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2 Spring J. Brzozowski
3 Internet-Draft J. Leddy
4 Intended status: Informational Comcast
5 Expires: October 15, 2017 C. Filsfils
6 R. Maglione, Ed.
7 M. Townsley
8 Cisco Systems
9 April 13, 2017
11 IPv6 SPRING Use Cases
12 draft-ietf-spring-ipv6-use-cases-10
14 Abstract
16 The objective of this document is to illustrate some use cases that
17 need to be taken into account by the Source Packet Routing in
18 Networking (SPRING) architecture in the context of an IPv6
19 environment.
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 October 15, 2017.
38 Copyright Notice
40 Copyright (c) 2017 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. IPv6 SPRING use cases . . . . . . . . . . . . . . . . . . . . 4
57 2.1. SPRING in the Home Network . . . . . . . . . . . . . . . 4
58 2.2. SPRING in the Access Network . . . . . . . . . . . . . . 5
59 2.3. SPRING in the Data Center . . . . . . . . . . . . . . . . 6
60 2.4. SPRING in the Content Delivery Networks . . . . . . . . . 6
61 2.5. SPRING in the Core networks . . . . . . . . . . . . . . . 7
62 3. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 8
63 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
64 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
65 6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
66 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 9
67 7.1. Informative References . . . . . . . . . . . . . . . . . 9
68 7.2. Normative References . . . . . . . . . . . . . . . . . . 10
69 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 10
71 1. Introduction
73 Source Packet Routing in Networking (SPRING) architecture leverages
74 the source routing paradigm. An ingress node steers a packet through
75 a controlled set of instructions, called segments, by prepending the
76 packet with SPRING header. The SPRING architecture is described in
77 [I-D.ietf-spring-segment-routing].
79 In today's networks, source routing is typically accomplished by
80 encapsulating IP packets in MPLS LSPs that are signaled via RSVP-TE.
81 Therefore, there are scenarios where it may be possible to run IPv6
82 on top of MPLS, and as such, the MPLS Segment Routing architecture
83 described in [I-D.ietf-spring-segment-routing-mpls] could be
84 leveraged to provide spring capabilities in an IPv6/MPLS environment.
86 However, there are other cases and/or specific network segments (such
87 as for example the Home Network, the Data Center, etc.) where MPLS
88 may not be available or deployable for lack of support on network
89 elements or for an operator's design choice. In such scenarios a
90 non-MPLS based solution would be preferred by the network operators
91 of such infrastructures.
93 In addition there are cases where the operators could have made the
94 design choice to disable IPv4, for ease of management and scale
95 (return to single-stack) or due to an address constraint, for example
96 because they do not possess enough IPv4 addresses resources to number
97 all the endpoints and other network elements on which they desire to
98 run MPLS.
100 In such scenario the support for MPLS operations on an IPv6-only
101 network would be required. However today's IPv6-only networks are
102 not fully capable of supporting MPLS. There is ongoing work in the
103 MPLS Working Group, described in [RFC7439] to identify gaps that must
104 be addressed in order to allow MPLS-related protocols and
105 applications to be used with IPv6-only networks. This is an another
106 example of scenario where a solution relying on IPv6 without
107 requiring the use of MPLS could represent a valid option to solve the
108 problem and meet operators' requirements.
110 It is important to clarify that today, it is possible to run IPv6 on
111 top of an IPv4 MPLS network by using the mechanism called 6PE,
112 described in [RFC4798]. However this approach does not fulfill the
113 requirement of removing the need of IPv4 addresses in the network, as
114 requested in the above use case.
116 In summary there is a class of use cases that motivates an IPv6 data
117 plane. This document identifies some fundamental scenarios that,
118 when recognized in conjunction, strongly indicate an IPv6 data plane:
