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Versions: (draft-vasseur-mpls-number-0-bw-te-lsps)
00 01 02 03 04 05 06 07 08 09 10 11
12 RFC 5330
Networking Working Group JP. Vasseur, Ed.
Internet-Draft Cisco Systems, Inc
Intended status: Standards Track Matthew. R. Meyer
Expires: May 18, 2008 Global Crossing
K. Kumaki
KDDI Corporation
Alberto. Tempia Bonda
Telecom Italia
November 15, 2007
A Link-Type sub-TLV to convey the number of Traffic Engineering Label
Switched Paths signalled with zero reserved bandwidth across a link
draft-ietf-mpls-number-0-bw-te-lsps-07
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
Several Link-type sub-TLVs have been defined for OSPF and IS-IS in
the context of Multiprotocol Label Switching (MPLS) Traffic
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Engineering (TE) in order to advertise some link characteristics such
as the available bandwidth, traffic engineering metric,
administrative group and so on. By making statistical assumption
about the aggregated traffic carried onto a set of TE Label Switched
Paths (LSPs) signalled with zero bandwith (referred to as
unconstrained TE LSP in this document), and with the knowledge of the
number of unconstrained TE LSPs signalled across a link, algorithms
can be designed to load balance (existing or newly configured)
unconstrained TE LSP across a set of equal cost paths. This requires
knowledge of the number of unconstrained TE LSPs signalled across a
link. This document specifies a new Link-type Traffic Engineering
sub-TLV used to advertise the number of unconstrained TE LSP(s)
signalled across a link.
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].
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Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol extensions . . . . . . . . . . . . . . . . . . . . . . 5
3.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Elements of procedure . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Terminology
Terminology used in this document
CSPF: Constraint Shortest Path First
IGP : Interior Gateway Protocol
LSA: Link State Advertisement
LSP: Link State Packet
MPLS: Multiprotocol Label Switching
LSR: Label Switching Router
SRLG: Shared Risk Link Group
TE LSP: Traffic Engineering Label Switched Path
Unconstrained TE LSP: A TE LSP signalled with a bandwidth equal to 0
2. Introduction
It is not uncommon to deploy MPLS Traffic Engineering for the sake of
fast recovery relying on a local protection recovery mechanism such
as MPLS TE Fast Reroute (see [RFC4090]). In this case, a deployment
model consists of deploying a full mesh of TE LSPs signalled with
zero bandwidth (also referred to as unconstrained TE LSP in this
document) between a set of LSRs (Label Switching Router) and
protecting these TE LSPs against link, SRLG (Shared Risk Link Group)
and/or node failures with pre-established backup tunnels. The
traffic routed onto such unconstrained TE LSPs simply follows the IGP
shortest path (since the TE LSP computed by the path computation
algorithm (e.g. CSPF) will be no different than the IGP (Interior
Gateway Protocol) shortest path should the TE metric be equal to the
IGP metric) but is protected with MPLS TE Fast Reroute.
When a reoptimization process is triggered for an existing TE LSP,
the decision on whether to reroute that TE LSP onto a different path
is governed by the discovery of a lower cost path satisfying the
constraints (other metric such that the percentage of reserved
bandwidth or the number of hops can also be used). Unfortunately,
for instance in the presence of ECMPs (Equal Cost Multi-Paths) in
symmetrical networks when unconstrained TE LSPs are used, such
metrics (e.g. path cost, number of hops, ...) are usually ineffective
and may lead to poorly load balanced traffic.
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By making statistical assumption about the aggregated traffic carried
by a set of TE LSPs signalled with no bandwidth requirement (referred
to as unconstrained TE LSPs in this document), algorithms can be
designed to load balance (existing or newly configured) unconstrained
TE Label Switched Path (LSP) across a set of equal cost paths. This
requires knowledge of the number of unconstrained Traffic Engineering
Label Switched Path(s) (TE LSP) signalled across each link.
Note that the specification of load balancing algorithms is outside
the scope of this document and is referred to for the sake of
illustration of the motivation for gathering such information.
Furthermore, the knowledge of the number of unconstrained TE LSPs
signalled across each link can be used for other purposes (for
example to evaluate the number of affected TE LSPs in case of a link
failure).
A set of Link-type sub-TLVs have been defined for OSPF and IS-IS (see
[RFC3630] and [RFC3784]) in the context of MPLS Traffic Engineering
in order to advertise various link characteristics such as the
available bandwidth, traffic engineering metric, administrative group
and so on. As currently defined in [RFC3630] and [RFC3784] the
information related to the number of unconstrained TE LSP(s) is not
available. This document specifies a new Link-type Traffic
Engineering sub-TLV used to indicate the number of unconstrained TE
LSPs signalled across a link.
