IDR Working Group                                   G. Van de Velde, Ed.
Internet-Draft                                             W. Henderickx
Intended status: Standards Track                          Alcatel-Lucent                                   Nokia
Expires: September 18, 2016 January 9, 2017                                        K. Patel
                                                          A. Sreekantiah
                                                           Cisco Systems
                                                          March 17,
                                                                   Z. Li
                                                               S. Zhuang
                                                                   N. Wu
                                                     Huawei Technologies
                                                            July 8, 2016

                    Flowspec Indirection-id Redirect
             draft-vandevelde-idr-flowspec-path-redirect-02
             draft-vandevelde-idr-flowspec-path-redirect-03

Abstract

   Flow-spec

   Flowspec is an extension to BGP that allows for the dissemination of
   traffic flow specification rules.  This has many possible
   applications but the primary one for many network operators is the
   distribution of traffic filtering actions for DDoS mitigation.  The
   flow-spec standard RFC5575 [2] defines a redirect-to-VRF action for
   policy-based forwarding but this mechanism is not always sufficient,
   particular
   particularly if the redirected traffic needs to be steered into an
   engineered path or into a service plane.

   This document defines a new redirect-to-INDIRECTION_ID (32-bit or
   128-bit) flow-spec extended community known as redirect-to-
   indirection-id (32-bit) flowspec action to provide advanced
   redirection
   capabilities. capabilities on flowspec clients.  When activated, the
   flowspec Indirection-id extended community is used by a flowspec client to
   identify find the
   correct next-hop redirect information entry within a router locallized
   Indirection-id localised indirection-id mapping
   table.  This

   The functionality present in this draft allows a flowspec network controller
   to signal
   redirection towards a next-hop IP address, a shortest path tunnel, a
   traffic engineered tunnel or a next-next-hop engineered tunnel
   interface. decouple flowspec functionality from the creation and maintainance
   of the network's service plane itself including the setup of tunnels
   and other service constructs that could be managed by other network
   devices.

Requirements Language

   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 RFC 2119 [1].

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 September 18, 2016. January 9, 2017.

Copyright Notice

   Copyright (c) 2016 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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2   3
   2.  INDIRECTION_ID  indirection-id and INDIRECTION_ID Table indirection-id table . . . . . . . . . . .   3
   3.  Use Case Scenarios  . . . . . . . . . . . . . . . . . . . . .   4
     3.1.  Redirection shortest Path tunnel  . . . . . . . . . . . .   4
     3.2.  Redirection to path-engineered tunnels  . . . . . . . . .   4
     3.3.  Redirection to Next-next-hop tunnels  . . . . . . . . . .   5
   4.  Redirect to INDIRECTION-ID Communities indirection-id Community  . . . . . . . . . . . .   6
   5.  Redirect using locallized INDIRECTION_ID Router Mapping localised indirection-id mapping table . . .   7 .   8
   6.  Validation Procedures . . . . . . . . . . . . . . . . . . . .   8
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   8.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   9.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8   9
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .   8   9
     10.1.  Normative References . . . . . . . . . . . . . . . . . .   9  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .   9  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9  10

1.  Introduction

   Flow-spec

   Flowspec RFC5575 [2] is an extension to BGP that allows for the
   dissemination of traffic flow specification rules.  This has many
   possible applications but applications, however the primary one for many network
   operators is the distribution of traffic filtering actions for DDoS
   mitigation.

   Every flow-spec flowspec policy route is effectively a rule, consisting of a
   matching part (encoded in the NLRI field) and an action part (encoded
   in one or more BGP extended community). communities).  The flow-spec standard
   RFC5575 [2] defines widely-used filter actions such as discard and
   rate limit; it also defines a redirect-to-VRF action for policy-based
   forwarding.  Using the redirect-to-VRF action for redirecting to steer traffic
   towards an alternate destination is useful for DDoS mitigation but
   using this technology can be cumbersome when there is need to redirect steer
   the traffic onto an engineered traffic path.

