Unified Source Routing Instructions using MPLS Label Stack
draft-xu-mpls-unified-source-routing-instruction-04

Versions: 00 01 02 03 04                                                
Network Working Group                                              X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                             A. Bashandy
Expires: April 1, 2018                                             Cisco
                                                            H. Assarpour
                                                                Broadcom
                                                                   S. Ma
                                                                 Juniper
                                                           W. Henderickx
                                                                   Nokia
                                                             J. Tantsura
                                                              Individual
                                                      September 28, 2017


       Unified Source Routing Instructions using MPLS Label Stack
          draft-xu-mpls-unified-source-routing-instruction-04

Abstract

   MPLS Segment Routing (SR-MPLS in short) is an MPLS data plane-based
   source routing paradigm in which a sender of a packet is allowed to
   partially or completely specify the route the packet takes through
   the network by imposing stacked MPLS labels to the packet.  SR-MPLS
   could be leveraged to realize a unified source routing mechanism
   across MPLS, IPv4 and IPv6 data planes by using an MPLS label stack
   as a unified source routing instruction set while preserving backward
   compatibility with SR-MPLS.

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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   This Internet-Draft will expire on April 1, 2018.






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Copyright Notice

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

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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Use Cases . . . . . . . . . . . . . . . . . . . . . . . . . .   3
   4.  Packet Forwarding Procedures  . . . . . . . . . . . . . . . .   4
     4.1.  Forwarding Entry Construction . . . . . . . . . . . . . .   5
     4.2.  Packet Forwarding Procedures  . . . . . . . . . . . . . .   6
   5.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   9
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  10
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .  10
     9.2.  Informative References  . . . . . . . . . . . . . . . . .  10
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  13

1.  Introduction

   MPLS Segment Routing (SR-MPLS in short)
   [I-D.ietf-spring-segment-routing-mpls] is an MPLS data plane-based
   source routing paradigm in which a sender of a packet is allowed to
   partially or completely specify the route the packet takes through
   the network by imposing stacked MPLS labels to the packet.  SR-MPLS
   could be leveraged to realize a unified source routing mechanism
   across MPLS, IPv4 and IPv6 data planes by using an MPLS label stack
   as a unified source routing instruction set while preserving backward
   compatibility with SR-MPLS.  More specifically, the source routing
   instruction set information contained in a source routed packet could
   be uniformly encoded as an MPLS label stack no matter the underlay is
   IPv4, IPv6 or MPLS.




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   Although the source routing instructions are encoded as MPLS labels,
   this is a hardware convenience rather than an indication that the
   whole MPLS protocol stack and in particular the MPLS control
   protocols need to be deployed.  Note that the complexity associated
   with the whole MPLS protocol stack is largely due to the complex
   control plane protocols.

   Section 3 describes various use cases for the unified source routing
   instruction mechanism and Section 4 describes a typical application
   scenario and how the packet forwarding happens.

1.1.  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 [RFC2119].

2.  Terminology

   This memo makes use of the terms defined in [RFC3031] and
   [I-D.ietf-spring-segment-routing-mpls].

3.  Use Cases

   The unified source routing mechanism across IPv4, IPv6 and MPLS is
   useful at least in the following use cases:

   o  Incremental deployment of the SR-MPLS technology
      [I-D.xu-mpls-spring-islands-connection-over-ip].  Since there is
      no need to run any other label distribution protocol (e.g., LDP,
      see [I-D.ietf-spring-segment-routing-ldp-interop] for more
      details.) on those non-SR-MPLS routers for incremental deployment
      purposes, the network provisioning is greatly simplified, which is
      one of the major claimed benefits of the SR-MPLS technology (i.e.,
      running a single protocol).

   o  Overcome the load-balancing dilemma encountered by SR-MPLS.  In
      fact, this unified source routing mechanism is even useful in a
      fully upgraded SR-MPLS network since the load-balancing dilemma
      encountered by SR-MPLS [I-D.ietf-mpls-spring-entropy-label] due to
      the maximum Readable Label-stack Depth (RLD) hardware limitation
      [I-D.ietf-ospf-mpls-elc] [I-D.ietf-isis-mpls-elc]
      [I-D.ietf-idr-bgp-ls-segment-routing-rld] and the Maximum SID
      Depth (MSD) hardware limitation
      [I-D.ietf-ospf-segment-routing-msd]
      [I-D.ietf-isis-segment-routing-msd]
      [I-D.ietf-idr-bgp-ls-segment-routing-msd] by using the MPLS-in-UDP




