Networks and Distributed Systems

Computer networking

Computer networking is the engineering discipline that is concerned with the communication between computer devices or systems. Any set of computers or devices linked to each other with the capacity to exchange data is called a computer network. Networks are constructed with a combination of computer hardware and computer software.
Computer networks are used for a range of purposes:

1. To facilitate communications. Using a computer network, people are able to communicate easily and efficiently via email, chat rooms, instant messaging, telephone, video telephone calls as well as video conferencing.
2. To share hardware. Computers on a network can have access to and use hardware resources on the network, for instance printing documents on a shared network printer.
3. To share data, information and files. In a networked environment, authenticated users can access data and information that is stored on other computer systems on the network. The ability to provide access to information and data on shared storage devices is an essential attribute of many networks.
4. To share software. Users connected to a computer network can run application software on remote computers.
5. Data Protection and Redundancy. Networking computers together enables users to distribute copies of vital information across multiple locations hence ensuring that important information is not lost in case any one computer on the network failures. By using central backup systems, unique data and documents can be collected automatically from all computers in the network and backed up securely in case of accidental deletion or physical computer damage.
6. Distributing Computing Power. There are some organizations that require extraordinary computing power. Computer networking enables such organizations to distribute computational tasks across several computers in the network, breaking intricate problems into many smaller tasks, which are then distributed to individual computers. Every computer on the network executes its operations on its own share of the larger problem then returns the results to the controller, which assembles the results and makes conclusions that no single computer could accomplish individually.

Types of wired network technologies

   1. Twisted pair wire: This medium for telecommunication is the most commonly used. Twisted-pair cabling comprises copper wires which are twisted into pairs. Regular telephone wires comprise two insulated copper wires which are twisted into pairs. Computer network cables consist of four pairs of copper cables that can be used for both data and voice transmission. Using 2 wires twisted together helps in reducing electromagnetic induction as well as crosstalk. The speed of transmission ranges from 2 million bits/second to 100 million bits/second. There are two forms of twisted pair cabling; Shielded twisted-pair (STP) and Unshielded Twisted Pair (UTP) which are manufactured in diverse increments for different purposes.
   2. Coaxial cable: This is commonly used for office buildings, cable television systems and other worksites for LANs (local area networks). The cables are made of copper or aluminum wire covered with an insulating layer usually of a flexible material that has a high dielectric constant. All of these are then encased with a conductive layer. The insulation layer helps minimize distortion and interference. The speed of transmission ranges from 200 million to over 500 million bits/second.
   3. Optical fiber: This cable is made of one or more glass fiber filaments enclosed with protective layers. Fiber-optic cables transmit light that can travel over extensive distances. These cables are not affected in any way by electromagnetic radiation. The speed of transmission could reach trillions of bits/second.

Types of wireless network technologies

   1. Terrestrial microwave; these microwaves use earth-based receivers and transmitters. The equipments resemble satellite dishes. Terrestrial microwaves utilize a low-gigahertz range, limiting all communication to line-of-sight. The path between transmission stations is spaced approximately 30 miles from each other. Normally, microwave antennas are located on the top of a building, tower, hill, or mountain peak.