1. TCP/IP: Basics1 User Datagram Protocol (UDP) Another protocol at transport layer is UDP. It is Connectionless protocol i.e. no need to establish & terminate connection. UDP delivers independent messages, called datagrams between applications or processes on host computers  end-to-end protocol. Message-oriented: An application using UDP sends and receives individual message. UDP does not divide a message into packets. Message must fit datagram.

2. TCP/IP: Basics2 User Datagram Protocol (UDP) Each datagram is independent of others. Each UDP message has the IP address and port number of the destination and the source of the message. IP addresses may be omitted. UDP provides no sequencing, i.e., individual messages are not numbered. As a result datagrams may arrive out of sequence. There is no mechanism for reliability.

3. TCP/IP: Basics3 User Datagram Protocol (UDP) Used in applications where speed is more important than reliability for example voice and video transmission. Can not be used for data communication like files and messages. TCP is used.

4. TCP/IP: Basics4 User Datagram Protocol (UDP) For generality, endpoints of UDP are called protocol ports or ports. ''Best effort'' delivery - datagrams may be lost, delivered out of order, etc.

5. TCP/IP: Basics5 UDP & TCP: Layering Both TCP and UDP use IP to provide data delivery for application protocols Hardware Network Interface Internet (IP) Transport: UDP, TCP Application

6. TCP/IP: Basics6 UDP Headers UDP datagrams have a header that follows the hardware and IP headers: UDP header is very simple: Has Port numbers, Message length, Checksum DataApplicationUDPIPHardware

7. TCP/IP: Basics7 UDP Headers Data UDP ChecksumUDP Message Length UDP Destination portUDP Source port

8. TCP/IP: Basics8 Selecting UDP port numbers Communicating computers must agree on a port number – fixed beforehand. –''Server'' opens selected port and waits for incoming messages –''Client'' selects local port and sends message to selected port Services provided by many computers use reserved, well-known port numbers: e.g. ECHO. Other services use dynamically assigned port numbers.

9. TCP/IP: Basics9 Simple Network Management Protocol (SNMP) snmp161 Network Time Protocol (NTP)ntp123 Trivial File Transfer Protocol (TFTP)tftp69 DNSdomain53 System time (seconds since 1970)time37 Character generatorchargen19 Quote of the dayquote17 Time of day (ASCII)daytime13 System statisticssystat11 Discard inputdiscard9 Echo input back to senderecho7 DescriptionNamePort Well - Known Port Numbers