Bitcoin client communication time constraints
Bitcoin client decides that the other client is not responding when it receives report from operation system that the connection is dead.

Bitcoin relies on OS implementation of TCP to send and receive messages. For example, by default, when connection was already established and Round Trip Time is known, Windows will try to resend data segment five times doubling wait time after each resend before reporting connection as dead. So the total wait time is: "Round Trip Time" * 2^(5-1) .

P.S. Timeouts are different for each type of message, e.g. total connection initiation timeout equals to 6 seconds .
TCP/IP Configuration Parameters