if you allow external peering anywhere, the need for tunneling to the one and only border router at UCSD to go to Internet disappears since each subnet can peer with any other local network, even at a local Internet Exchange Point, and get transit to Internet locally. This means that a specific subnet will not depend on the global Internet connectivity to get to a local destination outside AMPRnet. The idea is to keep local traffic local.

We can use dedicated terrestrial wireless links at different amateur frequencies, amateur satellites or maybe even some dedicated wired stretches (god forbid :-) if nothing else is available. On stretches where we by no means can come up with a dedicated link, we can still tunnel.... The internal intradomain routing can be set up statically or using an intradomain routing protocol such as OSPF in each AMPRnet island and, if needed, export routes between islands using iBGP as opposed to the eBGP functionality used in Interdomain routing.