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Network Working Group                                              X. Xu
Internet-Draft                                                    Huawei
Intended status: Informational                              S. Sivabalan
Expires: February 5, 2015                                          Cisco
                                                               R. Raszuk
                                                              Individual
                                                             U. Chunduri
                                                                Ericsson
                                                         V. Lopezalvarez
                                                              Telefonica
                                                          August 4, 2014


            Connecting MPLS-SPRING Islands over IP Networks
             draft-xu-spring-islands-connection-over-ip-01

Abstract

   MPLS-SPRING is a 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 using stacked MPLS labels.  The
   current MPLS-SRPING architecture requires an end-to-end MPLS Label
   Switched Path (LSP) between any two MPLS-SPRING-enabled routers
   (e.g., two adjacent hops of a given explicit path).  In order to
   enable MPLS-SPRING-enabled routers to be deployed even when there are
   non-MPLS routers along the path between two MPLS-SPRING-enabled
   routers, it is desirable to have an alternative, which allows the use
   of IP-based tunnels (e.g., GRE tunnels) to connect two MPLS-SPRING-
   enabled routers.  This document describes a mechanism for such usage.

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
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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 February 5, 2015.





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Copyright Notice

   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
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Packet Forwarding Procedures  . . . . . . . . . . . . . . . .   3
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   5.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   6.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     7.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     7.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   4

1.  Introduction

   MPLS-SPRING [I-D.gredler-spring-mpls]
   [I-D.filsfils-spring-segment-routing-mpls] is a 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
   using stacked MPLS labels.  The current MPLS-SRPING architecture
   requires an end-to-end MPLS Label Switched Path (LSP) between any two
   MPLS-SPRING-enabled routers (e.g., two adjacent hops of a given
   explicit path).  In order to enable MPLS-SPRING-enabled routers to be
   deployed even when there are non-MPLS routers along the path between
   two MPLS-SPRING-enabled routers, it is desirable to have an
   alternative, which allows the use of IP-based tunnels (e.g., GRE
   tunnels [RFC4023] or UDP tunnels [I-D.ietf-mpls-in-udp]) to connect
   two MPLS-SPRING-enabled routers which are specified as adjacent hops
   of a given explicit path.  The tunnel destination address would be
   the address of next-hop MPLS-SPRING-enabled router along the explicit
   path, and this would cause the packet to be delivered to the next
   explicit hop.  In this procedure, the ingress and egress of the IP-



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   based tunnel MUST support MPLS-SPRING features including the MPLS
   forwarding capability, whereas those transit routers along the path
   between them don't need to support any MPLS-SPRING features including
   the MPLS forwarding capability.  The above mechanism is much useful
   for incrementally deployment of the MPLS-SPRING technology,
   especially in the MPLS-SPRING-based Service Function Chainning (SFC)
   case where only a few specific routers (e.g., service nodes and
   classifiers) are actually required to be MPLS-SPRING-capable.

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 [I-D.gredler-spring-mpls]
   and [I-D.filsfils-spring-segment-routing-mpls].

3.  Packet Forwarding Procedures

   Assume an MPLS-SPRING-enabled router X prepares to forward an MPLS
   packet to the next explicit hop Y which is identified by the top
   label of the MPLS packet, if the next-hop router Z which is
   physically adjacent to X is a non-MPLS-SPRING router, X would
   encapsulate the MPLS packet into an IP-based tunnel (e.g., GRE tunnel
   or UDP tunnel) where the tunnel destination is an IP address of Y
   (i.e., the /32 or /128 IGP prefix FEC corresponding to that top
   label) and the tunnel source is an IP address of X.  If the top label
   is a Penultimate Hop Popping (PHP) label, X SHOULD pop that top label
   before performing the encapsulation.  The IP encapsulated packet
   would be forwarded according to the IP forwarding table.  Upon
   receipt of that IP encapsulated packet, Y would decapsulate it and
   then process the decapsulated MPLS packet accordingly.

   As for which tunnel encapsulation type should be used by X, it can be
   manually specified on X or dynamically learnt from Y's advertisement
   of its tunnel encapsulation capability.  How to advertise the tunnel
   encapsulation capability is outside of the scope of this document.

4.  Acknowledgements

   Thanks Joel Halpern for his insightful comments on this draft.







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5.  IANA Considerations

   No action is required for IANA.

6.  Security Considerations

   TBD.

7.  References

7.1.  Normative References

   [I-D.filsfils-spring-segment-routing-mpls]
              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 with MPLS data plane", draft-filsfils-
              spring-segment-routing-mpls-03 (work in progress), August
              2014.

   [I-D.gredler-spring-mpls]
              Gredler, H., Rekhter, Y., Jalil, L., Kini, S., and X. Xu,
              "Supporting Source/Explicitly Routed Tunnels via Stacked
              LSPs", draft-gredler-spring-mpls-06 (work in progress),
              May 2014.

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

7.2.  Informative References

   [I-D.ietf-mpls-in-udp]
              Xu, X., Sheth, N., Yong, L., Pignataro, C., and F.
              Yongbing, "Encapsulating MPLS in UDP", draft-ietf-mpls-in-
              udp-05 (work in progress), January 2014.

   [RFC4023]  Worster, T., Rekhter, Y., and E. Rosen, "Encapsulating
              MPLS in IP or Generic Routing Encapsulation (GRE)", RFC
              4023, March 2005.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com





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   Siva Sivabalan
   Cisco

   Email: msiva@cisco.com


   Robert Raszuk
   Individual

   Email: robert@raszuk.net


   Uma Chunduri
   Ericsson

   Email: uma.chunduri@ericsson.com


   Victor Lopezalvarez
   Telefonica

   Email: victor.lopezalvarez@telefonica.com





























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