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Versions: (draft-xu-ospf-mpls-elc) 00 01 02
03 04 05
OSPF Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track S. Kini
Expires: July 7, 2018
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
January 3, 2018
Signaling Entropy Label Capability and Readable Label-stack Depth Using
OSPF
draft-ietf-ospf-mpls-elc-05
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 OSPF. In addition, this document introduces the Router
Non-OSPF Functional Capabilities TLV for advertising OSPF router's
actual non-OSPF functional capabilities. ELC is one of such non-OSPF
functional capabilities.
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
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Internet-Draft Signalling ELC and RLD using OSPF January 2018
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
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.
Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(https://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Non-OSPF Functional Capabilities TLV . . . . . . . . . . . . 3
4. Advertising ELC Using OSPF . . . . . . . . . . . . . . . . . 4
5. Advertising RLD Using OSPF . . . . . . . . . . . . . . . . . 4
6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 4
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
8. Security Considerations . . . . . . . . . . . . . . . . . . . 5
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
9.1. Normative References . . . . . . . . . . . . . . . . . . 5
9.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
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 OSPF
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[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 [RFC6790] 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 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 [RFC7770].
3. Non-OSPF Functional Capabilities TLV
This document defines the Router Non-OSPF Functional Capabilities TLV
for advertisement in the OSPF Router Information LSA. An OSPF router
advertising an OSPF RI LSA MAY include the Router Non-OSPF Functional
Capabilities TLV. If included, it MUST be included in the first
instance of the LSA. Additionally, the TLV MUST reflect the
advertising OSPF router's actual non-OSPF functional capabilities in
the flooding scope of the containing OSPF RI LSA.
The format of the Router Non-OSPF Functional Capabilities 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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Non-OSPF Functional Capabilities |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Non-OSPF Functional Capabilities 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-OSPF 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-OSPF Functional Capabilities TLV MAY be followed by optional
TLVs that further specify a non-OSPF functional capability. In
contrast to the OSPF Router Functional Capabilities TLV, the non-OSPF
functional capabilities advertised in this TLV have no impact on the
OSPF protocol operation. The specifications for non-OSPF functional
capabilities advertised in this TLV MUST describe protocol behavior
and address backwards compatibility.
4. Advertising ELC Using OSPF
One bit of the Non-OSPF Functional Capability Bits 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.
5. Advertising RLD Using OSPF
A new TLV within the body of the OSPF RI LSA, called RLD 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 2.3 of [RFC7770] 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 line cards
with different capabilities of reading the maximum label stack depth,
the router MUST advertise the smallest one in the RLD 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: RLD TLV Format
6. Acknowledgements
The authors would like to thank Yimin Shen, George Swallow, Acee
Lindem, Carlos Pignataro and Bruno Decraene for their valuable
comments and suggestions.
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7. IANA Considerations
This document requests IANA to allocate one TLV type from the OSPF RI
TLVs registry for the Non-OSPF Functional Capabilities TLV.
Futhermore, this document requests IANA to creat a subregistry for
"Non-OSPF Functional Capability Bits" within the "Open Shortest Path
First v2 (OSPFv2) 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. All Non-
OSPF Functional Capability TLV additions are to be assigned through
IETF Review [RFC5226].
This document also requests IANA to allocate one TLV type from the
OSPF RI TLVs registry for the RLDC TLV.
8. Security Considerations
The security considerations as described in [RFC7770] is applicable
to this document. This document does not introduce any new security
risk.
9. References
9.1. Normative 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-07 (work in
progress), October 2017.
[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>.
[RFC7770] Lindem, A., Ed., Shen, N., Vasseur, JP., Aggarwal, R., and
S. Shaffer, "Extensions to OSPF for Advertising Optional
Router Capabilities", RFC 7770, DOI 10.17487/RFC7770,
February 2016, <https://www.rfc-editor.org/info/rfc7770>.
9.2. Informative References
[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-24 (work in progress), December 2017.
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[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.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<https://www.rfc-editor.org/info/rfc5226>.
[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
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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