《计算机网络 Computer Networking》课程PPT教学课件（A Top Down Approach，8th edition）Chapter 3 Transport Layer

Chapter 3 James F.Kurose Keith W.Ross Transport Layer A note on the use of these PowerPoint slides: We're making these slides freely available to all(faculty,students, readers).They're in PowerPoint form so you see the animations;and can add,modify,and delete slides (including this one)and slide content to suit your needs.They obviously represent a lot of work on our part. COMPUTER In return for use,we only ask the following: NETWORKING If you use these slides(e.g.,in a class)that you mention their A TOP-DOWN APPROACH source(after all,we'd like people to use our book!) If you post any slides on a www site,that you note that they are adapted from(or perhaps identical to)our slides,and note our copyright of this material. Computer Networking:A For a revision history,see the slide note for this page. Top-Down Approach Thanks and enjoy!JFK/KWR 8th edition All material copyright 1996-2020 Jim Kurose,Keith Ross J.F Kurose and K.W.Ross,All Rights Reserved Pearson,2020 Transport Layer:3-1

Computer Networking: A Top-Down Approach 8 th edition Jim Kurose, Keith Ross Pearson, 2020 Chapter 3 Transport Layer A note on the use of these PowerPoint slides: We’re making these slides freely available to all (faculty, students, readers). They’re in PowerPoint form so you see the animations; and can add, modify, and delete slides (including this one) and slide content to suit your needs. They obviously represent a lot of work on our part. In return for use, we only ask the following: ▪ If you use these slides (e.g., in a class) that you mention their source (after all, we’d like people to use our book!) ▪ If you post any slides on a www site, that you note that they are adapted from (or perhaps identical to) our slides, and note our copyright of this material. For a revision history, see the slide note for this page. Thanks and enjoy! JFK/KWR All material copyright 1996-2020 J.F Kurose and K.W. Ross, All Rights Reserved Transport Layer: 3-1

Transport layer:overview Our goal: understand principles learn about Internet transport behind transport layer layer protocols: services: UDP:connectionless transport ·multiplexing, TCP:connection-oriented reliable demultiplexing transport reliable data transfer TCP congestion control 。flow control 。congestion control Transport Layer:3-2

Transport layer: overview Our goal: ▪ understand principles behind transport layer services: • multiplexing, demultiplexing • reliable data transfer • flow control • congestion control ▪ learn about Internet transport layer protocols: • UDP: connectionless transport • TCP: connection-oriented reliable transport • TCP congestion control Transport Layer: 3-2

Transport layer:roadmap -Transport-layer services Multiplexing and demultiplexing Connectionless transport:UDP Principles of reliable data transfer Connection-oriented transport:TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer:3-3

Transport layer: roadmap ▪ Transport-layer services ▪ Multiplexing and demultiplexing ▪ Connectionless transport: UDP ▪ Principles of reliable data transfer ▪ Connection-oriented transport: TCP ▪ Principles of congestion control ▪ TCP congestion control ▪ Evolution of transport-layer functionality Transport Layer: 3-3

Transport services and protocols application transport provide logical communication mob network data link between application processes national or global ISP running on different hosts logica transport protocols actions in end systems: local or sender:breaks application messages end-end transport into segments,passes to network layer home network receiver:reassembles segments into messages,passes to application layer network two transport protocols available to data link physical Internet applications enterprise ·TCP,UDP network Transport Layer:3-4

Transport services and protocols ▪ provide logical communication between application processes running on different hosts mobile network home network enterprise network national or global ISP local or regional ISP datacenter network content provider network application transport network data link physical application transport network data link physical ▪ transport protocols actions in end systems: • sender: breaks application messages into segments, passes to network layer • receiver: reassembles segments into messages, passes to application layer ▪ two transport protocols available to Internet applications • TCP, UDP Transport Layer: 3-4

Transport vs.network layer services and protocols household analogy: 12 kids in Ann's house sending letters to 12 kids in Bill's house: ■hosts=houses ■processes=kids "app messages=letters in envelopes HERE was an old woman who lived in a shoe. She had so many children,she didn't know what to do Transport Layer:3-5

Transport vs. network layer services and protocols household analogy: 12 kids in Ann’s house sending letters to 12 kids in Bill’s house: ▪ hosts = houses ▪ processes = kids ▪ app messages = letters in envelopes ▪ transport protocol = Ann and Bill who demux to in-house siblings ▪ network-layer protocol = postal service Transport Layer: 3-5

Transport vs.network layer services and protocols -network layer:logical household analogy: communication between 12 kids in Ann's house sending letters to 12 kids in Bill's hosts house: transport layer:logical ■hosts=houses communication between ■processes=kids "app messages=letters in processes envelopes relies on,enhances,network layer services Transport Layer:3-6

Transport vs. network layer services and protocols ▪network layer: logical communication between hosts ▪transport layer: logical communication between processes • relies on, enhances, network layer services household analogy: 12 kids in Ann’s house sending letters to 12 kids in Bill’s house: ▪ hosts = houses ▪ processes = kids ▪ app messages = letters in envelopes ▪ transport protocol = Ann and Bill who demux to in-house siblings ▪ network-layer protocol = postal service Transport Layer: 3-6

Transport Layer Actions Sender: application is passed an application- ap app.msg layer message transport ■determines segment Th app.msg header fields values network(IP) ■creates segment network(IP) link passes segment to IP link physical physical Transport Layer:3-7

physical link network (IP) application physical link network (IP) application transport Transport Layer Actions Sender: ▪ is passed an application- app. msg layer message ▪ determines segment header fields values ▪ creates segment ▪ passes segment to IP transport TThh app. msg Transport Layer: 3-7

Transport Layer Actions Receiver: application receives segment from IP application 工 ■checks header values trapp.msg extracts application-layer transport message network(IP) demultiplexes message up network(IP) link to application via socket link nhysical physical Th app.msg Transport Layer:3-8

physical link network (IP) application physical link network (IP) application transport Transport Layer Actions transport Receiver: app. msg ▪ extracts application-layer message ▪ checks header values ▪ receives segment from IP Th app. msg ▪ demultiplexes message up to application via socket Transport Layer: 3-8

Two principal Internet transport protocols application transport TCP:Transmission Control Protocol mob network data link physica reliable,in-order delivery national or global ISP ·congestion control logica ·flow control 。connection setup local or -UDP:User Datagram Protocol regionalsp end-end transport unreliable,unordered delivery home network no-frills extension of "best-effort"IP appucation -services not available: transport network data link ·delay guarantees physical bandwidth guarantees enterprise network Transport Layer:3-9

Two principal Internet transport protocols mobile network home network enterprise network national or global ISP local or regional ISP datacenter network content provider network application transport network data link physical application transport network data link physical ▪TCP: Transmission Control Protocol • reliable, in-order delivery • congestion control • flow control • connection setup ▪UDP: User Datagram Protocol • unreliable, unordered delivery • no-frills extension of “best-effort” IP ▪ services not available: • delay guarantees • bandwidth guarantees Transport Layer: 3-9

Chapter 3:roadmap Transport-layer services -Multiplexing and demultiplexing Connectionless transport:UDP Principles of reliable data transfer Connection-oriented transport:TCP Principles of congestion control TCP congestion control Evolution of transport-layer functionality Transport Layer:3-10

Chapter 3: roadmap ▪ Transport-layer services ▪ Multiplexing and demultiplexing ▪ Connectionless transport: UDP ▪ Principles of reliable data transfer ▪ Connection-oriented transport: TCP ▪ Principles of congestion control ▪ TCP congestion control ▪ Evolution of transport-layer functionality Transport Layer: 3-10