3-Lect_3 (3).pdf

Computer Networks LEC #3 Computer Networks Communicating LECOver #2 the Network Communicating Physical components of aOver network the Network Lecture Outlines Network Devices. Network Transmission Me...

Computer Networks LEC #3 Computer Networks Communicating LECOver #2 the Network Communicating Physical components of aOver network the Network Lecture Outlines Network Devices. Network Transmission Medium.. Intranet, extranet, internet Network ❑A network is simply a collection of computers or other hardware devices that are connected together using special hardware and software, to allow them to exchange information and cooperate. ❑The main purpose of a network is to share resources: ❖ A file A folder A printer A disk drive ❖ Or just about anything else that exists on a computer.  Network Devices ❑ Equipment that connects directly to a network segment is referred to as a device. ❑ These devices are broken up into two classifications: ❑ end-user devices ❑ Intermediate network devices End-user devices Intermediate devices Intermediate Network Devices Bridge Hub Repeater Switch Router Repeater a. Without Repeater b. With Repeater. A repeater is a network device Repeaters regenerate or amplify signals used to regenerate a signal. distorted before retransmitting it. A repeater does not perform intelligent routing like a bridge Resides on Layer 1(physical or router. layer ) of the OSI model. Hub (multi-port repeater) ❖A network hub is a node that broadcasts data to every computer or device connected to it. ❖When a data frame transmits to a hub, the hub immediately resends it to all connecting links. ❖Hubs expand one Ethernet connection into many. For example, a four-port hub connects up to four machines. ❖Resides on Layer 1 (physical layer ) of the OSI model. Bridge ❖The bridge is used to divide LANs into multiple segments. ❖It makes intelligent decisions about whether to pass signals onto the next segment of a network. ❖When a bridge sees a frame on the network, it looks at the destination MAC address, and compares it to the forwarding table to determine how to pass the data. ❖Connects two or more LANs in the same domain. ❖Resides on Layer 2(Data Link Layer) of the OSI model. Switch ❖switches add more intelligence to data transfer management. ❖Split large networks into small segments, decreasing the number of users sharing the same network resources and bandwidth. ❖It uses forwarding tables to determine the destination of data being sent by one computer to another on the network. ❖Switch not only can determine whether data should remain on a LAN or not, but they can transfer the data only to the host that needs that data. ❖Resides on Layer 2 of the OSI model. 9  Router ❖It connects at least two networks together (e.g. two LANs or WANs or a LAN to WAN). ❖It uses standardized protocols to move packets efficiently to their destination. ❖More sophisticated than bridges, it connecting networks of different types (for example, star and token ring) ❖Forwards data depending on the Network address (IP), not the Hardware (MAC) address. (routing table). ❖Resides on Layer 3 of the OSI model. 10 Modem (MODulator/DEModulator) ❖It is a hardware device used to convert the digital data used by your computer into an analog signal used on phone lines and then converting it back once received on the other end. ❖Types of computer modems: Internal modem: It is installed as interface cards inside the computer. External modem: It is more expensive and connect to the serial port on the computer using connector. It is useful when several users need to share a modem. PCMCIA modem: It is credit-card-sized modem for laptop computers used by mobile workers. Voice/data/fax modem: It is used for file transfer, sending and receiving faxes, and voice mail using associated software.  Additional Network Hardware Devices ❖Network Interface Cards (NICs): A network interface card (NIC) is a card plugged into a motherboard and provides ports for the network media connections. It allows computers to be joined together in a network. ❖Proxy server Isolates internal network computers from the internet. A proxy server It allows hosts to make indirect network connections to other network services. A host connects to the proxy server, and then requests a connection, file, or other resource available on a different server. The proxy provides the resource by connecting to the specified server. 12 Network Transmission Media Network Transmission Media ❑ Network media is the channel over which a message travels ✓ Copper cable: The signals are patterns of electrical pulses. ✓ Fiber-optic cable: The signals are patterns of light. ✓ Wireless: The signals are patterns of microwave transmissions. ❑ Choose Medium Depend on: Wiring configurations. Distance and location limitations. Speed. Security. Budget. Network Transmission Media ❖Electrical (copper cable): Twisted pair : Four pairs of wires twisted to certain specifications. Available in shielded and unshielded versions. Coaxial Cable: Single copper conductor in the center surrounded by a plastic layer for insulation and a braided metal outer shield. 15 Network Transmission Media ❖Fiber-optic - A cable, consisting of a center glass core surrounded by layers of plastic, that transmits data using light rather than electricity. ❖Atmosphere/Wireless – Uses Electromagnetic waves. whose frequency range is above that of microwaves, but it is below the visible spectrum (radio, microwave, infrared). 16 Fiber Optic versus Copper Cabling Implementation issues Copper media Fibre-optic Bandwidth supported 10 Mbps – 10 Gbps 10 Mbps – 100 Gbps Relatively short Relatively High Distance (1 – 100 meters) (1 – 100,000 meters) Immunity to EMI and RFI ( ‫التداخل‬ High Low ‫)الكهرومغناطيسي والتداخل الراديوي‬ (Completely immune) High Immunity to electrical hazards Low (Completely immune) Media and connector costs Lowest Highest Installation skills required Lowest Highest Safety precautions Lowest Highest Intranet, Extranet, and Internet  Intranet and Extranet Intranet ▪Intranet means private LANs and WANs connection that belongs to an organization and is designed to be accessible only by the organization's members, or others with authorization. ▪For example, schools may have intranets that include information on class schedules, online curriculum, and discussion forums. ▪ Intranets help to eliminate paperwork and speed up workflows. The intranet may be accessible to staff working outside of the organization by using secure connections to the internal network. Extranet An organization may use an extranet to provide secure and safe access to individuals who work for a different organizations but require company data. Examples: I. A company providing access to outside suppliers/contractors. II. A hospital providing a booking system to doctors so they can make appointments for their patients. III.A local office of education providing budget and personnel information to the schools in its district. Internet Internet The internet is defined as a global mesh of interconnected networks Connecting to the Internet CABLE: Typically offered by cable television service providers, the Internet data signal is carried on the same coaxial cable that delivers cable television. ❑ DSL (Dedicated subscriber Line) - Provides a high bandwidth, always on, connection to the Internet. ❑ It requires a special high-speed modem that separates the DSL signal from the telephone signal and provides an Ethernet connection to a host computer or LAN. ❑ DSL runs over a telephone line, with the line split into three channels. Dial-up Telephone - An inexpensive option that uses any phone line and a modem. Satellite - Satellite service is a good option for homes or offices that do not have access to DSL or cable. Cellular - Cellular Internet access uses a cell phone network to connect. Example : 1. Converted to Binary. 2. NIC generates signals. 3. Passed among LAN devices. 4. Exit the local area (router). Example : 5. Bits are transmitted to devices that interconnect the networks. Example : 6. Passed among local devices at the destination. 7. The destination device converts the bits into human readable form. Summary Video1 https://www.bing.com/videos/search?q=differences+between+con necting+devices+in+network&&view=detail&mid=C0B7D44E532191 FC2E05C0B7D44E532191FC2E05& 26