Section 2.31 The TCP/IP reference model the de facto Internet standard demonstrates arbitrary nature of layers –various models are possible –OSI & TCP/IP are the two most important

Section 2.32 The TCP/IP reference model Specifications for development: –information flows regardless of the condition of the network –packets get to their destination every time –packets can travel from any point to any other point TCP/IP resulted –DoD project –standard on which the Internet has grown

Section 2.33 Layers of the TCP/IP model Four layers: –A pplication –T ransfer –I nternet –N etwork Access IMPORTANT--even though the names may be the same as the OSI layers, do not confuse the layers of the two models. The layers include different functions in each model.

Section 2.34 Application Layer One application layer handles all high-level protocols –Includes the functions of the OSI Presentation & Session layers –Assumes data is properly packaged for the next layer Handles issues of representation, encoding, and dialog control

Section 2.35 Transport Layer Quality of service –Reliability, flow control, error correction Uses TCP protocol –Transmission Control Protocol –Reliable, low-error –Packages application layer data into segments

Section 2.36 Internet Layer Sends source packets across the internetwork independent of path Uses IP –Internet Protocol Best Path determination Packet Switching –Logical connection formed by packets between hosts

Section 2.37 Network Access Layer Also Host to Network layer Deals with issues that an IP packet requires to actually make a physical link Includes LAN & WAN technology Includes all the OSI physical and data link layer details

Section 2.38 TCP/IP Protocols-- Application Layer Application layer protocols: –FTP: File Transfer Protocol –HTTP: Hypertext Transfer Protocol –SMTP: Simple Mail Transport Protocol –DNS: Domain Name Service –TFTP: Trivial File Transport Protocol Emphasizes flexibility for software developers

Section 2.39 TCP/IP Protocols-- Transport Layer TCP: Transmission Control Protocol UDP: User Datagram Protocol

Section TCP/IP Protocols-- Internet Layer Only one protocol –IP: Internet Protocol Deliberate design –Any computer can communicate at any time

Section Comparing TCP/IP with OSI

Section Comparing TCP/IP with OSI Similarities –both have layers –both have application layers, though they include very different services –both have comparable transport and network layers –packet switched (not circuit switched) technology is assumed –networking professionals need to know both

Section Comparing TCP/IP with OSI Differences –TCP/IP combines the presentation and session layer issues into the application layer –TCP/IP combines the OSI data link layer and physical layers into one layer--the network access layer –TCP/IP appears simpler because it has fewer layers –TCP/IP protocols are the standards around which the Internet is built

Section Conceptual nature of the OSI model No networks are built around specific OSI protocols Everyone uses the OSI model to guide their thinking –You will use the OSI model, but the TCP/IP protocols