120 1. There is a need or desire to impose source-routing semantics
121 within an application or at the edge of a network (for example, a
122 CPE or home gateway)
124 2. There is a strict lack of an MPLS dataplane in a portion of the
125 end to end path
127 3. There is a need or desire to remove routing state from any node
128 other than the source, such that the source is the only node that
129 knows and will know the path a packet will take, a priori
131 4. There is a need to connect millions of addressable segment
132 endpoints, thus high routing scalability is a requirement. IPv6
133 addresses are inherently summarizable: a very large operator
134 could scale by summarizing IPv6 subnets at various internal
135 boundaries. This is very simple and is a basic property of IP
136 routing. MPLS node segments are not summarizable. To reach the
137 same scale, an operator would need to introduce additional
138 complexity, such as mechanisms known with the industry term
139 Seamless MPLS [I-D.ietf-mpls-seamless-mpls].
141 In any environment with requirements such as those listed above, an
142 IPv6 data plane provides a powerful combination of capabilities for a
143 network operator to realize benefits in explicit routing, protection
144 and restoration, high routing scalability, traffic engineering,
145 service chaining, service differentiation and application flexibility
146 via programmability.
148 2. IPv6 SPRING use cases
150 This section will describe some scenarios where MPLS may not be
151 present and it will highlight the need for the spring architecture to
152 take them into account.
154 The use cases described in the section do not constitute an
155 exhaustive list of all the possible scenarios; this section only
156 includes some of the most common envisioned deployment models for
157 IPv6 Segment Routing. In addition to the use cases described in this
158 document the spring architecture should be able to be applied to all
159 the use cases described in [RFC7855] for the spring MPLS data plane,
160 when an IPv6 data plane is present.
162 2.1. SPRING in the Home Network
164 An IPv6-enabled home network provides ample globally routed IP
165 addresses for all devices in the home. An IPv6 home network with
166 multiple egress points and associated provider-assigned prefixes
167 will, in turn, provide multiple IPv6 addresses to hosts. A homenet
168 performing Source and Destination Routing
169 ([I-D.ietf-rtgwg-enterprise-pa-multihoming]) will ensure that packets
170 exit the home at the appropriate egress based on the associated
171 delegated prefix for that link.
173 A spring enabled home provides the ability to steer traffic into a
174 specific path from end-hosts in the home, or from a customer edge
175 router in the home. If the selection of the source routed path is
176 enabled at the customer edge router, that router is responsible for
177 classifying traffic and steering it into the correct path. If hosts
178 in the home have explicit source selection rules, classification can
179 be based on source address or associated network egress point,
180 avoiding the need for DPI-based implicit classification techniques.
181 If the traffic is steered into a specific path by the host itself, it
182 is important to know which networks can interpret the spring header.
183 This information can be provided as part of host configuration as a
184 property of the configured IP address.
186 The ability to steer traffic to an appropriate egress or utilize a
187 specific type of media (e.g., low-power, WIFI, wired, femto-cell,
188 bluetooth, MOCA, HomePlug, etc.) within the home itself are obvious
189 cases which may be of interest to an application running within a
190 home network.
192 Steering to a specific egress point may be useful for a number of
193 reasons, including:
195 o Regulatory
197 o Performance of a particular service associated with a particular
198 link
200 o Cost imposed due to data-caps or per-byte charges
202 o Home vs. work traffic in homes with one or more teleworkers, etc.
204 o Specific services provided by one ISP vs. another
206 Information included in the spring header, whether imposed by the
207 end-host itself, a customer edge router, or within the access network
208 of the ISP, may be of use at the far ends of the data communication
209 as well. For example, an application running on an end-host with
210 application-support in a data center can utilize the spring header as
211 a channel to include information that affects its treatment within
212 the data center itself, allowing for application-level steering and
213 load-balancing without relying upon implicit application
214 classification techniques at the data-center edge. Further, as more
215 and more application traffic is encrypted, the ability to extract
216 (and include in the spring header) just enough information to enable
217 the network and data center to load-balance and steer traffic
218 appropriately becomes more and more important.
220 2.2. SPRING in the Access Network
222 Access networks deliver a variety of types of traffic from the
223 service provider's network to the home environment and from the home
224 towards the service provider's network.
226 For bandwidth management or related purposes, the service provider
227 may want to associate certain types of traffic to specific physical
228 or logical downstream capacity pipes.
230 This mapping is not the same thing as classification and scheduling.
231 In the Cable access network, each of these pipes are represented at
232 the DOCSIS [DOCSIS] layer as different service flows, which are
233 better identified as differing data links. As such, creating this
234 separation allows an operator to differentiate between different
235 types of content and perform a variety of differing functions on
236 these pipes, such as byte capping, regulatory compliance functions,
237 and billing.
