Use of Multipath with MPLS and MPLS Transport Profile (MPLS-TP)
RFC 7190

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Internet Engineering Task Force (IETF)                     C. Villamizar
Request for Comments: 7190             Outer Cape Cod Network Consulting
Category: Informational                                       March 2014
ISSN: 2070-1721

    Use of Multipath with MPLS and MPLS Transport Profile (MPLS-TP)

Abstract

   Many MPLS implementations have supported multipath techniques, and
   many MPLS deployments have used multipath techniques, particularly in
   very high-bandwidth applications, such as provider IP/MPLS core
   networks.  MPLS Transport Profile (MPLS-TP) has strongly discouraged
   the use of multipath techniques.  Some degradation of MPLS-TP
   Operations, Administration, and Maintenance (OAM) performance cannot
   be avoided when operating over many types of multipath
   implementations.

   Using MPLS Entropy Labels (RFC 6790), MPLS Label Switched Paths
   (LSPs) can be carried over multipath links while also providing a
   fully MPLS-TP-compliant server layer for MPLS-TP LSPs.  This document
   describes the means of supporting MPLS as a server layer for MPLS-TP.
   The use of MPLS-TP LSPs as a server layer for MPLS LSPs is also
   discussed.

Status of This Memo

   This document is not an Internet Standards Track specification; it is
   published for informational purposes.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Not all documents
   approved by the IESG are a candidate for any level of Internet
   Standard; see Section 2 of RFC 5741.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   http://www.rfc-editor.org/info/rfc7190.

Villamizar                    Informational                     [Page 1]
RFC 7190               MPLS and MPLS-TP Multipath             March 2014

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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   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Definitions . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  MPLS as a Server Layer for MPLS-TP  . . . . . . . . . . . . .   5
     3.1.  MPLS-TP Forwarding and Server-Layer Requirements  . . . .   5
     3.2.  Methods of Supporting MPLS-TP Client LSPs over MPLS . . .   7
   4.  MPLS-TP as a Server Layer for MPLS  . . . . . . . . . . . . .  11
   5.  Summary . . . . . . . . . . . . . . . . . . . . . . . . . . .  11
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  12
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .  13
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
     8.2.  Informative References  . . . . . . . . . . . . . . . . .  13

1.  Introduction

   Today the requirement to handle large aggregations of traffic can be
   met by a number of techniques that we will collectively call
   "multipath".  Multipath applied to parallel links between the same
   set of nodes includes Ethernet Link Aggregation [IEEE-802.1AX], link
   bundling [RFC4201], or other aggregation techniques, some of which
   could be vendor specific.  Multipath applied to diverse paths rather
   than parallel links includes Equal-Cost Multipath (ECMP) as applied
   to OSPF, IS-IS, or BGP, and equal-cost Label Switched Paths (LSPs).
   Some vendors support load splitting across equal-cost MPLS LSPs where
   the load is split proportionally to the reserved bandwidth of the set
   of LSPs.

   RFC 5654 requirement 33 requires the capability to carry a client
   MPLS Transport Profile (MPLS-TP) or MPLS layer over a server MPLS-TP
   or MPLS layer [RFC5654].  This is possible in all cases with one
   exception.  When an MPLS LSP exceeds the capacity of any single

Villamizar                    Informational                     [Page 2]
RFC 7190               MPLS and MPLS-TP Multipath             March 2014

   component link, it MAY be carried by a network using multipath
   techniques, but it SHOULD NOT be carried by a single MPLS-TP LSP due
   to the inherent MPLS-TP capacity limitation imposed by MPLS-TP
   Operations, Administration, and Maintenance (OAM) fate-sharing