Client-server architecture server: always-on host *permanent IP address data centers for scaling clients: communicate with server client/server may be intermittently connected may have dynamic IP addresses do not communicate directly with each other Application Layer 2-7Application Layer 2-7 Client-server architecture server:  always-on host  permanent IP address  data centers for scaling clients:  communicate with server  may be intermittently connected  may have dynamic IP addresses  do not communicate directly with each other client/server