349 the subscriber's IPv6 prefix could be used to identify the region 350 where the customer is located. In such environment the IPv6 source 351 address could be used by the Edge nodes of the network to steer 352 traffic and forward it through a specific path other than the optimal 353 path. 355 The need to setup a source-based path, going through some specific 356 middle/intermediate points in the network may be related to different 357 requirements: 359 o The operator may want to be able to use some high bandwidth links 360 for specific type of traffic (like video) avoiding the need for 361 over-dimensioning all the links of the network; 363 o The operator may want to be able to setup a specific path for 364 delay sensitive applications; 366 o The operator may have the need to be able to select one (or 367 multiple) specific exit point(s) at peering points when different 368 peering points are available; 370 o The operator may have the need to be able to setup a source based 371 path for specific services in order to be able to reach some 372 servers hosted in some facilities not always reachable through the 373 optimal path. 375 All these scenarios would require a form of traffic engineering 376 capabilities in IP core networks not running MPLS and not willing to 377 run it. 379 IPv4 protocol does not provide such functionalities today and it is 380 not the intent of this document to address the IPv4 scenario, both 381 because this may create a lot of backward compatibility issues with 382 currently deployed networks and for the security issues that may 383 raise. 385 The described use cases could be addressed with the SPRING 386 architecture by having the Edge nodes of network to impose a Segment 387 List on specific traffic flows, based on certain classification 388 criteria that would include source IPv6 address. 390 3. Acknowledgements 392 The authors would like to thank Brian Field, Robert Raszuk, John G. 393 Scudder and Yakov Rekhter for their valuable comments and inputs to 394 this document. 396 4. IANA Considerations 398 This document does not require any action from IANA. 400 5. Security Considerations 402 There are a number of security concerns with source routing at the IP 403 layer [RFC5095]. The new IPv6-based routing header will be defined 404 in way that blind attacks are never possible, i.e., attackers will be 405 unable to send source routed packets that get successfully processed, 406 without being part of the negations for setting up the source routes 407 or being able to eavesdrop legitimate source routed packets. In some 408 networks this base level security may be complemented with other 409 mechanisms, such as packet filtering, cryptographic security, etc. 411 6. Informative References 413 [I-D.bhandari-dhc-class-based-prefix] 414 Systems, C., Halwasia, G., Gundavelli, S., Deng, H., 415 Thiebaut, L., Korhonen, J., and I. Farrer, "DHCPv6 class 416 based prefix", draft-bhandari-dhc-class-based-prefix-05 417 (work in progress), July 2013. 419 [I-D.filsfils-rtgwg-segment-routing-use-cases] 420 Filsfils, C., Francois, P., Previdi, S., Decraene, B., 421 Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., 422 Ytti, S., Henderickx, W., Tantsura, J., Kini, S., and E. 423 Crabbe, "Segment Routing Use Cases", draft-filsfils-rtgwg- 424 segment-routing-use-cases-02 (work in progress), October 425 2013. 427 [I-D.filsfils-rtgwg-segment-routing] 428 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 429 Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., 430 Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, 431 "Segment Routing Architecture", draft-filsfils-rtgwg- 432 segment-routing-01 (work in progress), October 2013. 434 [I-D.filsfils-spring-segment-routing-mpls] 435 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., 436 Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R., 437 Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe, 438 "Segment Routing with MPLS data plane", draft-filsfils- 439 spring-segment-routing-mpls-00 (work in progress), October 440 2013. 442 [I-D.ietf-mpls-seamless-mpls] 443 Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz, 444 M., and D. Steinberg, "Seamless MPLS Architecture", draft- 445 ietf-mpls-seamless-mpls-06 (work in progress), February 446 2014. 448 [I-D.ietf-sfc-problem-statement] 449 Quinn, P. and T. Nadeau, "Service Function Chaining 450 Problem Statement", draft-ietf-sfc-problem-statement-03 451 (work in progress), April 2014. 453 [I-D.kumar-sfc-dc-use-cases] 454 Surendra, S., Obediente, C., and M. Tufail, "Service 455 Function Chaining Use Cases In Data Centers", draft-kumar- 456 sfc-dc-use-cases-01 (work in progress), March 2014. 458 [I-D.lepape-6man-prefix-metadata] 459 Pape, M., Systems, C., and I. Farrer, "IPv6 Prefix Meta- 460 data and Usage", draft-lepape-6man-prefix-metadata-00 461 (work in progress), July 2013. 463 [I-D.previdi-6man-segment-routing-header] 464 Previdi, S., Filsfils, C., Field, B., and I. Leung, "IPv6 465 Segment Routing Header (SRH)", draft-previdi-6man-segment- 466 routing-header-00 (work in progress), March 2014. 468 [I-D.quinn-sfc-nsh] 469 Quinn, P., Guichard, J., Fernando, R., Surendra, S., 470 Smith, M., Yadav, N., Agarwal, P., Manur, R., Chauhan, A., 471 Elzur, U., McConnell, B., and C. Wright, "Network Service 472 Header", draft-quinn-sfc-nsh-02 (work in progress), 473 February 2014. 475 [I-D.troan-homenet-sadr] 476 Troan, O. and L. Colitti, "IPv6 Multihoming with Source 477 Address Dependent Routing (SADR)", draft-troan-homenet- 478 sadr-01 (work in progress), September 2013. 480 [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation 481 of Type 0 Routing Headers in IPv6", RFC 5095, December 482 2007. 484 Authors' Addresses 486 John Brzozowski 487 Comcast 489 Email: john_brzozowski@cable.comcast.com 491 John Leddy 492 Comcast 494 Email: John_Leddy@cable.comcast.com 496 Ida Leung 497 Rogers Communications 498 8200 Dixie Road 499 Brampton, ON L6T 0C1 500 CANADA 502 Email: Ida.Leung@rci.rogers.com 504 Stefano Previdi 505 Cisco Systems 506 Via Del Serafico, 200 507 Rome 00142 508 Italy 510 Email: sprevidi@cisco.com 512 Mark Townsley 513 Cisco Systems 515 Email: townsley@cisco.com 516 Christian Martin 517 Cisco Systems 519 Email: martincj@cisco.com 521 Clarence Filsfils 522 Cisco Systems 523 Brussels 524 BE 526 Email: cfilsfil@cisco.com 528 Roberta Maglione (editor) 529 Cisco Systems 530 181 Bay Street 531 Toronto M5J 2T3 532 Canada 534 Email: robmgl@cisco.com