Outlines requirements and time allocation 3.2 Multiplexing and Demultiplexing Application(多路复用与多路分解) 20分钟 gathering data from multiple app processes,enveloping data with header(later used for demultiplexing) Demultiplexing: delivering received segments to correct app layer processes TCP/UDP segment fommat multiplex ing/demultipexing 20分钟 based on sender,receiver port numbers,IP addresses source,dest port #s in each segment recall well-known port numbers for specific applications (讲解Multiplexing and Demultiplexing工作原理，重点介绍运输层数据报格式，用 启发、讨论式教学方式教学。) 3.3 Connectionless Transport:UDP(无连接运输：UDP) 3.3.1 UDP Segment Structure 30分钟 UDPsegment format [source port #]+[dest port ]+[length]+[checksum] +[Application data(message)] 3.3.2 UDP Checksum Sender: treat segment contents as sequence of 16-bit integers checksum:addition(1's complement sum)of segment contents sender puts checksum value into UDPchecksum field Receiver: 20分钟 ecksum equals checksum field value NO-error detected YES-no error detected.But maybe errors nonetheless?More later. (重点讲解UDP数据报格式，UDP检验码，用启发、讨论式教学方式教学。) 复习本次课的主要内容。 5分钟
16 Outlines, requirements and time allocation 3.2 Multiplexing and Demultiplexing Application（多路复用与多路分解） Multiplexing: gathering data from multiple app processes, enveloping data with header (later used for demultiplexing) Demultiplexing: delivering received segments to correct app layer processes TCP/UDP segment format multiplexing/demultiplexing: based on sender, receiver port numbers, IP addresses source, dest port #s in each segment recall: well-known port numbers for specific applications （讲解 Multiplexing and Demultiplexing 工作原理，重点介绍运输层数据报格式，用 启发、讨论式教学方式教学。） 3.3 Connectionless Transport: UDP（无连接运输：UDP） 3.3.1 UDP Segment Structure UDP segment format [source port #] + [dest port # ]+ [length] + [checksum] + [Application data(message)] 3.3.2 UDP Checksum Sender: treat segment contents as sequence of 16-bit integers checksum: addition (1’s complement sum) of segment contents sender puts checksum value into UDP checksum field Receiver: compute checksum of received segment check if computed checksum equals checksum field value: NO - error detected YES - no error detected. But maybe errors nonetheless? More later . （重点讲解 UDP 数据报格式，UDP 检验码，用启发、讨论式教学方式教学。） 复习本次课的主要内容。 20 分钟 20 分钟 30 分钟 20 分钟 5 分钟
Teaching Plan Name Zhang Yu-fei Academic Year 2013-2013 Term 2 Date 2013.04.10 Period 5-7 Textbook COMPUTER NETWORK10计算机科学与技术本科 Content Chapter3运输层 Teaching 3 urs Objectives 掌握可靠性传输协议内容：掌握可靠的管道数据传输协议。 Key points Principles of Reliable Data Transfer Poinso Go-Back-N(GBN),Selective Repeat(SR) Contfor sefuy http/wwwfeeditrtx http://wwwrf-dioror/f/rfe323.txt Teaching equipment Multimedia Related knowedge TCPAP Teaching methods 启发式、讨论式教学 Outlines requirements and time allocation 复习上次课的重要内容 5分钟 3.4 Principles of Reliable Data Transfer(可靠数据传输的原理) 3 4 1 Building a reliable Data transfer Rdt1.0:eliabe transfer over a reliable channel 15分钟 separate FSMs for sender,receiver Rdt2.0:channel with bit errors 15分钟 underlying channel may flip bits in packet rror dete megative acknowledgements NAKs)eceiver tells sender that pkt had ers sender retransmits pkt on receipt of NAK Rdt2.1:sender,handles garbled ACK/NAKs 20分钟 Rdt2.2:a NAK-free protocol g NAKs only receiver must explicitly include seq of pkt being ACKed duplicate ACK at sender results in same action as NAK:retransmit current pkt Rdt3.0:channels with errors and loss 20分钟 sender waits "reasonable"amount of time for ACK retransmits if noACK received in this time (重点讲解Reliable Data Transfer协议；用启发、讨论式教学方式教学。) 17
