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Networking- computer connections
The document discusses computer networks and data communications. It describes how networks allow computers to be connected over long distances to share resources and process data in a distributed manner. The key components of a network include sending and receiving devices connected by a communications link. Different types of networks exist depending on the distance between nodes, from local area networks (LANs) to wide area networks (WANs). The document outlines various methods for data transmission, network topologies, protocols, and applications of computer networking.
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Networking- computer connections
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- 2. Data Communications Sendand receive information over communications lines Centralized Data Processing All processing, hardware, software in one central location Inefficient Inconvenient
- 3. Distributed Data Processing Computers at a distance from central computer Can do some processing on their own Can access the central computer
- 4. Network Uses communication equipmentto connect two or more computers and their resources PC based LAN – shares data and resources among users in close proximity WAN – shares data among users who are geographically distant Basic Components Sending device Communications link Receiving device
- 5. Network Design TransmissionMedia Topology – Physical layout of components Protocol – Rules governing communication Distance/proximity LAN, CAN, MAN, WAN Technology Peer-to-peer File server Client/server
- 6. Data Transmission Digitallines Sends data as distinct pulses Need digital line Analog lines Sends a continuous electrical signal in the form of a wave Conversion from digital to analog needed Telephone lines, coaxial cables, microwave circuits
- 7. Analog Transmission Alterthe carrier wave Amplitude – height of the wave is increased to represent 1 Frequency – number of times wave repeats during a specific time interval can be increased to represent a 1
- 8. Modem- Data Transmission •Analog signal converted back to digital Demodulation • Sent over analog phone line Transmission • Computer digital signals converted to analog Modulation
- 9. Digital Transmission Lines Cable Modem Coaxial cables/ Dish TV Does not interfere with cable TV reception Up to 100 Mbps Always on, Shared capacity, Security? Integrated Services for Digital Network (ISDN) A set of communication standards/protocols for simultaneous digital transmission of voice, video, data, and other network services ISDN is today primarily used for voice and fax traffic DSL- Digital Subscriber Line Uses conventional telephone lines Uses multiple frequencies/many transmitting at once No industry standard Phone line shared between computer and voice Cellular Modems Speed Cost Convenience Compatibility
- 10. Transmission using clock Asynchronous Start/stop transmission Start signal Group – generally one character Stop signal Less speed, less traffic Synchronous Blocks of data transmitted at a time Send bit pattern Align internal clock of sending / receiving devices Send data Send error-check bits More complex, expensive, speed
- 11. Asynchronous and Synchronous Sendingand receiving devices must work together to communicate Dedicated Clock for data transmission!
- 12. Direction of dataflow- Duplex Setting Simplex One direction Television broadcasting Arrival/departure screens at airport Half-duplex Either direction, but one way at a time CB radio Bank deposit sent, confirmation received Full-duplex Both directions at once Telephone conversation
- 13. Communications Media Physicalmeans of transmission Bandwidth Range of frequencies that the medium can carry Measure of capacity
- 14. Cables Wired Twistedpair Coaxial cable Fiber optic cable Wireless Uses infrared or low-power radio wave transmissions No cables Easy to set up and reconfigure Slower transmission rates Small distance between nodes
- 15. Twisted Pair- WirePair Considerations Inexpensive Susceptible to electrical interference (noise) Example- Telephone systems Shielded twisted pair Metallic protective sheath Reduces noise Increases speed Physical characteristics Requires two conductors Twisted around each other to reduce electrical interference Plastic sheath
- 16. Coaxial Cable Higherbandwidth Less susceptible to noise Used in cable TC systems Physical characteristics Center conductor wire Surrounded by a layer of insulation Surrounded by a braided outer conductor Encased in a protective sheath
- 17. Fiber Optics Transmitsusing light Higher bandwidth Less expensive Immune to electrical noise More secure – easy to notice an attempt to intercept signal Physical characterizes Glass or plastic fibers Very thin (thinner than human hair) Material is light
- 18. Microwave Transmission Consideration High frequency is larger data capacity Line-of-site ~ shorter distance Cost effective Easy to implement Weather can cause interference microwave relay Physical characteristics Roughly 1-30 GHz ~ 30 cm-1.0 cm Data signals sent through atmosphere Signals cannot bend of follow curvature of earth Relay stations required
- 19. Satellite Transmission asa Microwave Relay
- 20. Satellite Transmission Microwavetransmission with a satellite acting as a relay Long distance Components Earth stations – send and receive signals Transponder – satellite Receives signal from earth station (uplink) Amplifies signal Changes the frequency Retransmits the data to a receiving earth station (downlink)
- 21. Dhaka to Luxemburg Request made Twisted pair in the phone lines on the East Coast Microwave and satellite transmission across the country Twisted pair in the phone lines on the West coast Data transferred Twisted pair in the phone lines on the West Coast Microwave and satellite transmission across the country Twisted pair in the phone lines on the East coast
- 22. Network Topology Physical layout-Star, Ring, Bus … Node – any device connected to the network (topology). E.g. Server, Computer, Printer, Other peripheral
- 23. Network Topology Star Central hub Allmessages routed through hub Hub prevents collisions Node failure – no effect on overall network Hub failure – network fails Ring Travel around circular connection in one direction Node looks at data as it passes • Addressed to me? • Pass it on if not my address No danger from collisions Node failure – network fails Bus Single pathway All nodes attached to single line Collisions result in re-send Node failure – no effect on overall network
- 24. LAN- Local AreaNetwork Consideration Connections over short distances Low Cost- equipment, maintenance Easy setup Components PCs Network cable NIC Connects computer to the wiring in the network Circuitry to handle Sending, Receiving, Error checking
