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Versions: 00 01

Internet Engineering Task Force                             F. Brockners
Internet-Draft                                               S. Bhandari
Intended status: Standards Track                                F. Maino
Expires: August 17, 2014                                        D. Lewis
                                                                   Cisco
                                                       February 13, 2014


                  LISP Extensions for Segment Routing
                       draft-brockners-lisp-sr-01

Abstract

   Segment Routing (SR) combines source routing and tunneling to steer
   traffic through the transit network.  The Locator/ID Separation
   Protocol (LISP) separates IP addresses into Endpoint Identifiers
   (EIDs) and Routing Locators (RLOCs) and also leverages tunneling
   mechanisms.  Mapping between EIDs and RLOCs is facilitated by the
   LISP mapping system.  Combining LISP and SR enables the LISP mapping
   system to provide SR information to encapsulating routers so that
   traffic can be steered in the transit network or the list of segments
   a particular packet traverses is recorded in the packet header.

   This document describes extensions required to the Locator/ID
   Separation Protocol (LISP) to enable a LISP mapping system to
   communicate list of segment identifiers or the request to record the
   list of segments a particular packet traverses to the encapsulating
   router.

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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   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 17, 2014.

Copyright Notice




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   Copyright (c) 2014 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
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   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Conventions  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Use cases that combine LISP and SR . . . . . . . . . . . . . .  4
     3.1.  Traffic steering/traffic engineering . . . . . . . . . . .  4
     3.2.  Traffic tracing  . . . . . . . . . . . . . . . . . . . . .  5
   4.  LISP extensions to support SR  . . . . . . . . . . . . . . . .  5
     4.1.  Deployment Scenario  . . . . . . . . . . . . . . . . . . .  7
     4.2.  Example ELPs . . . . . . . . . . . . . . . . . . . . . . .  7
       4.2.1.  Example: ELP with only SR used . . . . . . . . . . . .  7
       4.2.2.  Example: ELP with SR and reencapsulating routers
               combined . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  9
   6.  Manageability Considerations . . . . . . . . . . . . . . . . .  9
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . .  9
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 10
   9.  Change log . . . . . . . . . . . . . . . . . . . . . . . . . . 10
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     10.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11















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1.  Introduction

   Segment Routing (SR) allows for a flexible definition of end-to-end
   paths within network topologies by encoding paths as sequences of
   topological sub-paths, called "segments" as described in
   [I-D.filsfils-rtgwg-segment-routing].  Segment routing can be applied
   to IPv6 with a new type of routing extension header.  The Locator/ID
   Separation Protocol [RFC6830] specifies an architecture and mechanism
   for replacing the addresses currently used by IP with two separate
   name spaces: Endpoint IDs (EIDs), used within sites; and Routing
   Locators (RLOCs), used on the transit networks that make up the
   Internet infrastructure.  To achieve this separation, LISP defines
   protocol mechanisms for mapping from EIDs to RLOCs.  In addition,
   LISP assumes the existence of a database to store and propagate those
   mappings globally.

   When LISP is combined with SR, the EID to RLOC mapping information
   can be extended with segment routing information.  This allows for a
   closer correlation between the transit network, that is sometimes
   also referred to as the underlay network, and the overlay network.
   It is beyond the scope of this document to describe how the LISP
   mapping system obtains a segment list for a particular EID-to-RLOC
   mapping.  This draft outlines use-cases for combining LISP and SR as
   well as extensions to the LISP Canonical Address Format (LCAF) for
   traffic engineering (LCAF type 10) [I-D.ietf-lisp-lcaf].  These
   extensions are to be integrated into a future revision of
   [I-D.ietf-lisp-lcaf].


2.  Conventions

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].

   This document uses the Terminology as defined in
   [I-D.filsfils-rtgwg-segment-routing] and [I-D.ietf-lisp-lcaf].

