Local area network

1

LAN – local area network

overview:

1. Types of networks

2. Network topology

3. LAN local area networks

4. Introduction to TCP/IP

5. IEEE-802.11 / Wireless LAN

2

Networks:

A group of two or more computer systems linked together. There are many types of computer networks, including:

•local-area networks (LANs) : The computers are geographically close together (that is in the same building). (# relevant for Ecolog-Net)

•wide-area networks (WANs) : The computers are farther apart and are connected by telephone 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 user's home that connects a person's digital devices.

3

Network topology

Topology/structure Advantages Disadvantages

Bus structure -easy to install

-simply expandable

-short cable lengths

-net expansion limits

-by cable interrupt the 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

-simple extension

-high reliability

-high wiring expenditure

-net failure in case of failure or overloading of the hubs

(# relevant for Ecolog-Net)

4


Simple 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.

5


Hub:

A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN. A hub contains multiple ports. When a packet arrives at one port, it is copied to the other ports so that all segments of the LAN can see all packets.

Switch:

In networks, a device that filters and forwards packets between LAN segments.

6


Network with Internet entrance and print server

Router: A device that forwards data packets along networks.A router is connected to at least two networks, commonly two LANs or WANs or a LAN and its ISP’s network (Internet Service Provider).Routers are located at gateways, the places where two or more networks connect.

7


Radio network - Wireless LAN - WLAN

Instead 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.

8


Access point:AP Short for Access Point, a hardware device or a computer's software that acts as a communication hub for users of a wireless device to connect to a wired LAN. APs are important for providing heightened wireless security and for extending the physical range of service a wireless user has access to.

Network interface card:Often abbreviated as NIC, an expansion board you insert into a computer so the computer can be connected to a network. Most NICs are designed for a particular type of network, protocol, and media, although some can serve multiple networks.

9

Introduction to TCP/IP

TCP and IP were developed by a Department of Defence (DOD) research project to connect a number different networks designed by different vendors into a network of networks (the "Internet"). It was initially successful because it delivered a few basic services that everyone needs (file transfer, electronic mail, remote logon) across a very large 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 computer communications in today's networked world.

10


IP: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).

11


TCP:Abbreviation of Transmission Control Protocol.TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

TCP - is responsible for verifying the correct delivery of data from client to server. Data can be lost in the intermediate network. TCP adds support to detect errors or lost data and to trigger retransmission until the data is correctly and completely received.

12

IEEE-802.11 / Wireless LAN

IEEE:Abbreviation of Institute of Electrical and Electronics Engineers.The IEEE is best known for developing standards for the computer and electronics industry. In particular, the IEEE 802 standards for local-area networks are widely followed.

802.11:802.11 refers to a family of specifications developed by the IEEE for wireless LAN technology. 802.11 specifies an over-the-air interface between a wireless client and a base station or between two wireless clients.

13

IEEE-802.11 / Wireless LAN

•802.11 -- applies to wireless LANs and provides 1 or 2 Mbps transmission in the 2.4 GHz band using either frequency hopping spread spectrum (FHSS) or direct sequence spread spectrum (DSSS).

•802.11a -- an extension to 802.11 that applies to wireless LANs and provides up to 54 Mbps in the 5GHz band. 802.11a uses an orthogonal frequency division multiplexing encoding scheme rather than FHSS or DSSS.

•802.11b (also referred to as 802.11 High Rate or Wi-Fi) -- an extension to 802.11 that applies to wireless LANS and provides 11 Mbps transmission (with a fallback to 5.5, 2 and 1 Mbps) in the 2.4 GHz band. 802.11b uses only DSSS. 802.11b was a 1999 ratification to the original 802.11 standard, allowing wireless functionality comparable to Ethernet.

•802.11g -- applies to wireless LANs and provides 20+ Mbps in the 2.4 GHz band

•Wi-Fi – Wireless Fidelity

14

the datalogger company

Joachim Gau

ELPRO-BUCHS AG - Langäulistrasse 62 - CH-9471 Buchs SG – Switzerland

Tel: +41 (0)81 750 03 11 - Fax.: +41 (0)81 750 03 17

Mail: [email protected], ~ Internet: www.elpro.com,

Technology

Local area network