   This draft proposes a new redirect-to-Indirection-id flow-spec redirect-to-indirection-id flowspec action
   facilitating an anchor point for policy-based forwarding onto an
   engineered path or into a service plane.  The router flowspec client
   consuming and utilizing the new flowspec rule makes indirection-id extended-
   community finds the redirection information within a local localised
   indirection-id mapping between table.  The localised mapping table is a table
   construct providing at one side the
   flowspec signalled redirect Indirection-id table key and locally available
   redirection information referenced by at the Indirection-id.  This
   locally available redirection information is derived from out-of-band
   programming or signalling. other side
   next-hop information.  The table key consists out the combination of
   indirection-id type and indirection-id 32-bit value.

   The redirect-to-Indirection-id redirect-to-indirection-id flowspec action is encoded in a newly
   defined BGP extended Indirection_ID community.

   The construction  In addition, the type of redirection
   can be configured as an extended community indirection-id type field.

   This draft defines the Indirection-id redirect table indirection-id extended-community and the
   technology used
   wellknown indirection-id types.  The specific solution to create an engineered path construct
   the localised indirection-id mapping table are out-of-scope of this
   document.

2.  INDIRECTION_ID  indirection-id and INDIRECTION_ID Table indirection-id table

   An INDIRECTION_ID indirection-id is an abstract number (32-bit or 128-bit value) used as
   identifier for a localised redirection indirection decision. e.g.  When  The indirection-id
   will allow a
   BGP flowspec controller intends client to redirect traffic into a flow using te redirect-
   to-INDIRECTION_ID action then it has the ability to redirect the flow
   to service plane
   or onto an engineered traffic path.  e.g.  When a destination abstracted as the INDIRECTION_ID.  The device
   receiving the BGP flowspec rule will use
   controller signals a flowspec client the INDIRECTION_ID to
   identify indirection-id extended
   community, then the next-hop and flowspec client uses the relevant tunnel encapsulations that
   need indirection-id to be pushed by make a localised
   recursive lookup using to retrieve next-hop information
   located within the INDIRECTION_ID found in a
   localised indirection mapping table.

   The INDIRECTION_ID Table indirection-id table is a router localised table.  The
   indirection-id table
   content is constructed out of INDIRECTION_IDs and corresponding
   redirect information which may be of rescursive or non-recursive
   nature.  When the redirect information table keys mapped to
   flowspec client localised redirection information.  The table key is non-recursive, then
   created by the
   represented information MUST be sufficient to identify combination of the local
   egress interface indirection-id type and the corresponding required encapsulations.
   However, if the information is recursive, then
   indirection-id 32-bit value.  Each entry in the represented
   information MUST be indirection-table key
   maps to sufficient information (parameters regarding encapsulation,
   interface, QoS, etc...) to identify the local egress interface
   and corresponding encapsulations using additional recursions. successfully redirect traffic.

3.  Use Case Scenarios

   This section describes use-case scenarios when deploying redirect-to-
   INDIRECTION_ID.
   indirection-id.

3.1.  Redirection shortest Path tunnel

   A first use-case is allowing a BGP Flowspec controller to send a
   single flowspec policy message (redirect-to-INDIRECTION_ID#1) route (i.e. flowspec_route#1) to many BGP
   flowspec consuming routers. clients.  This message is instructing flowspec route signals the Flowspec
   recipient routers clients
   to redirect traffic onto a tunnel to towards a single IP destination
   address.

   For this first use-case scenario, each the flowspec recipient router has a
   tunnel configured following client receives from
   the shortest path towards a tunnel IP
   destination address.  Each tunnel can have its own unique
   encapsulation associated.  Each tunnel is associated with an
   INDIRECTION_ID, and for this example it is on all recipient routers
   INDIRECTION_ID#1.  Both manual and orchestrated tunnel provisioning
   is supported, however for large scale deployment automation is
   advisable.

   When using this setup, a BGP flowspec controller can send a single
   BGP Flowspec NLRI with redirect-to-INDIRECTION_ID#1.  This BGP
   Flowspec NLRI is received by all recipient routers.  Each of flowspec route (i.e. flowspec_route#1)
   including the
   recipient routers performs a locallised recursive lookup for
   INDIRECTION_ID#1 in redirect-to-indirection-id extended community.  The
   redirect-to-indirection-id extended community contains the INDIRECTION_ID Table and identifies key
   (indirection-id type + indirection-id 32-bit value) to select the
   corresponding locallised next-hop information from the flowpsec client localised
   indirection-id table.  The resulting next-hop information for this
   use-case is a remote tunnel redirect information.  This
   locallised end-point IP address with accordingly
   sufficient tunnel encapsulation information is now used to forward the packet
   accordingly.