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      encapsulation [RFC7510] where the source port of the UDP tunnel
      header is used as an entropy field.

   o  A poor man's light-weight alternative to SRv6
      [I-D.ietf-6man-segment-routing-header].  At least, it could be
      deployed as an interim until full featured SRv6 is available on
      more platforms.  Since the Source Routing Header (SRH)
      [I-D.ietf-6man-segment-routing-header] consisting of an ordered
      list of 128-bit long IPv6 addresses is now replaced by an ordered
      list of 32-bit long label entries (i.e., label stack), the
      encapsulation overhead and forwarding performance issues
      associated with SRv6 are eliminated.

   o  A new IPv4 source routing mechanism which has overcome the
      security vulnerability issues associated with the traditional IPv4
      source routing mechanism.

   o  Traffic Engineering scenarios where only a few routers (e.g., the
      entry and exit nodes of each plane in the dual-plane network case
      or the egress node in the Egress Peer Engineering (EPE) case) are
      specified as segments of explicit paths.  In this way, only a few
      routers are required to support the SR-MPLS capability while all
      the other routers just need to support IP forwarding capability,
      which would significantly reduce the deployment cost of the SR-
      MPLS technology.

   o  MPLS-based Service Function Chaining (SFC)
      [I-D.xu-mpls-service-chaining].  Based on the unified source
      routing mechanism as described in this document, only SFC-related
      nodes including Service Function Forwarders (SFF), Service
      Functions (SF) and classifiers are required to recognize the SFC
      encapsulation header in the MPLS label stack form, while the
      intermediate routers just need to support vanilla IP forwarding
      (either IPv4 or IPv6).  In other words, it undoubtedly complies
      with the transport-independence requirement for the SFC
      encapsulation header as listed in the SFC architecture document
      [RFC7665].

4.  Packet Forwarding Procedures

   The primary objective of this document is to describe how SR-MPLS
   capable routers and IP-only routers can seamlessly co-exist and
   interoperate.  This section describes the forwarding information base
   (FIB) entry and the forwarding behavior that allow the deployment of
   SR-MPLS when some routers are IPv4 only or IPv6 only.  Note that OSPF
   or ISIS is assumed to be enabled in the following examples as
   described in Section 4.1 and 4.2, in fact, it's no doubt that BGP
   could be used as a replacement.



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4.1.  Forwarding Entry Construction

   This sub-section describes the how to construct the forwarding
   information base (FIB) entry on an SR-MPLS-capable router when some
   or all of the next-hops along the shortest path towards a prefix-SID
   are IPv4-only or IPv6-only routers.  Consider the router "A"
   receiving a labeled packet whose top label L(E) corresponds to the
   prefix-SID is "SID(E)" of prefix "P(E)" advertised by the router "E".
   Suppose the ith next-hop router "NHi" along the shortest path from
   the router "A" towards the prefix-SID "SID(E)" is not SR-MPLS
   capable.  That is both routers "A" and "E" are SR-MPLS capable but
   the next hop "NHi" along the shortest path from "A" to "E".  The
   following applies:

   o  It is assumed that the router "E" advertises the SR-Capabilities
      sub-TLV as described in and
      [I-D.ietf-ospf-segment-routing-extensions], which includes the
      SRGB because router "E" is SR-MPLS capabile.

   o  The owning router "E" MUST advertise the encapsulation endpoint
      and the tunnel type using [I-D.ietf-isis-encapsulation-cap] and/or
      [I-D.ietf-ospf-encapsulation-cap] .

   o  If "A" and "E" are in different areas/levels, then

      *  The OSPF Tunnel Encapsulation TLV
         [I-D.ietf-ospf-encapsulation-cap] and/or the ISIS Tunnel
         Encapsulation sub-TLV [I-D.ietf-isis-encapsulation-cap] are
         flooded domain-wide.

