Basic of Layer 4

Provides transparent transfer of data between end hosts.

Provides (or doesn't provide) various services to applications:

• reliable data transfer

• error recovery

• data sequencing

• flow control

Provides Layer 4 addressing (port numbers).

• Identify the Application Layer protocol.

• Provides session multiplexing.

In this context, port, does not refer to the physical interfaces/ports on network devices.

• The following ranges have been designated by IANA (Internet Assigned Numbers Authority)

  • Well-known port numbers: 0 -1023

  • Registered port numbers: 1024 - 49151

  • Ephemeral/private/dynamic port numbers: 49152 - 65535