TCP/IP architectureSlide 2TCP/IP architecture—application layerTCP/IP architecture—transport layerSlide 5Slide 6The procedure executed at routersSlide 8TCP/IP big picture: how the layers work togetherSlide 10Slide 11Slide 12Example1—Workstation sends a IP datagram to the server (cont.)Slide 14Example2: server sends IP datagram to PC (cont.)Slide 16Slide 17Big picture: web document browsingSlide 19Slide 20Sever processes multiple requestsSlide 22Berkeley socket interfaceSlide 24Slide 25Slide 26Application protocols and TCP/IP utilities1TCP/IP architecture•A set of protocols allowing communication across diverse networks•Out of ARPANET•Emphasize on robustness regarding to failure•Emphasize on Flexibility in operating on diverse networks•As a result, TCP/IP architecture2ApplicationLayerTransportLayerInternetLayerNetworkInterfaceApplicationLayerTransportLayerInternetLayerNetworkInterface(a)(b)Figure 2.10TCP/IP network architectureTCP/IP model does not require strict layering3TCP/IP architecture—application layer•Provide services that can be used by other applications•Incorporate the functions of top 3 OSI layers •E.g., HTTP protocol, format in request, dialogue between client and server–http request/response contains format information, so transformation.–a web page may contain text, graphics, Macromedia Flash objects and perhaps a Java applet . Different files, different downloads, the browser keeps tracks of downloads.4TCP/IP architecture—transport layer•Application layer directly run over the transport layer, corresponding to OSI transport layer.•Two kinds of services: TCP & UDP.•TCP—Transmission Control Protocol, reliable connect-oriented transfer of a byte stream.•UDP—User Datagram Protocol, best-effort connectionless transfer of individual messages.5ApplicationTransportInternetNetwork InterfaceApplicationTransportInternet Network InterfaceInternet Network InterfaceNetwork 1 Network 2Machine AMachine BRouter/GatewayFigure 2.11TCP/IP architecture-- Internet layer 1. Transfer of information across networks through gateways/routers2. Corresponding to OSI network layer: routing and congestion control3. Global unique IP address and IP packets4. Best-effort connectionless IP packet transfer: no setup, routed independently, robust, out of order, duplicate, or lose of packet6ApplicationTransportInternetNetwork InterfaceApplicationTransportInternet Network InterfaceInternetNetwork InterfaceSNetwork 1 Network 2Machine AMachine BRouter/GatewayFigure 2.11TCP/IP architecture-- Network interface layer1. Concerned with network-specific aspects of the transfer of packets2. Corresponding to part of OSI network layer and data link layer3. Different network interfaces: X.25, ATM, frame relay, Ethernet, etc IP packetPacketof network1Packetof network1IP packetIP packetPacketof network2IP packetPacketof network27The procedure executed at routers1. Router receives a frame from one network (e.g., N1) through its physical layer2. The data link entity for N1 extracts the IP packet from the frame and passes the IP packet up to its network entity.3. The network entity checks destination IP address (finds the packet is not for itself) and determines the next hop based on destination IP address (i.e., routing) , this next hop router will be in another network (e.g. N2)4. Network entity passes the IP packet down to the data link entity for N2 5. Data link entity for N2 encapsulates the IP packet in a frame of N2 and passes the frame down to physical layer for transmission to the next router through network N2.8HTTPSMTPRTPTCPUDPIPNetwork Interface 1Network Interface 3Network Interface 2DNSFigure 2.12TCP/IP protocol graphApp.TransportInternetTCP/UDP Provides a network independentplatformIP provides independence from underlyingnetworks(e.g., Ethernet driver) (e.g., PPP driver)9TCP/IP big picture: how the layers work together•Examples of each of the layers•How the layers interact across the interfaces•How PDUs of a layer are built and what key information is in the header•Relationship between physical address and IP address•How an IP packet is routed across several networks10Net InterfaceIPTCP/UDPHTTP etc.Net InterfacesIPNet InterfaceIPTCP/UDPHTTP etc.Ethernet PPPRouterrouter(1,1)s(1,2)w(2,1)(1,3) r(2,2)PPPEthernet(a)(b)ServerPCFigure 2.13 An internet consisting of an Ethernet LAN and a point-to-point link11router(1,1)s(1,2)w(2,1)(1,3) r(2,2)PPPEthernetFigure 2.13•PPP is also a specific network•IP address: network ID + host ID, such as (1,1),(2,2)…•Physical address (such as s, r,…): •For Ethernet, each machine in an Ethernet has an NIC card with a global unique flat 48-bit address•For PPP, no need for physical address•Router has two IP addresses: (1,3), (2,1)12Ethernet driverIPTCP/UDPHTTP etc.Ethernet driverIPTCP/UDPHTTP etc.Ethernetrouter(1,1)s(1,2)w(2,1)(1,3) r(2,2)PPPEthernet(a)(b)ServerFigure 2.13Workstation(1,2)(1,1) data w,s, IP (1,2)(1.1) data w,s, IP (1,2)(1.1) data(1,2)(1,1) data0. Assumed server’s IP is known to workstation, if not,… 1.Workstation (IP entity) finds server’s physical address2.IP entity forms and passes IP packet down to Ethernet driver along with physical addresses w, s3. Ethernet driver forms Ethernet frame and broadcast4. Server NIC captures the frame due to its address s5. Find it is an IP so pass up to IP entityExample 1:Workstation sends an IP datagram to the server13Example1—Workstation sends a IP datagram to the server (cont.)•How does workstation know the server’s IP address?First search in its cache, if not found, query by DNS and cache it•IP entity in workstation knows that the server is in the same network, why? Because of the same network ID•How to know the server’s physical address ? –looks up its mapping table to try to find server’s physical address s. if server’s physical address is not known,–by ARP (Address Resolution Protocol) to find it.14Net InterfaceIPTCP/UDPHTTP etc.Net InterfaceSIPNet InterfaceIPTCP/UDPHTTP etc.EthernetPPPRouterrouter(1,1)s(1,2)w(2,1)(1,3) r(2,2)PPPEthernet(a)(b)ServerPCFigure 2.13 Example 2: server sends a IP datagram to PC(1,1)(2,2) datas,r,IP (1,1)(2,2) data(1,1)(2,2) datar,pc,IP (1,1)(2,2) data(1,1)(2,2) data1. Server forms IP packet with PC as destination 2. Server sends packet to router first by broadcast3. Router finds the packet is not for itself, so sends to PC4. PC finds the IP packet is for it,so