[ih] Exterior Gateway Protocol

[tony.li at tony.li]

>  This all relates to the original thinking about Border Gateways. Later, people did start doing BGP other than between Border Gateways sharing a network number / prefix.  There was, of course, "Interior BGP" between Border Routers of the same AS.  And there was the later application of BGP to connect to route servers.
>  Does anyone know whether any of those later applications did depend on inter-AS routing already working?  If so, how was the layer violation handled (or problems arising from it not being handled)?



Yes, IBGP is used, pretty much ubiquitously and has a dependency on the IGP.  Because the IGPs cannot support the route scale of the Internet, interior routers are forced to run IBGP. Thus, we’re forced into a situation where each router is running both BGP and IGP.  Some people have experimented with pushing their IGP routing into BGP as well, but that largely hasn’t worked well because convergence can only proceed one hop at a time.

Tony