Opaque OSPFv2 LSAs in OSPFv3

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Opaque OSPFv2 LSAs in OSPFv3

• Kireeti Kompella

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Summary of Document
OSPF v2 Opaque LSA
Proposed OSPF v3 LSA

LS Age LS Age Opt Opt 9,10,11
Opq Type Opaque ID Opaque ID Opaque ID Opaque ID
Advertising Router Advertising Router Advertising Router Advertising Router Advertising Router
LS Sequence Number LS Sequence Number LS Sequence Number LS Sequence Number LS Sequence Number
LS Cksum LS Cksum LS Cksum Length Length
Opaque Information Opaque Information Opaque Information Opaque Information Opaque Information
LS Age LS Age Flags Flags Func
Opq Type Opaque ID Opaque ID Opaque ID Opaque ID
Advertising Router Advertising Router Advertising Router Advertising Router Advertising Router
LS Sequence Number LS Sequence Number LS Sequence Number LS Sequence Number LS Sequence Number
LS Cksum LS Cksum LS Cksum Length Length
Opaque Information Opaque Information Opaque Information Opaque Information Opaque Information
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Summary

• Map v2 LS type of 9, 10 and 11 to a single new LS
  Function Code, with the S2, S1 bits used to
  indicate flooding
• LS ID is identical
• Opaque information is identical

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Issue

• Backdoor problem
• What does this mean?
• Is this really an issue?
• Even if it is, all that needs to be done is to
  validate that the two existing v2 Opaque LSAs can
  migrate over, and make sure new ones follow this
  rule

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Real Question

• Is v3 OSPF for IPv6, or is it an improvement
  over v2?
• I.e., should I be able to run an IPv4 network
  with OSPF v3?
• If so, v3 should be a superset of v2
• If not, remove all IPv4 prefix information from v3

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V3 as Superset of V2

• If v3 is a reasonable superset of v2, then one
  can migrate cleanly from v2 to v3
• If not, all sorts of functions break during the
  migration

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Alternative

• Define new LS Function Codes for each Opaque LSA
  type
• One for TE, one for Grace LSAs, etc.
• Problem what is the length of the Opaque ID
  24 bits or 32?
• Same problem I had with a 16-bit Instance ID,
  thus has to be 32 bits
• But that breaks migration

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Pros and Cons

• For v2 Opaque LSA in v3
• Pros code reuse, v3 ? v2, migration
• Con theoretical backdoor issue
• For translating Opaque LSAs one-by-one
• Pros ?
• Cons breaks compatibility between v2 and v3,
  hurts migration, cant use v3 for IPv4, more work
  all around

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Next Steps

• Articulate clearly what the issues are with the
  backdoor problem
• Weigh the pros and cons
• Make a pragmatic decision