Modern Telecommunication Networks Syed A. Rizvi 1
Introduction Most modern telecommunication systems transfer information in digital format. 2
Introduction (Continued) The information may consist of voice, video, computer data, etc. 3
Essential Components Essential components of a modern communication system include: 1. Computers (for information processing) 2. Input/output devices to send or receive data Input devices: keyboard, microphone, video camera, computer storage devices, etc. Output devices: display, printer, speakers, storage media 3. Communication channels: telephone lines, coaxial cable, fiber optic cable, wireless links etc. 4
Essential Comp.(Continued) 4. Supporting hardware to connect heterogeneous subnetworks: Modems, multiplexers, routers, etc. 5. Communications software 5
Communication Channels 1. Twisted wires: The oldest transmission medium Low cost Relatively slow for data transmission 2. Coaxial Cable: Consists of thickly insulated copper wire Can transmit larger amount of data Faster than twisted wire 3. Fiber Optics Cables: 1. Consists of thousands of strands of clear glass fiber 6
Communication Channels (Continued) 2. Thickness of the glass fiber is as small as the thickness of a human hair 3. Data is transmitted into pulses of light 4. More suitable for providing high-speed backbone network Advantages: 1. Lighter and more durable that coaxial cable and twisted wire 2. Can handle a very large volume of data Disadvantages: 1. Difficult to work with 2. Relatively expensive 7
Communication Channels (Continued) 1. Wireless links: Data (information) is transmitted through atmosphere via electro-magnetic waves 8
Network Topologies Star Topology: 9
Network Topologies: Star All computers in a star network are connected to each other through a host computer Host computer directs the incoming messages to the correct destination computer If the host computer goes down it affects the operation of whole star network Individual computer can be brought down for maintenance or removed without affecting the rest of the star network 10
Network Topologies (Continued) Bus network: 11
Network Topologies: Bus All computers are connected through a common line (could be a twisted wire, coaxial cable, fiber optics cable etc.) Each message is broadcasted in both directions to the entire network If a computer goes down, it does not affect the rest of the network Bus network handles one message at a time If two or more computers send messages simultaneously a collision occurs, the messages must be re-sent 12
Network Topologies (Continued) Token Ring Network: 13
Network Topologies: Token Ring In a ring network, computers are connected via a closed loop wired connection Data is transmitted in one direction A token is passed through the ring and any computer in need of transmitting the data holds the token and starts transmitting the message The computer with the delivery address receives the data When the message arrives at the source computer it signals the completion of the transmission 14
Network Topologies: Token Ring The computer holding the token then passes the token to the next computer If the next computer needs to send the data it will hold the token and start transmitting the message; otherwise, it will pass the token to the next computer 15
Local Area Network (LAN) Local area network covers a limited area such as a building or a few buildings in a close proximity 16
LAN (Continued) LAN generally use Bus or Ring topology Usually connects computer and related equipment with in 2000 feet radius Often used to connect PCs/workstation to shared printers and file-servers etc. A special computer known as network gateway connects the LAN to other networks Both wired and wireless LAN technologies are available Wide area networks (WAN) span a large geographical area and contain thousands of LANs and other heterogeneous networks in an entire continents 17
Enterprise Networking An enterprise network connects PCs, workstations, NCs, LANs, and other organization-wide computing resources together as well as to Internet 18