Networking Working Group JP. Vasseur
Internet-Draft Cisco Systems, Inc
Expires: August 5, 2006 February 1, 2006
A Link-Type sub-TLV to convey the number of unconstrained Traffic
Engineering Label Switch Paths signalled across a link
draft-vasseur-mpls-nb-te-lsp-00
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Copyright (C) The Internet Society (2006).
Abstract
Several Link-type sub-TLVs have been defined for OSPF and ISIS in
the
context of MPLS Traffic Engineering in order to convery some link
characteristics such as the available bandwidth, traffic enginering
metric, adminstrative group and so on. There are various
circumstances where it would be useful to also know the number of
unconstrained Traffic Engineering Label Switched Path(s) (TE LSP).
This document specifies a new Link-type Traffic Engineering sub-TLV
used to advertise the number of unconstrained TE LSP(s) signalled
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across a specific 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].
Table of Contents
1.
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2.
Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Protocol
extensions . . . . . . . . . . . . . . . . . . . . . . 4
3.1.
ISIS . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2.
OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Elements of
procedure . . . . . . . . . . . . . . . . . . . . . 4
5. IANA
Considerations . . . . . . . . . . . . . . . . . . . . . . 4
6. Security
Considerations . . . . . . . . . . . . . . . . . . . . 5
7.
Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 5
8.
References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
8.1. Normative
References . . . . . . . . . . . . . . . . . . . 5
8.2. Informative
References . . . . . . . . . . . . . . . . . . 5
Author's
Address . . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright
Statements . . . . . . . . . . 7
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1. Introduction
Several Link-type sub-TLVs have been defined for OSPF and ISIS (see
[ISIS-TE] and [OSPF-TE]) in the context of MPLS Traffic Engineering
in order to advertise various link characteristics such as the
available bandwidth, traffic enginering metric, adminstrative group
and so on. There are various circumstances where it would be useful
to also know the number of unconstrained Traffic Engineering Label
Switch Path(s) (TE LSP).
It is not uncommon to deploy MPLS Traffic Engineering for the
sake of
fast recovery with MPLS TE Fast Reroute (see [FAST-REROUTE]). In
this case, a common deployment model consists of deploying a full
mesh of unconstrained TE LSPs between a set of LSRs and protect
these
TE LSPs thanks to pre-established backup tunnels against link, SRLG
and/or node failures.
When a set of unconstrained TE LSPs is deployed, various algorithms
can be designed so as efficiently load balance the traffic
carried by
such unconstrained TE LSPs provided that the number of unconstrained
TE LSPs traversing each link in the network is known. As currently
defined in [OSPF-TE] and [ISIS-TE] the information related to the
number of unconstrained TE LSP(s) is not available. 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. Furthermore, the
knowledge of the number of unconstrained TE LSPs signalled across
each link can be used for other purposes (e.g. management, ...).
This document specifies a new Link-type Traffic Engineering sub-TLV
used to indicate the number of unconstrained TE LSP signalled across
a specific link.
2. Terminology
Terminology used in this document LSR: Label Switch Router.
TE LSP: MPLS Traffic Engineering Label Switched Path.
Backup tunnel: the TE LSP that is used to backup up one of the many
TE LSPs in many-to-one backup (as defined in [FAST-REROUTE]).
Unconstrained TE LSP: A TE LSP signalled with a bandwidth
requirement
equal to 0.
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3. Protocol extensions
A new Sub-TLV named NB-O-BW-LSP is defined that specifies the number
of unconstrained TE LSPs signalled across a link.
3.1. ISIS
The NB-0-BW-LSP TLV is OPTIONAL and MUST appear at most once within
the extended IS reachability TLV (type 22) specified in [ISIS-TE].
The NB-0-BW-LSP consists of:
Type (1 octet): To be assigned by IANA (Recommended value = 19)
Length (1 octet): 4
Value (4 octets): field value that comprises the number of
unconstrained TE LSP(s) signalled across the link.
3.2. OSPF
The NB-0-BW-LSP 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 [OSPF-TE]. The NB-0-BW-LSP consists
of:
Type (2 octets): To be assigned by IANA (Recommended value = 19)
Length (2 octets): 4
Value (4 octets): field value that comprises the number of
unconstrained TE LSP(s) signalled across the link.
4. Elements of procedure
An implementation may decide to implement a dual-thresholds
mechanism
so as to trigger the origination of an updated OSPF LSA or ISIS LSP.
Similalry 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 ISIS sub-TLV
(NB-0-BW-LSP) carried within the TLV 22 (suggested value =19)
IANA will assign a new code point for the newly defined OSPF sub-TLV
(NB-0-BW-LSP) carried within the Link TLV (Type 2) of the Traffic
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Engineering LSA (suggested value=19).
6. Security Considerations
This document raises no new security issues for IS-IS and OSPF.
7. Acknowledgements
8. References
8.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
8.2. Informative References
[FAST-REROUTE]
P. Pan, G. Swallow, A. Atlas et al., RFC 4090, "Fast
Reroute Extensions to RSVP-TE for LSP Tunnels", May 2005.
[ISIS-TE] T. Li, H. Smit, draft-ietf-isis-te-bis-00.txt, "IS-IS
extensions for Traffic Engineering", August 2005.
[OSPF-TE] Katz, et al., RFC 3630, "Traffic Engineering (TE)
Extensions to OSPF Version 2", September 2003.
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Author's Address
JP Vasseur
Cisco Systems, Inc
1414 Massachusetts Avenue
Boxborough, MA 01719
USA
Email: jpv@cisco.com
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