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Network Working Group                                              X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                                 S. Kini
Expires: April 13, 2015                                         Ericsson
                                                            S. Sivabalan
                                                             C. Filsfils
                                                                   Cisco
                                                            S. Litkowski
                                                                  Orange
                                                        October 10, 2014


             Signaling Entropy Label Capability Using OSPF
                       draft-xu-ospf-mpls-elc-01

Abstract

   Multi Protocol Label Switching (MPLS) has defined a mechanism to load
   balance traffic flows using Entropy Labels (EL).  An ingress LSR
   cannot insert ELs for packets going into a given tunnel unless an
   egress LSR has indicated via signaling that it can process ELs on
   that tunnel.  This draft defines a mechanism to signal that
   capability using OSPF.  This mechanism is useful when the label
   advertisement is also done via OSPF.

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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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on April 13, 2015.

Copyright Notice

   Copyright (c) 2014 IETF Trust and the persons identified as the
   document authors.  All rights reserved.





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   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.  Advertising ELC Using OSPF  . . . . . . . . . . . . . . . . .   3
   4.  Advertising RLSDC Using OSPF  . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   3
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   Multi Protocol Label Switching (MPLS) has defined a method in
   [RFC6790] to load balance traffic flows using Entropy Labels (EL).
   An ingress LSR cannot insert ELs for packets going into a given
   tunnel unless an egress LSR has indicated that it can process ELs on
   that tunnel.  [RFC6790] defines the signaling of this capability
   (a.k.a Entropy Label Capability - ELC) via signaling protocols.
   Recently, mechanisms are being defined to signal labels via link
   state Interior Gateway Protocols (IGP) such as OSPF
   [I-D.ietf-ospf-segment-routing-extensions] . In such scenario the
   signaling mechanisms defined in [RFC6790] are inadequate.  This draft
   defines a mechanism to signal the ELC using OSPF.  This mechanism is
   useful when the label advertisement is also done via OSPF.  In
   addition, in the cases where stacked LSPs are used for whatever
   reasons (e.g., SPRING-MPLS [I-D.gredler-spring-mpls]
   [I-D.filsfils-spring-segment-routing-mpls]), it would be useful for
   ingress LSRs to know each LSR's capability of reading the maximum
   label stack deepth.  This capability, referred to as Readable Label
   Stack Deepth Capability (RLSDC) can be used by ingress LSRs to
   determine whether it's necessary to insert an EL for a given LSP
   tunnel in the case where there has already been at least one EL in
   the label stack [I-D.kini-mpls-spring-entropy-label] . Of course,



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   even it has been determined that it's neccessary to insert an EL for
   a given LSP tunnel, if the egress LSR of that LSP tunnel has not yet
   indicated that it can process ELs for that tunnel, the ingress LSR
   MUST NOT include an entropy label for that tunnel as well.

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 [RFC6790] and [RFC4970].

3.  Advertising ELC Using OSPF

   The OSPF Router Information (RI) Opaque LSA defined in [RFC4970] is
   used by OSPF routers to announce their capabilities.  A new TLV
   within the body of this LSA, called ELC TLV is defined to advertise
   the capability of the router to process the ELs.  It is formatted as
   described in Section 2.1 of [RFC4970].  This TLV is applicable to
   both OSPFv2 and OSPFv3.  The Type for the ELC TLV needs to be
   assigned by IANA and it has a Length of zero.  The scope of the
   advertisement depends on the application but it is recommended that
   it SHOULD be AS-scoped.

4.  Advertising RLSDC Using OSPF

   A new TLV within the body of the OSPF RI LSA, called RLSDC TLV is
   defined to advertise the capability of the router to read the maximum
   label stack depth.  It is formatted as described in Section 2.1 of
   [RFC4970] with a Type code to be assigned by IANA and a Length of
   one.  The Value field is set to the maximum readable label stack
   deepth in the range between 1 to 255.  The scope of the advertisement
   depends on the application but it is RECOMMENDED that it SHOULD be
   domain-wide.  If a router has multiple linecards with different
   capabilities of reading the maximum label stack deepth, the router
   MUST advertise the smallest one in the RLSDC TLV.  This TLV is
   applicable to both OSPFv2 and OSPFv3.

5.  Acknowledgements

   The authors would like to thank Yimin Shen and George Swallow for
   their comments.






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6.  IANA Considerations

   This memo includes a request to IANA to allocate two TLV types from
   the OSPF RI TLVs registry.

7.  Security Considerations

   This document does not introduce any new security risk.

8.  References

8.1.  Normative References

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

   [RFC4970]  Lindem, A., Shen, N., Vasseur, JP., Aggarwal, R., and S.
              Shaffer, "Extensions to OSPF for Advertising Optional
              Router Capabilities", RFC 4970, July 2007.

8.2.  Informative 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.

   [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-02 (work in progress), August 2014.

   [I-D.kini-mpls-spring-entropy-label]
              Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., Xu, X., Henderickx, W., and J. Tantsura,
              "Entropy labels for source routed stacked tunnels", draft-
              kini-mpls-spring-entropy-label-01 (work in progress),
              September 2014.



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   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, November 2012.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com


   Sriganesh Kini
   Ericsson

   Email: sriganesh.kini@ericsson.com


   Siva Sivabalan
   Cisco

   Email: msiva@cisco.com


   Clarence Filsfils
   Cisco

   Email: cfilsfil@cisco.com


   Stephane Litkowski
   Orange

   Email: stephane.litkowski@orange.com

















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