239 In a cable operator's environment, these downstream pipes could be a
240 specific QAM [QAM], a DOCSIS [DOCSIS] service flow or a service
241 group.
243 Similarly, the operator may want to map traffic from the home sent
244 towards the service provider's network to specific upstream capacity
245 pipes. Information carried in a packet's spring header could provide
246 the target pipe for this specific packet. The access device would
247 not need to know specific details about the packet to perform this
248 mapping; instead the access device would only need to know the
249 interpretation of the spring header and how to map it to the target
250 pipe.
252 2.3. SPRING in the Data Center
254 Some Data Center operators are transitioning their Data Center
255 infrastructure from IPv4 to native IPv6 only, in order to cope with
256 IPv4 address depletion and to achieve larger scale. In such
257 environment, source routing (through Segment Routing IPv6) can be
258 used to steer traffic across specific paths through the network. The
259 specific path may also include a given function one or more nodes in
260 the path are requested to perform.
262 In addition one of the fundamental requirements for Data Center
263 architecture is to provide scalable, isolated tenant networks. In
264 such scenario Segment Routing can be used to identify specific nodes,
265 tenants, and functions and to build a construct to steer the traffic
266 across that specific path.
268 2.4. SPRING in the Content Delivery Networks
270 The rise of online video applications and new, video-capable IP
271 devices has led to an explosion of video traffic traversing network
272 operator infrastructures. In the drive to reduce the capital and
273 operational impact of the massive influx of online video traffic, as
274 well as to extend traditional TV services to new devices and screens,
275 network operators are increasingly turning to Content Delivery
276 Networks (CDNs).
278 Several studies showed the benefits of connecting caches in a
279 hierarchical structure following the hierarchical nature of the
280 Internet. In a cache hierarchy one cache establishes peering
281 relationships with its neighbor caches. There are two types of
282 relationship: parent and sibling. A parent cache is essentially one
283 level up in a cache hierarchy. A sibling cache is on the same level.
284 Multiple levels of hierarchy are commonly used in order to build
285 efficient caches architecture.
287 In an environment, where each single cache system can be uniquely
288 identified by its own IPv6 address, a list containing a sequence of
289 the caches in a hierarchy can be built. At each node (cache) in the
290 list, the presence of the requested content if checked. If the
291 requested content is found at the cache (cache hits scenario) the
292 sequence ends, even if there are more nodes in the list; otherwise
293 next element in the list (next node/cache) is examined.
295 2.5. SPRING in the Core networks
297 MPLS is a well-known technology widely deployed in many IP core
298 networks. However there are some operators that do not run MPLS
299 everywhere in their core network today, thus moving forward they
300 would prefer to have an IPv6 native infrastructure for the core
301 network.
303 While the overall amount of traffic offered to the network continues
304 to grow and considering that multiple types of traffic with different
305 characteristics and requirements are quickly converging over single
306 network architecture, the network operators are starting to face new
307 challenges.
309 Some operators are looking at the possibility to setup an explicit
310 path based on the IPv6 source address for specific types of traffic
311 in order to efficiently use their network infrastructure. In case of
312 IPv6 some operators are currently assigning or plan to assign IPv6
313 prefix(es) to their IPv6 customers based on regions/geography, thus
314 the subscriber's IPv6 prefix could be used to identify the region
315 where the customer is located. In such environment the IPv6 source
316 address could be used by the Edge nodes of the network to steer
317 traffic and forward it through a specific path other than the optimal
318 path.
320 The need to setup a source-based path, going through some specific
321 middle/intermediate points in the network may be related to different
322 requirements:
324 o The operator may want to be able to use some high bandwidth links
325 for specific type of traffic (like video) avoiding the need for
326 over-dimensioning all the links of the network;
328 o The operator may want to be able to setup a specific path for
329 delay sensitive applications;
331 o The operator may have the need to be able to select one (or
332 multiple) specific exit point(s) at peering points when different
333 peering points are available;
335 o The operator may have the need to be able to setup a source based
336 path for specific services in order to be able to reach some
337 servers hosted in some facilities not always reachable through the
338 optimal path;
340 o The operator may have the need to be able to provision guaranteed
341 disjoint paths (so-called dual-plane network) for diversity
342 purposes
344 All these scenarios would require a form of traffic engineering
345 capabilities in IP core networks not running MPLS and not willing to
346 run it.
