I just learned about Eduroam:

Eduroam which stands for Education Roaming, is a RADIUS-based infrastructure that uses 802.1X security technology to allow for inter-institutional roaming. Being part of eduroam allows users visiting another institution connected to eduroam to log on to the WLAN using the same credentialsusername and passwordthe user would use if he were at his home institution. Depending on local policies at the visited institutions, eduroam participants may also have additional resources at their disposal. All this with a minimum administrative overhead.

Apparently UiO is a member through Uninett, and I see that there are lots of other members around Europe. I always have some kind of problem when connecting to networks at other institutions, so I am looking forward to test how Eduroam works next time I’m out travelling.