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Transcript
Introduction to Networking Overview • • • • • We will briefly cover: The role of data networking Key components of any data network Converged networks Network architectures • We will start with a high-level view and end with a low-level view of networking Introduction to Networking Why do we use networks? • “Connectivity”, the need to communicate (with whom?) • Hardware resource sharing • e.g. printers, mapped drives • Application sharing • e.g. administrative systems • Group working • e.g. video conferences • Backup and data security • e.g. duplicate data in separate physical location • Remote configuration and management • e.g. technical staff can audit, fix and install software remotely Introduction to Networking Networks supporting the way we live • • • • • • The Internet - an integral part of our daily routines Decide what to wear using online current weather conditions Find the least congested route to your destination Display weather and traffic video from webcams Check your bank balance and pay bills electronically Receive and send e-mail, or make an Internet phone call, at an Internet cafe over lunch • Download new recipes and cooking techniques • Post and share your photographs, home videos, and experiences with friends or with the world. Introduction to Networking Networks supporting the way we live • Education • E-learning • Resources • Businesses • Intranets - enables businesses to communicate and perform transactions among global employee and branch locations • Extranets - provides suppliers, vendors, and customers limited access to corporate data • Remote workers - data network enables them to work as if they were on-site, with access to all the network-based tools normally available for their jobs • Socializing • Online games, interest groups, Instant messaging • Online entertainment Introduction to Networking Data Communication System Elements • Messages: Information that travels from one device to another • Devices: Systems on the network that exchange messages with each other • Protocols: Rules or agreements to govern how the messages are sent, directed, received and interpreted • Medium: A means of interconnecting devices to transport messages from one to another Introduction to Networking Why segment messages? • Communication (music, video or an e-mail message) • sent across a network as one massive continuous stream of bits • no other device would be able to send or receive messages on the same network while this data transfer was in progress • large streams of data would result in significant delays • if a link failed during transmission, the complete message would be lost - and then have to be retransmitted in full • So divide the data into smaller, more manageable pieces to send over the network • Segmentation • many different conversations can be interleaved on the network • segmentation can increase the reliability of network communications Introduction to Networking Circuit Switching • A temporary path, or circuit, is created through the various switching locations to use for the duration of the multi-segment message transmission • If any link or device participating in the circuit fails, the transfer is dropped • Priority is given to maintaining existing circuit connections, at the expense of new circuit requests • Since there is a finite capacity to create new circuits, it is possible to occasionally get a message that all circuits are busy and a call cannot be placed Introduction to Networking Circuit Switching Introduction to Networking Information as “packets” • Imagine writing a long letter to someone • But only having postcards on which to write… • You would write your letter, then send lots of individual postcards • Each one would need a stamp and an address • And you would have to number the postcards • What if one postcard failed to arrive? Introduction to Networking Packet Switching • Messages are chopped up into small chunks called “packets” before transmission • Each packet has an “address” attached • Each packet could be sent via a different route, depending on network traffic and available routes • Packets are received at the destination (sometimes out of order) and the message is reassembled Introduction to Networking Packet Switching Introduction to Networking Devices • Message source and destination • Computers, telephones, cameras, music systems, printers and game consoles • Intermediary devices • components that make it possible for message to be directed across the network - exist between the source and destination devices • Router, switch, access point, proxy server, snoop/filter system… Introduction to Networking Devices Introduction to Networking Protocols • Devices interconnected by medium to provide services must be governed by rules • The format or structure of the message • The method by which networking devices share information about pathways with other networks • How and when error and system messages are passed between devices • The setup and termination of data transfer sessions • some common services and a protocol most directly associated • WWW – HTTP • E-mail – SMTP • IP Telephony- SIP • TCP/IP (Transmission Control Protocol/Internet Protocol) • primary protocol of the Internet • used in home and business networks • TCP/IP specify the formatting, addressing and routing mechanisms that ensure messages are delivered to the correct recipient Introduction to Networking Medium • Devices must be interconnected • Wired • Copper – electrical signal • twisted pair telephone wire • coaxial • Unshielded Twisted Pair (UTP) • Optical Fiber – light signal • Wireless • Earth's atmosphere or space microwaves signals • home wireless connection • terrestrial wireless connection • Satellite communication Introduction to Networking Data Communications • Local Area Networks (LANs) link together systems within the same site, often the same lab or floor • Wide Area Networks (WANs) link together sites that may be distributed over a large geographic area • Example: Staffordshire University network • There is a variety of (often incompatible) hardware and software systems available for networking • Large businesses may have multiple LANs per site, interconnected across sites by WANs or MANs Introduction to Networking Criteria and Balances • High Speed - usually lowest in LANs, high in WANs and highest in backbones (but note that some WANs are slow, LANs are getting faster) • Low Latency - long delay times cause confusion and inefficiency • High Reliability - a network full of error messages and repeated information is inefficient • Cost, maintainability, ease of management, security, scalability, robustness, fitness for purpose