Spring EE4272 Switch vs. Router Switch:  Def. 1: A network node that forwards packets from inputs to outputs based on header information in each packet. It differs from a router mainly in that it typically does not interconnect networks of different types. (Peterson)  Switch fabric: The component of a switch that directs packets from their inputs to the correct outputs. (Peterson) Router:  Def. 1: A network node connected to two or more networks that forwards packets form on network to another. (Peterson)  Def. 2: An internetworking device that connects two computer networks. It makes use of an internet protocol and assumes that all of the attached devices on the networks use the same communications architecture and protocols. A router operates at OSI layer 3. (Stallings)

Spring EE4272 Cost-Effective Resource Sharing Must share (multiplex) network resources (nodes and links) among multiple users B B C C A A B C A B C A DMUXMUX (a) (b) Trunk group

Spring EE4272 Conventional Multiplexing Strategies Synchronous Time- Division Multiplexing (STDM) With TDM, each channel gets all of the bandwidth periodically during brief intervals of time. Frequency-Division Multiplexing (FDM) With FDM, each channel continuously gets a fraction of the bandwidth

Spring EE4272 Net Interface IP TCP HTTP Net Interface IP Net Interface IP TCP HTTP EthernetPPP Router router PPP Ethernet (a) (b) PC

Spring EE4272 Application 1 Socket socket interface user kernel Application 2 user kernel Underlying communication Protocols Communications network Socket socket interface Socket API

Spring EE4272 Socket API