   Abbreviations used in this document:

      AFI: Address Family Identifier

      EID: Endpoint Identifier

      ELP: Explicit Locator Path

      ETR: Egress Tunnel Router




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      ITR: Ingress Tunnel Router

      LCAF: LISP Canonical Address Format

      LISP: Locator/ID Separation Protocol

      OAM: Operation Administration Maintenance

      RLOC: Routing Locator

      SR: Segment Routing

      SID: Segment Identifier

      Segment List: Ordered list of segment identifiers


3.  Use cases that combine LISP and SR

   Use-cases that combine LISP and SR include traffic steering/traffic
   engineering as well as traffic tracing in the underlay network.

3.1.  Traffic steering/traffic engineering

   LISP combined with SR can be used to steer traffic in the underlay
   network: The mapping system communicates a segment list to the LISP
   ingress tunnel router (ITR) when resolving the EID-to-RLOC mapping as
   part of a LISP Map-Reply.  This extension allows the LISP mapping
   system to provide a list of segment identifiers to encapsulating
   routers so that traffic can be steered in the transit network.  In a
   typical setup the LISP ingress tunnel router would retrieve the
   segment list from the mapping system along with the associated RLOC
   using the EID as the lookup key.  The ITR encapsulates the packet to
   the RLOC, also including the segment list in the segment routing
   extension header.  The packet is forwarded to the ETR using segment
   routing techniques.  The ETR decapsulates the packet and delivers the
   packet to the destination EID.  Given that in SR with IPv6 transport
   the entire segment list is available in the SR-specific extension
   header of the outer IPv6 header, the LISP egress tunnel router, which
   is the tunnel endpoint is also informed about the path a particular
   packet took in the transport network.

   LISP with SR for traffic engineering adds to the LISP traffic
   engineering use-cases described in [I-D.farinacci-lisp-te].  LISP
   combined with SR offers traffic engineering without using
   reencapsulating tunnels [RFC6830].  Reencapsulating tunnels and SR
   with LISP are complementary traffic engineering techniques and could
   be combined.  SR could for example be used in an explicit locator



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   path (ELP) to further traffic engineer a path between two
   reencapsulating routers.

3.2.  Traffic tracing

   LISP combined with SR can be used to get more information about the
   path a packet took in the underlay network without sending extra
   probe traffic.  When SR is applied to IPv6, the segment list
   describing the path that a packet takes through the network can be
   recorded in the SR-specific extension header of the outer IPv6 packet
   header.  This activity is referred to as segment tracing.  Segment
   tracing can be performed independently from steering traffic using SR
   techniques.  It can also be used in a transit network which performs
   normal IPv6 routing.  When tracing is enabled, the segment ID of
   every segment that a packet traverses is recorded in the SR-specific
   extension header.  This means that the egress tunnel router receives
   information about the path, represented by the segment list, a
   particular packet has taken in the underlay network.  Different from
   OAM mechanisms which send active probe packets, tracing information
   can be made available for production traffic.  The egress tunnel
   router can choose to provide the traced segment list back to the
   mapping system, for example through a LISP Map-Register.  This
   information can be used to ensure path symmetry send/receive traffic
   in the transit network, or can serve other OAM or statistical
   purposes.


4.  LISP extensions to support SR

   Segment routing information can be contained within the LISP mapping
   system.  A segment identifier is a 32-bit identification either for a
   topological instruction or a service instruction.  See
   [I-D.filsfils-rtgwg-segment-routing] for details.

   An EID can be associated with one or multiple ordered lists of
   segment identifiers, also referred to as "segment lists", encoding
   the topological and service source route of a packet.  The segment
   list can serve either traffic engineering or operational purposes.
   In case of traffic engineering purposes, the segment list describes
   the set of segments a packet visits when traversing the transit
   network.  The segment list enables the ITR to steer traffic using
   segment routing techniques.  For operations and maintenance use, the
   segment list documents the set of segments a packet visited on its
   way through the transit network.  It is beyond the scope of this
   document to describe the detailed procedures how the LISP mapping
   system obtains a segment list for a particular EID-to-RLOC mapping.

