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Versions: (draft-vasseur-mpls-number-0-bw-te-lsps)
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12 RFC 5330
Networking Working Group JP. Vasseur, Ed.
Internet-Draft Cisco Systems, Inc
Intended status: Standards Track Matthew. R. Meyer
Expires: June 15, 2007 Global Crossing
K. Kumaki
KDDI Corporation
Alberto. Tempia Bonda
Telecom Italia
December 12, 2006
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-05
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Copyright Notice
Copyright (C) The Internet Society (2006).
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 on
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 the 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 . . . . . . . . . . . . . . . . . . . . 6
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7
Intellectual Property and Copyright Statements . . . . . . . . . . 9
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1. Terminology
Terminology used in this document
CSPF: Constraint Shortest Path First
MPLS: Multiprotocol Label Switching
LSA: Link State Advertisement.
LSP: Link State Packet.
LSR: Label Switching Router.
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 TE 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 unconstrained TE LSPs (TE LSP signalled
with zero bandwidth) between a set of LSRs and protecting these TE
LSPs against link, SRLG and/or node failures with pre-established
backup tunnels. The traffic routed onto such unconstrained TE LSP
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 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 are usually ineffective and may lead to poorly load balanced
traffic.
By making statistical assumption on the aggregated traffic carried
onto a set of TE LSPs signalled with no bandwidth requirement
(referred to as unconstrained TE LSP 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
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paths. This requires the knowledge of the number of unconstrained
Traffic Engineering Label Switched Path(s) (TE LSP) signalled across
a link.
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.
Note that the specification of load balancing algorithms is outside
of the scope of this document and merely listed for the sake of
illustration of the motivation for gathering such information.
TE LSPs signalled with zero bandwidth that are configured and
provisioned through a management system are not included in the count
that is reported.
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).
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 Number of 0-bandwidth TE LSP(s) sub-TLV is OPTIONAL and MUST
appear at most once within the extended IS reachability TLV (type 22)
specified in [RFC3784].
The IS-IS Number of 0-bandwidth TE LSP(s) sub-TLV format is defined
below:
Type (1 octet): To be assigned by IANA (suggested value = 18)
Length (1 octet): 2
Value (2 octets): number of unconstrained TE LSP(s) signalled across
the link.
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3.2. OSPF
The Number of 0-bandwidth TE LSP(s) sub-TLV is OPTIONAL and MUST
appear at most 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
draft-ietf-ospf-ospfv3-traffic-07.txt. 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 Number of 0-bandwidth TE LSP(s) sub-TLV format is defined
below:
Type (2 octets): To be assigned by IANA (suggested value = 18)
Length (2 octets): 4
Value (4 octets): number of unconstrained TE LSP(s) signalled across
the link.
4. Elements of procedure
An implementation MAY decide to implement a dual-thresholds mechanism
based on the number of unconstrained TE LSPs to govern the
origination of updated OSPF LSA or ISIS LSP. Similarly to other MPLS
Traffic Engineering link characteristics, LSA/LSP origination trigger
mechanisms are outside of the scope of this document.
5. IANA Considerations
IANA will assign a new code point for the newly defined IS-IS Number
of 0-bandwidth TE LSP(s) sub-TLV carried within the TLV 22 (suggested
value =18).
IANA will assign a new code point for the newly defined OSPF Number
of 0-bandwidth TE LSP(s) sub-TLV carried within the Link TLV (Type 2)
of the Traffic Engineering LSA (suggested value=18).
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.
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7. Acknowledgements
The authors would like to thank Jean-Louis Le Roux, Adrian Farrel,
Daniel King, Acee Lindem and Loa Anderson for their useful inputs.
8. References
8.1. Normative References
[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.
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.
[OSPFv3-TE] Lindem, A. et al., "Traffic Engineering Extensions to OSPF
version 3", draft-ietf-ospf-ospfv3-traffic, work in progress.
Authors' Addresses
JP Vasseur (editor)
Cisco Systems, Inc
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: jpv@cisco.com
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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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