Local Area Network - LAN Concept

Local Area Network - LAN : It is a network built in a small area. A Local Area Network (LAN) connection is a very secure connection because only the computers that are connected in it can transfer data among themselves, and it cannot be interfered with by external computers. That's why it is considered to be the most secure and safe.

The shortest LAN connection that can be made is by connecting two computers together. If you're wondering what the biggest LAN connection can be, it depends on your router switch. The more routers or switches you have, the more computers you can connect to. Through this article, complete information about Local Area Network will be given, so you have to read till the end so that your misconception about LAN can be removed.

What is Local Area Network - LAN?

As the name suggests, Local Area Network (LAN) is a network that is located for a limited areas. A LAN is a network consisting of two or more devices. In simple language, this network can also be established between 2 computers and can be arranged in thousand computers.  A group of computers, peripherals, and other devices that inter-operate, usually connected by no more than 1,000 feet of cable, and which allows people to share resources.

Local Area Network area ranges from about 500 meters to 1 kilometer, such as for office, home, airport, organization, school, college, business or any building or a group of them. We widely use LAN in schools, organizations, offices, and small businesses, data sharing, document printing and data saving.

To connect LAN network, we need Switch or Hub which is connected through Rj45 connector. It determines on our usage how many computers we have to connect together. We can also say that Ethernet cable is used by LAN to make connectivity among themselves. It is also believed that the speed of computers connected to LAN is also good.

Local Area Networks make our work very easy, such as offices, schools, colleges, due to being connected to each other LAN, they can also share their documents among themselves. You can also take out print. If you share a file to an Employee. So only that employee has that file open. And it can be accessed easily. And he can also take out the print of it.

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History of Local Area Networks - LAN

However, many different options have been used in the development history of LAN so let's try to know the development history of LAN. For the first time in the 1960s, more computers were installed in some large universities and there was a need for internet speed between these computers. Many techniques were used between 1970 and 1973.

Then during 1973 and 1974, Ethernet was developed in a company called XEROX PARC. And it was first used commercially in a bank called Chase Manhattan in New York. Thus we can say that New York is the first country which first used the LAN commercially.

Electronic voting took place in 1979 in the European Parliament controlling hundreds of microprocessors and was the first installation of a LAN via Ethernet. Then time passed and by gradually improving it, it was widely used today.

You can READ HERE : # FDDI Network : Fiber Distributed Data Interface

What are the types of Local Area Network?

Mainly LAN is considered in two types-

 

(1) LAN with cable 

(2) Wireless Local Area Network (WLAN)

LAN with cable : It is connected with a network cable, such as with one computer, another computer is also connected to the same cable and with the same printer, scanner, mouse, keyboard etc.

Wireless Local Area Network (WLAN) : A wireless computer network connects two or more computers using communication. The area of ​​this network is limited, such as within areas such as a school, home, computer laboratory, building and campus or office.

READ HERE : Bandwidth : The Concept of Bandwidth

How big area of ​​the LAN?

A LAN is established by the joining of two or more devices. Some devices like scanners, printers are permanently connected to the LAN and while some devices are temporarily connected like computers, laptops, mobiles, they can be connected and disconnected at any time.

And these two types of devices join together to form a LAN and the area of ​​the LAN is determined by how many devices you want to connect and in how many areas.

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Components used in LAN

Network Operating System : A family of programs that run on both a client and a server over a network. This can be either a separate program loaded (LANtastic) or part of the operating system (Microsoft).

Servers : computers that share their resources (hard disk drives, attached peripherals, communication circuit) with clients and other servers.

Networked Peripherals : Peripheral equipment contains specialized processors to run networking server software. They can be connected to a computer or can be connected directly to the LAN.

Network Interface Card (NIC) or LAN adapter card (located in the PC) : Connects the PC to the network via a cable. The function of NIC is that amplifies and encodes the data to be transmitted over the network. Software drivers are situated between the NIC and the network communication software. Network Software makes it possible to use the devices as if they were attached to the user’s own computer.

