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Local area network


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Local area network

  1. 1. LAN – local area networkoverview:2. Types of networks3. Network topology4. LAN local area networks5. Introduction to TCP/IP6. IEEE-802.11 / Wireless LAN 1
  2. 2. Networks:A group of two or more computer systems linked together. There are many typesof computer networks, including:•local-area networks (LANs) : The computers are geographically close together (thatis in the same building). (# relevant for Ecolog-Net)•wide-area networks (WANs) : The computers are farther apart and are connected bytelephone lines or radio waves.•campus-area networks (CANs): The computers are within a limited geographic area,such as a campus or military base.•metropolitan-area networks (MANs): A data network designed for a town or city.•home-area networks (HANs): A network contained within a users home thatconnects a persons digital devices. 2
  3. 3. Network topology Topology/structure Advantages Disadvantages Bus structure -easy to install -net expansion limits -simply expandable -by cable interrupt the -short cable lengths net precipitates -complicated access methods Ring structure -large net expansion -complex error tracing -high wiring expenditure -when disturbances net failure Star structure -simple cross-linking -high wiring expenditure -simple extension -net failure in case of -high reliability failure or overloading of the hubs (# relevant for Ecolog-Net) 3
  4. 4. LAN – local area networkSimple network:A simple network consists of at least two computers, which are connected by a direct connection (crossover cable) or with a Hub or Switch. 4
  5. 5. LAN – local area networkHub:A common connection point for devices in a network. Hubs are commonly used toconnect segments of a LAN. A hub contains multiple ports. When a packet arrives atone port, it is copied to the other ports so that all segments of the LAN can see allpackets.Switch:In networks, a device that filters and forwards packets between LAN segments. 5
  6. 6. LAN – local area networkNetwork with Internet entrance and print serverRouter: A device that forwards data packets along networks.A router is connected to at least two networks, commonly two LANs or WANs or a LANand its ISP’s network (Internet Service Provider).Routers are located at gateways, the places where two or more networks connect. 6
  7. 7. LAN – local area networkRadio network - Wireless LAN - WLANInstead of cable-based connections;A simple Wireless LAN is a local network with an ACCESS POINT for WLAN adapter(network interface cards with antenna), which is attached to the computer or inserted. 7
  8. 8. LAN – local area networkAccess point:AP Short for Access Point, a hardware device or a computers software that acts as acommunication hub for users of a wireless device to connect to a wired LAN. APs areimportant for providing heightened wireless security and for extending the physicalrange of service a wireless user has access to.Network interface card:Often abbreviated as NIC, an expansion board you insert into a computer so thecomputer can be connected to a network. Most NICs are designed for a particular typeof network, protocol, and media, although some can serve multiple networks. 8
  9. 9. Introduction to TCP/IPTCP and IP were developed by a Department of Defence (DOD) research project toconnect a number different networks designed by different vendors into a network ofnetworks (the "Internet"). It was initially successful because it delivered a few basicservices that everyone needs (file transfer, electronic mail, remote logon) across a verylarge number of client and server systems.The substantial advantages of TCP/IP:•TCP/IP is bound to no manufacturer.•TCP/IP is usable in LANs and WANs.•TCP/IP makes application independent of the transmission system.The TCP/IP protocol has become the de facto standard for computercommunications in todays networked world. 9
  10. 10. Introduction to TCP/IPIP:Abbreviation of Internet Protocol.IP specifies the format of packets, also called datagrams, and the addressing scheme.IP is responsible for moving packet of data from node to node (a processing location).IP forwards each packet based on a four byte destination address (the IP number). 10
  11. 11. Introduction to TCP/IPTCP:Abbreviation of Transmission Control Protocol.TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol dealsonly with packets, TCP enables two hosts to establish a connection and exchangestreams of data. TCP guarantees delivery of data and also guarantees that packets willbe delivered in the same order in which they were sent.TCP - is responsible for verifying the correct delivery of data from client to server. Datacan be lost in the intermediate network. TCP adds support to detect errors or lost dataand to trigger retransmission until the data is correctly and completely received. 11
  12. 12. IEEE-802.11 / Wireless LANIEEE:Abbreviation of Institute of Electrical and Electronics Engineers.The IEEE is best known for developing standards for the computer and electronicsindustry. In particular, the IEEE 802 standards for local-area networks are widelyfollowed.802.11:802.11 refers to a family of specifications developed by the IEEE for wireless LANtechnology. 802.11 specifies an over-the-air interface between a wireless client and abase station or between two wireless clients. 12
  13. 13. IEEE-802.11 / Wireless LAN•802.11 -- applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4GHz band using either frequency hopping spread spectrum (FHSS) or direct sequencespread spectrum (DSSS).•802.11a -- an extension to 802.11 that applies to wireless LANs and provides up to 54Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexingencoding scheme rather than FHSS or DSSS.•802.11b (also referred to as 802.11 High Rate or Wi-Fi) -- an extension to 802.11 thatapplies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2and 1 Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a 1999ratification to the original 802.11 standard, allowing wireless functionality comparable toEthernet.•802.11g -- applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band•Wi-Fi – Wireless Fidelity 13
  14. 14. the datalogger companyJoachim GauELPRO-BUCHS AG - Langäulistrasse 62 - CH-9471 Buchs SG – SwitzerlandTel: +41 (0)81 750 03 11 - Fax.: +41 (0)81 750 03 17Mail:, ~ Internet:, 14