      *  The OSPF SID/label range TLV
         [I-D.ietf-ospf-segment-routing-extensions] and the ISIS SR-
         Capabilities Sub-TLV [I-D.ietf-isis-segment-routing-extensions]
         are advertised domain-wide.  This way router "A" knows the
         characteristics of the owning router "E".

      *  When the owning router "E" is running ISIS and advertises the
         prefix "P(E) ", the router "E" uses the extended reachability
         TLV (TLVs 135, 235, 236, 237) and associates the IPv4/IPv6 and/
         or IPv4/IPv6 source router ID sub-TLV(s) [RFC7794].

      *  When the owning router "E" is running OSPF and advertises the
         prefix "P(E)", the router "E" uses the OSPFv2 Extended Prefix
         Opaque LSA [RFC7684] and sets the flooding scope to AS-wide.

      *  When the owning router "E" is running ISIS and advertises the
         ISIS capabilities TLV (TLV 242) [RFC7981], it must set the
         "router-ID" field to a valid value or include IPV6 TE router-



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         ID sub-TLV (TLV 12), or do both.  The "S" bit (flooding scope)
         of the ISIS capabilities TLV (TLV 242) MUST be set to "1" .

   o  Router "A" programs the FIB entry corresponding to the "SID(E)" as
      follows:

      *  If NP (OSPF) or P (ISIS) flag is clear,

      *

         +  pop the outer label.

      *  If NP (OSPF) or P (ISIS) is set,

      *

         +  the outer label is SID(E) plus the lower bound of the SRGB
            of "E".

      *  Encapsulate the packet according to the encapsulation
         advertised in [I-D.ietf-isis-encapsulation-cap] or
         [I-D.ietf-ospf-encapsulation-cap].

      *  Send the packet towards the next hop "NHi".

4.2.  Packet Forwarding Procedures

     +-----+       +-----+       +-----+        +-----+        +-----+
     |  A  +-------+  B  +-------+  C  +--------+  D  +--------+  H  |
     +-----+       +--+--+       +--+--+        +--+--+        +-----+
                      |             |              |
                      |             |              |
                   +--+--+       +--+--+        +--+--+
                   |  E  +-------+  F  +--------+  G  |
                   +-----+       +-----+        +-----+

          +--------+
          |IP(A->E)|
          +--------+                 +--------+
          |  L(G)  |                 |IP(E->G)|
          +--------+                 +--------+        +--------+
          |  L(H)  |                 |  L(H)  |        |IP(G->H)|
          +--------+                 +--------+        +--------+
          | Packet |     --->        | Packet |  --->  | Packet |
          +--------+                 +--------+        +--------+
                             Figure 1





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   As shown in Figure 1, Assume Router A, E, G and H are SR-MPLS-capable
   routers while the remaining are only capable of forwarding IP
   packets.  Router A, E, G and H advertise their Segment Routing
   related information via IS-IS or OSPF.  Now assume router A wants to
   send a given IP or MPLS packet via an explicit path of {E->G->H},
   router A would impose an MPLS label stack corresponding to that
   explicit path on the received IP packet.  Since there is no Label
   Switching Path (LSP) towards router E, router A would replace the top
   label indicating router E with an IP-based tunnel for MPLS (e.g.,
   MPLS-over-UDP [RFC7510]) towards router E and then send it out.  In
   other words, router A would pop the top label and then encapsulate
   the MPLS packet with an IP-based tunnel towards router E.  When the
   IP-encapsulated MPLS packet arrives at router E, router E would strip
   the IP-based tunnel header and then process the decapsulated MPLS
   packet accordingly.  Since there is no LSP towards router G which is
   indicated by the current top label of the decapsulated MPLS packet,
   router E would replace the current top label with an IP-based tunnel
   towards router G and send it out.  When the packet arrives at router
   G, router G would strip the IP-based tunnel header and then process
   the decapsulated MPLS packet.  Since there is no LSP towards router
   H, router G would replace the current top label with an IP-based
   tunnel towards router H.  Now the packet encapsulated with the IP-
   based tunnel towards router H is exactly the original packet that
   router A had intended to send towards router H.  If the packet is an
   MPLS packet, router G could use any IP-based tunnel for MPLS (e.g.,
   MPLS-over-UDP [RFC7510]).  If the packet is an IP packet, router G
   could use any IP tunnel for IP (e.g., IP-in-UDP
   [I-D.xu-intarea-ip-in-udp]).  That original IP or MPLS packet would
   be forwarded towards router H via an IP-based tunnel.  When the
   encapsulated packet arrives at router H, router H would decapsulate
   it into the original packet and then process it accordingly.

