Components of Network: LANs do not use the telephone network. Its networks are constructed with standard set of components. As discussed below:
Note: it is high time to mention here is that although chatting facility is of immense importance and use, our youth, especially the students, are misusing it for hours and hours thus, wasting their precious time of study.
- All networks need some system for interconnection. In some LANs, a shared network cable connects the nodes. Low-cost LANs are connected with twisted wire pairs, but many LANs use coaxial cable or fiber optic cable, which are both more expensive and faster. Some LANs are wireless, using infrared or radio wave transmissions instead of cables. Wireless networks are easy to set up and reconfigure, since there are no cables to connect the devices, but they have slower transmission rates and limit the distance between nodes.
- A network-interface card (NIC), connects each computer to the wiring in the network. NIC is a circuit board that fits in one of the computer’s internal expansion slots. Some computers have built in NIC.
- Similar networks can be connected by a bridge, which recognizes the messages on a network and passes on those addressed to nodes in other network.
- A gateway is a collection of hardware and software resources that lets a node communicate with a computer on another different network. A gateway, for example, could connect an attorney on a local area network to a legal service offered through a wide-area-network (WAN will be discussed after this topic).
- A router is a device that connects two or more networks it consist of a combination of hardware and software. The hardware can be a network server, a separate computer, or a special black box device. The hardware includes the physical interfaces to the various networks in the internetwork. These interfaces can be Token Ring. Ethernet, TI, Frame Relay, asynchronous transfer mode (ATM), or any number of other technologies. The two main pieces of software in a router are the operating system and the routing protocol. Management software can be another software component of a router.
LAN’s Protocols: networks have certain rules, called Protocols, to send and receive data, and it is defined in the network software. The most common of them are explained as under:
- Ethernet: currently, this is the most commonly used protocol. It uses a high-speed network cable and bus topology, so it is relatively simple and cheaper. Since all the nodes (computers) use the same cable to send and receive data, they must follow a set of rules about when to communicate, otherwise, two or more computers could transmit at the same time, causing lost messages. Before transmitting the data, a node listens” to find out if the cable is in use. If so, the node must wait. When the cable is free from other transmission, the node can begin transmitting immediately. This process is also known as CSMA/CD (Carrier sense Multiple Access with Collision Detection).
- If by chance, two nodes transmit data at the same time, the messages collide. When a collision occurs, a special message, lasting a fraction of a second, is sent out over the network to indicate that it is jammed. Each node stops transmitting, waits a random period of time, and then transmits again. Since the wait period for each node is random, t is unlikely that they will begin transmitting at the same time again.
Token Ring
It is closely associated with IBM, works on the concept of a ring network topology and a token (a kind of electronic signal). The method of controlling access to the shared network cable is called token passing.
Only one token is available on the network. When a node on the network wishes to transmit, it first captures the token, only then it can transmit data. When the node has sent its message, it releases the token back to the network. Since only one token is circulating around the network, only one device is able to access the network at a time. Thus no collision occurs but the only disadvantage is its slow data transfer rate.
ARCnet: the ARCnet (Attached Resource Computer network) has both a topology and networking technology all its own. It uses either twisted-pair wire or coaxial cable, and the star topology is informed with hubs attached to the network.
The original ARCnet protocol was very slow, but it became popular because it was inexpensive, reliable, and easy to set up and to expand. Fast ARCnet increased the transmission rate to 100 Mbits per second and includes the capability to use fiber optic cable.
- TCP/IP (Transmission Control Protocol / internet Protocol): TCP/IP is the protocol used by every computer on the internet. A protocol is a set of rules and procedures that defines how computer receive and transmit data over the network. Every computer on the internet must have TCP/IP configured.
- TCP/IP ensures a reliable connection between the computers communicating over the internet. It also defines a mechanism through which every computer on the internet is identified separately.
- TCP/IP software differs for different computers but it always present the same interface to the network. It does not matter if the system on the other end is a supercomputer, a mainframe, minicomputer or microcomputer; as long as it is using TCP/IP, it can send and receive data through the internet.
- ISDN(Integrated Seraries Digital Network): ISDN is a set of international communication standreds for software control of transmitting voice, video, and data simultaneously as digital signals over twisted-pair telephone lines. Basic rate ISDN provides better quality than analog connections and more reliable digital connections at higher speeds than those offered by analog connections
- DSL (Digital Subscriber Line): DLS provide high speed, digital data trandmission from homes and businesses over existing telephone lines. The exiting lines are analog and the transmission is digital, so modems are necessary with DSL technology. DSL is a popular alternative to ISDN.