Unconstrained TE LSPs that are configured and provisioned through a
management system are not included in the count that is reported.
3. Protocol extensions
The Number of 0-bandwidth TE LSP(s) Sub-TLV is defined that specifies
the number of TE LSPs signalled with zero bandwidth across a link.
3.1. IS-IS
The Unconstrained TE LSP Count Sub-TLV is OPTIONAL and MUST NOT
appear more than once within the extended IS reachability TLV (type
22) specified in [RFC3784].
The IS-IS Unconstrained TE LSP Count Sub-TLV format is defined below:
Type (1 octet): To be assigned by IANA (suggested value = 23)
Length (1 octet): 2
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Value (2 octets): number of unconstrained TE LSP(s) signalled across
the link.
3.2. OSPF
The OSPF Unconstrained TE LSP Count TLV is OPTIONAL and MUST NOT
appear more than once within the Link TLV (Type 2) that is itself
carried within the Traffic Engineering LSA specified in [RFC3630] or
the OSPFv3 Intra-Area-TE LSA (function code 10) defined in
[I-D.ietf-ospf-ospfv3-traffic]. If a second instance of the Number
of 0-bandwidth TE LSP(s) sub-TLV is present, the receiving system
MUST only process the first instance of the sub-TLV.
The OSPF Unconstrained TE LSP Count Sub-TLV format is defined below:
Type (2 octets): To be assigned by IANA (suggested value = 23)
Length (2 octets): 4
Value (4 octets): number of unconstrained TE LSP(s) signalled across
the link.
4. Elements of procedure
The absence of the Unconstrained TE LSP Count (sub-)TLV should be
interpreted as an absence of information about the link.
Similarly to other MPLS Traffic Engineering link characteristics,
LSA/LSP origination trigger mechanisms are outside the scope of this
document.
5. IANA Considerations
IANA has defined a sub-registry for the sub-TLVs carried in the IS-IS
TLV 22. IANA is requested to assign a new TLV code-point for the
Unconstrained TE LSP Count sub-TLV carried within the TLV 22.
Suggested Value TLV Name Reference
23 Unconstrained TE LSP Count (sub-)TLV This document
IANA has defined a sub-registry for the sub-TLVs carried in an OSPF
TE Link TLV (type 2). IANA is requested to assign a new sub-TLV
code-point for the Unconstrained TE LSP Count sub-TLV carried within
the TE Link TLV.
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Suggested Value TLV Name Reference
23 Unconstrained TE LSP Count (sub-)TLV This document
6. Security Considerations
The function described in this document does not create any new
security issues for the OSPF and the IS-IS protocols. Security
considerations are covered in [RFC2328] and [RFC2470] for the base
OSPF protocol and in [RFC1194] for IS-IS.
7. Acknowledgements
The authors would like to thank Jean-Louis Le Roux, Adrian Farrel,
Daniel King, Acee Lindem, Lou Berger, Attila Takacs and Loa Anderson
for their useful inputs.
8. References
8.1. Normative References
[I-D.ietf-ospf-ospfv3-traffic]
Ishiguro, K., "Traffic Engineering Extensions to OSPF
version 3", draft-ietf-ospf-ospfv3-traffic-09 (work in
progress), September 2007.
[RFC1194] Zimmerman, D., "Finger User Information Protocol",
RFC 1194, November 1990.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2470] Crawford, M., Narten, T., and S. Thomas, "Transmission of
IPv6 Packets over Token Ring Networks", RFC 2470,
December 1998.
[RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
(TE) Extensions to OSPF Version 2", RFC 3630,
September 2003.
[RFC3784] Smit, H. and T. Li, "Intermediate System to Intermediate
System (IS-IS) Extensions for Traffic Engineering (TE)",
RFC 3784, June 2004.
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8.2. Informative References
[RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute
Extensions to RSVP-TE for LSP Tunnels", RFC 4090,
May 2005.
Authors' Addresses
JP Vasseur (editor)
Cisco Systems, Inc
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: jpv@cisco.com
Matthew R. Meyer
Global Crossing
3133 Indian Valley Tr.
Howell, MI 48855
USA
Email: mrm@gblx.net
Kenji Kumaki
KDDI Corporation
Garden Air Tower Iidabashi, Chiyoda-ku,
Tokyo, 102-8460
JAPAN
Email: ke-kumaki@kddi.com
Alberto Tempia Bonda
Telecom Italia
via G. Reiss Romoli 274
Torino, 10148
ITALIA
Email: alberto.tempiabonda@telecomitalia.it
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