Notes of Introduction to Computer Networks.ppt
- 2. A network is a group of interconnected two or more computers that are linked in order to share resources such as printers , exchange files, or allow electronic communications. The computers on a network may be linked through cables, telephone lines, radio waves, satellites, or infrared light beams.
- 4. Resource Sharing Hardware (computing resources, disks, printers) Software (application software) Information Sharing Easy accessibility from anywhere (files, databases) Search Capability (WWW) Communication Email Message broadcast Remote computing Distributed processing (GRID Computing)
- 5. Speed. Networks provide a very rapid method for sharing and transferring files. Resource Sharing. Sharing resources is another area in which a network exceeds stand-alone computers. Most organizations cannot afford enough laser printers, fax machines, modems, scanners for each computer.
- 6. Ease of communication E-mail aids in personal and professional communication for all personnel, and it facilitates the dissemination of general information to the entire staff. If connected to the Internet, staff can communicate with others throughout the world. Flexible Access. Networks allow users to access their files from computers throughout the entire organization.
- 7. Workgroup Computing. Networks allow many users to work on a document or project concurrently. For example, architects located at various floors within a building could simultaneously contribute their ideas about new building complex to the same document. Security Files and programs on a network can be designated as "copy inhibit," so that you do not have to worry about illegal copying of programs. Also, passwords can be established for specific directories to restrict access to authorized users.
- 8. The network topology defines the way in which computers, printers, and other devices are connected. A network topology describes the layout of the wire and devices as well as the paths used by data transmissions.
- 9. Therefore: A network Topology is the physical layout of network hardware, which include computers, cables and other peripherals.
- 10. Bus Topology Commonly referred to as a linear bus, all the devices on a bus topology are connected by one single cable.
- 11. A bus topology consists of a main run of cable with a terminator at each end. All nodes (file server, workstations, and peripherals) are connected to the linear cable in a row.
- 12. Advantages of a Bus Topology •Easy to connect a computer or peripheral to a linear bus. •Requires less cable length than a star topology. Disadvantages of a Bus Topology •Entire network shuts down if there is a break in the main cable. •Terminators are required at both ends of the backbone cable. •Difficult to identify the problem if the entire network shuts down.
- 13. The star topology is the most commonly used architecture in Ethernet LANs. When installed, the star topology resembles spokes in a bicycle wheel. A star topology is designed with each node (file server, workstations, and peripherals) connected directly to a central network point eg a hub or a switch.
- 15. Larger networks use the extended star topology also called tree topology. When used with network devices that filter frames or packets, like bridges, switches, and routers, this topology significantly reduces the traffic on the wires by sending packets only to the wires of the destination host.
- 16. Advantages of a Star Topology • Easy to install and wire. • No disruptions to the network when connecting or removing devices. • Easy to detect faults and to remove parts. Disadvantages of a Star Topology • Requires more cable length than a linear topology. • If the hub or concentrator fails, nodes attached are disabled. • More expensive than linear bus topologies because of the cost of the hubs/concentrators.
- 17. In a Ring topology, computers are connected so that signals travel around the network from one computer to another in a logical ring.
- 18. A frame travels around the ring, stopping at each node. If a node wants to transmit data, it adds the data as well as the destination address to the frame. The frame then continues around the ring until it finds the destination node, which takes the data out of the frame.
- 20. Advantages of a Ring Topology Equal access for all computers. Even performance despite many users. Disadvantages of a Ring Topology • Failure of one computer may impact the rest of the network . • Problems hard to isolate.
- 21. The mesh topology connects all devices (nodes) to each other for redundancy and fault tolerance. It is used in WANs to interconnect LANs and for mission critical networks like those used by banks and financial institutions. Implementing the mesh topology is expensive and difficult.
- 23. What would you consider when choosing a topology? Cost A bus network may be the least expensive way to install a network; you do not have to purchase concentrators. Length of cable needed. The linear bus network uses shorter lengths of cable.
- 24. Future growth. With a star topology, expanding a network is easily done by adding another concentrator. Cable type. The most commonly used cable is unshielded twisted pair, which is most often used with star topologies.
- 25. Physical Media Interconnecting Devices Computers Networking Software Applications
- 26. Networking media can be defined simply as the means by which signals (data) are sent from one computer to another (either by cable or wireless means).
- 27. HUB, Switches, Routers, Wireless Access Points, Modems etc.
- 28. In a client/server network arrangement, network services are located in a dedicated computer whose only function is to respond to the requests of clients. The server contains the file, print, application, security, and other services in a central computer that is continuously available to respond to client requests.
- 29. E-mail Searchable Data (Web Sites) E-Commerce News Groups Internet Telephony (VoIP) Video Conferencing Chat Groups Instant Messengers Internet Radio
- 30. Depending upon the geographical area covered by a network, it is classified as: Local Area Networks (LAN) Metropolitan Area Network (MAN) Wide Area Network (WAN) Personal Area Network (PAN)
- 31. Local Area Network A Local Area Network (LAN) is a network that is confined to a relatively small area. It is generally limited to a geographic area such as a room, school, or building. Rarely are LAN computers more than a mile apart.
- 32. LAN’s enable the sharing of resources such as files or hardware devices that may be needed by multiple users Is limited in size, typically spanning a few hundred meters, and no more than a mile Is fast, with speeds from 10 Mbps to 10 Gbps Requires little wiring, typically a single cable connecting to each device Has lower cost compared to MAN’s or WAN’s
- 33. LAN’s can be either wired or wireless. Twisted pair, coax or fibre optic cable can be used in wired LAN’s. Every LAN uses a protocol a set of rules that governs how packets are configured and transmitted. Nodes in a LAN are linked together with a certain topology. These topologies include: Bus Ring Star LANs are capable of very high transmission rates (100s Mb/s to G b/s).
- 34. Speed Cost Security E-mail Resource Sharing
- 35. Expensive To Install Requires Administrative Time File Server May Fail Cables May Break
- 36. A metropolitan area network(MAN) is a large computer network that usually spans a city or a large campus. A MAN is optimized for a larger geographical area than a LAN, ranging from several blocks of buildings to entire cities. A MAN might be owned and operated by a single organization, but it usually will be used by many individuals and organizations.
- 37. A MAN often acts as a high speed network to allow sharing of regional resources. A MAN typically covers an area of between 5 and 50 km diameter. Examples of MAN: Telephone company network that provides a high speed DSL to customers and cable TV network.
- 39. WAN covers a large geographic area such as country, continent or even whole of the world. A WAN is two or more LANs connected together. The LANs can be many miles apart. To cover great distances, WANs may transmit data over leased high-speed phone lines or wireless links such as satellites.
- 41. Multiple LANs can be connected together using devices such as bridges, routers, or gateways, which enable them to share data. The world's most popular WAN is the Internet.
- 42. A PAN is a network that is used for communicating among computers and computer devices (including telephones) in close proximity of around a few meters within a room. It can be used for communicating between the devices themselves, or for connecting to a larger network such as the internet. PAN’s can be wired or wireless
- 43. A personal area network(PAN) is a computer network used for communication among computer devices, including telephones and personal digital assistants, in proximity to an individual's body. The devices may or may not belong to the person in question. The reach of a PAN is typically a few meters.