17 Teaching Plan Name Zhang Yu-fei Academic Year 2013-2013 Term 2 Date 2013.04.10 Period 5-7 Textbook COMPUTER NETWORK Specialty and Stratification 10 计算机科学与技术 本科 Content Chapter 3 运输层 Teaching hours 3 Objectives 掌握可靠性传输协议内容；掌握可靠的管道数据传输协议。 Key points Principles of Reliable Data Transfer Points difficult to understand Go-Back-N(GBN), Selective Repeat(SR) Content for self study http://www.rfc-editor.org/rfc/rf c793.txt, http://www.rfc-editor.org/rfc/rfc1323.txt Teaching equipment Multimedia Related knowledge TCP/IP Teaching methods 启发式、讨论式教学 Outlines, requirements and time allocation 复习上次课的重要内容 3.4 Principles of Reliable Data Transfer（可靠数据传输的原理） 3.4.1 Building a Reliable Data Transfer Rdt1.0: reliable transfer over a reliable channel underlying channel perfectly reliable: no bit erros, no loss of packets separate FSMs for sender, receiver Rdt2.0: channel with bit errors underlying channel may flip bits in packet error detection acknowledgements (ACKs): receiver tells sender that pkt received OK negative acknowledgements (NAKs): receiver tells sender that pkt had errors sender retransmits pkt on receipt of NAK Rdt2.1: sender, handles garbled ACK/NAKs Rdt2.2: a NAK-free protocol same functionality as rdt2.1, using NAKs only instead of NAK, receiver sends ACK for last pkt received OK receiver must explicitly include seq # of pkt being ACKed duplicate ACK at sender results in same action as NAK: retransmit current pkt Rdt3.0: channels with errors and loss sender waits “reasonable” amount of time for ACK retransmits if no ACK received in this time （重点讲解 Reliable Data Transfer 协议；用启发、讨论式教学方式教学。） 5 分钟 15 分钟 15 分钟 20 分钟 20 分钟
Outlines requirements and time allocation 42 Pipelined Reliable Data Transfer Protoco 20分钟 Pipelining:sender allows multiple,"in-flight",yet-to-be-acknowledged pkts range of sequence numbers must be increased buffering at sender and/or receiver Two generic foms of pipelined protocols go-Back-N,selective repeat 3.4.3Go-Back-N(GBN) 25分钟 Sender: k-bit seq in pkt header "window"of up to N.consecutive unack'ed pkts allowed ACK(n)ACKs all pkts up to,including"cumultive ACK" may deceive duplicate ACKs (see receiver) timer for each in-flight pkt timeout(n):retransmit pkt n and all higher seq#pkts in window Receiver simple: ACK-only:always send ACK for comrectly-received pkt with highest in-orders# may generate duplicate ACKs need only remember expectedseqnum out-of-order pkt: discard(don't buffer)>no receiver buffering! ACK pkt with highest in-order seq 344 Selective Repeat(SR) 25分钟 receiver individually acknowledges all correctly received pkts buffers pkts,as needed,for eventual in-order delivery to upper layer sender only resends pkts for which ACK not received sender timer for each unACKed pkt sender window N consecutive seq#'s again limits seq#s of sent,unACKed pkts (对比讲解Go-Back-N(GBN)和Selective Repeat(SR)区别；用启发、讨论式教学方 5分钟 式教学。) 复习本次课的主要内容
