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
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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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