台北科技大学：《计算机网络》（英文版） NP04 11 Introduction

User Datagram Protocol (UDP) Chuan-Ming liu CSIE NTUT Spring 04, TAIWan CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 1 User Datagram Protocol (UDP) Chuan-Ming Liu CSIE, NTUT Spring ’04, TAIWAN

CONTENTS PROCESS-TO-PROCESS COMMUNICATION · USER DATAGRAM · CHECKSUM UDP OPERATION USE OF UDP UDP PACKAGE CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 2 CONTENTS • PROCESS-TO-PROCESS COMMUNICATION • USER DATAGRAM • CHECKSUM • UDP OPERATION • USE OF UDP • UDP PACKAGE

Introduction Transport layer protocol is to Create a process-to-process communication Provide control mechanisms Provide a connection mechanism for the processes CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 3 Introduction Transport layer protocol is to – Create a process-to-process communication – Provide control mechanisms – Provide a connection mechanism for the processes

Application la ayer SMTP FTP TFTP DNS SNMP BOOTP Transport layer TCP UDP IGMP ICMP Network IP ARP RARP Data link layer Underlying lan or Wan technology Physical CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 4

PROCESS TO PROCESS COMMUNICATION CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 5 PROCESS TO PROCESS COMMUNICATION 11.1

UDPⅴ ersus Ip Processes Processes (Running application programs) (Running application programs) Internet Domain of ip protoco Domain of UDP protocol CSIE NTUT TANAN Figure 11-2

CSIE, NTUT, TAIWAN 6 Figure 11-2 UDP versus IP

Port numbers client-server paradigm Process on the local host called client. needs services from a process on the remote host, called server Both processes(client and server) have the same name For communication. we need to define Local host Local process Remote host Remote process CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 7 Port Numbers • client-server paradigm – Process on the local host, called client, needs services from a process on the remote host, called server – Both processes (client and server) have the same name • For communication, we need to define – Local host – Local process – Remote host – Remote process

Port numbers Local and remote hosts are defined using Ip addresses Processes are defined by so called port number The port number in TCP/P are integers between 0 to 65.535 Client process randomly selects a port number by the udp-ephemeral port number TCP/IP uses universal port numbers for servers -well-known port numbers CSIE NTUT TANAN

CSIE, NTUT, TAIWAN 8 Port Numbers • Local and remote hosts are defined using IP addresses • Processes are defined by so called port number • The port number in TCP/IP are integers between 0 to 65,535 • Client process randomly selects a port number by the UDP – ephemeral port number • TCP/IP uses universal port numbers for servers – well-known port numbers

Port numbers Daytime Daytime client server F2.00 UDP UDP D13200 1352,0 Data CSIE NTUT TANAN Figure 11-3

CSIE, NTUT, TAIWAN 9 Figure 11-3 Port numbers

IP addresses versus port numbers Port numbe selects the process 193.14.26.7 IP header IP address 193.14.26.7 selects the host UDP header Figure 11-4

CSIE, NTUT, TAIWAN 10 Figure 11-4 IP addresses versus port numbers