   Note that in the above description, it's assumed that the label
   associated with each prefix-SID advertised by the owner of the
   prefix-SID is a Penultimate Hop Popping (PHP) label (e.g., the NP-
   flag [I-D.ietf-ospf-segment-routing-extensions] associated with the
   corresponding prefix SID is not set).

   Figure 2 demostrates the packet walk in the case where the label
   associated with each prefix-SID advertised by the owner of the
   prefix-SID is not a Penultimate Hop Popping (PHP) label (e.g., the
   NP-flag [I-D.ietf-ospf-segment-routing-extensions] associated with
   the corresponding prefix SID is set).








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     +-----+       +-----+       +-----+        +-----+        +-----+
     |  A  +-------+  B  +-------+  C  +--------+  D  +--------+  H  |
     +-----+       +--+--+       +--+--+        +--+--+        +-----+
                      |             |              |
                      |             |              |
                   +--+--+       +--+--+        +--+--+
                   |  E  +-------+  F  +--------+  G  |
                   +-----+       +-----+        +-----+

          +--------+
          |IP(A->E)|
          +--------+                 +--------+
          |  L(E)  |                 |IP(E->G)|
          +--------+                 +--------+        +--------+
          |  L(G)  |                 |  L(G)  |        |IP(G->H)|
          +--------+                 +--------+        +--------+
          |  L(H)  |                 |  L(H)  |        |  L(H)  |
          +--------+                 +--------+        +--------+
          | Packet |     --->        | Packet |  --->  | Packet |
          +--------+                 +--------+        +--------+
                             Figure 2

   Although the above description is based on the use of prefix-SIDs,
   the unified source routing instruction approach is actually
   applicable to the use of adj-SIDs as well.  For instance, when the
   top label of a received MPLS packet indicates an given adj-SID and
   the corresponding adjacent node to that adj-SID is not MPLS-capable,
   the top label would be replaced by an IP-based tunnel towards that
   adjacent node and then forwarded over the correponding link indicated
   by that adj-SID.

   When encapsulating an MPLS packet with an IP-based tunnel header
   (e.g., a UDP header as per [RFC7510]), the corresponding entropy
   field (i.e., the source port in the MPLS-in-UDP case) should be
   filled with an entropy value that is generated by the encapsulator to
   uniquely identify a flow.  However, what constitutes a flow is
   locally determined by the encapsulator.  For instance, if the MPLS
   label stack contains at least one entropy label and the encapsulator
   is capable of reading that entropy label, the entropy label value
   could be directly copied to the entropy field (e.g., the source port
   of the UDP header).  Otherwise, the encapsulator may have to perform
   a hash on the whole label stack or the five-tuple of the MPLS payload
   if the payload is determined as an IP packet.  To avoid re-performing
   hash on the whole packet when re-encapsulating the packet with an IP-
   based tunnel header (e.g., a UDP tunnel header), especially when the
   encapsulator could not obtain at least one entropy label due to some
   reasons (e.g., 1) there is no EL at all in the label stack; 2) the
   encapsulator couldn't recognize the ELI; 3) the encapsulator could



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   not read the EL due to the RLD limit), it's RECOMMENDED that the
   entropy value contained in the packet (e.g., the UDP source port
   value) is kept when stripping the IP-based tunnel header (e.g., the
   UDP tunnel header).  As such, the entropy value could be directly
   copied to the entropy field (e.g., the source port of the UDP tunnel
   header) when re-encapsulating the packet with an IP-based tunnel
   header (e.g., a UDP tunnel header).  As such, the load-balancing
   dilemma encountered by SR-MPLS as described in
   [I-D.ietf-mpls-spring-entropy-label] due to the maximum Readable
   Label-stack Depth (RLD) hardware limitation [I-D.ietf-ospf-mpls-elc]
   [I-D.ietf-isis-mpls-elc] and the Maximum SID Depth (MSD) hardware
   limitation [I-D.ietf-ospf-segment-routing-msd]
   [I-D.ietf-isis-segment-routing-msd] is gone.  That's the reason why
   this unified source routing mechanism is even useful in a fully
   upgraded SR-MPLS network environment.

