Connecting MPLS-SPRING Islands over IP Networks
draft-xu-spring-islands-connection-over-ip-03

Network Working Group                                              X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                               R. Raszuk
Expires: June 6, 2015                                      Mirantis Inc.
                                                             U. Chunduri
                                                                Ericsson
                                                        December 3, 2014

            Connecting MPLS-SPRING Islands over IP Networks
             draft-xu-spring-islands-connection-over-ip-03

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 imposing stacked MPLS labels to
   the packet.  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

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   This Internet-Draft will expire on June 6, 2015.

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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.ietf-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 imposing stacked MPLS labels to the packet.  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., MPLS-in-IP/GRE tunnel [RFC4023], MPLS-in-
   L2TPv3 tunnel [RFC4817] or MPLS-in-UDP tunnel [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

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   and egress of the IP-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.ietf-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.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Shakir, R., Tantsura, J.,
              and E. Crabbe, "Segment Routing with MPLS data plane",
              draft-ietf-spring-segment-routing-mpls-00 (work in
              progress), December 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., Yongbing, F.,
              Callon, R., and D. Black, "Encapsulating MPLS in UDP",
              draft-ietf-mpls-in-udp-07 (work in progress), October
              2014.

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

   [RFC4817]  Townsley, M., Pignataro, C., Wainner, S., Seely, T., and
              J. Young, "Encapsulation of MPLS over Layer 2 Tunneling
              Protocol Version 3", RFC 4817, March 2007.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com

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   Robert Raszuk
   Mirantis Inc.

   Email: robert@raszuk.net

   Uma Chunduri
   Ericsson

   Email: uma.chunduri@ericsson.com

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