draft-ietf-mpls-number-0-bw-te-lsps-06.txt   draft-ietf-mpls-number-0-bw-te-lsps-07.txt 
Networking Working Group JP. Vasseur, Ed. Networking Working Group JP. Vasseur, Ed.
Internet-Draft Cisco Systems, Inc Internet-Draft Cisco Systems, Inc
Intended status: Standards Track Matthew. R. Meyer Intended status: Standards Track Matthew. R. Meyer
Expires: December 27, 2007 Global Crossing Expires: May 18, 2008 Global Crossing
K. Kumaki K. Kumaki
KDDI Corporation KDDI Corporation
Alberto. Tempia Bonda Alberto. Tempia Bonda
Telecom Italia Telecom Italia
June 25, 2007 November 15, 2007
A Link-Type sub-TLV to convey the number of Traffic Engineering Label A Link-Type sub-TLV to convey the number of Traffic Engineering Label
Switched Paths signalled with zero reserved bandwidth across a link Switched Paths signalled with zero reserved bandwidth across a link
draft-ietf-mpls-number-0-bw-te-lsps-06 draft-ietf-mpls-number-0-bw-te-lsps-07
Status of this Memo Status of this Memo
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Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
** UPDATE OSPFv3 **
Several Link-type sub-TLVs have been defined for OSPF and IS-IS in Several Link-type sub-TLVs have been defined for OSPF and IS-IS in
the context of Multiprotocol Label Switching (MPLS) Traffic the context of Multiprotocol Label Switching (MPLS) Traffic
Engineering (TE) in order to advertise some link characteristics such Engineering (TE) in order to advertise some link characteristics such
as the available bandwidth, traffic engineering metric, as the available bandwidth, traffic engineering metric,
administrative group and so on. By making statistical assumption on administrative group and so on. By making statistical assumption
the aggregated traffic carried onto a set of TE Label Switched Paths about the aggregated traffic carried onto a set of TE Label Switched
(LSPs) signalled with zero bandwith (referred to as unconstrained TE Paths (LSPs) signalled with zero bandwith (referred to as
LSP in this document), and with the knowledge of the number of unconstrained TE LSP in this document), and with the knowledge of the
unconstrained TE LSPs signalled across a link, algorithms can be number of unconstrained TE LSPs signalled across a link, algorithms
designed to load balance (existing or newly configured) unconstrained can be designed to load balance (existing or newly configured)
TE LSP across a set of equal cost paths. This requires the knowledge unconstrained TE LSP across a set of equal cost paths. This requires
of the number of unconstrained TE LSPs signalled across a link. This knowledge of the number of unconstrained TE LSPs signalled across a
document specifies a new Link-type Traffic Engineering sub-TLV used link. This document specifies a new Link-type Traffic Engineering
to advertise the number of unconstrained TE LSP(s) signalled across a sub-TLV used to advertise the number of unconstrained TE LSP(s)
link. signalled across a link.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119]. document are to be interpreted as described in RFC 2119 [RFC2119].
Table of Contents Table of Contents
1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4 1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Protocol extensions . . . . . . . . . . . . . . . . . . . . . . 5 3. Protocol extensions . . . . . . . . . . . . . . . . . . . . . . 5
3.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. IS-IS . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.2. OSPF . . . . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Elements of procedure . . . . . . . . . . . . . . . . . . . . . 6 4. Elements of procedure . . . . . . . . . . . . . . . . . . . . . 6
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 6 6. Security Considerations . . . . . . . . . . . . . . . . . . . . 7
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 7
8.1. Normative References . . . . . . . . . . . . . . . . . . . 7 8.1. Normative References . . . . . . . . . . . . . . . . . . . 7
8.2. Informative References . . . . . . . . . . . . . . . . . . 7 8.2. Informative References . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 7 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 8
Intellectual Property and Copyright Statements . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . . . 9
1. Terminology 1. Terminology
Terminology used in this document Terminology used in this document
CSPF: Constraint Shortest Path First CSPF: Constraint Shortest Path First
MPLS: Multiprotocol Label Switching IGP : Interior Gateway Protocol
LSA: Link State Advertisement. LSA: Link State Advertisement
LSP: Link State Packet. LSP: Link State Packet
LSR: Label Switching Router. MPLS: Multiprotocol Label Switching
TE LSP: Traffic Engineering Label Switched Path. LSR: Label Switching Router
Unconstrained TE LSP: A TE LSP signalled with a bandwidth equal to 0. 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 2. Introduction
It is not uncommon to deploy MPLS TE for the sake of fast recovery It is not uncommon to deploy MPLS Traffic Engineering for the sake of
