Network Hierarchies (Types by Architecture)

The connections between the various PCs in a network also can fit one of two logical

hierarchies. The alternatives form a class system among PCs. Some networks treat all

PCs the same; others elevate particular computers to a special, more important role.

Although the network server the same role in either case, these two hierarchical

systems enforce a few differences in how the network is used.

Peer-to-Peer Networks

Peer-to-Peer means that there is no dedicated file server as you would find in big,

complex networks. All PCs can have their own, local storage, and each PC is (or can

be) granted access to the disk drives and printers connected to the others. Even in Peer-to-Peer networks, some PCs are likely to be more powerful than others or have largerdisk drives or some such distinction.

The advantage of Peer-to-Peer is , no need to by an expensive file server. Not only will

that save cash, it can give you the security of redundancy. The failure of a server puts

an entire network out of action. The failure of network peer only eliminates that peer;

the rest of the network continues to operate. And also we can duplicate the data on two

or more peers.

Client / Server Networks

A Client / Server network provides for centralized control of network resources. One or more computers, called Servers, share the resources on the network. All other computers, called clients or workstations, uses the resources. Most modern servers are designed to be fault-tolerant. That is, they will continue to run without interruption despite a fault, such as the failure of a hardware subsystem. Most servers also use the most powerful available microprocessors, not from need but because the price difference is tiny once the additional ruggedness and storage are factored in-and because most managers think that the single most important PC in a network should be the most powerful.

Peer-to-Peer Networks

(Suitable for Small to Medium Size Organizations)

Advantages :

1. No dedicated server.

2. Less expensive.

3. Easy to install and maintain.

4. Good file, printer, and CD-ROM sharing.

Disadvantages:

1. Slow operation.

2. Not good for database applications.

3. Less reliable (server is workstation).

4. Low Security

5. Limited expandability.

Client / Server Networks

(Suitable for Medium to Large Size Organizations)

Advantages :

1. Fast operation.

2. Expandable.

3. Will work with any application.

4. Handles shared database applications.

5. More reliable (dedicated server).

6. Highest level of security.

7. Applications can be shared.

Disadvantages:

1. Needs dedicated server.

2. More expensive to buy.

3. More expensive to maintain

Types of Networks

Types of Networks (By Scale)

 1. LAN – Local Area Network

Connects a number of computers located geographically close to one another. For example, two computers directly connected to each other can be considered to be a LAN. A corporate network that services multiple adjacent buildings can also be considered as a LAN.

2. WLAN - Wireless Local Area Network A type of local-area network that uses high-frequency radio waves rather than wires to communicate between nodes

3. CAN –Campus-Area Networks A network that connects two or more LANs but that is limited to a specific and

contiguous geographical area such as a college campus

, industrial complex, or a military base. A CAN, may be considered a type of MAN (metropolitan area network),

but is generally limited to an area that is smaller than a typical MAN.

4. MAN- Metropolitan Area Network Connects computers or LANs within the Town / City / Metropolitan area by using Leased / Dedicated lines, ISDN, ADSL (Telephone lines) or Fiber Optic Cables. A MAN typically covers an area of between 5 and 50 km range.

5. WMAN- Wireless Metropolitan Area Network

Connects computers or LANs within the Town City / Metropolitan area by using long

range wireless technology called Microwave.

6. WAN- Wide Area Network Ties / connects together computers or LANs in locations that could be distributed

throughout the country or even overseas by using PSTN, ISDN, Fiber Optic Cables. Most WANs comprise a number of LANs connected by long-distance, high-speed data-links.

7. WWAN- Wireless Wide Area Network Ties / connects together computers or LANs in locations that could be distributed throughout the country or even overseas by using Satellite links.

8. GAN – Global Area Network Refers to any network that is composed of different interconnected computer networks (WANs) and also covers an unlimited geographical area

9. PAN – Personal Area Network is a computer network

used for communication among computer devices (including telephones and personal digital assistants) close to one person. Personal area networks may be wired with computer buses such as USB , IrDA, Bluetooth and FireWire etc

10. SAN – Storage Area Network In computing , a storage area network ( SAN ) is an architecture to attach remote computer storage devices (such as disk arrays , tape libraries and optical jukeboxes ) to servers in such a way that, to the operating system , the devices appear as locally attached. Although cost and complexity is dropping,

as of 2007 , SANs are still uncommon outside larger

enterprises

.