Data Communications and Networking CSCS 311 Lecture 4 Amjad Hussain Zahid

Data Communications and Networking

CSCS 311

Lecture 4

Amjad Hussain Zahid

Lecture Focus:

Data Communications and NetworkingLecture 4

Networking Distributed Processing Network Criteria Physical Structures Categories of Networks


Categories of Networks:

THREE Categories

Local Area Network (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN)

NETWORK

Local Area Network

( LAN )

Metropolitan Area Network

( MAN )

Wide Area Network

( WAN )

The category into which a network falls is determined by its size(area).

According to geographical limits, the networks are divided into following categories:



Local Area Network ( LAN )

A Local Area Network is usually privately owned and links the devices in a single office, building or campus. Widely used to connect personal computers and workstations in company

offices and factories with high speed data Transfer rate up to 100 Mbps.

LAN size is limited to a few kilometers.

One of the computers may be given a large capacity disk drive and may become a server to the other clients. Software can be stored on this server and used as needed by the whole group.

In general, a LAN will use only one type of transmission medium.

This is generally less expensive Technology.







Depending on the needs of an organization and the type of technology used, a LAN can be as simple as two PCs and a printer in someone's home / office; or it can extend throughout a company and include audio and video peripherals.




LANs are designed to allow resources to be shared between personal computers or workstations. The resources to be shared may include hardware (e.g., a printer), software

(e.g., an application program), or data. A common example of a LAN, found in many business

environments, links a workgroup of task-related computers, for example, engineering workstations or accounting PCs.

In addition to size, LANs are distinguished from other types of networks by their transmission media and topology.

The most common LAN topologies are bus, ring, and star. Early LANs had data rates in the 4 to 16 megabits per second

(Mbps) range. Today, speeds are normally 100 or 1000 Mbps.




The scope of the LAN is small, typically a single building or a cluster of buildings. This difference in geographic scope leads to different technical solutions.

It is usually the case that the LAN is owned by the same organization that owns the attached devices.

The internal data rates of LANs are typically much greater than those of wide area networks.




Traditionally, LANs make use of a broadcast network approach rather than a switching approach. With a broadcast communication network, there are no intermediate

switching nodes. At each station, there is a transmitter / receiver that communicates over a

medium shared by other stations. A transmission from any one station is broadcast to and received by all

other stations.




LAN Technology

The essential technology ingredients underlying all forms of local area networks are:

Topology, Transmission medium, and Medium access control technique.

Four topologies are in common use: bus, tree, ring, star. The most common transmission media for local networking are

twisted pair (unshielded and shielded), coaxial cable (baseband and broadband), and optical fiber.









Metropolitan Area Network ( MAN )

A network that can span a geographical area the size of a city. MAN is a network with a size between a LAN and a WAN. It is designed for customers who need a high-speed connectivity,

normally to the Internet, and have endpoints spread over a city or part of city. A good example of a MAN is the part of the telephone company network

that can provide a high-speed DSL line to the customer. Another example is the cable TV network that originally was designed for

cable TV, but today can also be used for high-speed data connection to the Internet.




Error rates and delay may be slightly higher than might be obtained on a LAN.

A MAN might be owned and operated by a single organization, or may be a service provided by a public company such as a local telephone company.

It may be a single network such a cable television network so that resource may be shared as device to device

It may also be a means of connecting LANs into a larger network.

The term metropolitan area network (MAN) is not often used anymore.






Wide Area Network ( WAN )

A WAN provides long distance transmission of data, voice, image and video information over large geographic areas that may comprise a country, a continent, or even the whole world. Data travels Interconnect multiple LANs.

WANs may utilize public, leased or private communication equipments. WAN provides connection via telephone lines, radio link or satellites.

Internet: When two or more networks are connected, they become an internetwork or internet.

It has more error chances due to the distance. It is more Complex and Sophisticated and Expensive

Technology than LANs.




The most common example of a WAN is the Internet (Internetwork, an alternate form for WAN).

At its simplest, a WAN is a combination of at least two LANs. You may think a WAN as a larger LAN with at least two LANs

acting as network segments on the WAN. Just as LANs require their own types of hardware to function

(e.g. bridges), WANs also use their own protocols and technologies (e.g. routers).

Speed 100 kilobits/second.







A WAN can be as complex as the backbones that connect the Internet or as simple as a dial-up line that connects a home computer to the Internet.

We normally refer to the first as a switched WAN and to the second as a point-to-point WAN.

The switched WAN connects the end systems, which usually comprise a router (internetworking connecting device) that connects to another LAN or WAN.

The point-to-point WAN is normally a line leased from a telephone or cable TV provider that connects a home computer or a small LAN to an Internet service provider (ISP). This type of WAN is often used to provide Internet access.









Interconnection of Networks: (Internetwork)

Today, it is very rare to see a LAN, a MAN, or a LAN in isolation; they are connected to one another. When two or more networks are connected, they become an internetwork, or internet.

As an example, assume that an organization has two offices, one on the east coast and the other on the west coast. The established office on the west coast has a bus topology LAN; the newly opened office on the east coast has a star topology LAN.




The president of the company lives somewhere in the middle and needs to have control over the company from his home.

To create a backbone WAN for connecting these three entities (two LANs and the president's computer), a switched WAN (operated by a service provider such as a telecom company) has been leased. To connect the LANs to this switched WAN, however, three point-to-point WANs are required. These point-to-point WANs can be a high-speed DSL line offered by a telephone company or a cable modern line offered by a cable TV provider.



A heterogeneous network made of four WANs and two LANs


Let’s take a look at some scenarios and solutions

Question 1: I have a network that spans three buildings within the

same block. What type of network is this?

Answer: LAN


Question 2: My company has four offices within Chicago. The

headquarters are located centrally in Chicago, and an office is located on each of the north, south, west, and east sides of Chicago. What type of network is this?

Answer: MAN


Question 3: My company has three offices, which are connected by

satellite links to create a network. One office is in New York, another in Los Angeles, and the third in Lahore. What type of network is this?

Answer: WAN

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Data Communications and Networking CSCS 311 Lecture 4 Amjad Hussain Zahid