Network Working Group X. Xu
Internet-Draft Alibaba Inc
Intended status: Standards Track S. Kini
Expires: March 29, 2019
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
September 25, 2018
Signaling Entropy Label Capability and Entropy Readable Label Depth
Using IS-IS
draft-ietf-isis-mpls-elc-06
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. In
addition, this document introduces the Non-IGP Functional
Capabilities Sub-TLV for advertising IS-IS router's actual non-IGP
functional capabilities. ELC is one of such non-IGP functional
capabilities.
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/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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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 March 29, 2019.
Copyright Notice
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document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Non-IGP Functional Capabilities Sub-TLV . . . . . . . . . . . 3
4. Advertising ELC Using IS-IS . . . . . . . . . . . . . . . . . 4
5. Advertising ERLD Using IS-IS . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7
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.
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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
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. Non-IGP Functional Capabilities Sub-TLV
This document defines the Non-IGP Functional Capabilities Sub-TLV
with Sub-TLV type of TBD1 within the body of the IS-IS Router
Capability TLV. An IS-IS router advertising an IS-IS Router
Capability TLV MAY include the Non-IGP Functional Capabilities Sub-
TLV. The Sub-TLV MUST reflect the advertising IS-IS router's actual
non-IGP functional capabilities in the flooding scope of the
containing Router Capability TLV.
The format of the Router Non-IGP Functional Capabilities Sub-TLV is
as follows:
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=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Non-IGP Functional Capabilities |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Non-IGP Functional Capabilities Sub-TLV Format
Type: TBD1.
Length: Indicates the length of the value portion in octets and
will be a multiple of 4 octets dependent on the number of
capabilities advertised. Initially, the length will be 4,
denoting 4 octets of non-IGP functional capability bits.
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Value: A variable-length sequence of capability bits rounded to a
multiple of 4 octets padded with undefined bits. Initially, there
are 4 octets of capability bits. Bits are numbered left to right
starting with the most significant bit being bit 0.
The Non-IGP Functional Capabilities Sub-TLV MAY be followed by
optional Sub-TLVs that further specify a non-IGP functional
capability. The specifications for non-IGP functional capabilities
advertised in this Sub-TLV MUST describe protocol behavior and
address backwards compatibility.
4. Advertising ELC Using IS-IS
One bit of the Non-IGP Functional Capability Bits (Bit 0 is desired)
is to be assigned by the IANA for the ELC [RFC6790]. If a router has
multiple line cards, the router MUST NOT announce the ELC [RFC6790]
unless all of its linecards are capable of processing ELs.
How to apply the ELC advertisement to the inter-area, inter-AS and
inter-protocol scenarios is outside the scope of this document.
5. Advertising ERLD Using IS-IS
A new MSD-type of the 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.
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
6. Acknowledgements
The authors would like to thank Yimin Shen, George Swallow, Acee
Lindem, Les Ginsberg, Ketan Talaulikar, Jeff Tantsura, Bruno Decraene
and Carlos Pignataro for their valuable comments.
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7. IANA Considerations
This document requests IANA to allocate one sub-TLV type of the
Router Capability TLV registry for the Non-IGP Functional
Capabilities Sub-TLV. Futhermore, this document requests IANA to
creat a subregistry for "Non-IGP Functional Capability Bits" within
the "Interior Gateway Protocol (IGP) Parameters" registry. This
subregistry is comprised of the fields Bit Number, Capability Name,
and Reference. Initially, one bit is reqested to be assigned for the
ELC. The registration procedure is "Expert Review" as defined in
[RFC8126]. The following values are defined by this document:
Bit No. Capability Name Reference
----- --------------------- -------------
0 ELC This document
1-31 Unassigned This document
Figure 3: Non-IGP Functional Capability Bits Registry
IANA is requested to allocate a MSD type (the type code of 2 is
desired) from the "IGP MSD Types" registry for ERLD.
8. Security Considerations
The security considerations as described in [RFC4971] is applicable
to this document. This document does not introduce any new security
risk.
9. References
9.1. 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-16 (work in progress),
September 2018.
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[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.
[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>.
[RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and
U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4
and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794,
March 2016, <https://www.rfc-editor.org/info/rfc7794>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
9.2. 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.
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Authors' Addresses
Xiaohu Xu
Alibaba Inc
Email: xiaohu.xxh@alibaba-inc.com
Sriganesh Kini
Email: sriganeshkini@gmail.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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