Network Working Group X. Xu
Internet-Draft Alibaba Inc
Intended status: Standards Track S. Kini
Expires: January 26, 2019
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
July 25, 2018
Signaling Entropy Label Capability and Entropy Readable Label Depth
Using IS-IS
draft-ietf-isis-mpls-elc-04
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 and performing EL-based load-balancing, referred to
as Entropy Readable Label Depth (ERLD), in the cases where stacked
LSPs are used for whatever reasons. This document defines mechanisms
to signal these two capabilities using IS-IS. These mechanisms are
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.
Internet-Drafts are working documents of the Internet Engineering
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on January 26, 2019.
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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 ERLD 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 . . . . . . . . . . . . . . . . . 5
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-
IS.
In addition, in the cases where stacked LSPs are used for whatever
reasons (e.g., SR-MPLS [I-D.ietf-spring-segment-routing-mpls]), it
would be useful for ingress LSRs to know each intermediate LSR's
capability of reading the maximum label stack depth and performing
EL-based load-balancing. This capability, referred to as Entropy
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Readable Label Depth (ERLD) as defined in
[I-D.ietf-mpls-spring-entropy-label] 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].
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].
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. 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 ERLD Using IS-IS
A new MSD-type of the IS-IS Node MSD sub-TLV
[I-D.ietf-isis-segment-routing-msd], called ERLD is defined to
advertise the ERLD of a given router . As shown in Figure 2, it is
formatted as described in [I-D.ietf-isis-segment-routing-msd] with a
new MSD-Type code to be assigned by IANA (the type code of 2 is
desired) and the Value field is set to the ERLD in the range between
0 to 255. The scope of the advertisement depends on the application.
If a router has multiple linecards with different capabilities of
reading the maximum label stack deepth, the router MUST advertise the
smallest one.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MSD-Type=TBD2 | ERLD |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: ERLD MSD-Type Format
5. Acknowledgements
The authors would like to thank Yimin Shen, George Swallow, Acee
Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura and Carlos
Pignataro for their valuable comments.
6. IANA Considerations
IANA is requested to allocate one sub-TLV type of the IS-IS Router
Capability TLV for ELC and a MSD type (the type code of 2 is desired)
from the "IGP MSD Types" registry for ERLD.
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
[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-19 (work in progress), July
2018.
[I-D.ietf-isis-segment-routing-msd]
Tantsura, J., Chunduri, U., Aldrin, S., and L. Ginsberg,
"Signaling MSD (Maximum SID Depth) using IS-IS", draft-
ietf-isis-segment-routing-msd-13 (work in progress), July
2018.
[I-D.ietf-spring-segment-routing-mpls]
Bashandy, A., Filsfils, C., Previdi, S., Decraene, B.,
Litkowski, S., and R. Shakir, "Segment Routing with MPLS
data plane", draft-ietf-spring-segment-routing-mpls-14
(work in progress), June 2018.
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[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>.
[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>.
8.2. Informative References
[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-12 (work in
progress), July 2018.
Authors' Addresses
Xiaohu Xu
Alibaba Inc
Email: xiaohu.xxh@alibabab-inc.com
Sriganesh Kini
Email: sriganeshkini@gmail.com
Siva Sivabalan
Cisco
Email: msiva@cisco.com
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Clarence Filsfils
Cisco
Email: cfilsfil@cisco.com
Stephane Litkowski
Orange
Email: stephane.litkowski@orange.com
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