EE 281 Lecture 6: Quick revision
Document Summary
The network layer (layer 3 of the osi stack) is responsible for machine-to-machine communication. The transport layer, one layer higher (layer 4), provides logical communication channels between applications. An application can create an arbitrary number of these channels, each of which has another endpoint on some process running on some host. Writing data onto this channel delivers it to the application that is reading data on the other end of this channel. The transport layer is responsible for implementing this abstraction. Routers in the network are unaware of this concept since they only provide network layer (machine-to-machine) services. There are multiple transport protocols available on top of ip, including tcp, udp, and sctp. Tcp and udp are by far the most popular of these. Two responsibilities of the transport layer are multiplexing and demultiplexing communication channels on the network and, in some cases, implementing reliable data transfer.