   For redirect traffic
   matching to shortest path tunnel it is required that the Flowspec policy towards a tunnel, each potentially using
   its own unique tunnel encapsulation.
   MUST be operational and allow packets to be exchanged between tunnel
   head- and tail-end.

3.2.  Redirection to path-engineered tunnels

   A second use-case is allowing a BGP Flowspec controller send

   For a single
   flowspec policy message (redirect-to-INDIRECTION_ID#2) to many BGP
   flowspec consuming routers.  This message second use-case, it is instructing expected that the Flowspec
   recipient routers to flowspec client
   redirect traffic matches the flowspec rule, onto a path engineered
   tunnel.

   For this use-case scenario, each flowspec recipient router has a  The path engineered tunnel configured. on the flowspec client SHOULD be
   created by out-of-band mechanisms.  Each tunnel can have its own unique
   encapsulation and engineered path associated.  Each engineered tunnel is
   associated with an INDIRECTION_ID, and
   deployed for this example it is on all
   recipient routers INDIRECTION_ID#2.  Both manual flowspec redirection, has a unque key as an identifier.
   consequently, the key (=indirection-id type and orchestrated indirection-id 32-bit
   value) uniquely identifies a single path engineered tunnel provisioning is supported, however for large scale deployment
   automation on the
   flowspec client.  The localised indirection-id mapping table is advisable.

   A first example using the
   collection of all keys corresponding all path engineered tunnels on
   the flowspec client.

   For this setup, is when a BGP second use-case scenario, the flowspec controller sends a single BGP Flowspec NLRI with redirect-to-INDIRECTION_ID#2.
   This BGP Flowspec NLRI is received by all recipient routers.  Each of
   flowspec route (i.e. flowspec_route#2) to the recipient routers performs a locallised recursive lookup for
   INDIRECTION_ID#2 in flowspec clients.  The
   flowspec clients, respectively receive the flowspec route.  The
   redirect-to-indirection-id extended community contains the INDIRECTION_ID Table and identifies key
   (indirection type + indirection-id 32-bit value) to select the
   corresponding locallised next-hop information from the flowpsec client localised
   indirection-id table.  The resulting next-hop information for this
   use-case is path engineered tunnel redirect information.  This
   locallised information and has sufficient
   tunnel encapsulation information is now used to redirect traffic
   matching forward the Flowspec policy towards a path engineered tunnel. packet according the
   expectations of the flowspec controller.

   A second concrete example of this use-case can be found in segment routed
   networks where path engineered tunnels can be setup by means of a
   controller signaling explicit paths to peering routers.  In such a
   case, the
   INDIRECTION_ID indirection-id references to a Segment Routing Binding SID. SID,
   while the indirection-id type references the Bindging SID semantic.
   The Binding SID is a segment identifier value (as per segment routing
   definitions in [I-D.draft-ietf-spring-segment-routing] [6]) used to
   associate with a an explicit path and can be setup by a controller
   using BGP as specified in [I-D.sreekantiah-idr-segment-routing-te]
   [5] or using PCE as detailed in draft-ietf-pce-segment-routing [7].
   When a BGP speaker receives a flow-spec route with a 'redirect to
   Binding SID' extended community, it installs a traffic filtering rule
   that matches the packets described by the NLRI field and redirects
   them to the explicit path associated with the Binding SID.  The
   explicit path is specified as a set/stack of segment identifiers as
   detailed in the previous documents.  The stack of segment identifiers
   is now imposed on packets matching the flow-spec rule to perform
   redirection as per the explicit path setup prior.  The encoding of
   the Binding SID value is specified in section 4, with the indirection
   indirection-id field now encoding the associated value for the
   binding SID.

3.3.  Redirection to Next-next-hop tunnels

   A Third use-case is allowing when a BGP Flowspec controller send sends a single
   flowspec policy message (redirect-to-INDIRECTION_ID#3) route to many BGP flowpsec clients to signal redirection
   towards next-next-hop tunnels.  In this use-case The flowspec consuming routers.  This message rule is
   instructing the Flowspec
   recipient routers client to redirect traffic onto a shortest or engineered
   path to using a tunnel end-point and onwards to the next-hop-interface on
   this end-point.  This type sequence
   of tunnel is used for example for Segment
   Routing Central Egress Path Engineering [4].