5.  Contributors

      Clarence Filsfils
      Cisco
      Email: cfilsfil@cisco.com

      Robert Raszuk
      Bloomberg LP
      Email: robert@raszuk.net

      Uma Chunduri
      Huawei
      Email: uma.chunduri@gmail.com

      Luis M. Contreras
      Telefonica I+D
      Email: luismiguel.contrerasmurillo@telefonica.com

      Luay Jalil
      Verizon
      Email: luay.jalil@verizon.com

      Gunter Van De Velde
      Nokia
      Email: gunter.van_de_velde@nokia.com

      Tal Mizrahi
      Marvell
      Email: talmi@marvell.com






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6.  Acknowledgements

   Thanks Joel Halpern, Bruno Decraene, Loa Andersson and Stewart Bryant
   for their insightful comments on this document.

7.  IANA Considerations

   No IANA action is required.

8.  Security Considerations

   TBD.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

9.2.  Informative References

   [I-D.ietf-6man-segment-routing-header]
              Previdi, S., Filsfils, C., Raza, K., Leddy, J., Field, B.,
              daniel.voyer@bell.ca, d., daniel.bernier@bell.ca, d.,
              Matsushima, S., Leung, I., Linkova, J., Aries, E., Kosugi,
              T., Vyncke, E., Lebrun, D., Steinberg, D., and R. Raszuk,
              "IPv6 Segment Routing Header (SRH)", draft-ietf-6man-
              segment-routing-header-07 (work in progress), July 2017.

   [I-D.ietf-idr-bgp-ls-segment-routing-msd]
              Tantsura, J., Chunduri, U., Mirsky, G., and S. Sivabalan,
              "Signaling Maximum SID Depth using Border Gateway Protocol
              Link-State", draft-ietf-idr-bgp-ls-segment-routing-msd-00
              (work in progress), July 2017.

   [I-D.ietf-idr-bgp-ls-segment-routing-rld]
              Velde, G., Henderickx, W., Bocci, M., and K. Patel,
              "Signalling ERLD using BGP-LS", draft-ietf-idr-bgp-ls-
              segment-routing-rld-00 (work in progress), July 2017.

   [I-D.ietf-isis-encapsulation-cap]
              Xu, X., Decraene, B., Raszuk, R., Chunduri, U., Contreras,
              L., and L. Jalil, "Advertising Tunnelling Capability in
              IS-IS", draft-ietf-isis-encapsulation-cap-01 (work in
              progress), April 2017.



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   [I-D.ietf-isis-mpls-elc]
              Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
              Litkowski, "Signaling Entropy Label Capability Using IS-
              IS", draft-ietf-isis-mpls-elc-02 (work in progress),
              October 2016.

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Filsfils, C., Bashandy, A., Gredler, H.,
              Litkowski, S., Decraene, B., and j. jefftant@gmail.com,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-13 (work in progress), June
              2017.

   [I-D.ietf-isis-segment-routing-msd]
              Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
              "Signaling MSD (Maximum SID Depth) using IS-IS", draft-
              ietf-isis-segment-routing-msd-04 (work in progress), June
              2017.

   [I-D.ietf-mpls-spring-entropy-label]
              Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and j. jefftant@gmail.com, "Entropy label for
              SPRING tunnels", draft-ietf-mpls-spring-entropy-label-06
              (work in progress), May 2017.

   [I-D.ietf-ospf-encapsulation-cap]
              Xu, X., Decraene, B., Raszuk, R., Contreras, L., and L.
              Jalil, "The Tunnel Encapsulations OSPF Router
              Information", draft-ietf-ospf-encapsulation-cap-08 (work
              in progress), September 2017.

   [I-D.ietf-ospf-mpls-elc]
              Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
              Litkowski, "Signaling Entropy Label Capability Using
              OSPF", draft-ietf-ospf-mpls-elc-04 (work in progress),
              November 2016.

