Internet DRAFT - draft-xu-isis-mpls-elc
draft-xu-isis-mpls-elc
Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track S. Kini
Expires: October 22, 2015 Ericsson
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
April 20, 2015
Signaling Entropy Label Capability Using IS-IS
draft-xu-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 that it can process ELs for 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.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on October 22, 2015.
Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Advertising ELC using IS-IS . . . . . . . . . . . . . . . . . 3
4. Advertising RLSDC using IS-IS . . . . . . . . . . . . . . . . 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 for
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
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.ietf-mpls-spring-entropy-label] . Of
course, even it has been determined that it's neccessary to insert an
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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 [RFC4971].
3. Advertising ELC using IS-IS
The IS-IS Router CAPABILITY TLV 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.
4. Advertising RLSDC using IS-IS
A new sub-TLV of the IS-IS Router CAPABILITY TLV, called RLSDC sub-
TLV is defined to advertise the capability of the router to read the
maximum label stack depth. 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 RLSDC sub-TLV.
5. Acknowledgements
The authors would like to thank Yimin Shen and George Swallow for
their valuable comments on the draft.
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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
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.
[RFC4971] Vasseur, JP., Shen, N., and R. Aggarwal, "Intermediate
System to Intermediate System (IS-IS) Extensions for
Advertising Router Information", RFC 4971, July 2007.
[RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic
Engineering", RFC 5305, October 2008.
8.2. Informative References
[I-D.ietf-isis-segment-routing-extensions]
Previdi, S., 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-03 (work in progress), October 2014.
[I-D.ietf-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-
ietf-mpls-spring-entropy-label-00 (work in progress),
March 2015.
[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.
[RFC6790] Kompella, K., Drake, J., Amante, S., Henderickx, W., and
L. Yong, "The Use of Entropy Labels in MPLS Forwarding",
RFC 6790, November 2012.
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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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