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Versions: (draft-martin-spring-segment-routing-ipv6-use-cases) 00 01 02 03 04 05 06 07 08 09

Spring                                                     J. Brzozowski
Internet-Draft                                                  J. Leddy
Intended status: Informational                                   Comcast
Expires: August 14, 2017                                    C.  Filsfils
                                                        R. Maglione, Ed.
                                                             M. Townsley
                                                           Cisco Systems
                                                       February 10, 2017


                         IPv6 SPRING Use Cases
                  draft-ietf-spring-ipv6-use-cases-09

Abstract

   Source Packet Routing in Networking (SPRING) architecture leverages
   the source routing paradigm.  A node steers a packet through a
   controlled set of instructions, called segments, by prepending the
   packet with SPRING header.  A segment can represent any instruction,
   topological or service-based.  A segment can have a local semantic to
   the SPRING node or global within the SPRING domain.  SPRING allows to
   enforce a flow through any topological path and service chain while
   maintaining per-flow state only at the ingress node to the SPRING
   domain.

   The objective of this document is to illustrate some use cases that
   need to be taken into account by the Source Packet Routing in
   Networking (SPRING) architecture.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on August 14, 2017.






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Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  IPv6 SPRING use cases . . . . . . . . . . . . . . . . . . . .   3
     2.1.  SPRING in the Home Network  . . . . . . . . . . . . . . .   5
     2.2.  SPRING in the Access Network  . . . . . . . . . . . . . .   6
     2.3.  SPRING in the Data Center . . . . . . . . . . . . . . . .   7
     2.4.  SPRING in the Content Delivery Networks . . . . . . . . .   7
     2.5.  SPRING in the Core networks . . . . . . . . . . . . . . .   8
   3.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   9
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   7.  Informative References  . . . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  11

1.  Introduction

   Source Packet Routing in Networking (SPRING) architecture leverages
   the source routing paradigm.  An ingress node steers a packet through
   a controlled set of instructions, called segments, by prepending the
   packet with SPRING header.  A segment can represent any instruction,
   topological or service-based.  A segment can represent a local
   semantic on the SPRING node, or a global semantic within the SPRING
   domain.  SPRING allows one to enforce a flow through any topological
   path and service chain while maintaining per-flow state only at the
   ingress node to the SPRING domain.

   The SPRING architecture is described in
   [I-D.ietf-spring-segment-routing].  The SPRING control plane is
   agnostic to the dataplane, thus it can be applied to both MPLS and
   IPv6.  In case of MPLS the (list of) segment identifiers are carried




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   in the MPLS label stack, while for the IPv6 dataplane, a new type of
   routing extension header is required.

   The details of the new routing extension header are described in
   [I-D.ietf-6man-segment-routing-header] which also covers the security
   considerations and the aspects related to the deprecation of the IPv6
   Type 0 Routing Header described in [RFC5095].

2.  IPv6 SPRING use cases

   In today's networks, source routing is typically accomplished by
   encapsulating IP packets in MPLS LSPs that are signaled via RSVP-TE.
   Therefore, there are scenarios where it may be possible to run IPv6
   on top of MPLS, and as such, the MPLS Segment Routing architecture
   described in [I-D.ietf-spring-segment-routing-mpls] could be
   leveraged to provide SPRING capabilities in an IPv6/MPLS environment.

   However, there are other cases and/or specific network segments (such
   as for example the Home Network, the Data Center, etc.) where MPLS
   may not be available or deployable for lack of support on network
   elements or for an operator's design choice.  In such scenarios a
   non-MPLS based solution would be preferred by the network operators
   of such infrastructures.

   In addition there are cases where the operators could have made the
   design choice to disable IPv4, for ease of management and scale
   (return to single-stack) or due to an address constraint, for example
   because they do not possess enough IPv4 addresses resources to number
   all the endpoints and other network elements on which they desire to
   run MPLS.

   In such scenario the support for MPLS operations on an IPv6-only
   network would be required.  However today's IPv6-only networks are
   not fully capable of supporting MPLS.  There is ongoing work in the
   MPLS Working Group, described in [RFC7439] to identify gaps that must
   be addressed in order to allow MPLS-related protocols and
   applications to be used with IPv6-only networks.  This is an another
   example of scenario where a solution relying on IPv6 without
   requiring the use of MPLS could represent a valid option to solve the
   problem and meet operators' requirements.

   It is important to clarify that today, it is possible to run IPv6 on
   top of an IPv4 MPLS network by using the mechanism called 6PE,
   described in [RFC4798].  However this approach does not fulfill the
   requirement of removing the need of IPv4 addresses in the network, as
   requested in the above use case.  Another way to run IPv6 on top of
   an MPLS network is to use Segment Routing MPLS which provides the




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   support for the IPv6 FEC.  Obviously such approach is applicable only
   for scenarios and network segments where MPLS is present.

