9.3 UDP Overview

Question 1

UDP

Answer 1

UDP is a best-effort transport protocol. UDP is a lightweight transport protocol that offers the same data segmentation and reassembly as TCP, but without TCP reliability and flow control.

UDP features include the following:

Data is reconstructed in the order that it is received.
Any segments that are lost are not resent.
There is no session establishment.
The sending is not informed about resource availability.

Question 2

UDP Header

Answer 2

UDP is a stateless protocol, meaning neither the client, nor the server, tracks the state of the communication session. If reliability is required when using UDP as the transport protocol, it must be handled by the application.

The blocks of communication in UDP are called datagrams, or segments. These datagrams are sent as best effort by the transport layer protocol.

The UDP header is far simpler than the TCP header because it only has four fields and requires 8 bytes (i.e., 64 bits)

Question 3

UDP Header Fields

Question 4

Applications that use UDP

Answer 4

There are three types of applications that are best suited for UDP:

Live video and multimedia applications - These applications can tolerate some data loss, but require little or no delay.
Examples include VoIP and live streaming video.

Simple request and reply applications - Applications with simple transactions where a host sends a request and may or may not receive a reply.
Examples include DNS and DHCP.

Applications that handle reliability themselves - Unidirectional communications where flow control, error detection, acknowledgments, and error recovery is not required, or can be handled by the application.
Examples include SNMP and TFTP.