Backbone : A network that connects smaller LANs. Only bridges, routers, hubs/concentrators, and possibly, company servers, should be connected to Backbone. End users are not connected to backbone. Backbones are typically high-speed and use fiber-optic cables.

Hub : Stand-alone equipment with 24 physical interfaces connecting the nodes to the server. An active hub reproduces the signal using a repeater. The hub acts as a junction box and can be stacked as well.

Concentrator : A chassis mounted rack where the hubs are stacked. The advantage of a concentrator is its ability to accommodate a large number of nodes.

Bridge : A "store and forward" device that splits the shared LAN. The division of shared LANs reduces the number of nodes for hub services and is useful for increasing the average bandwidth per node.

LANs must be connected by the bridges of same type, for example, Ethernet, because a bridge does not have the ability to translate between different protocols. They also do not have the ability to open the message, read it and forward it to the desired address.

Router : An intelligent " STORE & FORWARD " device just like to a bridge except for the following important differences:

• LANs connected to traditional routers must be of the same type, for example, Ethernet, because a router does not have the ability to translate between different protocols (at one time, gateways were the only devices that could perform this translation). ). Over the past several years, however, routers have incorporated the functions of a gateway and many can now do protocol translation.

• Unlike bridges, routers have the ability to open the message, read it to the desired address, and forward it accordingly (some have error correction). The router acts as a "firewall", that is, it prevents unauthorized users from gaining access to the network. The router removes the outer envelope information from the data packet, allowing the network created with the router to transfer data more efficiently.

Cable : Cable plays a big role in connecting many metros together, without cable it is impossible to connect many metros together. It is impossible to establish internet or network without cable.

Mainly three types of cables are used to connect many computers together. (1) Twisted pair cable (2) coaxial cable (3) fiber optic cable.

Switch : What is switch? This is also a device working on a physical layer. It is also used in place of hub because it is more intelligent than hub. It sends the incoming data to its destination.

Modem : What is modem? Modem converts analog signal to digital signal and digital signal to analog signal. This modem is mostly used in telephone wire. What is Router? We use it to send data. The router acts as a junction, from where the network passes to many destinations. From here the router reaches our destination and we call this whole process Routing that is why it is also called Routing device.

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Features of LAN

• It is for small and medium sectors.

• This is a very famous network which is used for our school, college, business, building use. In the today world most widely used local-area network (LAN) transport protocol.

• It is a private network.

• It is very easy to set up this network.

• In this we can connect many computers simultaneously.

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Advantages of Local Area Network

A LAN has advantages only when many devices are connected at the same time. And devices can use a single Internet connection to share files, documents, and other information with each other. For example, you can print from the printer, scan documents or other things with the scanner and control other devices.

A local area network (LAN) connects various terminals or computers in a building or a limited geographic area. The connection between devices can be wired or wireless. Token Ring, Rennet and Wireless LAN following the IEEE 802.11 standard are examples of LAN technologies.

The connection between devices can be wired or wireless. Ethernet, Token Ring and Wireless LAN are examples of standard LAN technologies using IEEE 802.11.

READ HERE : Ethernet Switching Fundamentals

LAN Network Topologies

LAN works on the following topology: 

1. Star Topology

2. Bus Topology

3. Ring Topology

4. Mesh Topology

5. Hybrid Topology

6. Tree Topology

I will not write any long article to tell about these topologies, rather you will understand everything very easily from the image given below-

LAN Architecture

At first all LANs were shared but allowing only one transmission at a time. Like this arrangement of network, each device waits for access to the LAN before transmitting. Bandwidth is shared between nodes.

It is notice that the number of nodes increases, the bandwidth for each node decreases. To alleviate the problem of shared LANs, bridges and routers were created to divide traffic into smaller LANs. This allowed fewer devices to be connected to each hub, in effect, increasing the bandwidth on it.

Do you know when do you use a bridge and when do you use a router? If you want to connect two different networks, use a router as shown below. Use a bridge if you want to connect two similar networks.