   In addition it is worth to note that in today's MPLS dual-stack
   networks IPv4 traffic is labeled while IPv6 traffic is usually
   natively routed, not label-switched.  Therefore in order to be able
   to provide Traffic Engineering "like" capabilities for IPv6 traffic
   additional/alternative encapsulation mechanisms would be required.

   In summary there is a class of use cases that motivate an IPv6 data
   plane.  The authors identify some fundamental scenarios that, when
   recognized in conjunction, strongly indicate an IPv6 data plane:

   1.  There is a need or desire to impose source-routing semantics
       within an application or at the edge of a network (for example, a
       CPE or home gateway)

   2.  There is a strict lack of an MPLS dataplane in a portion of the
       end to end path

   3.  There is a need or desire to remove routing state from any node
       other than the source, such that the source is the only node that
       knows and will know the path a packet will take, a priori

   4.  There is a need to connect millions of addressable segment
       endpoints, thus high routing scalability is a requirement.  IPv6
       addresses are inherently summarizable: a very large operator
       could scale by summarizing IPv6 subnets at various internal
       boundaries.  This is very simple and is a basic property of IP
       routing.  MPLS node segments are not summarizable.  To reach the
       same scale, an operator would need to introduce additional
       complexity, such as mechanisms known with the industry term
       Seamless MPLS.

   In any environment with requirements such as those listed above, an
   IPv6 data plane provides a powerful combination of capabilities for a
   network operator to realize benefits in explicit routing, protection
   and restoration, high routing scalability, traffic engineering,
   service chaining, service differentiation and application flexibility
   via programmability.

   This section will describe some scenarios where MPLS may not be
   present and it will highlight how the SPRING architecture could be
   used to address such use cases.

   The use cases described in the section do not constitute an
   exhaustive list of all the possible scenarios; this section only
   includes some of the most common envisioned deployment models for



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   IPv6 Segment Routing.  In addition to the use cases described in this
   document the SPRING architecture can be applied to all the use cases
   described in [RFC7855] for the SPRING MPLS data plane, when an IPv6
   data plane is present.

2.1.  SPRING in the Home Network

   An IPv6-enabled home network provides ample globally routed IP
   addresses for all devices in the home.  An IPv6 home network with
   multiple egress points and associated provider-assigned prefixes
   will, in turn, provide multiple IPv6 addresses to hosts.  A homenet
   performing Source and Destination Routing
   ([I-D.ietf-rtgwg-dst-src-routing]) will ensure that packets exit the
   home at the appropriate egress based on the associated delegated
   prefix for that link.

   A SPRING enabled home provides the possibility for imposition of a
   Segment List by end-hosts in the home, or a customer edge router in
   the home.  If the Segment List is enabled at the customer edge
   router, that router is responsible for classifying traffic and
   inserting the appropriate Segment List.  If hosts in the home have
   explicit source selection rules, classification can be based on
   source address or associated network egress point, avoiding the need
   for DPI-based implicit classification techniques.  If the Segment
   List is inserted by the host itself, it is important to know which
   networks can interpret the SPRING header.  This information can be
   provided as part of host configuration as a property of the
   configured IP address.

   The ability to steer traffic to an appropriate egress or utilize a
   specific type of media (e.g., low-power, WIFI, wired, femto-cell,
   bluetooth, MOCA, HomePlug, etc.) within the home itself are obvious
   cases which may be of interest to an application running within a
   home network.

   Steering to a specific egress point may be useful for a number of
   reasons, including:

   o  Regulatory

   o  Performance of a particular service associated with a particular
      link

   o  Cost imposed due to data-caps or per-byte charges

   o  Home vs. work traffic in homes with one or more teleworkers, etc.

   o  Specific services provided by one ISP vs. another



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   Information included in the Segment List, whether imposed by the end-
   host itself, a customer edge router, or within the access network of
   the ISP, may be of use at the far ends of the data communication as
   well.  For example, an application running on an end-host with
   application-support in a data center can utilize the Segment List as
   a channel to include information that affects its treatment within
   the data center itself, allowing for application-level steering and
   load-balancing without relying upon implicit application
   classification techniques at the data-center edge.  Further, as more
   and more application traffic is encrypted, the ability to extract
   (and include in the Segment List) just enough information to enable
   the network and data center to load-balance and steer traffic
   appropriately becomes more and more important.

2.2.  SPRING in the Access Network

   Access networks deliver a variety of types of traffic from the
   service provider's network to the home environment and from the home
   towards the service provider's network.