348 3. Contributors
350 Many people contributed to this document. The authors of this
351 document would like to thank and recognize them and their
352 contributions. These contributors provided invaluable concepts and
353 content for this document's creation.
355 Ida Leung
356 Rogers Communications
357 8200 Dixie Road
358 Brampton, ON L6T 0C1
359 CANADA
361 Email: Ida.Leung@rci.rogers.com
363 Stefano Previdi
364 Cisco Systems
365 Via Del Serafico, 200
366 Rome 00142
367 Italy
369 Email: sprevidi@cisco.com
371 Christian Martin
372 Cisco Systems
374 Email: martincj@cisco.com
376 4. Acknowledgements
378 The authors would like to thank Brian Field, Robert Raszuk, Wes
379 George, Eric Vyncke, Fred Baker, John G. Scudder and Yakov Rekhter
380 for their valuable comments and inputs to this document.
382 5. IANA Considerations
384 This document does not require any action from IANA.
386 6. Security Considerations
388 This document presents use cases to be considered by the spring
389 architecture and potential IPv6 extensions. As such, it does not
390 introduce any security considerations. However, there are a number
391 of security concerns with source routing at the IP layer [RFC5095].
392 It is expected that any solution that addresses these use cases to
393 also address any security concerns.
395 7. References
397 7.1. Informative References
399 [DOCSIS] "DOCSIS Specifications Page",
400 .
403 [I-D.ietf-mpls-seamless-mpls]
404 Leymann, N., Decraene, B., Filsfils, C., Konstantynowicz,
405 M., and D. Steinberg, "Seamless MPLS Architecture", draft-
406 ietf-mpls-seamless-mpls-07 (work in progress), June 2014.
408 [I-D.ietf-rtgwg-enterprise-pa-multihoming]
409 Baker, F., Bowers, C., and J. Linkova, "Enterprise
410 Multihoming using Provider-Assigned Addresses without
411 Network Prefix Translation: Requirements and Solution",
412 draft-ietf-rtgwg-enterprise-pa-multihoming-00 (work in
413 progress), March 2017.
415 [I-D.ietf-spring-segment-routing]
416 Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
417 and R. Shakir, "Segment Routing Architecture", draft-ietf-
418 spring-segment-routing-11 (work in progress), February
419 2017.
421 [I-D.ietf-spring-segment-routing-mpls]
422 Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
423 Litkowski, S., and R. Shakir, "Segment Routing with MPLS
424 data plane", draft-ietf-spring-segment-routing-mpls-08
425 (work in progress), March 2017.
427 [QAM] "QAM specification", .
430 [RFC4798] De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
431 "Connecting IPv6 Islands over IPv4 MPLS Using IPv6
432 Provider Edge Routers (6PE)", RFC 4798,
433 DOI 10.17487/RFC4798, February 2007,
434 .
436 [RFC5095] Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
437 of Type 0 Routing Headers in IPv6", RFC 5095,
438 DOI 10.17487/RFC5095, December 2007,
439 .
441 [RFC7439] George, W., Ed. and C. Pignataro, Ed., "Gap Analysis for
442 Operating IPv6-Only MPLS Networks", RFC 7439,
443 DOI 10.17487/RFC7439, January 2015,
444 .
446 7.2. Normative References
448 [RFC7855] Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
449 Litkowski, S., Horneffer, M., and R. Shakir, "Source
450 Packet Routing in Networking (SPRING) Problem Statement
451 and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
452 2016, .
454 Authors' Addresses
456 John Brzozowski
457 Comcast
459 Email: john_brzozowski@cable.comcast.com
461 John Leddy
462 Comcast
464 Email: John_Leddy@cable.comcast.com
465 Clarence Filsfils
466 Cisco Systems
467 Brussels
468 BE
470 Email: cfilsfil@cisco.com
472 Roberta Maglione (editor)
473 Cisco Systems
474 Via Torri Bianche 8
475 Vimercate 20871
476 Italy
478 Email: robmgl@cisco.com
480 Mark Townsley
481 Cisco Systems
483 Email: townsley@cisco.com