You can READ HERE : Ethernet Network Structures

The switch was developed due to the problem of lack of bandwidth. A switch is basically a multi-port bridge. Switched LANs allow a virtual dedicated point-to-point connection between multiple devices on the LAN, allowing access to the full bandwidth for each connection (similar to phone systems experiencing multiple simultaneous phone calls). With the help of a switch, each node has access to the full bandwidth. Switches work best in a uniform traffic flow, for example, 10 to 20 desktop computers communicating with each other, as opposed to a single device receiving most of the traffic.

In full-duplex switching, each node has the same bandwidth for both transmitting and receiving, which can be used simultaneously, effectively doubling the bandwidth requirement. The node can "talk" and "hear" at the same time as in a telephone call. In such circumstances, special NICs, hubs and a high through-put backplane are required.

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LAN Access Methods

How data shares among common network path determine by Access methods:

 

CSMA/CD :

In this method, the NIC of a node can continuously sense the traffic on the network. When a node has a frame to send, the NIC checks to see if the network path is clear. If so, it sends the data. If data "collides" because two nodes send it at the same time, each node will sense it, stop sending and wait for a random amount of time before attempting to put its data on the network again. Collisions represent only 1 to 10 percent of the active time in the network. Equal access is guaranteed only on a probabilistic basis. Ethernet uses CSMA/CD.

Token passing :

The Token Ring Network and the FDDI Network use token passing. A node can only transmit on the network if it has a token. The token moves around the ring and stops at each node to see if it has anything to send. When a node is ready to send data, it indicate as busy the token frame, attaches its data and destination information, and passes the token. The token continues to travel within the network until it reaches its destination.

At this point the recipient deletes the information and the token indicates on the frame that the information has been received. The token is returned to the originator where the confirmation is made, then the token is issued as "un-engaged".

The Token Ring needs a "manager" or active monitor for the ring. Active nodes interact using their serial numbers to determine which node is the active monitor. The monitor initiates the first "free" token and performs normal ring operation maintenance. This method must be provide the equal access to the network.

Demand Priority: 

Demand Priority Token is a deterministic access method similar to ring passing. The hub scans the ports sequentially to determine which data is ready to transmit. This avoids collisions that can happen with CSMA/CD.

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Ethernet

Ethernet is the most widely used LAN technology as defined under IEEE standards 802.3. The reason behind its wide applicability is that it is easy to understand, implement, maintain and allow low-cost network implementations.

Also Ethernet provides flexibility in terms of topology that is allowed. Ethernet typically uses a bus topology. Now we are familiar that Ethernet operates in two layers of the OSI model, the physical layer and the data link layer.

For Ethernet, the protocol data unit is the frame because we mainly deal with DLLs. To handle collisions, the access control mechanism used in Ethernet is CSMA/CD.

Manchester encoding technology is used in Ethernet. Since we're talking about IEEE 802.3 standard Ethernet, 0 is represented by a high-to-low transition, a 1 by a low-to-high transition. In both Manchester Encoding and Differential Manchester, the encoding baud rate is twice the bit rate. An Ethernet LAN consists of network nodes and interconnecting media or links. There can be two types of network nodes.

1. Data Terminal Equipment

Generally, DTEs convert user information into signals or retrieve received signals, these are the end devices . We can say that DTEs are devices of personal computers, workstations, file servers or print servers also referred to as end stations. These devices are at the source or at the destination of the data frame. Data terminal equipment can be a single piece of equipment or several devices that are interconnected and perform all the necessary functions to allow the user to communicate. A user can interact with a DTE or a DTE can be a user.

2. Data Communication Equipment

DCEs devices receive and forward frames across the network , this is also called the intermediate network devices . They can be standalone devices such as repellers, network switches, routers or perhaps communication interface units such as interface cards and modems. The DCE used as a signal conversion, coding and it may be a part of DTE or also called the intermediate equipment.