   For bandwidth management or related purposes, the service provider
   may want to associate certain types of traffic to specific physical
   or logical downstream capacity pipes.

   This mapping is not the same thing as classification and scheduling.
   In the Cable access network, each of these pipes are represented at
   the DOCSIS layer as different service flows, which are better
   identified as differing data links.  As such, creating this
   separation allows an operator to differentiate between different
   types of content and perform a variety of differing functions on
   these pipes, such as byte capping, regulatory compliance functions,
   and billing.

   In a cable operator's environment, these downstream pipes could be a
   specific QAM, a DOCSIS service flow or a service group.

   Similarly, the operator may want to map traffic from the home sent
   towards the service provider's network to specific upstream capacity
   pipes.  Information carried in a packet's SPRING header could provide
   the target pipe for this specific packet.  The access device would
   not need to know specific details about the packet to perform this
   mapping; instead the access device would only need to know how to map
   the SR SID value to the target pipe.








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2.3.  SPRING in the Data Center

   Some Data Center operators are transitioning their Data Center
   infrastructure from IPv4 to native IPv6 only, in order to cope with
   IPv4 address depletion and to achieve larger scale.  In such
   environment, source routing (through Segment Routing IPv6) can be
   used to steer traffic across specific paths.

   Another use case for SPRING in the datacenter is to cause a packet to
   follow a specific path through the network.  The specific path may
   also include a given function one or more nodes in the path are
   requested to perform.  In such scenario Segment Routing can be used
   to steer the packet across a specific list of nodes, tenants and
   functions.  Each node, tenant and function will be identified by a
   Segment Routing Identifier (SID), thus the list of SID's will specify
   how the traffic will have to traverse a specific path.

   One of the fundamental requirements for Data Center architecture is
   to provide scalable, isolated tenant networks.  The transition to
   IPv6 and the introduction of Segment Routing IPv6 open up the
   possibility to achieve tenant's isolation without additional headers.

2.4.  SPRING in the Content Delivery Networks

   The rise of online video applications and new, video-capable IP
   devices has led to an explosion of video traffic traversing network
   operator infrastructures.  In the drive to reduce the capital and
   operational impact of the massive influx of online video traffic, as
   well as to extend traditional TV services to new devices and screens,
   network operators are increasingly turning to Content Delivery
   Networks (CDNs).

   Several studies showed the benefits of connecting caches in a
   hierarchical structure following the hierarchical nature of the
   Internet.  In a cache hierarchy one cache establishes peering
   relationships with its neighbor caches.  There are two types of
   relationship: parent and sibling.  A parent cache is essentially one
   level up in a cache hierarchy.  A sibling cache is on the same level.
   Multiple levels of hierarchy are commonly used in order to build
   efficient caches architecture.

   In an environment, where each single cache system can be uniquely
   identified by its own IPv6 address, a Segment List containing a
   sequence of the caches in a hierarchy can be built.  At each node
   (cache) present in the Segment List a TCP session to port 80 is
   established and if the requested content is found at the cache (cache
   hits scenario) the sequence ends, even if there are more nodes in the
   list.



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2.5.  SPRING in the Core networks

   MPLS is a well-known technology widely deployed in many IP core
   networks.  However there are some operators that do not run MPLS
   everywhere in their core network today, thus moving forward they
   would prefer to have an IPv6 native infrastructure for the core
   network.

   While the overall amount of traffic offered to the network continues
   to grow and considering that multiple types of traffic with different
   characteristics and requirements are quickly converging over single
   network architecture, the network operators are starting to face new
   challenges.

   Some operators are looking at the possibility to setup an explicit
   path based on the IPv6 source address for specific types of traffic
   in order to efficiently use their network infrastructure.  In case of
   IPv6 some operators are currently assigning or plan to assign IPv6
   prefix(es) to their IPv6 customers based on regions/geography, thus
   the subscriber's IPv6 prefix could be used to identify the region
   where the customer is located.  In such environment the IPv6 source
   address could be used by the Edge nodes of the network to steer
   traffic and forward it through a specific path other than the optimal
   path.

   The need to setup a source-based path, going through some specific
   middle/intermediate points in the network may be related to different
   requirements:

   o  The operator may want to be able to use some high bandwidth links
      for specific type of traffic (like video) avoiding the need for
      over-dimensioning all the links of the network;

   o  The operator may want to be able to setup a specific path for
      delay sensitive applications;

   o  The operator may have the need to be able to select one (or
      multiple) specific exit point(s) at peering points when different
      peering points are available;

   o  The operator may have the need to be able to setup a source based
      path for specific services in order to be able to reach some
      servers hosted in some facilities not always reachable through the
      optimal path;

   o  The operator may have the need to be able to provision guaranteed
      disjoint paths (so-called dual-plane network) for diversity
      purposes



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   All these scenarios would require a form of traffic engineering
   capabilities in IP core networks not running MPLS and not willing to
   run it.

