Some comments from Robert offline cause me to issue a correction. As BFD sessions are bidirectional we are talking about a Combination of (n,2) – so in the case of 500 nodes the actual number of BFD sessions network-wide is 124750.
Les From: Lsr <[email protected]> On Behalf Of Les Ginsberg (ginsberg) Sent: Monday, January 10, 2022 4:34 PM To: Robert Raszuk <[email protected]> Cc: Greg Mirsky <[email protected]>; Christian Hopps <[email protected]>; Aijun Wang <[email protected]>; Shraddha Hegde <[email protected]>; Tony Li <[email protected]>; Hannes Gredler <[email protected]>; lsr <[email protected]>; Peter Psenak (ppsenak) <[email protected]> Subject: Re: [Lsr] BGP vs PUA/PULSE Robert – The numbers are network-wide – not per node. And no one has mentioned config as an issue in this thread – though no doubt some operators might have concerns in that area. Les From: Robert Raszuk <[email protected]<mailto:[email protected]>> Sent: Monday, January 10, 2022 4:30 PM To: Les Ginsberg (ginsberg) <[email protected]<mailto:[email protected]>> Cc: Greg Mirsky <[email protected]<mailto:[email protected]>>; Tony Li <[email protected]<mailto:[email protected]>>; Christian Hopps <[email protected]<mailto:[email protected]>>; Aijun Wang <[email protected]<mailto:[email protected]>>; Shraddha Hegde <[email protected]<mailto:[email protected]>>; Hannes Gredler <[email protected]<mailto:[email protected]>>; lsr <[email protected]<mailto:[email protected]>>; Peter Psenak (ppsenak) <[email protected]<mailto:[email protected]>> Subject: Re: [Lsr] BGP vs PUA/PULSE Hi Les, [LES:] Even a modest sized N = 100 (which is certainly not a high number) leads to 10000 BFD sessions. N= 500 => 250,000 sessions. Etc. Are you doing N^2 ? Why ? All you need to keep in mind is number of those sessions per PE so in worst case (N-1) - here 99 and 499. And as we already established, configuration is optional as you can use auto config. Thx, R. [LES:] Nodes which can support thousands of BFD sessions are likely already using many BFD sessions for other purposes. In particular, fast detection of local failures is always going to be a priority – so if a node has thousands of neighbors – it will likely have thousands of single hop BFD sessions. Not to mention the plethora of other OAM uses cases being defined. And the network-wide traffic impact as these new BFD sessions are largely multi-hop. Are you really arguing that the introduction of many thousands of BFD sessions is something we should not be concerned about? Les Les
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