! Transport Layer

Layer 4 – The Transport Layer

     Layer 4, the transport layer of the OSI model, offers end-to-end communication between end devices through a network. Depending on the application, the transport layer either offers reliable, connection-oriented or connectionless, best-effort communications.

    Some of the functions offered by the transport layer include:

• Application identification

• Client-side entity identification

• Confirmation that the entire message arrived intact

• Segmentation of data for network transport

• Control of data flow to prevent memory overruns

• Establishment and maintenance of both ends of virtual circuits

• Transmission-error detection

• Realignment of segmented data in the correct order on the receiving side

• Multiplexing or sharing of multiple sessions over a single physical link

     The most common transport layer protocols are the connection-oriented TCP Transmission Control Protocol (TCP) and the connectionless UDP User Datagram Protocol (UDP).

ref: www.globalknowledge.com