relying on a local protection recovery mechanism such as MPLS TE Fast fast recovery relying on a local protection recovery mechanism such
Reroute (see [RFC4090]). In this case, a deployment model consists as MPLS TE Fast Reroute (see [RFC4090]). In this case, a deployment
of deploying a full mesh of unconstrained TE LSPs (TE LSP signalled model consists of deploying a full mesh of TE LSPs signalled with
with zero bandwidth) between a set of LSRs and protecting these TE zero bandwidth (also referred to as unconstrained TE LSP in this
LSPs against link, SRLG and/or node failures with pre-established document) between a set of LSRs (Label Switching Router) and
backup tunnels. The traffic routed onto such unconstrained TE LSP protecting these TE LSPs against link, SRLG (Shared Risk Link Group)
simply follows the IGP shortest path (since the TE LSP computed by and/or node failures with pre-established backup tunnels. The
the path computation algorithm (e.g. CSPF) will be no different than traffic routed onto such unconstrained TE LSPs simply follows the IGP
the IGP shortest path should the TE metric be equal to the IGP shortest path (since the TE LSP computed by the path computation
metric) but is protected with MPLS TE Fast Reroute. 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, When a reoptimization process is triggered for an existing TE LSP,
the decision on whether to reroute that TE LSP onto a different path 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 is governed by the discovery of a lower cost path satisfying the
constraints (other metric such that the percentage of reserved constraints (other metric such that the percentage of reserved
bandwidth or the number of hops can also be used). Unfortunately, bandwidth or the number of hops can also be used). Unfortunately,
for instance in the presence of ECMPs (Equal Cost Multi-Paths) in for instance in the presence of ECMPs (Equal Cost Multi-Paths) in
symmetrical networks when unconstrained TE LSPs are used, such symmetrical networks when unconstrained TE LSPs are used, such
metrics are usually ineffective and may lead to poorly load balanced metrics (e.g. path cost, number of hops, ...) are usually ineffective
traffic. and may lead to poorly load balanced traffic.
By making statistical assumption on the aggregated traffic carried By making statistical assumption about the aggregated traffic carried
onto a set of TE LSPs signalled with no bandwidth requirement by a set of TE LSPs signalled with no bandwidth requirement (referred
(referred to as unconstrained TE LSP in this document), algorithms to as unconstrained TE LSPs in this document), algorithms can be
can be designed to load balance (existing or newly configured) designed to load balance (existing or newly configured) unconstrained
unconstrained TE Label Switched Path (LSP) across a set of equal cost TE Label Switched Path (LSP) across a set of equal cost paths. This
paths. This requires the knowledge of the number of unconstrained requires knowledge of the number of unconstrained Traffic Engineering
Traffic Engineering Label Switched Path(s) (TE LSP) signalled across Label Switched Path(s) (TE LSP) signalled across each link.
a 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 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 [RFC3630] and [RFC3784]) in the context of MPLS Traffic Engineering
in order to advertise various link characteristics such as the in order to advertise various link characteristics such as the
available bandwidth, traffic engineering metric, administrative group available bandwidth, traffic engineering metric, administrative group
and so on. As currently defined in [RFC3630] and [RFC3784] the and so on. As currently defined in [RFC3630] and [RFC3784] the
information related to the number of unconstrained TE LSP(s) is not information related to the number of unconstrained TE LSP(s) is not
available. This document specifies a new Link-type Traffic available. This document specifies a new Link-type Traffic
Engineering sub-TLV used to indicate the number of unconstrained TE Engineering sub-TLV used to indicate the number of unconstrained TE
LSPs signalled across a link. LSPs signalled across a link.
Note that the specification of load balancing algorithms is outside Unconstrained TE LSPs that are configured and provisioned through a
of the scope of this document and merely listed for the sake of management system are not included in the count that is reported.
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 3. Protocol extensions
The Number of 0-bandwidth TE LSP(s) Sub-TLV is defined that specifies 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. the number of TE LSPs signalled with zero bandwidth across a link.
3.1. IS-IS 3.1. IS-IS
The Number of 0-bandwidth TE LSP(s) sub-TLV is OPTIONAL and MUST The Unconstrained TE LSP Count Sub-TLV is OPTIONAL and MUST NOT
appear at most once within the extended IS reachability TLV (type 22) appear more than once within the extended IS reachability TLV (type
specified in [RFC3784]. 22) specified in [RFC3784].
