The way it's described sounds similar to SMTP, where intermediate servers hold the entire message and keep trying until they succeed (or time out).

Wikipedia's information is quite dense and hard to skim. (The "spray and wait" protocol does sound like fun, though.)

http://en.wikipedia.org/wiki/Delay_Tolerant_Networking

http://en.wikipedia.org/wiki/Routing_in_delay_tolerant_netwo...

Lag.

It is fun to consider a problem where the speed of light is just too slow. Even when Mars is at its closest and the atmosphere is impossibly ideal, radio waves would take 3.1 minutes to get there.

Man, that would make a lot of internet-related things unusable from Mars and beyond: online gaming, flash, software updates, etc.

It would also make use of a DVCS like git a must for interplanetary hosting services.