Will network RPC block if a client does not respond?

I'm assuming network RPC calls are reliable. If a client does not respond to an RPC call, is the server stuck until it receives a response?

Ideally it would buffer things somehow, so that execution could continue even if a client dies completely.

 

RPC calls are asynchronous so they wont block the server in the sense that it will stop running until the RPC is sent and received.

They are reliable as well, and the order they are sent is the order they will be received (if received at all).

I am not sure what happens behind the scenes when a player disconnects. But if they do not respond to the server for a period of time, they will be disconnected from the server. OnPlayerDisconnected will be called, and I would bet that the RPCs destined for that player would just disappear.