[DEV DOCS] Networking in distributed

We require a page in distributed docs to outline how networking works

* What kind of servers do we have
* How do they speak to each others, e.g. what is a comm, what is a batchedcomm, what is a stream
* When and why do we pool comms and when is a comm long living
* What happens (or should happen) if a comm breaks (e.g. stream comm broken removes a worker while direct comms are usually retried/handled)
* When do we use what kind of comm?
* What kind of RPC protocol are we using?

This list is exhaustive. This issue can be used to refine what the content should look like