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Versions: (draft-xu-isis-mpls-elc) 00 01 02

ISIS Working Group                                                 X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                                 S. Kini
Expires: April 17, 2017                                         Ericsson
                                                            S. Sivabalan
                                                             C. Filsfils
                                                                   Cisco
                                                            S. Litkowski
                                                                  Orange
                                                        October 14, 2016


             Signaling Entropy Label Capability Using IS-IS
                      draft-ietf-isis-mpls-elc-02

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 IS-IS.  This mechanism is useful when the label
   advertisement is also done via IS-IS.

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].

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
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   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 April 17, 2017.




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Copyright Notice

   Copyright (c) 2016 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
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . .   3
   4.  Advertising RLDC Using IS-IS  . . . . . . . . . . . . . . . .   3
   5.  Usage and Applicability . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   9.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   4
     9.1.  Normative References  . . . . . . . . . . . . . . . . . .   4
     9.2.  Informative References  . . . . . . . . . . . . . . . . .   5
   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 IS-IS
   [I-D.ietf-isis-segment-routing-extensions] . In such scenario the
   signaling mechanisms defined in [RFC6790] are inadequate.  This draft
   defines a mechanism to signal the ELC using IS-IS.  This mechanism is
   useful when the label advertisement is also done via IS-IS.  In
   addition, in the cases where stacked LSPs are used for whatever
   reasons (e.g., SPRING-MPLS [I-D.ietf-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



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   as Readable Label Deepth Capability (RLDC) 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.ietf-mpls-spring-entropy-label] . Of course,
   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.

2.  Terminology

   This memo makes use of the terms defined in [RFC6790] and [RFC4971].

3.  Advertising ELC Using IS-IS

   The IS-IS Router CAPABILITY TLV as defined in [RFC4971] is used by
   IS-IS routers to announce their capabilities.  A new sub-TLV of this
   TLV, called ELC sub-TLV is defined to advertise the capability of the
   router to process the ELs.  It is formatted as described in [RFC5305]
   with a Type code to be assigned by IANA and a Length of zero.  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, the router MUST NOT advertise the ELC unless all of the
   linecards are capable of processing ELs.

         0                   1                   2                   3
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type=TBD1    |    Length=0   |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 1: ELC sub-TLV Format

4.  Advertising RLDC Using IS-IS

   A new sub-TLV of the IS-IS Router CAPABILITY TLV, called RLDC sub-TLV
   is defined to advertise the capability of the router to read the
   maximum label stack depth.  As shown in Figure 2, it is formatted as
   described in [RFC5305] 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 RLDC sub-TLV.







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         0                   1                   2                   3
         0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
        |    Type=TBD2    |   Length=1    |     RLD       |
        +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
                         Figure 2: RLDC sub-TLV Format

5.  Usage and Applicability

   The ELC is used by ingress LSRs to determine whether an EL could be
   inserted into a given LSP tunnel.  The RLDC is 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.  This document only describes how to signal the ELC
   and RLDC using IS-IS.  As for how to apply those capabilities when
   inserting EL(s) into LSP tunnel(s), it's outside the scope of this
   document and accordingly would be described in
   [I-D.ietf-mpls-spring-entropy-label].

6.  Acknowledgements

   The authors would like to thank Yimin Shen, George Swallow, Acee
   Lindem and Carlos Pignataro for their valuable comments.

7.  IANA Considerations

   This memo includes a request to IANA to allocate two sub-TLV types
   within the IS-IS Router Capability TLV.

8.  Security Considerations

   The security considerations as described in [RFC4971] is appliable to
   this document.  This document does not introduce any new security
   risk.

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,
              <http://www.rfc-editor.org/info/rfc2119>.








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   [RFC4971]  Vasseur, JP., Ed., Shen, N., Ed., and R. Aggarwal, Ed.,
              "Intermediate System to Intermediate System (IS-IS)
              Extensions for Advertising Router Information", RFC 4971,
              DOI 10.17487/RFC4971, July 2007,
              <http://www.rfc-editor.org/info/rfc4971>.

9.2.  Informative References

   [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-08 (work in progress), October
              2016.

   [I-D.ietf-mpls-spring-entropy-label]
              Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and j. jefftant@gmail.com, "Entropy labels for
              source routed tunnels with label stacks", draft-ietf-mpls-
              spring-entropy-label-04 (work in progress), July 2016.

   [I-D.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., Horneffer, M., Shakir, R.,
              jefftant@gmail.com, j., and E. Crabbe, "Segment Routing
              with MPLS data plane", draft-ietf-spring-segment-routing-
              mpls-05 (work in progress), July 2016.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <http://www.rfc-editor.org/info/rfc5305>.

   [RFC6790]  Kompella, K., Drake, J., Amante, S., Henderickx, W., and
              L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
              RFC 6790, DOI 10.17487/RFC6790, November 2012,
              <http://www.rfc-editor.org/info/rfc6790>.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxiaohu@huawei.com








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   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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