1. 1 UDP : User Datagram Protocol Computer Network System Sirak Kaewjamnong

2. 2 UDP : User Datagram Protocol RFC 768 connectionless protocol (no connection establishment) provide unreliable service use socket as TCP

3. 3 UDP Encapsulation With Ethernet frame protocol type in IP header = 17 Ethernet headerIP headerUDP headerdata UDP datagram

4. 4 Ports Port : A 16 bits address allocated for the most common application level service UDP and TCP use port addressing to deliver information to applications Service are known by port number –FTP 20, TELNET 23, SMTP 25, HTTP 80

5. 5 Ports Port numbers are generally allocated by 0 not used 1- 255 Reserves port to well known service 256 - 1023 Other reserve port 1024 - 65535 user defined server ports UNIX store general used ports in /etc/service

6. 6 Sockets Socket : a pair of the IP address and the port number 172.28.80.96, 5160 IP address is a unique to a node, the port is unique on a node the socket gives a unique identification of an application layer service IP address Port number

7. 7 Socket Address A connections identified by the socket address at its to ends –client socket : 172.28.80.96,3000; 192.168.100.3,21 –server socket : 192.168.100.3,21 ; 172.28.80.96,3000 IP 172.28.80.96 Client port: 3000 IP 192.168.100.3 Server port: 21 connection

8. 8 UDP Format Source and destination port : 16, 16 identify applications at ends of the connection length: 16 - length of datagram including header and data checksum :16 -one ’ s complement of header and data including pseudo data Source port :16Destination port: 16 UDP length :16Checksum : 16 data 0 15 16 31

9. 9 UDP Pseudo Header 0 7 8 15 16 31 Source IP address : 32 Destination IP address : 32 Zero:8Protocol : 8UDP length :16 Source port : 16Destination port : 16 UDP length : 16Checksum : 16 Data …. Pseudo header UDP header

10. 10 UDP Pseudo Header Include destination for double checking that destination is correct if datagrams be an odd number of bytes, UDP append a pad byte of 0, just for computation 0 indicates no checksum (checksum disable) if compute checksum is 0, it stores as all one bits (65,535)

11. 11 UDP for Application TFTP DNS RPC, NFS SNMP