OSPF Working Group X. Xu
Internet-Draft Huawei
Intended status: Standards Track S. Kini
Expires: April 21, 2017
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
October 18, 2016
Signaling Entropy Label Capability Using OSPF
draft-ietf-ospf-mpls-elc-03
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.
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 http://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 April 21, 2017.
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Copyright Notice
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This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Non-OSPF Functional Capabilities TLV . . . . . . . . . . . . 3
4. Advertising ELC Using OSPF . . . . . . . . . . . . . . . . . 4
5. Advertising RLDC Using OSPF . . . . . . . . . . . . . . . . . 4
6. Usage and Applicability . . . . . . . . . . . . . . . . . . . 4
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 5
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5
9. Security Considerations . . . . . . . . . . . . . . . . . . . 5
10. References . . . . . . . . . . . . . . . . . . . . . . . . . 5
10.1. Normative References . . . . . . . . . . . . . . . . . . 5
10.2. Informative References . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6
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
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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,
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.
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.
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.
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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. If a router has multiple linecards, the
router MUST NOT announce the ELC unless all of its linecards are
capable of processing ELs.
5. 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 2.3 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 linecards
with different capabilities of reading the maximum label stack
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
6. Usage and Applicability
The ELC is used by ingress LSRs to determine whether an EL could be
inserted into a given LSP tunnel. The RLDC 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 ELC
and RLDC using OSPF. As for how to apply those capabilities when
inserting EL(s) into LSP tunnel(s), it's outside the scope of this
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document and accordingly would be described in
[I-D.ietf-mpls-spring-entropy-label].
7. Acknowledgements
The authors would like to thank Yimin Shen, George Swallow, Acee
Lindem and Carlos Pignataro for their valuable comments.
8. 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.
9. Security Considerations
The security considerations as described in [RFC7770] is appliable to
this document. This document does not introduce any new security
risk.
10. References
10.1. 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>.
[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, <http://www.rfc-editor.org/info/rfc7770>.
10.2. Informative References
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[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-04 (work in progress), July 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-09 (work in progress), July 2016.
[I-D.ietf-spring-segment-routing-mpls]
Filsfils, C., Previdi, S., Bashandy, A., Decraene, B.,
Litkowski, S., Horneffer, M., Shakir, R.,
jefftant@gmail.com, j., and E. Crabbe, "Segment Routing
with MPLS data plane", draft-ietf-spring-segment-routing-
mpls-05 (work in progress), July 2016.
[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
DOI 10.17487/RFC5226, May 2008,
<http://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,
<http://www.rfc-editor.org/info/rfc6790>.
Authors' Addresses
Xiaohu Xu
Huawei
Email: xuxiaohu@huawei.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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