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Versions: (draft-martin-spring-segment-routing-ipv6-use-cases) 00 01 02 03 04 05 06 07 08 09 10 11

Spring                                                     J. Brzozowski
Internet-Draft                                                  J. Leddy
Intended status: Informational                                   Comcast
Expires: December 15, 2017                                   C. Filsfils
                                                        R. Maglione, Ed.
                                                             M. Townsley
                                                           Cisco Systems
                                                           June 13, 2017

                         IPv6 SPRING Use Cases


   The Source Packet Routing in Networking (SPRING) architecture
   describes how Segment Routing can be used to steer packets through an
   IPv6 or MPLS network using the source routing paradigm.  This
   document illustrates some use cases for Segment Routing in an IPv6
   only environment.

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
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   Internet-Drafts are draft documents valid for a maximum of six months
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   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on December 15, 2017.

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
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   carefully, as they describe your rights and restrictions with respect

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   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 . . . . . . . . . . . . . . . . . . . .   2
     2.1.  SPRING in the Home Network  . . . . . . . . . . . . . . .   2
     2.2.  SPRING in the Access Network  . . . . . . . . . . . . . .   4
     2.3.  SPRING in Data Center . . . . . . . . . . . . . . . . . .   4
     2.4.  SPRING in Content Delivery Networks . . . . . . . . . . .   5
     2.5.  SPRING in Core networks . . . . . . . . . . . . . . . . .   5
   3.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   7
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     7.1.  Informative References  . . . . . . . . . . . . . . . . .   8
     7.2.  Normative References  . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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.  The SPRING architecture is described in
   [I-D.ietf-spring-segment-routing].  This document illustrates some
   use cases for SPRING/Segment Routing in an IPv6 only environment.

2.  IPv6 SPRING 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
   IPv6 Segment Routing.

   In addition to the use cases described in this document, all the
   SPRING use cases [RFC7855] are also applicable to the SRv6 data

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

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   will, in turn, provide multiple IPv6 addresses to hosts.  A homenet
   performing Source and Destination Routing
   ([I-D.ietf-rtgwg-enterprise-pa-multihoming]) 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 ability to steer traffic into a
   specific path from end-hosts in the home, or from a customer edge
   router in the home.  If the selection of the source routed path is
   enabled at the customer edge router, that router is responsible for
   classifying traffic and steering it into the correct path.  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 traffic is steered into a specific path 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

   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

   Information included in the SPRING header, 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 SPRING header 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

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   and more application traffic is encrypted, the ability to extract
   (and include in the SPRING header) 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 [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 (Quadrature Amplitude Modulation) [QAM], a DOCSIS (Data
   Over Cable Service Interface Specification) [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 the
   interpretation of the SPRING header and how to map it to the target

2.3.  SPRING in 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, as enabled by Segment Routing IPv6, can
   be used to steer traffic across specific paths through the network.
   The specific path may also include a given function one or more nodes
   in the path are requested to perform.

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   In addition one of the fundamental requirements for Data Center
   architecture is to provide scalable, isolated tenant networks.  In
   such scenarios, Segment Routing can be used to identify specific
   nodes, tenants, and functions and to build a construct to steer the
   traffic across that specific path.

2.4.  SPRING in 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 list containing a sequence of
   the caches in a hierarchy can be built.  At each node (cache) in the
   list, the presence of the requested content is checked.  If the
   requested content is found at the cache (cache hits scenario) the
   sequence ends, even if there are more nodes in the list; otherwise
   next element in the list (next node/cache) is examined.

2.5.  SPRING in Core networks

   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

   Some operators are currently building, or plan to build in the near
   future, an IPv6 only native infrastructure for their core network.
   These operators are also 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,

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   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

   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

   All these scenarios would require a form of traffic engineering
   capabilities in an IPv6 only network environment.

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.

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

      Email: Ida.Leung@rci.rogers.com

      Stefano Previdi
      Cisco Systems
      Via Del Serafico, 200
      Rome  00142

      Email: sprevidi@cisco.com

      Christian Martin
      Cisco Systems

      Email: martincj@cisco.com

4.  Acknowledgements

   The authors would like to thank Brian Field, Robert Raszuk, Wes
   George, Eric Vyncke, Fred Baker, John G.  Scudder, Adrian Farrel,
   Alvaro Retana, Bruno Decraene 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

   This document presents use cases to be considered by the SPRING
   architecture and potential IPv6 extensions.  As such, it does not
   introduce any security considerations.  However, there are a number
   of security concerns with source routing at the IP layer [RFC5095].
   It is expected that any solution that addresses these use cases to
   also address any security concerns.

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7.  References

7.1.  Informative References

   [DOCSIS]   "DOCSIS Specifications Page",

              Baker, F., Bowers, C., and J. Linkova, "Enterprise
              Multihoming using Provider-Assigned Addresses without
              Network Prefix Translation: Requirements and Solution",
              draft-ietf-rtgwg-enterprise-pa-multihoming-00 (work in
              progress), March 2017.

              Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              and R. Shakir, "Segment Routing Architecture", draft-ietf-
              spring-segment-routing-11 (work in progress), February

   [QAM]      "QAM specification", <ITU-T Recommendation J.83 Annex B

   [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,

7.2.  Normative References

   [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

   Email: john_brzozowski@cable.comcast.com

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   John Leddy

   Email: John_Leddy@cable.comcast.com

   Clarence Filsfils
   Cisco Systems

   Email: cfilsfil@cisco.com

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

   Email: robmgl@cisco.com

   Mark Townsley
   Cisco Systems

   Email: townsley@cisco.com

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