Network Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track S. Kini
Expires: November 4, 2016 Ericsson
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
May 3, 2016
Signaling Entropy Label Capability Using OSPF
draft-ietf-ospf-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 OSPF. This mechanism is useful when the label
advertisement is also done via OSPF.
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 November 4, 2016.
Copyright Notice
Copyright (c) 2016 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 OSPF . . . . . . . . . . . . . . . . . 3
4. Advertising RLDC Using OSPF . . . . . . . . . . . . . . . . . 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 OSPF
[I-D.ietf-ospf-segment-routing-extensions] . In such scenario the
signaling mechanisms defined in [RFC6790] are inadequate. This draft
defines a mechanism to signal the ELC using OSPF. This mechanism is
useful when the label advertisement is also done via OSPF. 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 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,
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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.
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 [RFC4970].
3. Advertising ELC Using OSPF
The OSPF Router Information (RI) Opaque LSA defined in [RFC4970] is
used by OSPF routers to announce their capabilities. A new TLV
within the body of this LSA, called ELC TLV is defined to advertise
the capability of the router to process the ELs. As showed in
Figure 1, it is formatted as described in Section 2.1 of [RFC4970].
The Type for the ELC TLV needs to be assigned by IANA and it has a
Length of zero. The scope of the advertisement depends on the
application but it is recommended that it SHOULD be AS-scoped. If a
router has multiple linecards, the router MUST NOT announce the ELC
unless all of its linecards are capable of processing ELs. This TLV
is applicable to both OSPFv2 and OSPFv3.
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 TLV Format.
4. Advertising RLDC Using OSPF
A new TLV within the body of the OSPF RI LSA, called RLDC TLV is
defined to advertise the capability of the router to read the maximum
label stack depth. As showed in Figure 2, it is formatted as
described in Section 2.1 of [RFC4970] 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 depth 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
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deepth, the router MUST advertise the smallest one in the RLDC TLV.
This TLV is applicable to both OSPFv2 and OSPFv3.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| RLD |
+-+-+-+-+-+-+-+-+
Figure 2: RLDC TLV Format
5. Usage and Applicability
The EL capability is used by ingress LSRs to determine whether an EL
could be inserted into a given LSP tunnel. The RLD capability 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 EL capability and RLD capability using OSPF. 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 TLV types from
the OSPF RI TLVs registry.
8. Security Considerations
The security considerations as described in [RFC4970] 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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[RFC4970] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 4970, DOI 10.17487/RFC4970, July
2007, <http://www.rfc-editor.org/info/rfc4970>.
9.2. Informative References
[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-03 (work in progress), April 2016.
[I-D.ietf-ospf-segment-routing-extensions]
Psenak, P., Previdi, S., Filsfils, C., Gredler, H.,
Shakir, R., Henderickx, W., and J. Tantsura, "OSPF
Extensions for Segment Routing", draft-ietf-ospf-segment-
routing-extensions-08 (work in progress), April 2016.
[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-04 (work in
progress), March 2016.
[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
Sriganesh Kini
Ericsson
Email: sriganesh.kini@ericsson.com
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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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