IST362. Transport Layer Protocols. UDP.

Transport Layer Protocols.

A transport layer protocol provides for logical connection between application processes running on different hosts.

A network layer protocol provides for logical connection between hosts.

Example about two houses (families exchanging letters).

Multiplexing and demultiplexing (port numbers). Well known port numbers (old version) and new one.

Speed -- Faster speed because of connectionless.
Resources -- No connection state, hence this protocol does not require much resources on both end hosts.
Packet header overhead -- This protocol doesn't send much extra information, hence its header is very small (only 8 bytes).
Application-level control over what data is sent, and when -- Due to absence of any congestion control UDP immediately passes data to the network layer.


1	Source port number (UDP service ID for sender of this packet)
2	Destination port number (UDP service ID for receiver of this packet)
3	UDP packet length (byte length includes UDP header and data)
4	UDP checksum (UDP header and data and portions of IP header included)
...	Data
...	Data

source port: port number of the sender
destination port: port number of the receiver
packet length: length in bytes of UDP header and data
checksum (of header and data): standard IP checksum algorithm applied to UDP header and data. See this page for an example of check sum calculation. For more detailed information see RFC-1071.

For official description of UDP see RFC-768.