I have two low-bandwidth connections in my network: VPN to the local office, and a slow line to central office. The P4 server is in central office, and we have a P4 proxy in the local office.
All my P4 activity currently goes through our local proxy, and is incredibly slow. Even when I need to transfer files I've already transferred, they still have to come over the VPN.
I could run a proxy on my own machine, but then files already on the local office proxy would have to come from central office again, requiring extra bandwidth on the already overloaded slow line.
Ideally, I would run a P4 proxy on my own machine, which attached not to the central office P4 server but to the local office P4 proxy. That way each file needs to traverse each slow link only once.