Chapter 3 Transport Layer computer networking A note on the use of these ppt slides: 当变 Computer Networking: (including this one)and slide content to suit your needs.They obviously A Top Down Approach represent a lot of work on our part.In retum for use,we only ask the following: Featuring the Internet f you use these slides (e.g.,in a class)in substantially unaltered form, 3nd edition. that you mention their source (after all,we'd like people to use our book!) If you post any slides in substantially unaltered form on a ww site,that Jim Kurose,Keith Ross you note that they are adapted from(or perhaps identical to)our slides,and Addison-Wesley,July note our copyright of this material. 2004. Thanks and enjoy!JFK/KWR All material copyright 1996-2004 J.F Kurose and K.W.Ross,All Rights Reserved Transport Layer 3-1
Transport Layer 3-1 Chapter 3 Transport Layer Computer Networking: A Top Down Approach Featuring the Internet, 3nd edition. Jim Kurose, Keith Ross Addison-Wesley, July 2004. A note on the use of these ppt slides: We’re making these slides freely available to all (faculty, students, readers). They’re in powerpoint form so you 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) in substantially unaltered form, that you mention their source (after all, we’d like people to use our book!) ❑ If you post any slides in substantially unaltered form 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. Thanks and enjoy! JFK/KWR All material copyright 1996-2004 J.F Kurose and K.W. Ross, All Rights Reserved
Chapter 3:Transport Layer Our goals: understand principles learn about transport behind transport layer protocols in the layer services: Internet: o multiplexing/demultipl o UDP:connectionless exing transport o reliable data transfer o TCP:connection-oriented o flow control transport o congestion control o TCP congestion control Transport Layer 3-2
Transport Layer 3-2 Chapter 3: Transport Layer Our goals: understand principles behind transport layer services: multiplexing/demultipl exing 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
Chapter 3 outline 3.1 Transport-layer 3.5 Connection-oriented services transport:TCP 3.2 Multiplexing and o segment structure demultiplexing o reliable data transfer 3.3 Connectionless o flow control transport:UDP o connection management 3.4 Principles of ▣3.6 Principles of reliable data transfer congestion control 3.7 TCP congestion control Transport Layer 3-3
Transport Layer 3-3 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 provide logical communication application between app processes running on different hosts transport protocols run in end systems o send side:breaks app physica messages into segments passes to network layer o rcy side:reassembles segments into messages, passes to app layer more than one transport protocol available to apps o Internet:TCP and UDP Transport Layer 3-4
Transport Layer 3-4 Transport services and protocols provide logical communication between app processes running on different hosts transport protocols run in end systems send side: breaks app messages into segments, passes to network layer rcv side: reassembles segments into messages, passes to app layer more than one transport protocol available to apps Internet: TCP and UDP application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link network physical data link physical
Transport vs.network layer network layer:logical Household analogy: communication 12 kids sending letters to between hosts 12 kids transport layer:logical ▣processes=kids communication app messages letters between processes in envelopes o relies on,enhances, ▣hosts=houses network layer services ▣transport protocol= Ann and Bill network-layer protocol postal service Transport Layer 3-5
Transport Layer 3-5 Transport vs. network layer network layer: logical communication between hosts transport layer: logical communication between processes relies on, enhances, network layer services Household analogy: 12 kids sending letters to 12 kids processes = kids app messages = letters in envelopes hosts = houses transport protocol = Ann and Bill network-layer protocol = postal service
Internet transport-layer protocols reliable,in-order plication delivery (TCP) network o congestion control o flow control o connection setup unreliable,unordered delivery:UDP o no-frills extension of "best-effort"IP services not available: data link physical o delay guarantees o bandwidth guarantees Transport Layer 3-6
Transport Layer 3-6 Internet transport-layer protocols reliable, in-order delivery (TCP) congestion control flow control connection setup unreliable, unordered delivery: UDP no-frills extension of “best-effort” IP services not available: delay guarantees bandwidth guarantees application transport network data link physical application transport network data link physical network data link physical network data link physical network data link physical network data link network physical data link physical
Chapter 3 outline 3.1 Transport-layer 3.5 Connection-oriented services transport:TCP 3.2 Multiplexing and o segment structure demultiplexing o reliable data transfer 3.3 Connectionless o flow control transport:UDP o connection management 3.4 Principles of ▣3.6 Principles of reliable data transfer congestion control 3.7 TCP congestion control Transport Layer 3-7
Transport Layer 3-7 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/demultiplexing Demultiplexing at rcv host: Multiplexing at send host:_ delivering received segments gathering data from multiple to correct socket sockets,enveloping data with header(later used for demultiplexing) =socket process application P3 P1 D2 P4 application transport transport network network network link link link physical physical physical host 1 host 2 host 3 Transport Layer 3-8
Transport Layer 3-8 Multiplexing/demultiplexing delivering received segments to correct socket Demultiplexing at rcv host: gathering data from multiple sockets, enveloping data with header (later used for demultiplexing) Multiplexing at send host: application transport network link physical P1 application transport network link physical application transport network link physical P3 P2 P4 P1 host 1 host 2 host 3 = socket = process
How demultiplexing works host receives IP datagrams o each datagram has source 32 bits IP address,destination IP address source port dest port o each datagram carries 1 transport-layer segment other header fields o each segment has source, destination port number (recall:well-known port application numbers for specific data applications) (message) host uses IP addresses port numbers to direct segment to appropriate socket TCP/UDP segment format Transport Layer 3-9
Transport Layer 3-9 How demultiplexing works host receives IP datagrams each datagram has source IP address, destination IP address each datagram carries 1 transport-layer segment each segment has source, destination port number (recall: well-known port numbers for specific applications) host uses IP addresses & port numbers to direct segment to appropriate socket source port # dest port # 32 bits application data (message) other header fields TCP/UDP segment format
Connectionless (UDP)demultiplexing Create UDP sockets with When host receives UDP port numbers: segment: DatagramSocket mySocketl new o checks destination port DatagramSocket(99111); number in segment DatagramSocket mySocket2 new o directs UDP segment to DatagramSocket(99222); socket with that port UDP socket identified by number two-tuple: IP datagrams with different source IP (dest IP address,dest port number) addresses and/or source port numbers may be directed to the same socket Transport Layer 3-10
Transport Layer 3-10 Connectionless (UDP) demultiplexing Create UDP sockets with port numbers: DatagramSocket mySocket1 = new DatagramSocket(99111); DatagramSocket mySocket2 = new DatagramSocket(99222); UDP socket identified by two-tuple: (dest IP address, dest port number) When host receives UDP segment: checks destination port number in segment directs UDP segment to socket with that port number IP datagrams with different source IP addresses and/or source port numbers may be directed to the same socket