Hi Les, in this case, using multi-hop BFD will add, in my estimation, 10 Mbyte/sec of extra traffic if the network is IPv4. Is it a real scaling concern these days?
Regards, Greg On Mon, Jan 10, 2022 at 4:44 PM Les Ginsberg (ginsberg) <ginsb...@cisco.com> wrote: > 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 <lsr-boun...@ietf.org> *On Behalf Of * Les Ginsberg (ginsberg) > *Sent:* Monday, January 10, 2022 4:34 PM > *To:* Robert Raszuk <rob...@raszuk.net> > *Cc:* Greg Mirsky <gregimir...@gmail.com>; Christian Hopps < > cho...@chopps.org>; Aijun Wang <wangai...@tsinghua.org.cn>; Shraddha > Hegde <shrad...@juniper.net>; Tony Li <tony...@tony.li>; Hannes Gredler < > han...@gredler.at>; lsr <lsr@ietf.org>; Peter Psenak (ppsenak) < > ppse...@cisco.com> > *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 <rob...@raszuk.net> > *Sent:* Monday, January 10, 2022 4:30 PM > *To:* Les Ginsberg (ginsberg) <ginsb...@cisco.com> > *Cc:* Greg Mirsky <gregimir...@gmail.com>; Tony Li <tony...@tony.li>; > Christian Hopps <cho...@chopps.org>; Aijun Wang <wangai...@tsinghua.org.cn>; > Shraddha Hegde <shrad...@juniper.net>; Hannes Gredler <han...@gredler.at>; > lsr <lsr@ietf.org>; Peter Psenak (ppsenak) <ppse...@cisco.com> > *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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