Topology refers to the way in which the network of computers is connected. Each topology is suited to specific tasks and has its own advantages and disadvantages. The choice of topology is dependent upon type and number of equipment being used, planned applications and rate of data transfer required, response time, and cost. Topology can also be defined as the geometrically interconnection pattern by which the stations (nodes/computers) are connected using suitable transmission media (which can be point-to-point and broadcast).
Think of a topology as a network's virtual shape or structure. This shape does not necessarily correspond to the actual physical layout of the devices on the network. For example, the computers on a home LAN may be arranged in a circle in a family room, but it would be highly unlikely to find a ring topology there. Network topologies are categorized into the following basic types:
Bus networks (not to be confused with the system bus of a computer) use a common backbone to connect all devices. A single cable, the backbone functions as a shared communication medium that devices attach or tap into with an interface connector. A device wanting to communicate with another device on the network sends a broadcast message onto the wire that all other devices but only the intended recipient actually accepts and processes the message.
bus networks work best with a limited number of Networking made it easy 2 Compiled by devices. If more than a few dozen computers are added to a network bus, performance problems will likely result. In addition, if the backbone cable fails, the entire network effectively becomes unusable.
In a ring network, every device has exactly two neighbors for communication purposes. All messages travel through a ring in the same direction (either "clockwise" or "counterclockwise"). A failure in any cable or device breaks the loop and can take down the entire network. To implement a ring network, one typically uses FDDI, SONET, or Token Ring technology. Ring topologies are found in some office buildings or school campuses.
Many home networks use the star topology. A star network features a central connection point called a "hub" that may be a hub, switch or router. Devices typically connect to the hub with Unshielded Twisted Pair (UTP) Ethernet. Compared to the bus topology, a star network generally requires more cable, but a failure in any star network cable will only take down one computer's network access and not the entire LAN. (If the hub fails, however, the entire network also fails.)
Tree topologies integrate multiple star topologies together onto a bus. In its simplest form, only hub devices connect directly to the tree bus, and each hub functions as the "root" of a tree of devices. This bus/star hybrid approach supports future expandability of the network much better than a bus (limited in the number of devices due to the broadcast traffic it generates) or a star (limited by the number of hub connection points) alone.
5) Mesh Topology
Mesh topologies involve the concept of routes. Unlike each of the previous topologies, messages sent on a mesh network can take any of several possible paths from source to destination. (Recall that even in a ring, although two cable paths exist, messages can only travel in one direction.) Some WANs, most notably the Internet, employ mesh routing. A mesh network in which every device connects to every other is called a full mesh. As shown in the illustration below, partial mesh networks also exist in which some devices connect only indirectly to others.
- The Internet is a net consisting of complex network of computers connected by high speed communication technologies.
- The Internet has penetrated and benefited every field – be it education, sports, news, business, etc.
- A web page can be designed using HTML.
- The Internet has converted the world into a global village.
- The Internet has led to faster globalisation. A web page is an electronic document that we can see on the Internet.
- Web browser is software required to view web pages.
- Mosaic was the first web browser.
- www is stand for World Wide Web.
- Electronic mail can be sent and received through any e-mail account.
- Downloading is saving of files from the Internet to our computer.
- Attachments are the extra files that we can send with our email.
- E-commerce stands for electronic-commerce which means buying and selling over the Internet.
- M-commerce is an emerging field which stands for mobile commerce.
- Teleconferencing is having online conference with the facility of exchanging thoughts using an audio.
- Videoconferencing means having online conference with the facility of seeing and listening to other participants.
- Telecommunication is the use of electronic system to send and receive voice, data and video messages.
- Broadly there are five components of communication system, namely information/ message, device, application, protocol and network.
- Voice communication requires telephone instruments like telephone, mobile or VoIP phones for PSTN, wireless or data network.
- Data communication allows transfer of information and remote management of devices.
- Data communication is undertaken by directly connected computers, printers, etc. in a Local Area Network.
- Long distance data communication is done through point to point connections using PSTN or wireless networks.
- Broadcasting of audio and telecasting of video service such as radio and television is done through wireless links.
- Ethernet is the most popular LAN technology for data communication which provides communication speed up to 10Gbps.
- Internet Protocol (IP) connects the computer across similar or diverse networks.
- In IP, data packets are transmitted in packets containing unique IP addresses for the source and the destination.
- IP automatically routes the packet to its destination through any available path.
- Convergence of technologies is required to meet the next generation unified applications where all the three forms of data are required to be transmitted simultaneously.
- IP is internationally accepted protocol through which all different forms of data can be communicated.
- The approach to convergence is to make all components of communication systems IP enabled.
- While trying to achieve convergence, effort is on to use existing infrastructure with partial upgradation.
- Broadband and IPTV are two next generation technologies which use PSTN to provide unified services for voice, data and video.
- VoIP is a data communication technology which allows IP phones and computers to connect to telephones through PSTN and mobile networks.
- Unified messaging system is provided by web service providers which can be used to access multiple services like e-mail, chat, call and entertainment from a single computer system with Internet connection.
- Standardisation is very important for interoperability of various components in any system,
- There are organisations which develop standards, rules and specification for a product that the manufacturers have to meet.