Local computer networks-LAN. Principles of construction, major components and basic topologies of LAN networks.
Local computer networks, the LAN
the LAN LANs are most widespread computer networks . They provide a number of advantages’s operating and simple to build in small (maximum distance of 2 subscriber to several km). LAN networks practically solve problems of user in one subregion.
“Local network” means a communication network with the following characteristics:
- The network is confined to a small space, usually a building or group of buildings;
- E network based on a common communications environment;
- The speed of data transfer is high – between 1Mbps and 100Mbps, as modern hardware allows speeds of 1 Gbps.
Defined by Abbreviationfinder, the LAN is becoming more popular in all organizations to increase productivity by using PCs.Here we will focus on design (usually called topology) hardware and software, normally used in small LAN to work in a group. The aim is to explain the terminology used by network specialists and the relationship between the individual parts.
Hardware components of the LAN: raborni stations-WS (work station), network interface cards-NIC, transmission medium-cable or other hub (repeater hub) server, bridge (bridge), router (router), switch switch:
- WS-these are the terminal devices through which the user logs in the network and performs processing of information;
- Network interface cards-this is a printed circuit board that connects between the computer and the LAN, so the computer becomes WS. Features Level 1 and 2 of the OSI model-communicates with the transmission medium
- Common transmission medium (cable, radio or IR environment). The cables are UTP, STP, coaxial and optical; UTP and STP are twisted pair. With STP, there shlirmovka and isolation (shielding). Speeds achieved by UTP and STP-up to 10Mbit / s. STP is noise tolerant. Coaxial cable (copper wire, insulation)-100Mbit / s-is expensive; fiber-optic cable – light wave, multiple for shorter distances Single-for longer, more expensive, but has a higher noise immunity;
- HUB (repeater hub)-Hub is a generic term for a device that acts as a central point for cables in the LAN. The simplest type hubs are devices that simply connect together cables. They are called hubs. In addition, there hubs with additional features including bridges, which connect the various network segments and routers that connect different types of local and global networks. These devices are specialized and are used in large and complex networks. Hub performs the basic functions of a repeater and / or hub and WS connected to the transmission medium. HUB-but it and switch. The most commonly performs the 2 functions;
- Server-a computer that has a rich processing capabilities, it has a host of common resources (file, print, etc.); administrative resources, resources for network communication resources for security protection;
- File Servers-large database files (large memory and fast). Service – application; tail;waiting => should be rules on the service – FIFO, deterministic priority, dynamic priority;
- Print Server-There peripherals such as printers (printer);
- Application-applications (user programs) for processing all or a certain number of subscribers to the network;
- Administration server-network management, control, special resources;
- Network server-network resources;
- Bridges-provides transfer of info. one domain of a LAN to another domain of the same LAN network;
- Switch-performs commutation in accordance with an address prizkan (MAC address).A typical communication networks. It can include the output of the local network.
Access to shared resources on a LAN has two technologies:
- -to-a peer a peer(equal access -resursite are distributed on all the network WS) WS there are any resources for general use. Use a small office;
- Client-server-in the LAN than there are WS and servers. Each as applications installed on the server are shared. The server connects to customers through service requests that server serves in different ways. Remote access, remote.
Technology to access shared resources on a server, installed shared resource.Ensuring the use of these resources becomes in the following ways:
- -to-a peer a peer p2p – technology equal access or clinet-server. In P2P – resources are allocated across all WS network (they are equal). All WS can use the resources of the other station. Disadvantages – expensive WS anywhere in the network, there are serious difficulties in organizing file management; very complex password protection.This technology is vvazmozhna and appropriate in very small LAN;
- Server-Clinet – architecture client / server can accommodate virtually unlimited number of users. In this architecture PCs connected to the network are designated either as clients or servers. From a hardware perspective, the server is nothing more than a workstation dedicated to the service of other workstations (clients). Data required by the customer are not located on the local machine, taken from the server.If the customer wants to send data to another client (eg e-mail), they are transmitted to the server, which sends them to the appropriate workstation. The server acts as a central storage of data files that are accessible to all workstations on the network.Therefore, the server is often called a file server. Advantages: provides economical creation of LAN; A wide variety of facilities in operation; Could effectively control access to resources (remote access).
Topoligiya local LAN network
1. Physical topology-a physical connection between the elements in a LAN-describes how connected WS, servers physically together. There are three basic topologies:
- star-is star.
Use combinations of three basic topology.
2. Logical topology-describes what basic logical connections are in a LAN.
- Bus topology. As a break of 2 seats remain 3 samosotyatelni stations;
- ring topology-the exchange of information is carried by the transmission medium, which has a ring shape. If the break can not exchange information;
- Hierarchical connection between the ring and star. Routers are full each binder with everyone. Very resistant in the event of collapse of connections. Uneconomic.
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