Depending on length of time the network is "out" there's a avariety of things that could occur. In general, the master would kick off a bgsave and the slave would re-bootstrap once it received said snapshot.
that's totally correct. In the case of a redis replication, the ssh tunnel failing would be quite costly, since the whole database will have to be send again since the slave would do a SYNC op. And that can be multiple GB in our case. But so far, we haven't experience it.