4th Lecture - Configurations and Network Topology PDF

ECE 110 Communications 3: Data Communications Configurations and Network Topology Prepared by: Engr. Lovely Mae Dagsa, MSc., ECT Course Instructor  NETWORK Uses communication equipment to connect LAN – shares data and WAN – shares data...

ECE 110 Communications 3: Data Communications Configurations and Network Topology Prepared by: Engr. Lovely Mae Dagsa, MSc., ECT Course Instructor  NETWORK Uses communication equipment to connect LAN – shares data and WAN – shares data two or more PC based resources among users among users who are computers and their in close proximity geographically distant resources  BASIC COMPONENTS o Sending device o Communications link o Receiving device  NETWORK DESIGN Transmission Media Topology – Physical layout of components Protocol – Rules governing communication - LAN Distance - WAN - Peer-to-peer Technology - File server - Client/server  DATA TRANSMISSION o Digital lines o Sends data as distinct pulses o Need digital line o Analog lines o Sends a continuous electrical signal in the form of a wave o Conversion from digital to analog needed o Telephone lines, coaxial cables, microwave circuits  ANALOG TRANSMISSION o Alter the carrier wave o Amplitude – height of the wave is increased to represent 1 o Frequency – number of times wave repeats during a specific time interval can be increased to represent a 1  MODEM o Modulate - Convert from digital to analog o Demodulate - Convert from analog to digital o Speeds up to 56,000 bps (56K)  MODEM Transmission process o Modulation – Computer digital signals converted to analog. o Sent over analog phone line. o Demodulation – Analog signal converted back to digital.  DSL o Uses conventional telephone lines o Uses multiple frequencies to simulate many modems transmitting at once o No industry standard - Cost - Speed o Phone line shared between computer and voice  CABLE MODEM o Coaxial cables o Does not interfere with cable TV reception o Up to 10 million bps o Always on o Shared capacity o Security problem  CELLULAR MODEM o Uses cellular telephone system o Slow speed  ISDN Integrated Services Digital Network o Digital transmission o Speeds of 128,000 bps o Connect and talk at same time o Need - Adapter - Upgraded phone service o Initial costs high o Ongoing monthly fees may be high o Not available in all areas  Transmission Asynchronous and Synchronous Sending and receiving devices must work together to communicate ASYNCHRONOUS TRANSMISSION o Start/stop transmission o Start signal o Group – generally one character o Stop signal o Low-speed communications  SYNCHRONOUS TRANSMISSION o Blocks of data transmitted at a time o Send bit pattern o Align internal clock of sending / receiving devices o Send data o Send error-check bits o More complex o More expensive o Faster transmission  NETWORK CABLE o Twisted pair o Coaxial cable o Fiber optic cable o Wireless o Uses infrared or low-power radio wave transmissions o No cables o Easy to set up and reconfigure o Slower transmission rates o Small distance between nodes  TWISTED PAIR WIRE PAIR o Inexpensive o Susceptible to electrical interference (noise) o Telephone systems o Physical characteristics o Requires two conductors o Twisted around each other to reduce electrical interference o Plastic sheath o Shielded twisted pair o Metallic protective sheath o Reduces noise o Increases speed  COAXIAL CABLE o Higher bandwidth o Less susceptible to noise o Used in cable TC systems o Physical characteristics o Center conductor wire o Surrounded by a layer of insulation o Surrounded by a braided outer conductor o Encased in a protective sheath  FIBER OPTICS o Transmits using light o Higher bandwidth o Less expensive o Immune to electrical noise o More secure – easy to notice an attempt to intercept signal o Physical characterizes o Glass or plastic fibers o Very thin (thinner than human hair) o Material is light  MICROWAVE TRANSMISSION o Line-of-site o High speed o Cost effective o Easy to implement o Weather can cause interference o Physical characteristics o Data signals sent through atmosphere o Signals cannot bend of follow curvature of earth o Relay stations required  SATELLITE TRANSMISSION o Microwave transmission with a satellite acting as a relay o Long distance o Components o Earth stations – send and receive signals o Transponder – satellite o Receives signal from earth station (uplink) o Amplifies signal o Changes the frequency o Retransmits the data to a receiving earth station (downlink) SATELLITE TRANSMISSION  NETWORK TOPOLOGY o Network topologies describe the ways in which the elements of a network are mapped. They describe the physical and logical arrangement of the network nodes. o The physical topology of a network refers to the configuration of cables, computers, and other peripherals Components of a Network Topology Diagrams  NETWORK TOPOLOGY o Physical layout o Bus Topology o Start Topology o Ring Topology o Mesh Topology o Tree Topology o Hybrid Topology o Node – any device connected to the network o Server o Computer o Printer o Other peripheral  BUS TOPOLOGY o All the nodes (file server, workstations, and peripherals) on a bus topology are connected by one single cable. o 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. o Popular on LANs because they are inexpensive and easy to install. BUS TOPOLOGY  BUS TOPOLOGY Advantages of Bus Topology o It is Cheap, easy to handle and implement. o Require less cable o It is best suited for small networks. Disadvantages of Bus Topology o The cable length is limited. This limits the number of stations that can be connected. o This network topology can perform well only for a limited number of nodes.  