   For this use-case scenario, each flowspec recipient router constructs
   redirect information using two tunnel components. indirection-id extended communities.  The first
   component sequence of indirection-
   ids is managed using Tunnel IDs (TID). i.e. a shortest or engineered path towards a network egress
   router.  The second component is the interface used on this network
   egress router to which the redirected traffic needs to classic example would
   be steered
   upon.  The combination of these two components allows steering DDoS mitigation towards the next-hop of the egress router, allowing for example the Segment Routing Central Egress Path
   Engineering using BGP Flowspec [4].

   The redirection towards a next-next-hop tunnel can be done by using
   either a single INDIRECTION_ID representing the combined path to the
   egress router and steering the  To steer DDoS traffic to the egress interface, or by
   using individual INDIRECTION_IDs each representing a tunnel component
   (One INDIRECTION_ID value to identify the path towards the egress
   router and another INDIRECTION_ID value to identify the egress
   interface on this egress router towards the next-next-hop).  When
   using individual INDIRECTION_IDs it is required to use INDIRECTION_ID
   community Tunnel IDs (TID) each identifying a component of the
   complete redirect path attached to the NLRI.

   i.e. when using next-next-hop tunnels, peer
   engineering paths, a BGP flowspec controller can
   send first indirection-id will steer traffic onto a single BGP Flowspec NLRI with redirect-to-INDIRECTION_ID#3.
   This BGP Flowspec NLRI
   tunnel to an egress router, while a second indirection-id is received by all recipient routers.  Each of used
   steer the recipient routers performs traffic at this egress router onto a locallised recursive lookup particular interface
   or towards a peer.  The flowspec client will for
   INDIRECTION_ID#3 in the INDIRECTION_ID Table and identifies the
   corresponding locallised tunnel redirect information (=path this use-case
   dynamically append all segment routing segments to steer the
   egress router and DDoS
   traffic through the next-hop egress interface on EPE path.

   To achieve this router).
   Traffic matching type of redirection to next-next-hop tunnels,
   multiple indirection-ids, each using a unique Tunnel ID are imposed
   upon a the flowspec policy is redirected towards rule.  The Tunnel ID will allow the
   recursively found redirection information.
   flowspec client to sequence the indirection-ids for correct next-
   next-hop tunnel constructs.

4.  Redirect to INDIRECTION-ID Communities indirection-id Community

   This document defines a new BGP extended community known as a
   Redirect-to-indirection-id extended community.  The  This extended
   communities have a type indicating they are transitive and IPv4-
   address-specific or IPv6-address-specific, depending on whether the
   INDIRECTION_ID
   community is 32-bit or 128-bit.  The sub-type value [to be
   assigned by IANA] indicates that the global administrator and local
   administrator fields encode a flow-spec 'redirect to INDIRECTION_ID'
   action.  In the new transitive extended community with the 4-byte or 16-byte global
   administrator field encodes the 32-bit or 128-bit INDIRECTION_ID's
   providing the INDIRECTION_ID to allow a local to Type and
   the router mapping
   reference Sub-Type field to an engineered Path. be assigned by IANA.  The 2-byte local administrator
   field format of this
   extended community is formatted as shown show in Figure 1.

      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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      | Type          |          Reserved     |B|TID|C|
                     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Sub-Type      | Flags(1 octet)| Indirection ID|
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Generalized indirection_id                   |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                                 Figure 1

   In the local administrator field

   The meaning of the extended community fields are as follows:

   Type: 1 octet to be assigned by IANA.

   Sub-Type: 1 octet to be assigned by IANA.

   Flags: 1 octet field.  Following Flags are defined.

                              0             1
                              0 1 2 3 4 5 6 7
                             +-+-+-+-+-+-+-+-+
                             | RES |  TID  |C|
                             +-+-+-+-+-+-+-+-+

                                 Figure 2

   The least-significant Flag bit is defined as the 'C' (or copy) bit.
   When the 'C' bit is set the redirection applies to copies of the
   matching packets and not to the original traffic stream.

   The 'TID' field identifies a 2 4 bit Table-id field.  This field is
   used to provide the router consuming the flowspec rule client an indication how and where to use the INDIRECTION_ID when redirecting traffic.

