Computer Networks are very helpful to everyone’s everyday lives even if we don’t know it. The definition of a computer network is a group of interconnected computers. Networks can be classified in many different ways. There are many different types of networks. Many different hardware components exist that are specially designed for computer networks. We use computer networks all the time even though most of the time, we don’t know it.
Networks can be classified into many different categories. They can be categorized depending on:
* Connection Method
* Network Topology
These different attributes of different networks help us classify networks into categories so we can identify them easier.
Connection method. Networks can be connected in many different ways. They can be connected with wires or wirelessly. Different wires can be used to interconnect machines. These wires include twisted-pair wire, coaxial cable, and fiber optics cables. A twisted-pair wire is what most people know as a normal telephone line. This wire consists of two insulated copper wires into a pair; these lines are used for voice and data transmission. The speed range for twisted-pair wires is 2 million bits to 100 million bits per second. Coaxial cables are most often used for cable TV, office buildings, and other worksites for local area networks. The cable consists of copper or aluminum wire wrapped in an insulating layer of a flexible material with a high dielectric constant; all of this is surrounded by a conductive layer. The speed range for coaxial cables is 200 million bits to over 500 million bits per second. Fiber optics cables consist of one or more filaments of glass fibers wrapped in a protective layer. They transmit light over long distances and higher bandwidths. Transmissions could range as far as trillions of bits per second. Different wireless technologies exist for network connection. These technologies include terrestrial microwaves, communications satellite, cellular and PCS systems, wireless LAN, Bluetooth, and The Wireless Web. Terrestrial microwaves use earth-based in transmitters and receivers. The equipment looks similar to satellite dishes. Terrestrial microwaves use a low gigahertz range which limits them to line of sight. Communication satellites use microwave radio as their telecommunication medium; this makes them so they can’t be deflected by Earth’s atmosphere. Cellular and PCS systems use several radio communication technologies. The systems are divided into different geographic areas. Each area has a low power transmitter or radio that relays calls from one area to another. Wireless LANs use a high frequency radio technology similar to digital cellular and low frequency radio technology. Wireless LANs use a wide spread spectrum to allow multiple devices to communicate in a limited area. Bluetooth is a short range wireless technology that operates around 1 Mbps ranging from 10 to 100 meters. Bluetooth is an open protocol for data transmission over short distances. The wireless web refers to connection to the internet via any portable devices, such as cell phones, pagers, and PDAs. The method of connection is just one way to classify a network.
Scale. Networks are often classified into:
* Local Area Network (LAN)
* Wide Area Network (WAN)
* Campus Area Network (CAN)
* Metropolitan Area Network (MAN)
* Personal Area Network (PAN)
* Virtual Private Network (VPN)
This depends on the individual networks’ size and purpose. The most common, though, would be LAN.
Network Topology. Networks can be classified by the network topology on which it they are based. Network topology is the way a devices see their logical relations between one machine and another; network topology can also be called network architecture. Different network topologies include bus networks, star networks, ring networks, mesh networks, and tree/hierarchical networks.
A bus network is a network architecture in which a set of clients are connected via a shared communications line called a bus.
A star network is a network architecture in which all the computers are connected to one central switch, bus, or computer (server).
A ring network typically won’t have a network because the computers are only connected to each other to form a ring. One device is connected to the two devices next to it and nothing else and all the devices are connect in the same way.
A mesh network is an architecture that allows for continuous connections and reconfiguration around broken or blocked paths by “hopping” from device to device until the destination is reached.
A tree network—also known as a hierarchical network—is a network architecture in which devices are connected on different levels. For example, one computer is connected to the internet, and two computers are connected to it; two computers are connected to each of those computers and so on.
Types of Networks
There are many different types of networks. Some common types of networks are listed in order of scale as follows:
1) Personal Area Network (PAN)
2) Local Area Network (LAN)
3) Campus Area Network (CAN)
4) Metropolitan Area Network (MAN)
5) Wide Area Network (WAN)
6) Global Area Network (GAN)
7) Virtual Private Network (VPN)
8) Internetwork (Internet)
Personal Area Network.
A Personal Area Network (PAN) is used for linking or communication of devices close to one person. For example, in a PAN, one might link a personal computer, a printer, a fax machine, a telephone, or a PDA together all in the same room in which they are sitting.
