Processes communicating process:program clients,servers running within a host client process:process within same host,two that initiates processes communicate communication using inter-process communication(defined server process:process that waits to be by OS) contacted processes in different hosts communicate by aside:applications with exchanging messages P2P architectures have client processes server processes Application Layer 2-9Application Layer 2-9 Processes communicating process: program running within a host  within same host, two processes communicate using inter-process communication (defined by OS)  processes in different hosts communicate by exchanging messages client process: process that initiates communication server process: process that waits to be contacted  aside: applications with P2P architectures have client processes & server processes clients, servers