计算机网络(自顶向下方法)配套课件Chapter3.ppt

Chapter 3: Transport Layer Our goals: understand principles behind transport layer services: multiplexing/demultiplexing reliable data transfer flow control congestion control learn about transport layer protocols in the Internet: UDP: connectionless transport TCP: connection-oriented transport TCP congestion control Vocabulary and Term Transport (传输/运输) Multiplex/De-multiplex (多路复用/多路分流) UDP (User Datagram Protocol) (用户数据报协议) TCP (Transmission Control Protocol) (传输控制协议) Reliability (Error/Loss) Control (可靠性（差错/丢失）控制) QoS (Quality of Service) (服务质量) Segments (报文段) datagram (数据报/报文段) Packet (包/分组) Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable data transfer 3.5 Connection-oriented transport: TCP segment structure reliable data transfer flow control connection management 3.6 Principles of congestion control 3.7 TCP congestion control Transport services and protocols Transport vs. network layer transport layer: logical communication between processes relies on, enhances, network layer services network layer: logical communication between hosts Transport vs. network layer Household analogy: 12 kids sending letters to 12 kids processes = kids application messages = letters in envelopes hosts = houses transport protocol = Ann and Bill network-layer protocol = postal service Internet transport-layer protocols Chapter 3 outline 3.1 Transport-layer services 3.2 Multiplexing and demultiplexing 3.3 Connectionless transport: UDP 3.4 Principles of reliable data transfer 3.5 Connection-oriented transport: TCP segment structure reliable data transfer flow control connection management 3.6 Principles of congestion control 3.7 TCP congestion control Multiplexing De-multiplexing Multiplexing/demultiplexing How de-multiplexing works host receives IP datagrams each datagram has source IP address, destination IP address each datagram carries 1 transport-layer segment each