What is a LAN (Local Area Network)?

A LAN (Local Area Network) is the connection between several computers and peripherals. The physical extension of a network is limited to a building or a 200-meter environment or can reach a distance of 1 km with repeaters.

LAN (Yerel Alan Ağı) Nedir?

What is LAN?

The most common application is to connect personal computers and workstations in offices, factories to exchange resources and exchange data/applications. In short, it enables connections between two or more computers.

The term local network includes the Hardware and Software required to connect different devices and process information.


The first networks are the same as those used by mainframes and connected terminals. These environments were implemented with IBM’s SNA (Network Systems Architecture) and Digital Network Architecture.

LANs (Local Area Networks) were born from the PC revolution. LANs allowed Users in a relatively small geographic area to exchange messages and files and access shared resources such as Network or File Servers or Application Servers.

With the advent of Netware, a new solution has emerged that offers much more sophisticated support for more than forty cards, cables and operating systems available than most competitors offer. Netware dominated the LAN area of ​​personal computers from 1983 to the mid-1990s when Microsoft launched Windows NT Advanced Server and Windows for WorkGroups.

Only Banyan VINES from all competitors of Netware had similar technical strength, but Banyan gained a secure base. Microsoft and 3Com worked together to create a simple network operating system consisting of 3Com’s 3+ Sharing kernel, Microsoft’s Lan Network Manager and IBM Server. None of these projects were very satisfying.


A company usually needs many computers for its own printers to print reports, data stored on one of the computers is very likely to be needed on other computers of the company. Therefore, the data must be shared with other computers on the network, as it will cause delays for two users to copy this data and reproduce storage resources unnecessarily.

The solution to these problems is called the local area network, it allows us to share Databases and Peripherals like a Printer using other communication tools like Modem, ISDN Card, Email and Chat.

It allows us to perform a distributed transaction, that is, tasks can be divided into different nodes and enable us to integrate the processes and data of each User into a corporate operating system. Having the ability to centralize information or procedures makes team management easier.

In addition, a local area network provides significant savings over time as information and labor management are provided. In addition, since many Peripherals are not required to purchase, less paper is consumed by employees and can use a single Broadband or Telephone connection shared by several networked computers.

Important Features

  • Broadcast technology with a shared transmission medium.
  • Transmission capacity between 1 Mbps and 1 Gbps.
  • The maximum extension does not exceed 3 km (an FDDI can reach 200 km).
  • Use of special communication tools.
  • The simplicity of the transmission environment you use (Coaxial Cable, Telephone Cables, and Fiber Optic).
  • Ease of making changes to hardware and software.
  • Wide variety of connected devices.
  • Possibility to connect with other networks.

Network Topology

Network topology defines the structure of a LAN network. Part of the topological definition is Physical Topology, the actual arrangement of Cables or the medium. The other section is the Logical Topology that defines the Hosts’ method of accessing data sending tools. The most commonly used topologies are:

Physical Topologies

A circular bus topology uses a single Backbone cable that must be terminated at both ends. All hosts connect directly to this backbone.

   Ring Topology

Ring topology connects one host to another and the last host to the first. This creates a physical cable loop.

   Star Topology

Star topology connects all cables to a central concentration point. Connects individual stars to each other by connecting Extended Star Topology Hubs or Switches. This topology can expand the reach and scope of the network. A hierarchical topology is like an expanded star. However, instead of connecting HUBs or switches, the system connects to a computer that controls the traffic of the topology.

   Mesh Topology

Mesh topology is applied to provide the highest possible protection to prevent service interruption. Using network topology in networked control systems of a nuclear power plant would be an excellent example. In this topology, each host has its own connections with other hosts. Although the Internet has multiple ways to any location, it does not adopt the Full Mesh Topology.

   Tree Topology

The Tree Topology has multiple connected terminals so that the network branches from a base server.

Logical Topologies

The logical topology of a LAN network is how servers communicate over the environment. The two most common types of logical topology are Broadcast and Token Transfer.

