Introduction to Data Communication
Data Communication is the transfer of data or information between a source and a receiver. The source transmits the data and the receiver receives it. The actual generation of the information is not part of Data Communications nor is the resulting action of the information at the receiver. Data Communication is interested in the transfer of data, the method of transfer and the preservation of the data during the transfer process.
In Local Area Networks, we are interested in “connectivity”, connecting computers together to share resources. Even though the computers can have different disk operating systems, languages, cabling and locations, they still can communicate to one another and share resources.
The purpose of Data Communications is to provide the rules and regulations that allow computers with different disk operating systems, languages, cabling and locations to share resources. The rules and regulations are called protocols and standards in Data Communications.
Telephones and networking work hand in hand. The telecommunications industry has been gradually integrating with the computer industry and the computer industry has been gradually integrating with the telecommunications industry. The common goal is to join distantly located Local Area Networks into Metropolitan and Wide Area Networks (MANs and WANs). How do you connect Local Area Networks across a city or country? You use a telecommunication carrier either a local carrier or long distance carrier.
The Internet is a good example of the collaboration between computers and the telephony industry. The Internet is a collection of computer networks connected by telecommunication systems. Most people don’t realize it but the telecommunications industry is the backbone for the Internet. Pretty much all data communications that leaves a LAN utilizes a telecommunication service.
At the end of 1996, there was a major milestone where more data was communicated in North America’s telecommunications system than voice. Currently, in 2005, the majority of communication on telephony circuits is data and the minority is voice. This doesn’t mean that the voice traffic is reducing in volume, it means that the data communications side has added a whole new dimension to telephony. In addition, there is even more voice communications now due to the explosion of use of cellular phones.
There are two main methods of sending data over telephone services: voice channels and data channels.
First thing that comes to mind when discussing telephone systems, is the phone at home. The dialup phone is called the Plain Old Telephone Set or System and uses the acronym POTS. A voice conversation using a POTS line uses the most basic of telephony services: the Voice Channel. This initially doesn’t seem to have much to do with Networks!
In data communications, we use voice channels for modem communication to connect to BBSs (Bulletin Board Services) or to connect to the Internet. We also use voice channels to connect LANs using remote access. Due to the bandwidth limits on the Voice Channel, the data transfer rate is relatively slow.
Voice Channel: Dial-up connection through a modem using standard telephone lines. The current transfer rate is close to 56 kbps using a V.90 modem. Typical Voice Channel communication rates are: 300, 1200, 2400, 9600, 14.4k, 19.2k, 28.8k, 33.6k and 56 kbps (bits per second).
Data channels are dedicated lines for communicating digitized voice and data. There are many different protocols (rules and standards) for data channels. Some common data channel services are T-1 lines, Frame Relay, X.25 and ADSL.
Data Channels are special communications channels provided by the “common carriers” such as Telus, Sprint, Bell Canada, etc… for transferring digital data. Data Channels are also called “Leased Lines”. They are “directly” connected and you don’t have to dial a connection number. The connections are up and running 24 hours per day. They appear as if there were a wire running directly between the source and destination. Typical transfer rates for data communication are: 56 k, 128k, 1.544 M, 2.08 M, 45M and 155 Mbps.
Common carriers charge for data connections by the following methods or combinations of thereof
- the amount of data transferred (megabytes per month)
- the transfer rate (bits per second)
- the amount of use (time per month)
- the quality of service
- the latency of transmission
A VIDEO EXPLAINING DATA COMMUNICATION
Introduction to Computer Networks
- Computer Network is a group of computers connected with each other through wires, optical fibres or optical links so that various devices can interact with each other through a network.
- The aim of the computer network is the sharing of resources among various devices.
- In the case of computer network technology, there are several types of networks that vary from simple to complex level.
Components of Computer Network:
Major components of a computer network are:
NIC (National interface card)
NIC is a device that helps the computer to communicate with another device. The network interface card contains the hardware addresses, the data-link layer protocol use this address to identify the system on the network so that it transfers the data to the correct destination.
There are two types of NIC: wireless NIC and wired NIC.
- Wireless NIC: All the modern laptops use the wireless NIC. In Wireless NIC, a connection is made using the antenna that employs the radio wave technology.
- Wired NIC: Cables use the wired NIC to transfer the data over the medium.
Hub is a central device that splits the network connection into multiple devices. When computer requests for information from a computer, it sends the request to the Hub. Hub distributes this request to all the interconnected computers.
Switch is a networking device that groups all the devices over the network to transfer the data to another device. A switch is better than Hub as it does not broadcast the message over the network, i.e., it sends the message to the device for which it belongs to. Therefore, we can say that switch sends the message directly from source to the destination.
Cables and connectors
Cable is a transmission media that transmits the communication signals. There are three types of cables:
- Twisted pair cable: It is a high-speed cable that transmits the data over 1Gbps or more.
- Coaxial cable: Coaxial cable resembles like a TV installation cable. Coaxial cable is more expensive than twisted pair cable, but it provides the high data transmission speed.
- Fibre optic cable: Fibre optic cable is a high-speed cable that transmits the data using light beams. It provides high data transmission speed as compared to other cables. It is more expensive as compared to other cables, so it is installed at the government level.
Router is a device that connects the LAN to the internet. The router is mainly used to connect the distinct networks or connect the internet to multiple computers.
Modem connects the computer to the internet over the existing telephone line. A modem is not integrated with the computer motherboard. A modem is a separate part on the PC slot found on the motherboard.
Uses of Computer Network
- Resource sharing: Resource sharing is the sharing of resources such as programs, printers, and data among the users on the network without the requirement of the physical location of the resource and user.
- Server-Client model: Computer networking is used in the server-client model. A server is a central computer used to store the information and maintained by the system administrator. Clients are the machines used to access the information stored in the server remotely.
- Communication medium: Computer network behaves as a communication medium among the users. For example, a company contains more than one computer has an email system which the employees use for daily communication.
- E-commerce: Computer network is also important in businesses. We can do the business over the internet. For example, amazon.com is doing their business over the internet, i.e., they are doing their business over the internet.
A VIDEO EXPLAINING COMPUTER NETWORKS