Transport layer is responsible for the overall end-to-end transfer of application data. Because different applications have different requirements, there are multiple Transport layer protocols. Transmission Control Protocol (TCP) and User Datagram Protocol (UDP). TCP and UDP headers. Port Addressing, socket pair. Types of port numbers: Well Known Ports (0 to 1023), Registered Ports (1024 to 49151) and Dynamic or Private ‘Ephemeral’ Ports (49152 to 65535). Netstat command : examines the open connections on a host. Transport Layer Functions. TCP Connection Establishment (3-way handshake). Connection Management - Flow Control through buffering, congestion avoidance, and windowing. Flow Control – Reducing the window size . TCP Connection Termination (4-way Handshake).