draft-ietf-ospf-mt-01.txt   draft-ietf-ospf-mt-02.txt 
Network Working Group Peter Psenak Network Working Group Peter Psenak
Internet Draft Sina Mirtorabi Internet Draft Sina Mirtorabi
Expiration Date: February 2005 Abhay Roy Expiration Date: September 2005 Abhay Roy
File name: draft-ietf-ospf-mt-01.txt Liem Nguyen File name: draft-ietf-ospf-mt-02.txt Liem Nguyen
Padma Pillay-Esnault Padma Pillay-Esnault
Cisco Systems Cisco Systems
February 2005 March 2005
Multi-Topology (MT) Routing in OSPF Multi-Topology (MT) Routing in OSPF
Status of This Memo Status of This Memo
This document is an Internet-Draft and is subject to all provisions This document is an Internet-Draft and is subject to all provisions
of section 3 of RFC 3667. By submitting this Internet-Draft, each of section 3 of RFC 3667. By submitting this Internet-Draft, each
author represents that any applicable patent or other IPR claims of author represents that any applicable patent or other IPR claims of
which he or she is aware have been or will be disclosed, and any of which he or she is aware have been or will be disclosed, and any of
which he or she become aware will be disclosed, in accordance with which he or she become aware will be disclosed, in accordance with
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Each MT has its own MT-ID metric field. When a link is not Each MT has its own MT-ID metric field. When a link is not
part of a given MT, the corresponding MT-ID metric is excluded from part of a given MT, the corresponding MT-ID metric is excluded from
the LSA. the LSA.
The Network-LSA does not contain any MT information since the DR is The Network-LSA does not contain any MT information since the DR is
shared by all MTs. Hence, there is no change to the Network-LSA. shared by all MTs. Hence, there is no change to the Network-LSA.
6.2 Inter-area and External Routing 6.2 Inter-area and External Routing
In Summary-LSAs, NSSA-LSAs, and AS-External-LSAs, the TOS metric In Summary-LSAs, NSSA-LSAs, and AS-External-LSAs, the TOS metric
field are defined as MT-ID metric fields and are used in order to fields are defined as MT-ID metric fields and are used in order to
advertise prefix and router reachability in the corresponding advertise prefix and router reachability in the corresponding
topology. topology.
When a router originates a Summary-LSA, NSSA-LSA, or AS-External-LSA When a router originates a Summary-LSA, NSSA-LSA, or AS-External-LSA
that belongs to a set of MTs, it will include the corresponding cost that belongs to a set of MTs, it will include the corresponding cost
for each MT-ID. By default, the router participates in the default for each MT-ID. By default, the router participates in the default
topology and uses the TOS0 metric for the default topology the same topology and uses the TOS0 metric for the default topology the same
as in standard OSPF [OSPF]. as in standard OSPF [OSPF].
Setting the P-bit in NSSA-LSAs is topology independent and pertains Setting the P-bit in NSSA-LSAs is topology independent and pertains
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in the metric field as a valid metric and consider the link or in the metric field as a valid metric and consider the link or
prefix as part of the default topology. prefix as part of the default topology.
In order to prevent the above problem, an MT capable router will In order to prevent the above problem, an MT capable router will
include all links as part of the default topology. If links need include all links as part of the default topology. If links need
to be removed from the default topology, an MT capable router to be removed from the default topology, an MT capable router
MUST be configured in MTRoutingExclusionCapability mode. In this MUST be configured in MTRoutingExclusionCapability mode. In this
mode, routers will assure that all other routers in the area are mode, routers will assure that all other routers in the area are
in the MTRoutingExclusionCapability mode before considering the in the MTRoutingExclusionCapability mode before considering the
MT-ID#0 metric in the SPF calculation. Only then can the TOS0 metric MT-ID#0 metric in the SPF calculation. Only then can the TOS0 metric
field be safely ignored during the default topology SPF computation. field in Router LSAs be safely ignored during the default topology
SPF computation.
Note that for any prefix or router to become reachable in a certain Note that for any prefix or router to become reachable in a certain
topology, a contiguous path inside that topology must exist between topology, a contiguous path inside that topology must exist between
the calculating router and the destination prefix or router. the calculating router and the destination prefix or router.
13. Migration from non-MT-Area to MT-area 13. Migration from non-MT-Area to MT-area
Introducing MT-OSPF into a network can be done gradually to allow Introducing MT-OSPF into a network can be done gradually to allow
MT routers and non-MT routers to participate in the default topology MT routers and non-MT routers to participate in the default topology
while MT routers participate in other topologies. while MT routers participate in other topologies.
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16. IANA Considerations 16. IANA Considerations
The T-bit as defined in [RFC1583] for a router's TOS capability is The T-bit as defined in [RFC1583] for a router's TOS capability is
redefined as the MT-bit in this document. Similarly, the TOS field redefined as the MT-bit in this document. Similarly, the TOS field
for Router-LSAs, Summary-LSAs, NSSA-LSAs, and AS-External LSAs as for Router-LSAs, Summary-LSAs, NSSA-LSAs, and AS-External LSAs as
defined in [OSPF] is redefined as MT-ID in this document. defined in [OSPF] is redefined as MT-ID in this document.
17. Normative References 17. Normative References
[M-ISIS] Przygienda, T., Shen, N., Sheth, N.,
"Multi Topology (MT) Routing in IS-IS",
draft-ietf-isis-wg-multi-topology-06.txt,
Work in progress.
[OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998. [OSPF] Moy, J., "OSPF Version 2", RFC 2328, April 1998.
[RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994. [RFC1583] Moy, J., "OSPF Version 2", RFC 1583, March 1994.
[NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option", [NSSA] Murphy, P., "The OSPF Not-So-Stubby Area (NSSA) Option",
RFC 3101, January 2003. RFC 3101, January 2003.
[RFC2119] Bradner, S., "Key words for use in RFC's to Indicate [RFC2119] Bradner, S., "Key words for use in RFC's to Indicate
Requirement Levels", RFC 2328, March 1977. Requirement Levels", RFC 2119, March 1997.
18. Informative References 18. Informative References
[M-ISIS] Przygienda, T., Shen, N., Sheth, N.,
"M-ISIS: Multi Topology (MT) Routing in IS-IS",
draft-ietf-isis-wg-multi-topology-07.txt,
Work in progress.
[STUB] Retana, A., Nguyen, L., White, R., Zinin, A. and D. [STUB] Retana, A., Nguyen, L., White, R., Zinin, A. and D.
McPherson, "OSPF Stub Router Advertisement", RFC 3137, June McPherson, "OSPF Stub Router Advertisement", RFC 3137, June
2001. 2001.
Appendix A. Appendix A.
LSA content defined in [OSPF] is modified to introduce the MT-ID. LSA content defined in [OSPF] is modified to introduce the MT-ID.
A.1 Router-LSAs A.1 Router-LSAs
 End of changes. 

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