Local Area Network.
A Local Area Network (LAN) is a computer network covering a small area like a house, office, or a group of buildings—a school, for example. Current wired LANs are likely to be based on Ethernet technology.
The defining characteristics of a LAN compared to a WAN are its smaller range, its higher bandwidths, and the lack of need for leased telecommunication lines. Current Ethernet or other IEEE 802.3 LAN technologies have a standard 10 Gbit/s (gigabits per second) data transfer rate, but some IEEE projects are investigating the standardization of 40 to 100 Gbit/s
Campus Area Network.
A Campus Area Network (CAN) is exactly what it says it is; it is network for campuses. A CAN is made up of interlinked LANs within a limited geographic range. A CAN is technically a form of a MAN, but specifically for the purpose of education. In the case of a university CAN, the network would likely link the LANs of the academic departments, the university library, and the student living quarters. The main purpose of a CAN is to help students access the internet and university resources.
Metropolitan Area Network.
A Metropolitan Area network links several LANs (same method as CAN, but the network doesn’t extend beyond the boundaries of the immediate city.
Wide Area Network.
A wide area network (WAN) is a network that covers a large area. This means that a WAN is not limited to the boundaries of a city, a state, or even sometimes a country. The largest and best known WAN is the internet.
Global Area Network.
Global area networks (GAN) are currently still in development; there is no common definition. In general, though, the goal of GANs is to support mobile communications across an arbitrary number of satellites, Wireless LANs and more. The key challenge is to allow the networks to “hand off” the user information from one network to the next.
Virtual Private Network.
A Virtual Private Network (VPN) is a network in which some of the links between devices are virtual circuits that are part of a larger network—like the internet.
Internetwork. An Internetwork is the connection of two or more distinct networks or network segments with a common routing technology. Internetwork is often shortened to internet. There are three classifications of Internetworks; they include:
Intranets and Extranets may or may not have connection to the Internet; however, if they are, they typically are protected from access to the internet without proper authorization.
An Intranet is a group of networks using the Internet Protocol and IP tools like web browsers and file transfer applications under the control of a single administrative entity. This administrative entity closes the intranet to all but specified users. A large Intranet will typically have a web server which provides users with organizational information. Often an intranet is the internal network of some kind of organization.
An Extranet is a network or internetwork that is limited to one business or entity, but also has limited connection to other networks of other trusted businesses or entities.
The Internet consists of governmental, educational, public, and private networks all interconnected world wide. The Internet is the backbone underlying the World Wide Web (WWW). The word ‘Internet’ is often capitalized as a proper noun because of historical reasons and to distinguish it form normal internetworks.
There are many different types of network hardware including servers, network interface cards, routers, network printers, fax, and more.
There are many different types of servers. There are file servers, print servers, home servers, and more. File servers are computers connected to a network and dedicated to holding mass amounts of files for all computers on a network. This way any user can log on to any computer and access his or her files with ease. A print server is a computer that accepts print jobs from other computers on the network and processes them by sending them to the appropriate printer. Home servers are basically the same as file servers accept they are designed for home use.
Network Interface Cards.
A Network Interface Card is a piece of computer hardware that allows a computer to communicate over a network. It provides physical access of a network to a computer.
A router is a networking device that determines which path networking traffic should go through. It is different from a hub because hubs don’t route the network traffic; they just send the traffic through all paths.
A network printer is a printer that connects directly to the network in the same way a computer would. Technically these kinds of printers are not necessary because any computer with an open port and a network connection can become a print server by sharing the printer, but it is easier to just plug it in than go through the process of sharing a printer.
A repeater is a network device that takes in a week signal and amplifies it. Repeaters can be used to keep a signal strong over a long distance or to transmit it over and obstruction such as a mountain.
A network hub has many ports; when it receives a signal, it copies it and transmits through all the ports.
A bridge connects multiple network segments. Rather than transmitting a signal through all ports, it learns which MAC addresses are at the other end of each port and only sends the signal through a specific port according to the MAC address the signal is destined to go.
Computer networks help us every day although we may not even know about it. Networks can be classified into several different categories. There are many different types of networks. There are lots of different types of software that is designed just for networking. Computer networks help us a lot.