TCP/IP Illustrated, Vol. 1 Quotes

“iterative and concurrent. An iterative server iterates through the following steps: I1. Wait for a client request to arrive. I2. Process the client request. I3. Send the response back to the client that sent the request. I4. Go back to step I1. The problem with an iterative server occurs when step I2 takes a long time. During this time no other clients are serviced. A concurrent server, on the other hand, performs the following steps: C1. Wait for a client request to arrive. C2. Start a new server instance to handle this client’s request. This may involve creating a new process, task, or thread, depending on what the underlying operating system supports. This new server handles one client’s entire request. When the requested task”
― W. Richard Stevens, TCP/IP Illustrated, Volume 1: The Protocols