   [I-D.ietf-ospf-segment-routing-extensions]
              Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
              Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
              Extensions for Segment Routing", draft-ietf-ospf-segment-
              routing-extensions-19 (work in progress), August 2017.

   [I-D.ietf-ospf-segment-routing-msd]
              Tantsura, J., Chunduri, U., Aldrin, S., and P. Psenak,
              "Signaling MSD (Maximum SID Depth) using OSPF", draft-
              ietf-ospf-segment-routing-msd-05 (work in progress), June
              2017.



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   [I-D.ietf-spring-segment-routing-ldp-interop]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B., and
              S. Litkowski, "Segment Routing interworking with LDP",
              draft-ietf-spring-segment-routing-ldp-interop-08 (work in
              progress), June 2017.

   [I-D.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-10
              (work in progress), June 2017.

   [I-D.xu-intarea-ip-in-udp]
              Xu, X., Lee, Y., and F. Yongbing, "Encapsulating IP in
              UDP", draft-xu-intarea-ip-in-udp-04 (work in progress),
              December 2016.

   [I-D.xu-mpls-service-chaining]
              Xu, X., Bryant, S., Assarpour, H., Shah, H., Contreras,
              L., daniel.bernier@bell.ca, d., jefftant@gmail.com, j.,
              Ma, S., and M. Vigoureux, "Service Chaining using Unified
              Source Routing Instructions", draft-xu-mpls-service-
              chaining-03 (work in progress), June 2017.

   [I-D.xu-mpls-spring-islands-connection-over-ip]
              Xu, X., Raszuk, R., Chunduri, U., Contreras, L., and L.
              Jalil, "Connecting MPLS-SPRING Islands over IP Networks",
              draft-xu-mpls-spring-islands-connection-over-ip-00 (work
              in progress), October 2016.

   [RFC2784]  Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
              Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
              DOI 10.17487/RFC2784, March 2000,
              <https://www.rfc-editor.org/info/rfc2784>.

   [RFC3031]  Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol
              Label Switching Architecture", RFC 3031,
              DOI 10.17487/RFC3031, January 2001,
              <https://www.rfc-editor.org/info/rfc3031>.

   [RFC4817]  Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
              J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
              Protocol Version 3", RFC 4817, DOI 10.17487/RFC4817, March
              2007, <https://www.rfc-editor.org/info/rfc4817>.







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   [RFC7510]  Xu, X., Sheth, N., Yong, L., Callon, R., and D. Black,
              "Encapsulating MPLS in UDP", RFC 7510,
              DOI 10.17487/RFC7510, April 2015,
              <https://www.rfc-editor.org/info/rfc7510>.

   [RFC7665]  Halpern, J., Ed. and C. Pignataro, Ed., "Service Function
              Chaining (SFC) Architecture", RFC 7665,
              DOI 10.17487/RFC7665, October 2015,
              <https://www.rfc-editor.org/info/rfc7665>.

   [RFC7684]  Psenak, P., Gredler, H., Shakir, R., Henderickx, W.,
              Tantsura, J., and A. Lindem, "OSPFv2 Prefix/Link Attribute
              Advertisement", RFC 7684, DOI 10.17487/RFC7684, November
              2015, <https://www.rfc-editor.org/info/rfc7684>.

   [RFC7794]  Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
              U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
              and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
              March 2016, <https://www.rfc-editor.org/info/rfc7794>.

   [RFC7981]  Ginsberg, L., Previdi, S., and M. Chen, "IS-IS Extensions
              for Advertising Router Information", RFC 7981,
              DOI 10.17487/RFC7981, October 2016,
              <https://www.rfc-editor.org/info/rfc7981>.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Ahmed Bashandy
   Cisco

   Email: bashandy@cisco.com


   Hamid Assarpour
   Broadcom

   Email: hamid.assarpour@broadcom.com








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   Shaowen Ma
   Juniper

   Email: mashao@juniper.net


   Wim Henderickx
   Nokia

   Email: wim.henderickx@nokia.com


   Jeff Tantsura
   Individual

   Email: jefftant@gmail.com



































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