January 22, 2014

Wired and Wireless Technologies in Computer Networking

Computer Networking has a physical component that is overlaid by the topology describing the way that network nodes are interconnected. The topology of a network is described by diagrams that use symbols denoting network nodes and network links.

The media used to interconnect devices that form a computer network may be:

  • Electrical cable
  • Optical fiber
  • Radio waves
  • Infrared signals

The first two categories define the “wired technologies” used in computer networking, while the last two are known as “wireless technologies”.

Wired Technologies

The following four categories are the best known and used to set up computer networks:

  • Twisted pair wire – It is maybe the most used medium, but also the slowest of all. It consists of pairs of twisted insulated copper wires that can be either unshielded or shielded. The transmission speeds may range from 2 Mbps to 10 Mbps.
  • Coaxial cable – It is an aluminum or copper wire included in an insulated layer of material with a high dielectric constant. The whole thing is wrapped in a conductive layer. The insulation is designed to minimize distortion and interference. Transmission speeds range from 200 Mbps to 500 Mbps.
  • Optical fiber – It is in fact glass fiber that uses light pulses to transmit data. Unlike metal wires, fiber glass is immune to electrical interference and has lower transmission loss. Moreover, optical fibers can carry several wavelengths of light simultaneously, increasing the rate at which information can be sent. Speeds can reach trillions of bits per second. Optical fibers are also used to interconnect continents through undersea cables.

Wireless Technologies

Computer networking based on wireless technologies does not use physical media to transmit signals, but does require relay stations to retransmit the signal if long distances have to be covered.

  • Terrestrial microwaves – They use Earth-based receivers and transmitters. These waves are situated in the low-gigahertz range, and, therefore, communications are limited to line-of-sight. Relays are situated at approximately every 48 km.
  • Communications satellites – They use microwave radio waves to communicate. These waves are not deflected by the atmosphere of the Earth. The satellites are placed in space, on a geosynchronous orbit at 35,400 km above the equator. They can receive and relay data, voice, and TV signals.
  • Radio technologies – They use high-frequency and low-frequency radio signals to transmit data. They enable communications between several devices in a restrained area.
  • Cellular and PCS systems – They divide a region into multiple geographic areas and use multiple radio communications technologies. Each area has a radio relay antenna or a low-power transmitter to direct calls from one area to another.
  • Free-space optical communication – Another system used in computer networking, working with invisible or visible light, it is usually limited at line-of-sight propagation.
November 14, 2013

Six Properties that Define Computer Networking

Computer Networking is the term that defines a system in which computers are interconnected so that they can exchange data. In fact, a “computer network”, also called “data network”, is a telecommunications system allowing information to be passed from one station to another, using data connections. The network is made of nodes, while the network links are made using either wired media or wireless transmissions of data. Maybe the most famous computer network is the Internet.

How Computer Networking Is Implemented

A network is composed of several computer devices that can initiate, route or terminate data transfers, called “nodes”. They can be either servers or personal computers as hosts of information, as well as hardware supporting the data transfers. It is said that two devices are networked when they can exchange information with one another.

The main goal of computer networks is to support applications like access to the WWW (World Wide Web), use of e-mail and messaging applications, as well as sharing resources, such as storage and application servers, printers, fax machines, presentation devices, and more.

There are a few things that differentiate computer networks, such as the physical media used for data transmission, the protocols utilized to organize the traffic through the network, the size of the network, its topology, and the organizational intent.

Properties That Define Computer Networks

Computer networking is a branch situated on the border of several disciplines, such as telecommunications, electrical engineering, computer engineering, computer science, and information technology, as it relies on both theoretical and practical applications of all these disciplines.

There is a set of six properties that can be identified in any computer network:

  • It facilitates interpersonal communications – by means of computer networks, people can communicate easily and effectively using instant messaging, e-mail, chat rooms, telephone calls, video telephone, and video conferencing.
  • Computer networks allow sharing of data, files, and other different types of information – users who are authorized to access the network have access to information stored on computers connected to the network.
  • Access to computing resources is allowed – connected users can share resources like printing or storage devices, as well as computing resources (distributed computing).
  • Networks may be insecure – hackers can break the security shield of a network and deploy viruses or malware, or simply prevent other users from accessing the network.
  • Networks may interfere with some other technologies – power lines may disturb radio communication or may interfere with other technologies like ADSL or VDSL.
  • Computer networks may be hard to set up – complex computer networking may require complicated set up procedures and may be costly for large organizations.
October 9, 2013

Computer Networking

Computer Networking is a process to connect two or more computers over shared network for exchanging data. These Networks are made by using Hardware and Software’s. Such as, Computers, Network Interfacing cards, operating software’s Microsoft, UNIX or Linux, cables and wires.

