tcpipchapter9userdatagramprotocoludp

Transport Layer ProtocollTransport Layer protocol: To serve as the intermediary between the application programs and the network operationslResponsibilities Chapter 9 UDPlProcess-to-process communicationlUser datagramlChecksumlUDP operationlUse of UDPlUDP packageProcess-to-Process Comm.Port NumbersProcess-to-Process CommunicationlUDP负责将负责将IP数据报交付给适当的进程数据报交付给适当的进程Port Numbers VS. C/SlPort number: to define the processesIP Address & Port Number5200113193.14.26.75200113IANA RangeslWell-known portslAssigned and controlled by IANAPort numberPort numberWell-known Portslhttp:/www.iana.org/assignments/port-numbersSocket （套接字）（套接字）Addressesl(IP address, Port number) Socket AddresslProcess-to-process communication needs 2 Socket AddressesChapter 9 UDPlProcess-to-process communicationlUser datagramlChecksumlUDP operationlUse of UDPlUDP packageUser DatagramlUser Datagram Protocol，UDPIPLANsMANsWANsICMPIGMPARPRARPNetworkNetworkLayerLayerNetworkNetworkAccess LayerAccess LayerTCPUDPTransportTransportLayerLayerUser Datagram Format65507 = 65535 65507 = 65535 IP headerIP headerUDP headerUDP header20208 8Chapter 9 UDPlProcess-to-process communicationlUser datagramlChecksumlUDP operationlUse of UDPlUDP packageChecksumlUDP checksumPseudo Header FormatChapter 9 UDPlProcess-to-process communicationlUser datagramlChecksumlUDP operationlUse of UDPlUDP packageUDP OperationlA transport protocolEncapsulation & DecapsulationQueues in UDPl队列是与端口相关联在一起的队列是与端口相关联在一起的l进程进程入队列入队列/出队列出队列 or 进程进程入队列入队列Multiplexing & DemultiplexingChapter 9 UDPlProcess-to-process communicationlUser datagramlChecksumlUDP operationlUse of UDPlUDP packageUse of UDPl简单、简短的应用简单、简短的应用l简单的请求简单的请求-响应通信，如查询操作、网络管理响应通信，如查询操作、网络管理lIP phone，利用，利用UDP快捷的特点快捷的特点l适用于具有内部流控和差错控制的进程，如适用于具有内部流控和差错控制的进程，如TFTPl组播或广播应用组播或广播应用l某些路由协议，如某些路由协议，如RIPChapter 9 UDPlProcess-to-process communicationlUser datagramlChecksumlUDP operationlUse of UDPlUDP packageUDP PackageDiscussionl伪首部使得伪首部使得IP层和层和UDP层的界线模糊不清层的界线模糊不清IPIPI I1 1NI1NI1NI2NI2NI3NI3I I2 2I I3 31717sPorsPort t封装封装UDPUDP计算计算CSCSSummaryl进程到进程的通信进程到进程的通信l端点（端点（IP地址，端口）地址，端口）