   Broadcast Topology

Broadcast Topology simply means that each Host sends its data to all other Hosts in the network environment. Stations do not have a queue to follow to use the network. Ethernet works on a first-come, first-serve basis.

   Token Transmission Topology

Token Transmission Topology controls access to the network by transmitting an electronic Token to each Host in turn. When a host receives the token, that host can send data over the network. If there is no data to be sent on the host machine, it passes the coin to the next host and the process is repeated. Two examples of networks using token transmission are Token Ring and Fiber Distributed Data Interface (FDDI). Arcnet is a variation of Token Ring and FDDI. Arcnet is the transmission of Tokensen’s Bus Topology.


The offer of local area networks is very wide, there are solutions for almost any situation. We can choose the cable type, Topology and even the transmission type that best suits our needs. However, the most common solutions for this entire offer are three: Ethernet, Token Ring, and Arcnet.

Comparison of Network Types

In order to select the most suitable network type according to the needs, we should consider different factors such as a number of stations, the maximum distance between them, wiring difficulty, response speed or sending information to other stations outside the network.

With reference to the previous parameters, we can compare the three types of networks discussed above. To do this, let’s assume that Ethernet and Arcnet types are installed with Coaxial Cable and Shielded Twisted Pair Cable Token Ring. Regarding installation facilities, it is the easiest to install due to Arcnet topology.

As for speed, Ethernet operates at 10/100/1000 Mb/s, Arcnet 2.5 Mb/s, and Token Ring at 4 Mb/s. Currently, Token Ring has a 16 Mb/s version, but a more expensive cable type is needed.

Compared to the price, Arcnet is the lowest cost; On the one hand, Token Ring turns out to have the highest price, as the cards inserted into PCs for such networks are cheaper, and on the other, the wiring is more accessible. Although PC cards are cheaper than those of the Ethernet network, their cables are expensive, among other things, because they require an MAU for each group of eight users.


Server: One of the computers that will share hardware and software resources with other computers on the network. Its characteristics are its computing power, the importance of the information it stores, and the connection with the resources you want to share.

Workstation: Computers that take on the role of workstations take advantage of, or remain in, the services provided by the Servers they can access, as well as the resources offered by the network.

Gateway: Hardware and Software that provides communication between the local network and large computers (Host computer). The Gateway adapts the host’s communication protocols to those on the network, and vice versa.

Bridge or Bridges: A hardware and software that allows two local networks to connect. The internal bridge is the bridge installed on the network server, and the external bridge is the bridge built on the Workstation of the same network. Bridges can also be local or remote. Local bridges are bridges that connect to networks in the same building, using both internal and external connections. Remote bridges connect different networks by making the connection over public networks such as telephone network, ISDN or packet switching network.

Network Card: Also known as NICs (Network Interface Card). It basically performs the intermediary function between the Computer and the Network. The communication protocols of the network are recorded in this. Communication with the computer is normally done through its expansion slots, whether ISA, PCI or PCMCIA. On some computers, this adapter is directly integrated into the motherboard.

Media: consists of cables and connectors that connect the components of the network. The most commonly used physical medium is twisted pair cable, cable pair, coaxial cable, and fiber optic.

Wiring Hubs: a bus LAN uses only network cards and coaxial cables at the stations in addition to the connectors, but this method makes it difficult to maintain the network as the entire network stops working if any connection fails. To avoid these problems, local area networks use cable hubs to make station connections, instead of distributing connections, the hub centralizes it on a single device, protects their light indicators and prevents one of them from causing a malfunction.

There are two types of wiring hubs:

1. Passive hubs: they function as a simple hub, the main function of which is to connect the entire Network.
2. Active hubs: In addition to the basic hub functions, they amplify and reproduce received signals before they are sent.

Cable hubs have two types of connections to join stations and other hubs, thereby increasing the size of the network. Cable connection hubs are classified based on the way they establish connections internally and distribute messages. This feature is called logical topology.

There are two main types:

1. Logical bus topology (HUB): these devices send signals from all connected outputs, making the network act as a bus.
2. Hubs with ring logic topology (MAU): the network acts as a ring that sends the signal arriving from one port to another.

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