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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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 July 7, 2018.
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document authors. All rights reserved.
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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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