Basics of Data Communication

2. Categories of Network

1.4.2 Categories of Network

 

There are three main types of networks: Local Area Network (LAN), Metropolitan Area Network (MAN), and Wide Area Network (WAN). The group a network belongs to depends on its Size, its physical architecture, the distance it covers and the operator.

1.              LAN is usually Privately owned and Links devices in single office, building or school. LAN is generally limited to a few kilometers of area. It may be privately owned and could be a network inside an office on one of the floors of a building or a LAN could be a network consisting of the computers in a full building. The idea behind LANs is that they let PCs and workstations share resources, like hardware and software. LAN will only use one way to send data. LAN Topologies most often used are Ring, Bus, and Star.

Local area networks, commonly referred to as LANs, are privately-owned networks that operate within a single building or campus, typically covering distances of up to a few kilometers. These systems are commonly utilized to link personal computers and workstations within corporate offices and manufacturing facilities, facilitating resource sharing (such as printers) and information exchange. LANs are characterized by three distinct features:

 (1) Their size, (2) their transmission technology, and (3) their topology.
Local Area Networks (LANs) have limitations on their size, resulting in a predictable worst-case transmission time that can be determined beforehand. Understanding this limit enables the utilization of specific design approaches that would not be feasible otherwise. It streamlines network management. Local Area Networks (LANs) may utilize a transmission technology that involves a cable to which all devices are connected, similar to the party lines employed by telephone companies in rural regions in the past. Conventional LANs operate at speeds ranging from 10 Mbps to 100 Mbps, exhibit minimal delay (in microseconds or nanoseconds), and demonstrate a low error rate. Modern LANs function at speeds of up to 10 Gbps.

2. Metropolitan Area Network (MAN) is characterized by its size, which falls between that of a Local Area Network (LAN) and a Wide Area Network (WAN). It exceeds the size of a LAN while remaining smaller than a WAN. It may encompass the entire network within a city such as Abuja. A metropolitan area network, commonly referred to as a MAN, encompasses an entire city. A prominent example of a MAN is the cable television network that operates in numerous cities. This system evolved from previous community antenna systems implemented in regions with inadequate over-the-air television reception. In the initial systems, a substantial antenna was positioned atop a nearby hill, and the signal was subsequently transmitted to the subscribers' residences. Initially, these were systems that were designed locally and developed on an ad hoc basis. Subsequently, companies commenced entering the market, securing contracts from municipal governments to implement comprehensive wiring solutions for entire cities. The subsequent phase involved the development of television programming and the establishment of dedicated channels exclusively for cable distribution. These channels were frequently specialized, focusing exclusively on categories such as news, sports, cooking, gardening, and others. However, from their inception until the late 1990s, they were designed exclusively for television reception. Cable television is not the only option available. Recent advancements in high-speed wireless Internet access have led to the establishment of another MAN, standardized as IEEE 802.16.

 

3. Wide Area Network (WAN) encompasses all networks within a geographically extensive region. The network throughout the state of Maharashtra has the potential to be classified as a WAN.   A wide area network (WAN) covers a country or continent. It houses user (application) program machines. We name these machines hosts. A communication subnet (subnet) links hosts. Typically, telephone companies or Internet service providers own and run the communication subnet, while consumers own the hosts (e.g., personal PCs). As the telephone system conveys words from speaker to listener, the subnet carries communications between hosts. Separating the network's communication (subnet) from its application (hosts) simplifies network design. Most wide area networks have transmission cables and switching units in the subnet. Transmission lines transfer data between equipment. These can be copper wire, optical fiber, or radio links. The majority of WANs have multiple transmission lines linking two routers. Two routers without a shared transmission line must interact indirectly through other routers. Each intermediate router receives a packet in its entirety, stores it until the relevant output line is free, and then forwards it. Store-and-forward or packet-switched subnets use this idea. Most wide area networks (excluding satellite ones) have store-and-forward subnets. Sometimes termed cells, little packets are the same size. The packet-switched WAN idea is crucial. The sending host breaks a message into packets with its number in sequence before sending it to the receiving host. The network receives these packets one by one quickly. The receiving host reassembles the packets into the original message and delivers it to the receiving process. Not all WANs use packet switching. Satellite WANs are another option. Each router sends and receives via antenna. All routers can hear the satellite's output and, in some situations, their peers' upward transmissions. A large point-to-point subnet may connect routers, but only some have satellite antennas. Satellite networks operate best when broadcasting is important.

 

 

1.1           PROTOCOL 
A protocol is an essential component of a data communications system. Communication cannot occur without a protocol. The sending device must ensure that the data is transmitted in a manner that allows the receiving device to accurately receive and interpret it. When a sender transmits a message, it may include text, numbers, images, and other forms of data, all of which are converted into bits and organized into blocks for transmission. Additionally, control information is often included to assist the receiver in interpreting the data accurately. For effective communication to take place, it is essential for both the sender and receiver to establish a mutual understanding of specific guidelines known as protocol. A protocol is established as a collection of regulations that directs data communications. A protocol outlines the specifics of communication, including the content, method, and timing of the exchange.

 

1.5.1 Elements of a Protocol

The protocol consists of three essential elements:

A.   Syntax: The term refers to the organization or arrangement of the data. The organization of data in a specific sequence.

B.    Semantics It defines the meaning of each segment of bits and specifies the interpretation of each segment. The document outlines the actions or decisions to be made based on the interpretation provided.

C.    Timing It informs the sender regarding the receiver's preparedness to accept the data.
The sender is informed of the appropriate rate at which data should be transmitted to the receiver to prevent overwhelming the receiver.