If you want to get a PhD there's definitely a lot of research going into networks. Especially at the big computing labs (read DOE). So like LLNL, ORNL, Sandia, Argonne. I don't work in this area, but I do work on/with HPC stuff so there's a lot of talk about all this stuff. It definitely seems to be a big part of the ECP movement/funding. Data transport and memory storage are two of the biggest problems I hear being talked about in ECP.