Network Types

  1. On the Basis of Geographical Divisions
    • LAN (Local Area Network) – It is limited to an area such as a college campus or an office building, and can communicate just three computers up to hundreds of computers.
    • WAN (Wide Area Network) – It is a Network made by combining a number of LAN Network. It can be made simple and easy or it can be very complicated.
    • Internet – It is a system of computers interconnecting to each other using IP and is spread across the whole world.
    • Intranet – This Network is similar to that of the Internet but it is used only as a private network. So the companies take this network for communication and sharing of information within the organization.
    • MAN (Metropolitan Area Network) – It is the network designed for the specific city.
  2. On Basis of Architecture
    • Peer to Peer – There is no dedicated server in this, so all computers act as client/server to each other. No one responsible to entire network. It is mainly used by small organizations where all users are located in the same area and there is no future expansion.
    • Client/Server – In this the most powerful computer is the server and others are client. It is the most competent method to manage the network, storing the data centrally and manage the entire database.
  3. On basis of Geometric Arrangement of computers
    • Ring System – All computers are connected to form a ring.
    • Star System – All computers are connected to a centrally located computer to form a star formation.
    • Bus System – All computers are connected to a single bus connected between them.

Protocols
These are the standards which enable computers to communicate with each other.
Some protocols are:

  1. TCP/IP – Point to Point protocol – Transmission control protocol/ Internet protocol – Backbone of Internet
  2. FTP – File Transfer Protocol – Used to send or receive files from remote hosts
  3. SMTP – Simple Mail Transfer Protocol – Used to send mails
  4. IPX/SPX – Internet Packet Exchange/Sequenced Packet Exchange – For Novell Network operating system
September 12, 2013

Four Communication Protocols Utilized in Computer Networking

Computer Networking implies the use of a communications protocol, which is a set of rules that regulates how information is exchanged over network links. According to the OSI model, the protocol is, in fact, a stack of protocols in which each protocol leverages all the services provided by the protocol situated below it.

As an example, the HTTP protocol runs over TCP, which runs over IP, which runs over IEEE 802.11. This stack is utilized in the communication between a wireless router and a personal computer while surfing the Web. IEEE 802.11 is a member of the protocol suite called Ethernet, while TCP and IP belong to the Internet Protocol Suite.

The use of the protocol layering technique is common in computer networking. However, many researchers criticize it for at least two reasons. The first critique refers to the fact that a higher layer may end by duplicating the functionality of the lower layers – for instance, error recovery on a per-link basis and the same procedure on an end-to-end basis. A second critique is related to the aspect that an implementation of the protocol at one layer could possibly require data, state and addressing information that cannot be found but at another layer.

Protocols Used in Computer Networking

The following protocols are largely used to support data transmission between computers connected to networks.

  • Ethernet – is a group of protocols used in local area networks (LAN), known as a set of standardizing procedures published by the IEEE (Institute of Electrical and Electronics Engineers) under the name IEEE 802. For home users, the best known member of the family is the IEEE 802.11, also known as WLAN (Wireless Local Area Network). Other members provide additional networking capabilities.
  • Internet Protocol Suite – is also known as TCP/IP, and is the basic protocol of modern internet working. It defines the specifications for addressing, identification, and routing.
  • Synchronous Optical Networking and Synchronous Digital Hierarchy – are also called SONET and SDH and are standard multiplexing protocols meant to transfer digital bit streams using lasers over optical fiber.
  • Asynchronous Transfer Mode, or ATM, is in fact a switching technique designed for telecommunication networks. This protocol is recommended for networks that handle traditional data traffic, but also real-time content like voice and video.

The protocols used in computer networking are chosen according to the destination of the network and the type of data that is expected to be transmitted between the computers connected to the network.

August 11, 2013

About CVSup

CVSup is a software package for distributing and updating collections of files across a network. It can efficiently and accurately mirror all types of files, including sources, binaries, hard links, symbolic links, and even device nodes. CVSup’s streaming communication protocol and multithreaded architecture make it most likely the fastest mirroring tool in existence today.

CVSup was conceived and developed by John Polstra, a consultant whose specialties include high-performance network communications.

In addition to being a great general-purpose mirroring tool, CVSup includes special features and optimizations specifically tailored to CVS repositories. By taking advantage of the special properties of the files contained in CVS repositories, CVSup is able to perform updates much faster than traditional systems. CVSup parses and understands the RCS files making up a CVS repository. When updates occur, CVSup extracts new deltas directly from the RCS files on the server and edits them into the client’s RCS files. Likewise, CVSup notes the addition of new symbolic tags to the files on the server and sends only the new tags to the client.

CVSup is able to merge new deltas and tags from the server with deltas and tags added locally on the client machine. This makes it possible for the client to check local modifications into his repository without their being obliterated by subsequent updates from the server.

In addition to distributing the RCS files themselves, CVSup is able to distribute specific checked-out versions. The client can specify a symbolic tag, a date, or both and CVSup will extract the appropriate versions from the server’s CVS repository. Checked-out versions do not need to be stored on the server, since CVSup can extract any version directly from the CVS repository. If the client has an existing checked-out tree, CVSup will apply the appropriate edits to update the tree or transform it into the requested version. Only the differences between the existing version and the desired version are sent across the network.

To update non-RCS files, CVSup uses the highly efficient rsync algorithm, developed by Andrew Tridgell and Paul Mackerras.

CVSup uses lightweight processes (threads) to implement a streaming protocol across the network. This completely eliminates the delays associated with the lock-step, request-reply form of communication used by many existing protocols, such as sup and NNTP. Information is transferred at the full available speed of the network in both directions at once. Network latency and server response delays are rendered practically irrelevant.

CVSup uses the “zlib” compression package to optionally compress all communications. This provides an additional 65-75% compression, on top of the diff-based compression already built into CVSup.