   IPv4 protocol does not provide such functionalities today and it is
   not the intent of this document to address the IPv4 scenario, both
   because this may create a lot of backward compatibility issues with
   currently deployed networks and for the security issues that may
   raise.

   The described use cases could be addressed with the SPRING
   architecture by having the Edge nodes of network to impose a Segment
   List on specific traffic flows, based on certain classification
   criteria that would include source IPv6 address.

3.  Contributors

   Many people contributed to this document.  The authors of this
   document would like to thank and recognize them and their
   contributions.  These contributors provided invaluable concepts and
   content for this document's creation.

      Ida Leung
      Rogers Communications
      8200 Dixie Road
      Brampton, ON  L6T 0C1
      CANADA

      Email: Ida.Leung@rci.rogers.com


      Stefano Previdi
      Cisco Systems
      Via Del Serafico, 200
      Rome  00142
      Italy

      Email: sprevidi@cisco.com

      Christian Martin
      Cisco Systems

      Email: martincj@cisco.com








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4.  Acknowledgements

   The authors would like to thank Brian Field, Robert Raszuk, Wes
   George, Eric Vyncke, Fred Baker, John G.  Scudder and Yakov Rekhter
   for their valuable comments and inputs to this document.

5.  IANA Considerations

   This document does not require any action from IANA.

6.  Security Considerations

   There are a number of security concerns with source routing at the IP
   layer [RFC5095].  Security mechanisms applied to Segment Routing over
   IPv6 networks are detailed in section 9 of
   [I-D.ietf-6man-segment-routing-header]

7.  Informative References

   [I-D.ietf-6man-segment-routing-header]
              Previdi, S., Filsfils, C., Field, B., Leung, I., Linkova,
              J., Aries, E., Kosugi, T., Vyncke, E., and D. Lebrun,
              "IPv6 Segment Routing Header (SRH)", draft-ietf-6man-
              segment-routing-header-05 (work in progress), February
              2017.

   [I-D.ietf-rtgwg-dst-src-routing]
              Lamparter, D. and A. Smirnov, "Destination/Source
              Routing", draft-ietf-rtgwg-dst-src-routing-03 (work in
              progress), November 2016.

   [I-D.ietf-spring-segment-routing]
              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-10 (work in progress), November
              2016.

   [I-D.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Shakir, R.,
              jefftant@gmail.com, j., and E. Crabbe, "Segment Routing
              with MPLS data plane", draft-ietf-spring-segment-routing-
              mpls-07 (work in progress), February 2017.








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   [RFC4798]  De Clercq, J., Ooms, D., Prevost, S., and F. Le Faucheur,
              "Connecting IPv6 Islands over IPv4 MPLS Using IPv6
              Provider Edge Routers (6PE)", RFC 4798,
              DOI 10.17487/RFC4798, February 2007,
              <http://www.rfc-editor.org/info/rfc4798>.

   [RFC5095]  Abley, J., Savola, P., and G. Neville-Neil, "Deprecation
              of Type 0 Routing Headers in IPv6", RFC 5095,
              DOI 10.17487/RFC5095, December 2007,
              <http://www.rfc-editor.org/info/rfc5095>.

   [RFC7439]  George, W., Ed. and C. Pignataro, Ed., "Gap Analysis for
              Operating IPv6-Only MPLS Networks", RFC 7439,
              DOI 10.17487/RFC7439, January 2015,
              <http://www.rfc-editor.org/info/rfc7439>.

   [RFC7855]  Previdi, S., Ed., Filsfils, C., Ed., Decraene, B.,
              Litkowski, S., Horneffer, M., and R. Shakir, "Source
              Packet Routing in Networking (SPRING) Problem Statement
              and Requirements", RFC 7855, DOI 10.17487/RFC7855, May
              2016, <http://www.rfc-editor.org/info/rfc7855>.

Authors' Addresses

   John Brzozowski
   Comcast

   Email: john_brzozowski@cable.comcast.com


   John Leddy
   Comcast

   Email: John_Leddy@cable.comcast.com


   Clarence Filsfils
   Cisco Systems
   Brussels
   BE

   Email: cfilsfil@cisco.com









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   Roberta Maglione (editor)
   Cisco Systems
   Via Torri Bianche 8
   Vimercate  20871
   Italy

   Email: robmgl@cisco.com


   Mark Townsley
   Cisco Systems

   Email: townsley@cisco.com






































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