The IS-IS Number of 0-bandwidth TE LSP(s) sub-TLV format is defined The IS-IS Unconstrained TE LSP Count Sub-TLV format is defined below:
below:
Type (1 octet): To be assigned by IANA (suggested value = 18) Type (1 octet): To be assigned by IANA (suggested value = 23)
Length (1 octet): 2 Length (1 octet): 2
Value (2 octets): number of unconstrained TE LSP(s) signalled across Value (2 octets): number of unconstrained TE LSP(s) signalled across
the link. the link.
3.2. OSPF 3.2. OSPF
The Number of 0-bandwidth TE LSP(s) sub-TLV is OPTIONAL and MUST The OSPF Unconstrained TE LSP Count TLV is OPTIONAL and MUST NOT
appear at most once within the Link TLV (Type 2) that is itself appear more than once within the Link TLV (Type 2) that is itself
carried within the Traffic Engineering LSA specified in [RFC3630] or carried within the Traffic Engineering LSA specified in [RFC3630] or
the OSPFv3 Intra-Area-TE LSA (function code 10) defined in the OSPFv3 Intra-Area-TE LSA (function code 10) defined in
draft-ietf-ospf-ospfv3-traffic-07.txt. If a second instance of the [I-D.ietf-ospf-ospfv3-traffic]. If a second instance of the Number
Number of 0-bandwidth TE LSP(s) sub-TLV is present, the receiving of 0-bandwidth TE LSP(s) sub-TLV is present, the receiving system
system MUST only process the first instance of the sub-TLV. MUST only process the first instance of the sub-TLV.
The OSPF Number of 0-bandwidth TE LSP(s) sub-TLV format is defined The OSPF Unconstrained TE LSP Count Sub-TLV format is defined below:
below:
Type (2 octets): To be assigned by IANA (suggested value = 18) Type (2 octets): To be assigned by IANA (suggested value = 23)
Length (2 octets): 4 Length (2 octets): 4
Value (4 octets): number of unconstrained TE LSP(s) signalled across Value (4 octets): number of unconstrained TE LSP(s) signalled across
the link. the link.
4. Elements of procedure 4. Elements of procedure
An implementation MAY decide to implement a dual-thresholds mechanism The absence of the Unconstrained TE LSP Count (sub-)TLV should be
based on the number of unconstrained TE LSPs to govern the interpreted as an absence of information about the link.
origination of updated OSPF LSA or ISIS LSP. Similarly to other MPLS
Traffic Engineering link characteristics, LSA/LSP origination trigger Similarly to other MPLS Traffic Engineering link characteristics,
mechanisms are outside of the scope of this document. LSA/LSP origination trigger mechanisms are outside the scope of this
document.
5. IANA Considerations 5. IANA Considerations
IANA will assign a new code point for the newly defined IS-IS Number IANA has defined a sub-registry for the sub-TLVs carried in the IS-IS
of 0-bandwidth TE LSP(s) sub-TLV carried within the TLV 22 (suggested TLV 22. IANA is requested to assign a new TLV code-point for the
value =18). Unconstrained TE LSP Count sub-TLV carried within the TLV 22.
IANA will assign a new code point for the newly defined OSPF Number Suggested Value TLV Name Reference
of 0-bandwidth TE LSP(s) sub-TLV carried within the Link TLV (Type 2)
of the Traffic Engineering LSA (suggested value=18). 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.
Suggested Value TLV Name Reference
23 Unconstrained TE LSP Count (sub-)TLV This document
6. Security Considerations 6. Security Considerations
The function described in this document does not create any new The function described in this document does not create any new
security issues for the OSPF and the IS-IS protocols. Security security issues for the OSPF and the IS-IS protocols. Security
considerations are covered in [RFC2328] and [RFC2470] for the base considerations are covered in [RFC2328] and [RFC2470] for the base
OSPF protocol and in [RFC1194] for IS-IS. OSPF protocol and in [RFC1194] for IS-IS.
7. Acknowledgements 7. Acknowledgements
The authors would like to thank Jean-Louis Le Roux, Adrian Farrel, The authors would like to thank Jean-Louis Le Roux, Adrian Farrel,
Daniel King, Acee Lindem and Loa Anderson for their useful inputs. Daniel King, Acee Lindem, Lou Berger, Attila Takacs and Loa Anderson
for their useful inputs.
8. References 8. References
8.1. Normative 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", [RFC1194] Zimmerman, D., "Finger User Information Protocol",
RFC 1194, November 1990. RFC 1194, November 1990.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998. [RFC2328] Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
[RFC2470] Crawford, M., Narten, T., and S. Thomas, "Transmission of [RFC2470] Crawford, M., Narten, T., and S. Thomas, "Transmission of
IPv6 Packets over Token Ring Networks", RFC 2470, IPv6 Packets over Token Ring Networks", RFC 2470,
 End of changes. 31 change blocks. 
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