   Bit 2 is defined to be the 'B' (Binding) bit.  When the 'B' bit is
   set,
   sequence the received indirection-ids to redirecting traffic.  TID
   value encoded in the global administrator 0 indicates that Table-id field is a Binding
   Segment Identifier value the use of which is detailed in section 3.2. NOT set and SHOULD be
   ignored.

   All bits other than the 'C', 'TID' 'C' and 'B' 'TID' bits in the local
   administrator field MUST be set to 0 by the
   originating BGP speaker and ignored by receiving BGP speakers.

   Indirection ID: 1 octet value.  This draft defines following
   indirection_id Types:

      0 - Localised ID

      1 - Node ID

      2 - Agency ID

      3 - AS (Autonomous System) ID

      4 - Anycast ID

      5 - Multicast ID

      6 - Tunnel ID (Tunnel Binding ID )

      7 - VPN ID

      8 - OAM ID

      9 - ECMP (Equal Cost Multi-Path) ID

      10 - QoS ID

      11 - Bandwidth-Guarantee ID
      12 - Security ID

      13 - Multi-Topology ID

5.  Redirect using locallized INDIRECTION_ID Router Mapping localised indirection-id mapping table

   When a BGP speaker receives a flow-spec flowspec policy route with a 'redirect
   to
   INDIRECTION_ID' indirection-id' extended community and this route represents the
   one and only best path, path or an equal cost multipath, it installs a
   traffic filtering rule that matches the packets described by the NLRI
   field and redirects them (C=0) or copies them (C=1) towards the INDIRECTION_ID
   indirection-id local recursed Path.
   The BGP speaker is expected to do a local INDIRECTION_ID Table lookup
   to identify path.  To construct the redirection information.

   The router local INDIRECTION_ID table contains a list of
   INDIRECTION_ID's each mapped to redirect information.  The redirect
   information can be non-recursive (i.e. there is only one option
   available in the INDIRECTION_ID Table) or recursive (i.e.  L3 VPN, L2
   VPN, a pre-programmed routing topology, etc... ).

   o  When the redirect information is non-recursive then the packet is
      redirected based upon the information found in the Table.

   o  In case of a next-hop tunnel, the traffic matching recursed
   path, the flowspec
      rule is redirected to the next-hop tunnel.  This tunnel could be
      instantiated through various means (i.e. manual configuration,
      PCEP, RSVP-TE, WAN Controller, Segment Routing, etc...).

   o  In case of redirection to client does a local next-hop interface, the traffic
      matching the flowspec rule is redirected to the local next-hop
      interface.

   o  In case the INDIRECTION_ID Table indirection-id mapping table
   lookup results in redirect
      information identifying an additional layer using the key comprised of recursion, then
      this will trigger the flow indirection-id 32-bit value and
   indirection-id type to be redirected based upon an
      additional routing lookup within retrieve the realm of the additional layer
      of recursion. correct redirection information.

6.  Validation Procedures

   The validation check described in RFC5575 [2] and revised in [3]
   SHOULD be applied by default to received flow-spec routes with a
   'redirect to INDIRECTION_ID' indirection-id' extended community.  This means that a
   flow-spec route with a destination prefix subcomponent SHOULD NOT be
   accepted from an EBGP peer unless that peer also advertised the best
   path for the matching unicast route.

   It is possible from a semenatics perspective to have multiple
   redirect actions defined within a single flowspec rule.  When a BGP
   flowspec NLRI has a 'redirect to INDIRECTION_ID' indirection-id' extended community
   attached resulting in valid redirection then it MUST take priority
   above all other redirect actions emposed.  However, if the 'redirect
   to INDIRECTION_ID' indirection-id' does not result in a valid redirection, then the
   flowspec rule must be processed as if the 'redirect to
   INDIRECTION_ID' indirection-
   id' community was not attached to the flowspec route and MUST provide
   an indication within the BGP routing table that the respective
   'redirect to INDIRECTION_ID' indirection-id' resulted in an invalid redirection
   action.

7.  Security Considerations

   A system using 'redirect-to-INDIRECTION_ID' 'redirect-to-indirection-id' extended community can
   cause during the redirect mitigation of a DDoS attack result in an
   overflow of traffic being received by the mitigation infrastructure.