RING TOPOLOGY o In a ring network, every device has exactly two neighbours for communication purposes. o All messages travel through a ring in the same direction. o A failure in any cable or device breaks the loop and can take down the entire network. o To implement a ring network we use the Token Ring technology. o A token, or small data packet, is continuously passed around the network. When a device needs to transmit, it reserves the token for the next trip around, then attaches its data packet to it. RING TOPOLOGY  RING TOPOLOGY Advantage of Ring Topology o Very orderly network where every device has access to the token and the opportunity to transmit. o Easier to Mange than a Bus Network o Good Communication over long distances o Handles high volume of traffic Disadvantages of Ring Topology o The failure of a single node of the network can cause the entire network to fail. o The movement or changes made to network  STAR TOPOLOGY o In a star network, each node (file server, workstations, and peripherals) is connected to a central device called a hub. o The hub takes a signal that comes from any node and passes it along to all the other nodes in the network. o Data on a star network passes through the hub, switch, or concentrator before continuing to its destination. o The hub, switch, or concentrator manages and controls all functions of the network. o The star topology reduces the chance of network failure by connecting all of the systems to a central node. STAR TOPOLOGY  STAR TOPOLOGY Advantages of Star Topology o Easy to manage o Easy to locate problems (cable/workstations) o Easier to expand than a bus or ring topology. o Easy to install and wire. o Easy to detect faults and to remove parts. Disadvantages of Star Topology o Requires more cable length than a linear topology. o If the hub or concentrator fails, nodes attached are disabled. o More expensive because of the cost of the concentrators.  TREE TOPOLOGY o A tree topology (hierarchical topology) can be viewed as a collection of star networks arranged in a hierarchy. o This tree has individual peripheral nodes which are required to transmit to and receive from one other only and are not required to act as repeaters or regenerators. o The tree topology arranges links and nodes into distinct hierarchies in order to allow greater control and easier troubleshooting. o This is particularly helpful for colleges, universities and schools so that each of the connect to the big network in some way. TREE TOPOLOGY  TREE TOPOLOGY Advantages of a Tree Topology o Point-to-point wiring for individual segments. o Supported by several hardware and software vendors. o All the computers have access to the larger and their immediate networks. Disadvantages of a Tree Topology o Overall length of each segment is limited by the type of cabling used. o If the backbone line breaks, the entire segment goes down. o More difficult to configure and wire than other topologies.  MESH TOPOLOGY o In this topology, each node is connected to every other node in the network. o Implementing the mesh topology is expensive and difficult. o In this type of network, each node may send message to destination through multiple paths. o While the data is travelling on the Mesh Network it is automatically configured to reach the destination by taking the shortest route which means the least number of hops. MESH TOPOLOGY  MESH TOPOLOGY Advantage of Mesh Topology o No traffic problem as there are dedicated links. o It has multiple links, so if one route is blocked then other routes can be used for data communication. o Points to point links make fault identification easy. Disadvantage of Mesh Topology o There is mesh of wiring which can be difficult to manage. o Installation is complex as each node is connected to every node. o Cabling cost is high.  HYBRID TOPOLOGY o A combination of any two or more network topologies. o A hybrid topology always accrues when two different basic network topologies are connected. o It is a mixture of above mentioned topologies. Usually, a central computer is attached with sub-controllers which in turn participate in a variety of topologies HYBRID TOPOLOGY  HYBRID TOPOLOGY Advantages of a Hybrid Topology o It is extremely flexible. o It is very reliable. Disadvantages of a Hybrid Topology o Expensive  ORIENTATION AND CLASS POLICIES The End. Next Topic: “Transmission Media”