Inferring the location points of traffic exchange between two networks

Jérôme Nicolle jerome at ceriz.fr
Fri Jan 15 10:42:45 UTC 2016


Hi Reza,

Le 13/01/2016 18:36, Reza Motamedi a écrit :
> My question is about BGP and what can be inferred from the output of
> different "show" commands, regarding the point of traffic exchange of two
> networks with different ASNs.

Unless you have a tremendous amount of peers and feeds to work with,
you'll have a hard time building a valid interconnection graph from BGP
cli outputs.

The best mapping outputs I have seen for now have been built using probe
clusters (either RIPE ATLAS or NLNOG Ring) with traceroutes, by merging
data from the observed routes AND both DNS and BGP.

DNS is quite usefull here as most of us use location codes in router's
FQDN. BGP will only help in matching subnets within ASes and corroborate
some discrete relationships.

Also note that each node in the directed graph may expose multiple
addresses, and that latency between routers isn't a reliable metric
(still a usefull indicator, YMMV)

Best regards,

-- 
Jérôme Nicolle



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