Signaling Entropy Label Capability and Readable Label-stack Depth Using IS-IS
draft-ietf-isis-mpls-elc-03

ISIS Working Group                                                 X. Xu
Internet-Draft                                                    Huawei
Intended status: Standards Track                                 S. Kini
Expires: July 7, 2018                                           Ericsson
                                                            S. Sivabalan
                                                             C. Filsfils
                                                                   Cisco
                                                            S. Litkowski
                                                                  Orange
                                                         January 3, 2018

Signaling Entropy Label Capability and Readable Label-stack Depth Using
                                 IS-IS
                      draft-ietf-isis-mpls-elc-03

Abstract

   Multiprotocol Label Switching (MPLS) has defined a mechanism to load
   balance traffic flows using Entropy Labels (EL).  An ingress Label
   Switching Router (LSR) cannot insert ELs for packets going into a
   given tunnel unless an egress LSR has indicated via signaling that it
   has the capability of processing ELs, referred to as Entropy Label
   Capability (ELC), on that tunnel.  In addition, it would be useful
   for ingress LSRs to know each LSR's capability of reading the maximum
   label stack depth, referred to as Readable Label-stack Depth (RLD),
   in the cases where stacked LSPs are used for whatever reasons.  This
   document defines mechanisms to signal these two capabilities using
   OSPF.  These mechanisms are 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 https://datatracker.ietf.org/drafts/current/.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . .   3
   4.  Advertising RLD Using IS-IS . . . . . . . . . . . . . . . . .   3
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   4
   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

   [RFC6790] describes a method to load balance Multiprotocol Label
   Switching (MPLS) traffic flows using Entropy Labels (EL).  [RFC6790]
   introduces the concept of Entropy Label Capability (ELC) and defines
   the signalings of this capability via MPLS 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 [RFC6790] using IS-IS.  This
   mechanism is useful when the label advertisement is also done via IS-

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   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 depth.  This capability, referred to as Readable Label-
   stack Depth (RLD) may be used by ingress LSRs to determine whether
   it's necessary to insert an EL for a given LSP of the stacked 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].

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.  As shown in Figure 1, 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 RLD Using IS-IS

   A new sub-TLV of the IS-IS Router CAPABILITY TLV, called RLD 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: RLD sub-TLV Format

5.  Acknowledgements

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

6.  IANA Considerations

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

7.  Security Considerations

   The security considerations as described in [RFC4971] is applicable
   to this document.  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,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [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,
              <https://www.rfc-editor.org/info/rfc4971>.

8.2.  Informative References

   [I-D.ietf-isis-segment-routing-extensions]
              Previdi, S., Ginsberg, L., Filsfils, C., Bashandy, A.,
              Gredler, H., Litkowski, S., Decraene, B., and J. Tantsura,
              "IS-IS Extensions for Segment Routing", draft-ietf-isis-
              segment-routing-extensions-15 (work in progress), December
              2017.

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   [I-D.ietf-mpls-spring-entropy-label]
              Kini, S., Kompella, K., Sivabalan, S., Litkowski, S.,
              Shakir, R., and J. Tantsura, "Entropy label for SPRING
              tunnels", draft-ietf-mpls-spring-entropy-label-07 (work in
              progress), October 2017.

   [I-D.ietf-spring-segment-routing-mpls]
              Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
              Litkowski, S., and R. Shakir, "Segment Routing with MPLS
              data plane", draft-ietf-spring-segment-routing-mpls-11
              (work in progress), October 2017.

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305, October
              2008, <https://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,
              <https://www.rfc-editor.org/info/rfc6790>.

Authors' Addresses

   Xiaohu Xu
   Huawei

   Email: xuxh.mail@gmail.com

   Sriganesh Kini
   Ericsson

   Email: sriganesh.kini@ericsson.com

   Siva Sivabalan
   Cisco

   Email: msiva@cisco.com

   Clarence Filsfils
   Cisco

   Email: cfilsfil@cisco.com

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   Stephane Litkowski
   Orange

   Email: stephane.litkowski@orange.com

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