You could always checkout the wait_type and last_wait_type from sys.dm_exec_requests.

However, I would have to ask what the problem is? Is this a performance problem you are looking into?

Network i/o could most likely be SQL Server waiting on a response from the application. We've seen instances like this before, where the developer complains that the database is slow. We see that their last request was processed and are now waiting on the application. Come to find out they went into some kind of loop within the application.