[ih] Exterior Gateway Protocol

[tony.li at tony.li]

> Were people trying to do things that I think would now be similar to BGP-multi-hop?

IBGP is necessarily multi-hop, so that’s been a requirement since day 1.  Multi-hop EBGP has been a hack that’s also been around 
since day 1, but was never officially sanctioned.  Yes, people use it and depend on it.

> I don't see how AS-level routing is needed between neighbors on opposite ends of link-networks.
> 
> What am I missing?


Topology.

Strictly speaking, AS-level routing is not necessary. You can do everything with other protocols and leaking/redistribution except that:

- No protocol other than BGP can support Internet (or service provider) route scale.

- Leaking/redistribution has no loop prevention mechanism.

Tony