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Re: Order of ASes in the BGP Path

  • From: Paul Jakma
  • Date: Mon Aug 29 14:52:12 2005 
On Mon, 29 Aug 2005, Abhishek Verma wrote:


Legend: {} denotes the sequence, while [] denotes the set

Path {1 2} [3 4] {5}

Would somebody mind if this was represented as {1 2 5} [3 4] ?
Yes, they are different paths. You are allowed to merge adjacent sequences, eg:

{1 2} {5} [3 4]

the two sequences can be merged, to give:

{1 2 5} [3 4]

You can *not* merge AS_SET's, as the current BGP specs imply an AS_SET has a fixed path-length, hence you should NOT merge the sets in:

{1 2} [3 4] [5 6]

into:

{1 2} [3 4 5 6]

as the former path has a length of 3, the latter a length of just 2 - merging sets could change their meaning. Note though that you're not at all likely to see such paths with BGP speakers implementing the RFC / draft-ietf-idr-bgp-26.txt draft.

regards,
--
Paul Jakma [email protected] [email protected] Key ID: 64A2FF6A
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