1 multi topology routing for ospfv3 (draft-mirtorabi-mt-ospfv3-00.txt) sina mirtorabi...
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Multi Topology Routing for OSPFv3
(draft-mirtorabi-mt-ospfv3-00.txt)
Sina Mirtorabi ([email protected])
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Agenda
• MTRv3 Goal
• Potential Solutions
• Proposed Solution
• Default topology
• New LSAs
• MT-ID
• MT routing operations
• Backward compatibility
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MTRv3 Goal
• Define multiple independent topology within a physical topology
Traffic separation across the network, an enterprise where different entities requires traffic separations
Use some links only for some type of traffic such as low delay
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Potential Solutions
• Using Different Instance IDs
Use Instance IDs in the range of an AF (draft-ietf-ospf-af-alt-00.txt) to have multiple topologies. Scaling issues due to multiple adjacencies, databases etc..
• Using an integrated approach with existing LSAs
Possible to replicate link descriptions in router-LSA for MTR. Issues with backward compatibility
Still doesn’t solve a need to associate prefixes with different topologies
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Proposed Solution
• Define new LSAs to carry MT information
• New LSAs will be ignored by old routers, so no backward compatibility issues
• New LSAs are being defined in a TLV style, so that they can also facilitate any future extension in OSPFv3
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Default Topology
• Default Topology is the topology that is built by using the existing LSAs as specified in OSPFv3
• Other non-default topologies are built by using the new LSAs
• Possibility to use new LSA for default topology when all routers are MT capable
• For that a configurable parameter RFC2740Compatibility is used to control the generation of existing or new LSAs for default topology
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New LSAs
LSA Function code LS Type Description
1 0xB001 E-Router-LSA
2 0xB002 E-Network-LSA
3 0xB003 E-Inter-Area-Prefix-LSA
4 0xB004 E-Intra-Area-Router-LSA
5 0xD005 E-AS-External-LSA
6 0xB006 E-Group-Membership-LSA
7 0xB007 E-NSSA-LSA
8 0x9008 E-Link-LSA
9 0x3009 E-Intra-Area-Prefix-LSA
1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6
U S2 S1 T LSA Function Code
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New LSAs (cont)
• New LSA payloads are TLV based
• TLV may contain sub-TLVs, this is explicitly indicated by setting a S bit
• E-Router LSA has link description TLV, describing link adjacencies. A Sub-TLV under each link description carries MT information
• Prefix LSAs has TLV under each Address Prefix carrying MT information (MT-ID and corresponding cost)
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E-Router-LSA
LS Age LS type
Link State ID
Advertising Router
LS sequence number
LS checksum Length
0 0 0 0 W V E B Options
TLV type TLV length
Link-type 0
Interface ID
Neighbor Interface ID
Neighbor Router ID
Sub-TLVs
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E-Intra-area-prefix-LSA
LS Age LS type
Link State ID
Advertising Router
LS sequence number
LS checksum Length
#Prefix Referenced LS type
Referenced Link State ID
Referenced Advertising Router
Prefix-Block length PrefixLength 0
Address Prefix
TLVs
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E-Inter-area-prefix-LSA
LS Age LS type
Link State ID
Advertising Router
LS sequence number
LS checksum Length
Prefix-Block length PrefixLength 0
Address Prefix
TLVs
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MT-ID Fields
• 8 bit MT-ID field present in various LSAs
• MT-ID is accompanied with a MT-ID Metric field which carries a metric specific to a MT
• MT-ID value 0 is reserved for carrying information about Default Topology in the new LSAs
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MT routing operations
• A Single adjacency is formed even if the link participates in multiple topologies
• OSPFv3 control packets are sent using IPv6 link local address which is MT independent
• Each topology’s SPT is calculated by using only MT-ID links and associated metric for that topology
• Network LSA is shared by all topologies
• During intra-area / Inter-area / external route calculation for a topology, only prefix belonging to a given MT with their associated metric are considered
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Backward Compatibility
• An MT capable router will interact (in Default Topology) with non-MT capable routers by using the existing LSAs
• When all routers are MT capable, RFC2740Compatibility can be set to disable and only extended LSAs are used for Default Topology
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We would like
draft-mirtorabi-mt-ospfv3-00.txt
to be accepted as a OSPF WG document