- 25. Connecting Networks- LANs Hubs Bridge – connects networks with similar protocols Switch (IP switches) Replacing routers Less expensive Faster Router – directs traffic via best path Gateway Connects LANs with dissimilar protocols Performs protocol conversion
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- 27. WAN- Wide AreaNetwork Link computers in geographically distant locations
- 28. Communication Service Provider Common carriers licensed by FCC in the US Bangladesh Telecommunication Regulatory Commission (BTRC) Bangladesh Telegraph and Telephone Board (BTTB) Switched/dial-up service Temporary connection between 2 points Ex: plain old telephone service (POTS) Dedicated service Permanent connection between 2 or more locations Ex: Build own circuits, Lease circuits (leased lines)
- 29. High Capacity DigitalLines T1 digital transmission system (American) a single physical wire pair can be used to carry many simultaneous voice conversations by time-division multiplexing connect major telephone exchanges 1.54 Mbps ~ 24 simultaneous voice connections T3 is 28 T1 lines = 43 Mbps Expensive, High-volume traffic E2 digital transmission system (European) E2: multiplexing level 2: 8 Mbit/s
- 30. Multiplexer Combines datastreams from slow-speed devices into single data stream Transmits over high-speed circuit (ex T1) Multiplexer on receiving end needed to restore to component data streams
- 31. Client/Server- e.g. afile server Clients Other computers on network Thin client – no processing Server Controls the network Hard disk holding shared files Organization of Resources
- 32. Client/Server How itworks Client sends request for service to server Server fulfills request and send results to client Client and server may share processing File Server System Server does authentication and transmits file to client Client does own processing Benefits Reduces volume of data traffic Allows faster response for each client Nodes can be less expensive computers Organization of Resources
- 33. Peer-to-Peer Technology Allcomputers have equal status Share data and devices as needed Disadvantage – slow transmission Hybrid- Contains elements of various organizations to optimize transmission speed and organizational needs
- 34. Protocol Set ofrules governing the exchange of data Assists with coordination of communications Was message received properly? TCP/IP- Internet standard Transmission Control Protocol / Internet Protocol All computers in world speak same language
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- 36. Ethernet Dominant protocol Bus or star topology Uses CSMA/CD- Carrier sense multiple access with collision detection Tries to avoid 2 or more computers communicating at the same time Computer listens and transmits when cable is not in use Collision results in waiting a random period and transmitting again Performance degrades with multiple collisions
- 37. Ring topology- TokenRing No danger from collisions Token passing Token has an address Node looks at token as it passes Addressed to me? Retrieve data Pass it on if not my address Send Empty token? Attach message Pass it on if not empty
- 38. Application of thenetwork File Transfer Software Download- Receive a file from another computer Upload- Send a file to another computer Terminal Emulation Software PC imitates a terminal for communication to mainframe Micro-to-mainframe link
- 39. Office Automation Communication Applications E-mail Facsimile (Fax) Groupware Teleconferencing Video conferencing ATM Electronic fund transfers Telecommuting Online services The Internet Electronic data interchange (EDI)
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- 41. Objectives Describe thebasic components of a network Explain the methods of data transmission, including types of signals, modulation, and choices among transmission modes Differentiate among the various kinds of communications links and appreciate the need for protocols Describe various network configurations List the components, types, and protocols of a local area network Appreciate the complexity of networking Describe some examples of networking
- 42. Contents Data Communications Network Data Transmission Communications Media Network Topology Local Area Network Wide Area Network Organization of Resources Protocol Software Communication Applications
Editor's Notes
- #10 ISDN- Integrated Services Digital Network Digital transmission Speeds of 128,000 bps Connect and talk at same time Need Adapter Upgraded phone service Initial costs high Ongoing monthly fees may be high Not available in all areas
- #26 A hub is a simple device that sends all data to all devices connected to the hub. A hub provides no error checking, and no filtering, it simply forwards everything. Every device connected to a hub shares the same broadcast domain and so is in the same collision domain. Sometimes hubs are divided into passive and active. A passive hub does nothing except provide a path fo A bridge is used to connect two networks, and therefore has one port for each network. A bridge operates at the Data Link layer (layer 2) of the OSI model; therefore, it can read the MAC (Media Access Control) addresses in the data packets. A bridge has internal RAM. When a bridge first starts up, it behaves like a hub. But as the bridge receives packets from each network, it builds a table of the source MAC addresses on each segment.r the data. An active hub regenerates the signal before sending it along. The operation of the switch is almost identical to that of a bridge. The MAC address table of a switch is built by inspecting the source MAC address of frames. Forwarding decisions are made using the destination address of frames. When the switch receives a frame, it looks at the destination MAC address and then forwards it out only the port associated with that MAC address. Like a bridge, a switch will always forward all broadcast and frames with unknown destinations to every port, with the exception of the port on which the transmission originated. Routers Forward packets based on information at layer 3 and above Establish network address translation (NAT) boundaries Terminate virtual circuits (VPNs) Encrypt and decrypt traffic Implement complex filters (stateful inspection, routing policy, etc.) Support modular physical interfaces of several types Switches Forward packets (frames, if you prefer) primarily at layer 2 Aggregate many connections into a few higher-bandwidth links Provide a much higher-throughput backplane Include mostly fixed copper or fiber Ethernet interfaces
- #30 Before the digital T-1 system, carrier wave systems such as 12-channel carrier systems worked by frequency division multiplexing; each call was an analog signal.