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is it possible for an ASN in the BGP path to determine what ASN has been the originator and the cause of withdraw message?

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No. As BGP is a distance vector protocol all we are able to tell is which neighbour we have received the withdraw message from.

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  • so when a withdrawal happens, how an isp could find out the ASN causing the problem so it could change it's provider to another upstream? – shbr uzu Mar 14 at 8:56
  • @shbruzu Usually a withdrawal happens from the originating AS. If this isn’t the case and a transit AS is experiencing issues then I would expect the route to be dampened thus favouring an alternate path. – ditrapanij Mar 14 at 13:54
  • Let's say an upstream AS in the middle of the path is causing the most of withdrawals. how this AS could be detected so that the provider could cancel the upstream contract permanently rather than relying on excessive BGP path changes? – shbr uzu Mar 14 at 16:09
  • @shbruzu, In that unlikely scenario I would expect that you would also see a few other prefixes flap during the same period which would help you isolate the fault to a subset of specific ASes along the path. Unfortunately without contacting the parties (excluding process of elimination) you will never be able to tell 100%. – ditrapanij Mar 16 at 10:44

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