   Segment routing extensions for LISP extend the Explicit Locator Path



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   (ELP) Canonical Address Format, which is LCAF type 10,
   see[I-D.ietf-lisp-lcaf] for details.  A new Address Family Identifier
   (AFI) in LISP Canonical Address Format (LCAF) type
   [I-D.ietf-lisp-lcaf] is required to carry the 32-bit segment
   identifier.  For a given EID lookup in the mapping database, the
   segment routing list in ELP LCAF type can be returned to provide a
   segment list to each locator in the Map-Reply locator set.  The ELP
   LCAF type can also be used to send the segment list that a particular
   packet traversed to the LISP mapping system using a Map-Register
   message defined in [RFC6833].

   The segment identification AFI to be allocated is described below:

        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = TBD_SID    |           Rsvd                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                              SID                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+



   AFI=TBD_SID: TBD_SID is a value allocated from [AFI] for segment
   identifiers.

   Rsvd: should be set to zero and ignored.

   SID: 4 byte segment identifier

   The explicit path to be followed in the underlay is then encoded
   using the AFI for segment ID in the LISP LCAF type 10 described in
   [I-D.ietf-lisp-lcaf].

   T-Bit: An additional bit in the Rsvd3 field is to be allocated in
   LCAF type 10.  The T-bit (T=1) is used by the LISP mapping system to
   indicate to an ITR that for particular EID-to-RLOC mapping the
   segments traversed by packets SHOULD be recorded as a segment list in
   the SR IPv6 extension header.  This bit is ignored if present in a
   Map-Register message.  A Map-Register message could be used by the
   ETR to inform the mapping system about the segments that a packet
   visited in the transit network.

   S-Bit: The S-bit SHOULD be set when AFI = TBD_SID.

   P-Bit: The P-bit SHOULD be ignored when AFI = TBD_SID.

   L-Bit: The L-bit SHOULD be ignored when AFI = TBD_SID.



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4.1.  Deployment Scenario

   As described in [RFC6833] LISP Mapping Service defines: the Map-
   Resolver, which accepts Map-Requests from an Ingress Tunnel Router
   (ITR) and "resolves" the EID-to-RLOC mapping using a mapping
   database; and the Map-Server, which learns authoritative EID-to-RLOC
   mappings from an Egress Tunnel Router (ETR) and publishes them in a
   database.  The LISP Extensions for Segment Routing described in this
   document primarily apply to deployment scenarios where MAP-Server and
   MAP-Resolver have visibility into or interface with a system that has
   knowledge of the network topology and can determine paths from source
   to destination RLOCs.  Implementations of the LISP mapping systems
   which complement Software Defined Networking (SDN) architectures,
   such as the implementation as part of the OpenDaylight
   project[ODLLISP] fall into this category.  In these deployments the
   LISP mapping system can retrieve the necessary information related to
   topology and path selection to implement the extensions defined in
   this document.  It allows the mapping system to provide the required
   information in the MAP resolve response to correlate overlay with
   underlay network and offer solutions to control the path taken in the
   underlay network.

4.2.  Example ELPs

4.2.1.  Example: ELP with only SR used

   This example shows the Explicit Locator Path (ELP) Canonical Address
   Format in a setup where segment routing is used in the transit
   network between ITR and ETR.  Traffic engineering using
   reencapsulating routers is not used.

   The reply to an EID-to-RLOC lookup contains the SIDs to be visited in
   the underlay network to reach the RLOC address returned in AFI=x.  In
   the example below SID_1,...,SID_p are to be used for segment routing
   towards the "Address" RLOC.  SID_p is the identifier of the last
   segment which takes the packet to the "Address" RLOC.















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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           AFI = 16387         |     Rsvd1     |     Flags     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Type = 10   |     Rsvd2     |               n               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = TBD_SID    |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         SID_1                                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = TBD_SID    |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         SID_p                                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = x          |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Address  ...                          |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

4.2.2.  Example: ELP with SR and reencapsulating routers combined

   This example shows the Explicit Locator Path (ELP) Canonical Address
   Format when using SR combined with reencapsulation routers.