8.  Acknowledgements

   This document received valuable comments and input from IDR working
   group including Adam Simpson, Mustapha Aissaoui, Jan Mertens, Robert
   Raszuk, Jeff Haas, Susan Hares and Lucy Yong

9.  IANA Considerations

   This document requests a new type and sub-type for the Redirect to
   indirection-id Extended community from the "Transitive IPv4-
   Address-Specific" extended community Extended
   community" registry.  The sub-type Type name shall be "Redirect to
   indirection-id Extended Community" and the Sub-type name shall be
   'Flow-spec Redirect to 32-bit Path-id'.

   This

   In addition, this document requests IANA to create a new sub-type from the "Transitive IPv6-
   Address-Specific" extended community registry.  The sub-type name
   shall be 'Flow-spec registry for
   Redirect to 128-bit Path-id'. indirection-id Extended Community INDIRECTION-IDs as
   follows:

   Under "Transitive Extended Community:"

   Registry: "Redirect Extended Community indirection_id"

   Reference: [RFC-To-Be]

   Registration Procedure(s): First Come, First Served

   Registry: "Redirect Extended Community indirection_id"

           Value    Code                              Reference

           0        Localised ID                      [RFC-To-Be]
           1        Node ID                           [RFC-To-Be]
           2        Agency ID                         [RFC-To-Be]
           3        AS (Autonomous System) ID         [RFC-To-Be]
           4        Anycast ID                        [RFC-To-Be]
           5        Multicast ID                      [RFC-To-Be]
           6        Tunnel ID (Tunnel Binding ID )    [RFC-To-Be]
           7        VPN ID                            [RFC-To-Be]
           8        OAM ID                            [RFC-To-Be]
           9        ECMP (Equal Cost Multi-Path) ID   [RFC-To-Be]
           10       QoS ID                            [RFC-To-Be]
           11       Bandwidth-Guarantee ID            [RFC-To-Be]
           12       Security ID                       [RFC-To-Be]
           13       Multi-Topology ID                 [RFC-To-Be]

                                 Figure 3

10.  References
10.1.  Normative References

   [1]        Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997,
              <http://xml.resource.org/public/rfc/html/rfc2119.html>.

   [2]        Marques, P., Sheth, N., Raszuk, R., Greene, B., Mauch, J.,
              and D. McPherson, "Dissemination of Flow Specification
              Rules", RFC 5575, DOI 10.17487/RFC5575, August 2009,
              <http://www.rfc-editor.org/info/rfc5575>.

10.2.  Informative References

   [3]        Uttaro, J., Filsfils, C., Alcaide, J., and P. Mohapatra,
              "Revised Validation Procedure for BGP Flow
              Specifications", January 2014.

   [4]        Filsfils, C., Previdi, S., Aries, E., Ginsburg, D., and D.
              Afanasiev, "Segment Routing Centralized Egress Peer
              Engineering", October 2015.

   [5]        Sreekantiah, A., Filsfils, C., Previdi, S., Sivabalan, S.,
              Mattes, P., and S. Lin, "Segment Routing Traffic
              Engineering Policy using BGP", October 2015.

   [6]        Filsfils, C., Previdi, S., Decraene, B., Litkowski, S.,
              Shakir, R., Bashandy, A., Horneffer, M., Henderickx, W.,
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Authors' Addresses

   Gunter Van de Velde (editor)
   Alcatel-Lucent
   Nokia
   Antwerp
   BE

   Email: gunter.van_de_velde@alcatel-lucent.com gunter.van_de_velde@nokia.com
   Wim Henderickx
   Alcatel-Lucent
   Nokia
   Antwerp
   BE

   Email: wim.henderickx@alcatel-lucent.com wim.henderickx@nokia.com

   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: keyupate@cisco.com

   Arjun Sreekantiah
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: asreekan@cisco.com

   Zhenbin Li
   Huawei Technologies
   Huawei Bld., No. 156 Beiquing Rd
   Beijing  100095
   China

   Email: lizhenbin@huawei.com

   Shunwan Zhuang
   Huawei Technologies
   Huawei Bld., No. 156 Beiquing Rd
   Beijing  100095
   China

   Email: zhuangshunwan@huawei.com
   Nan Wu
   Huawei Technologies
   Huawei Bld., No. 156 Beiquing Rd
   Beijing  100095
   China

   Email: eric.wu@huawei.com