Types Of Network

Published Date: 02 Nov 2017

LAN stands for Local Area Network. LAN connects computers within an organization or over relatively short distances. Some examples of simple LAN can be within an office building, school or sometimes even at homes where 2-3 computers are connected. In LAN there is a main computer which is called as server and remote computers accessing this server for data or any other communication are called as clients. LANs use Ethernet or Token Ring as connectivity technologies.

Wide Area Network - WAN

WAN, which stands for Wide Area Network, interconnects computers over long distances. WAN is a collection of LANs spread over large geographic locations. Internet is the largest WAN. For example, a company with offices in India, USA and Australia might have a LAN setup at each office. Through leased telephone lines, all three LANs can communicate with each other, forming a WAN.

The difference between WAN and LAN, is that the Wide Area Network uses dedicated computers at each end of the network that coordinate network traffic on the transmission lines. The use of these dedicated computers keeps the network running independently of any of the computers that use it.

Other Types of Area Networks

While LAN and WAN are the two basic types of networks, other networks are exists which are listed below.

Wireless Local Area Network - a LAN based on WiFi wireless network technology

Metropolitan Area Network - a network that spans over a large metropolitan area and it falls somewhere in between LAN and WAN.

Campus Area Network - a network spanning multiple LANs but smaller than a MAN, such as on a university or local business campus.

Storage Area Network - connects servers to data storage devices through a technology like Fibre Channel.

Overview of OSI Reference model

OSI (Open system Interconnection) reference model is a standard for communication and networking framework and implements protocols in seven layers.

The OSI model includes a set of protocols that define how data communications take place. OSI protocols were defined by the International organization for standardization (ISO).

The seven layers of OSI model are:

v Application layer(Layer 7)

v Presentation layer(Layer 6)

v Session layer(Layer 5)

v Transport layer(Layer 4)

v Network layer(Layer 3)

v Data link layer(Layer 2)

v Physical layer(Layer 1)

The OSI layers model has clear characteristics and functions for each layer. Layers 7 through 4 deals with end to end communications between data source and destinations and are termed as upper layers which deal with application issues, application layer is closest to the end user. Layers 3 to 1 deal with communications between network devices and termed as lower layers and they handle data transport issues. The physical layer and the data link layer are implemented in hardware and software. The lowest layer, the physical layer, is closest to the physical network medium (the wires, for example) and is responsible for placing data on the medium. The specific description for each layer is as follows.

APPLICATION LAYER - LAYER 7

Application layer provides facilitates interaction between user and an application and therefore helping him to communicate through the network. The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. When determining resource availability, the application layer must decide whether sufficient network resources for the requested communication exist. In synchronizing communication, all communication between applications requires cooperation that is managed by the application layer. Some examples of application layer implementations include Telnet, File Transfer Protocol (FTP), and Simple Mail Transfer Protocol (SMTP).

PRESENTATION LAYER - LAYER 6

The Presentation layer is responsible for protocol conversion, date encryption/decryption, Expanding graphics command and the date compression. This layer makes the communications between two host possible.The presentation layer, usually part of an operating system, converts incoming and outgoing data from one presentation format to another. Typical coding schemes include ASCII, EBCDIC, MPEG, GIF, and JPEG.

SESSION LAYER - LAYER 5

This layer is responsible for establishing the process-to-process communication between the host in the network. This layer is responsible for establishing and ending the sessions across the network. Opens manages, and closes conversations between two computers. It performs name recognition and the functions such as security, needed to allow two applications to communicate over the network, also provides error handling.

TRANSPORT LAYER - LAYER 4

This layer is responsible for end-to-end delivers of messages between the networked hosts. It first divides the streams of data into packets before transmission and then the receiving computer re-assembles the packets. It also checks for error free data delivery without loss or duplications. It ensures complete data transfer. Sequences data packets, and requests retransmission of missing packets. It also repackages messages for more efficient transmission over the network.

NETWORK LAYER - LAYER 3

This layer is responsible for translating the logical network address and names into their physical address ( MAC address). This layer is also responsible for addressing and managing network problems such as packet switching. It establishes, maintains and terminates network connections. Routes data packets across network segments. The most common network addressing protocols are IP, IPX, and AppleTalk. Typical routing protocols that run at this level are RIP, OSPF, IGRP, and NLSP.

DATALINK LAYER - LAYER 2

Data link layer is used by hubs and switches for their operation. It transmits frames of data from computer to computer on the same network segment. Ensures the reliability of the physical link established at layer 1. Standards define how data frames are recognized and provide the necessary flow control and error handling at the frame set. The data link layer is divided into two sublayers: The Media Access Control (MAC) layer and the Logical Link Control (LLC) layer. The MAC sublayer controls how a computer on the network gains access to the data and permission to transmit it. The LLC layer controls frame synchronization, flow control and error checking. The LLC manages communications between devices over a single link of a network.MAC is one of two sub layers that make up the Data Link Layer of the OSI model. The MAC layer is responsible for moving data packets to and from one Network Interface Card (NIC) to another across a shared channel.

PHYSICAL LAYER - LAYER 1

The Physical layer defines all the electrical and physical specifications for devices. This includes the layout of pins, voltages, and cable specifications. Hubs, repeaters and network adapters are physical-layer devices. It defines cabling and connections. Transmits data over the physical media. Physical Layer is also responsible for transmitting row bit stream over the physical cable.