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Transcript
FCN week 10 Network Standards and Models The need for standards Standards organisations OSI model TCP/IP model FCN week 10 Standards Processes or protocols that has been endorsed by the networking industry Ratified by a standards organization Documented agreements containing technical specifications or other precise criteria that stipulate how a particular product or service should be designed or performed Slide 2 FCN week 10 Organisations responsible for standards American National Standards Institute (ANSI) Electronics Industry Alliance (EIA) Institute of Electrical and Electronic Engineers (IEEE) International Organization for Standardization (ISO) International Telecommunication Union (ITU) FCN week 10 IEEE Networking Specifications Slide 4 FCN week 10 The Seven Layer OSI Model At the top, the Application layer provides OS services for application software The OSI model breaks the process of communication down into several layers Different stages data must/may go through as it travels from one device to another Nmemonics – Please do not throw sausage pizza away! All PC’s seem to network data poorly At the bottom, the Physical layer deals with wiring issues Application Presentation Session Transport Network Data link Physical Slide 5 FCN week 10 OSI model – Why bother? Real-world network protocols don’t implement the OSI seven layer protocol stack model But nearly all network protocols are based on a simplified layered model The layered model helps us think about the many processes involved in communicating over networks A good model provides support for thinking Slide 6 FCN week 10 OSI model – Why bother? Benefits include assists in protocol design fosters competition changes in one layer do not affect other layers provides a common language Slide 7 FCN week 10 The Application Layer Provides interface to the software enabling programs to use network devices Definition of the way that network services use the network Defines how many services work, including File sharing, Network Printing, Message Services etc E.g Application Program Interface (API) Routine that allows a program to interact with the operating system Belongs to the Application layer of OSI Model Applications HTTP Email Etc... Slide 8 FCN week 10 The Presentation Layer This layer “presents” data, which is to say it does some pre-processing, such as data compression encryption character set conversion Translates between the application and the network Slide 9 FCN week 10 The Session Layer A communications management layer Defines how two computers synchronise, maintain and close a communication session This includes such things as security authentication acknowledgement of data transfer establishing and relinquishing a connection identity Slide 10 FCN week 10 The Transport Layer Data packet management Ensures that chunks of data have been transferred without error – does lots of error and flow control Takes data and packs it into chunks or chops it up into chunks suitable for transmission Takes chunks and unpacks them or combines them into data streams Slide 11 FCN week 10 The Network Layer This is Internet Protocol address layer for path selection around the network Routing of packets uses IP addresses Network Layer Address Resides at Network level of OSI Model Follows hierarchical addressing scheme Can be assigned through operating system software Slide 12 FCN week 10 The Data Link Layer Decodes packets into what are called frames which contain Physical source and destination addressing data validity / error checking The network technology being used will influence how this layer works e.g. Ethernet, token ring ….. To accommodate shared access for multiple network nodes, the IEEE expanded the OSI Model by separating the Data Link layer into two sublayers Logical Link Control (LLC) sublayer Media Access Control (MAC) sublayer Slide 13 FCN week 10 The Physical Layer This is the physical networking media layer which includes the cabling technology Defines the transmission technique and the hardware definitions (connectors and so on) Networking may take place over copper cables, optical fibres, infra-red radiation, radio waves… and this variation should be transparent to the user Slide 14 FCN week 10 Communication Between Two Systems Slide 15 FCN week 10 TCP/IP The problem with the OSI model is a ‘concept’ not an actual implementation TCP/IP is a set of protocols used. FCN week 10 What is TCP/IP? TCP/IP stands for Transport Control Protocol / Internet Protocol suite. TCP/IP was created in 1983 to replace NCP. TCP/IP can successfully switch packets from all shapes and sizes and varieties of networks. Therfore TCP/IP has become the backbone of the Internet and its composite LANs and WANs, due to it's ability to switch packets from computer systems on any network to another network, regardless of network peculiarities, operating system differences and other packet differences Slide 17 FCN week 10 What is TCP/IP? The higher layer, Transmission Control Protocol, manages the assembling of a message or file into smaller packets that are transmitted over the Internet and received by a TCP layer that reassembles the packets into the original message. The lower layer, Internet Protocol, handles the address part of each packet so that it gets to the right destination. Each gateway computer on the network checks this address to see where to forward the message. Slide 18 FCN week 10 What is TCP/IP? Even though some packets from the same message are routed differently than others, they'll be reassembled at the destination. Uses the client/server model of communication in which a computer user (a client) requests and is provided a service (such as sending a Web page) by another computer (a server) in the network. TCP/IP communication is primarily point-to-point, meaning each communication is from one point (or host computer) in the network to another point or host computer. TCP/IP and the higher-level applications that use it are collectively said to be "stateless" because each client request is considered a new request unrelated to any previous one Slide 19 FCN week 10 What is TCP/IP? Being stateless frees network paths so that everyone can use them continuously. You will be familiar application protocols that use TCP/IP to get to the Internet. These include the World Wide Web's Hypertext Transfer Protocol (HTTP) File Transfer Protocol (FTP) Telnet (Telnet) which lets you logon to remote computers Simple Mail Transfer Protocol (SMTP). Slide 20 FCN week 10 TCP/IP vs OSI OSI Model TCP/IP Slide 21 FCN week 10 Layers with TCP/IP and OSI Model FCN week 10 Conclusion We have discussed:Organizations that set standards for networking Standard “root concepts” of networking Layered models of processes and layers in our conceptual model of networking Why protocols are required for interoperability Details of the seven layers of the OSI model Slide 23