   Segment routing and traffic engineering using reencapsulating routers
   can be combined.  In the example below, segment routing is used to
   steer traffic in the underlay between reencapsulating routers "f" and
   "g".  There is no segment routing used between any of the other
   reencapsulating router hops.





















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        0                   1                   2                   3
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |           AFI = 16387         |     Rsvd1     |     Flags     |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |   Type = 10   |     Rsvd2     |               n               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = x          |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Reencap Hop 1  ...                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = x          |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Reencap Hop f  ...                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = TBD_SID    |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         SID_1                                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = TBD_SID    |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         SID_p                                 |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = x          |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Reencap Hop g  ...                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |              AFI = x          |           Rsvd3       |T|L|P|S|
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                         Reencap Hop k  ...                    |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5.  IANA Considerations

   TBD.


6.  Manageability Considerations

   Manageability considerations will be addressed in a later version of
   this document..


7.  Security Considerations

   Security considerations will be addressed in a later version of this
   document.



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8.  Acknowledgements

   The authors would like to thank Dino Farinacci, Erik Nordmark and
   participants of the LISP wg for their input on this document.


9.  Change log

   Changes from 00 - 01

   o  Added a section on deployment scenario to clarify the
      applicability of the extension described in this draft.


10.  References

10.1.  Normative References

   [AFI]      "IANA, Address Family Identifier (AFIs), http://
              www.iana.org/assignments/address-family-numbers/
              address-family-numbers.xhtml", July 2013.

   [I-D.filsfils-rtgwg-segment-routing]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,
              Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
              "Segment Routing Architecture",
              draft-filsfils-rtgwg-segment-routing-00 (work in
              progress), June 2013.

   [I-D.ietf-lisp-lcaf]
              Farinacci, D., Meyer, D., and J. Snijders, "LISP Canonical
              Address Format (LCAF)", draft-ietf-lisp-lcaf-02 (work in
              progress), March 2013.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

10.2.  Informative References

   [I-D.farinacci-lisp-te]
              Farinacci, D., Lahiri, P., and M. Kowal, "LISP Traffic
              Engineering Use-Cases", draft-farinacci-lisp-te-03 (work
              in progress), July 2013.

   [I-D.filsfils-rtgwg-segment-routing-use-cases]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Milojevic, I., Shakir, R.,



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              Ytti, S., Henderickx, W., Tantsura, J., and E. Crabbe,
              "Segment Routing Use Cases",
              draft-filsfils-rtgwg-segment-routing-use-cases-00 (work in
              progress), June 2013.

   [I-D.sivabalan-pce-segment-routing]
              Sivabalan, S., Filsfils, C., Medved, J., Crabbe, E., and
              R. Raszuk, "PCE-Initiated Traffic Engineering Path Setup
              in Segment Routed Networks",
              draft-sivabalan-pce-segment-routing-00 (work in progress),
              June 2013.

   [ODLLISP]  "Open Day Light Lisp Flow Mapping, https://
              wiki.opendaylight.org/view/
              OpenDaylight_Lisp_Flow_Mapping:Architecture", Feb 2014.

   [RFC6830]  Farinacci, D., Fuller, V., Meyer, D., and D. Lewis, "The
              Locator/ID Separation Protocol (LISP)", RFC 6830,
              January 2013.

   [RFC6833]  Fuller, V. and D. Farinacci, "Locator/ID Separation
              Protocol (LISP) Map-Server Interface", RFC 6833,
              January 2013.


Authors' Addresses

   Frank Brockners
   Cisco
   Hansaallee 249, 3rd Floor
   DUESSELDORF, NORDRHEIN-WESTFALEN  40549
   Germany

   Email: fbrockne@cisco.com


   Shwetha Bhandari
   Cisco
   Cessna Business Park, Sarjapura Marathalli Outer Ring Road
   Bangalore, KARNATAKA 560 087
   India

   Email: shwethab@cisco.com








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   Fabio Maino
   Cisco
   San Jose
   USA

   Email: fmaino@cisco.com


   Darrel Lewis
   Cisco
   San Jose
   USA

   Email: darlewis@cisco.com





































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