OSPF Working Group X. Xu
Internet-Draft Alibaba Inc
Intended status: Standards Track S. Kini
Expires: February 2, 2019
S. Sivabalan
C. Filsfils
Cisco
S. Litkowski
Orange
August 01, 2018
Signaling Entropy Label Capability and Entropy Readable Label-stack
Depth Using OSPF
draft-ietf-ospf-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 OSPF. These mechanisms are
useful when the label advertisement is also done via OSPF. In
addition, this document introduces the Non-IGP Functional
Capabilities TLV for advertising OSPF router's actual non-IGP
functional capabilities. ELC is one of such non-IGP 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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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 February 2, 2019.
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
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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 ERLD 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 . . . . . . . . . . . . . . . . . 6
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., 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 [RFC7770].
3. Non-OSPF Functional Capabilities TLV
This document defines the Router Non-IGP Functional Capabilities TLV
with TLV type code of TBD1 within the body of the OSPF Router
Information LSA. An OSPF router advertising an OSPF RI LSA MAY
include the Router Non-IGP 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-IGP
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-IGP 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
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capabilities advertised. Initially, the length will be 4,
denoting 4 octets of Non-IGP Functional Capabilities Bits as
defined in [I-D.ietf-isis-mpls-elc].
Value: contains the Non-IGP Functional Capabilities Bits as
defined in [I-D.ietf-isis-mpls-elc].
The Non-IGP 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-IGP functional
capabilities advertised in this TLV MUST describe protocol behavior
and address backwards compatibility.
4. Advertising ELC Using OSPF
One bit of the Non-IGP Functional Capability Bits for is used to
indicate the ELC.
Assignment of a Non-IGP Functional Capability Bit for the ELC is
defined in [I-D.ietf-isis-mpls-elc].
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 ERLD Using OSPF
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. The scope of the advertisement
depends on the application.
Assignment of a MSD-Type for ERLD is defined in
[I-D.ietf-isis-mpls-elc].
If a router has multiple linecards with different capabilities of
reading the maximum label stack deepth, the router MUST advertise the
smallest one.
6. 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.
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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-IGP Functional CapabilitiesTLV.
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-isis-mpls-elc]
Xu, X., Kini, S., Sivabalan, S., Filsfils, C., and S.
Litkowski, "Signaling Entropy Label Capability and Entropy
Readable Label Depth Using IS-IS", draft-ietf-isis-mpls-
elc-05 (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-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-25 (work in progress), April 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.
[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>.
[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>.
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[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>.
[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-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@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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