18 Outlines, requirements and time allocation 3.4.2 Pipelined Reliable Data Transfer Protocol Pipelining: sender allows multiple, “in-flight”, yet-to-be-acknowledged pkts range of sequence numbers must be increased buffering at sender and/or receiver Two generic forms of pipelined protocols: go-Back-N, selective repeat 3.4.3 Go-Back-N(GBN) Sender: k-bit seq # in pkt header “window” of up to N, consecutive unack’ed pkts allowed ACK(n): ACKs all pkts up to, including seq # n - “cumulative ACK” may deceive duplicate ACKs (see receiver) timer for each in-flight pkt timeout(n): retransmit pkt n and all higher seq # pkts in window Receiver simple: ACK-only: always send ACK for correctly-received pkt with highest in-order seq # may generate duplicate ACKs need only remember expectedseqnum out-of-order pkt: discard (don’t buffer) -> no receiver buffering! ACK pkt with highest in-order seq # 3.4.4 Selective Repeat(SR) receiver individually acknowledges all correctly received pkts buffers pkts, as needed, for eventual in-order delivery to upper layer sender only resends pkts for which ACK not received sender timer for each unACKed pkt sender window N consecutive seq #’s again limits seq #s of sent, unACKed pkts （对比讲解 Go-Back-N(GBN)和 Selective Repeat(SR)区别；用启发、讨论式教学方 式教学。） 复习本次课的主要内容。 20 分钟 25 分钟 25 分钟 5 分钟
Teaching Plan Name Zhang Yu-fei Academic Year 2013-2013 Term 2 Date 2013.04.17 Period 5-7 Textbook COMPUTER NETWORK10计算机科学与技术本科 Content Chapter3运输层 3 Objectives 熟悉流控制原理过程：掌握TCP段结构：掌握TCP的可靠性及流控制方法。 Key points Flow Control Poinso Round Trip Time and Timeout Contfor sefuy Some good hyperlinks fp/etlab.ohio-stateedu/pub/jainpapercn_av.pdf Teaching equipment Multimedia Related knowedge TCP Teaching methods 启发式、讨论式教学 Outlines requirements and time allocation 复习上次课的重要内容 5分钟 3.5 Connection-Oriented Transport:TCP(面向连接的运输：TCP) 3 51 The TCP Connection 20分钟 full duplex data:bi-directional data flow in same connection connection-ol nd:handshaking flow controlled:sender will not overwhelm receiver point-to-point:one sender,one receiver reliable,in-order byte steam:no "message boundaries" pipelined:siz send receive buffers 20分钟 3.5.2 TCP Segment Structure source port dest port# sequence number ackn vledgement number head len revr window size checksum ptr urgent data Options(variable length) application data(variable length) 3.5.3 Sequence Number and Acknowledgment Numbers 20分钟 Seq.#'s:byte "numbe f first byt (讲解TCP提供的服务，TCP数据报结构；用启发、讨论式教学方式教学。 9
19 Teaching Plan Name Zhang Yu-fei Academic Year 2013-2013 Term 2 Date 2013.04.17 Period 5-7 Textbook COMPUTER NETWORK Specialty and Stratification 10 计算机科学与技术 本科 Content Chapter 3 运输层 Teaching hours 3 Objectives 熟悉流控制原理过程；掌握 TCP 段结构；掌握 TCP 的可靠性及流控制方法。 Key points Flow Control Points difficult to understand Round Trip Time and Timeout Content for self study Some good hyperlinks, ftp://netlab.ohio-state.edu/pub/jain/papers/cong_av.pdf Teaching equipment Multimedia Related knowledge TCP Teaching methods 启发式、讨论式教学 Outlines, requirements and time allocation 复习上次课的重要内容 3.5 Connection-Oriented Transport: TCP（面向连接的运输：TCP） 3.5.1 The TCP Connection full duplex data: bi-directional data flow in same connection connection-oriented: handshaking flow controlled: sender will not overwhelm receiver point-to-point: one sender, one receiver reliable, in-order byte steam: no “message boundaries” pipelined: TCP congestion and flow control set window size send & receive buffers 3.5.2 TCP Segment Structure source port # dest port # sequence number acknowledgement number head len rcvr window size checksum ptr urgent data Options (variable length) application data (variable length) 3.5.3 Sequence Number and Acknowledgment Numbers Seq. #’s: byte stream “number” of first byte in segment’s data ACKs: seq # of next byte expected from other side, cumulative ACK （讲解 TCP 提供的服务，TCP 数据报结构；用启发、讨论式教学方式教学。） 5 分钟 20 分钟 20 分钟 20 分钟