We can say in other words that Ethernet is a shared bus network with a CSMA/CD (Carrier-Sensing Multiple Access with Collision Detect) access scheme. The encoding scheme for 10 Mbps Ethernet is Manchester; Fast Ethernet uses 4B/5B, and Gigabit Ethernet uses the 8B/10B encoding scheme.

Most Ethernet configurations today use a central hub as specified by the LAN standard. The Ring architecture is hidden inside the hub, and is located in the LAN Management Center. The 10BaseT, 10BaseFB, and 10BaseFL versions of the Ethernet standard specify a hub-based Ethernet architecture.

Ethernet accounts for about 90 percent of the copper and fiber networking nodes installed today. Most network designers prefer to work with Ethernet because it is a stable, well understood LAN standard; And the network standards that emerged after Ethernet have not succeeded in changing that.

Some companies have adopted standards such as Token Ring and FDDI in niche markets, but they have not achieved the same market share. Ethernet's ability to adapt to fast signaling rates is one reason it remains popular. Because Ethernet is familiar with standards committees, adjusting standards to meet new data rate requirements is much easier than adopting an entirely new standard. Invention of Fast Ethernet and the emergence of Gigabit Ethernet, IEEE 802.3 is not likely to be replaced as soon in future and is in a good position in the world to remain the most-used LAN standard.

The requirement of speeds continue to increase, the market has shifted from 10 Mbps Ethernet to Fast and Gigabit Ethernet and eventually to 10 Gbps. Equipment manufacturers are offering their customers a way to make this transition easier 10/100 hub, which has both 10 Mbps and 100 Mbps connections. These hubs are popular today, but the market will probably shift to 100/1000 hubs in the next few years.

• Fast Ethernet: Fast Ethernet can transfer data at a rate of 100 Mbit/s.

• Gigabit Ethernet: Gigabit Ethernet transfer data rate of 1,000 Mbit/s (1 Gbit/s).

•10 Gigabit Ethernet: 10 Gigabit Ethernet is the recent generation and delivers data rates of 10 Gbit/s (10,000 Mbit/s). It is typically used for backbones in high-end applications requiring high data content.

READ HERE : Ethernet Testing and Test Procedures

ALOHA

The Aloha Protocol was a part of project designed at the University of Hawaii. Data transmission was provided between several Hawaiian Islands computers connected by packet radio networks. Aloha provide multiple access protocol in the data link layer. It also determine that how many terminals can be used in the medium without interference or collisions. There are two different kinds of ALOHA-

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Pure Aloha:

Pure Aloha is an un-slated, decentralized and simple to implement protocol. In Pure ALOHA stations simply broadcast frames whenever they want to send data. Doesn't check if channel is busy before broadcast. If two or more stations transmit simultaneously, a collision occurs and the frames are lost. Whenever a station transmits a frame, it expects an acknowledgment from the receiver.

Within the time period if it is not received, the station consider that the frame or acknowledgment has been destroyed. Then the station waits a random amount of time and sends the frame again. This randomness helps to avoid more collisions. This plan works well in small networks where the load is not high. But in massively loaded networks, this plan fails miserably. This is the development of slotted aloha.

Slotted Aloha:

It is very similar to Pure Aloha with the only difference being the mode of transmission. Instead of transmitting the exact on demand time, the sender waits for some time. In allocated ALOHA the shared channel's time is divided into discrete intervals called slots. Stations are only able to send one frame at the beginning of the slot and only one frame is sent per slot.

If any station is not able to channel the frame at the beginning of the slot then it will have to wait till the start of the next time slot. Possibility of a collision may be occur if two stations try to send at the same time slot in the beginning. Count of collisions can be minimize by a large margin and the performance will be good compared to pure aloha.

READ HERE : Ethernet Testing Procedure

Last Word

Dear friends, I have tried my best to provide complete information about Local Area Network to you. How do you like this article and tell me by commenting. If there is anything left to write about LAN then suggest me, I will try to complete in another article. If you liked the given information then share it with others.