Basics of Communication & NetworkingNetworkingSlide 3Communication BasicsSlide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Types of NetworksSlide 13Intranets and ExtranetsFirewallsTypes of LANsSlide 17Components of LANsSlide 19Communication ChannelsSlide 21Slide 22Slide 23Slide 241Basics ofCommunication & Networking2Networking•A computer network is a collection of computing devices that are connected in various ways in order to communicate and share resources•Usually, the connections between computers in a network are made using physical wires or cables–However, some connections are wireless, using radio waves or infrared signals•The generic term node or host to refer to any device on a network•A key issue related to computer networks is the data transfer rate, the speed with which data is moved from one place on a network to another3Networking•Computer networks have opened up an entire frontier in the world of computing called the client/server model–A file server is a computer that stores and manages files for multiple users on a network–A Web server is a computer dedicated to responding to requests (from the browser client) for Web pages–A mail server is a computer that stores email messages for multiple users and routes the messages to the email clients when a request is made.–Network printers …Client/Server interaction4Communication Basics•Properties of Transmission:–Each link has common attributes–1. Type of signal communicated (analog or digital)–2. The speed at which the signal is transmitted.–3. The type of data movement allowed on the channel.–4. The method used to transport the data.–5. Single channel and multichannel transmission.5Communication Basics•Type of signal communicated.–Analog - A continuously changing signal similar to that found in voice transmission (e.g., phone lines).–Digital - Signals consist of pulses of electrical energy that represent 0’s or 1’s.6Communication Basics•MODEM - MOdulator DEModulator–Outgoing: Converts binary data from computer (digital) into telephone compatible signals (analog).–Incoming: Converts telephone signal (analog) into binary data for the computer (digital).7Communication Basics•Type of data movement.–Three types of data movement can occur on a channel:Simplex transmission - One way transmission.Half-duplex transmission - Can flow only one way at a time.Full-duplex transmission - Two-way transmission at the same time.8Communication Basics•Method of transmission.–Two types of data transmission, each requiring a different modem.•Asynchronous transmission–data is sent one byte at a time, with each string of bits making up the byte bracketed with special control bits•Synchronous transmission–data is sent in blocks, with start and stop bit patterns (synch bytes) at the beginning and end of the blocks9Communication Basics•Single channel versus multi-channel transmission–Channel - A path of a signal.–Single channel - Capable of only sending/receiving one signal at a time.Phone line - Single line = single phone call at a time.–Multi-channel - Capable of more than one channel at a time.Fiber-optic cable, microwaves, Satellite transmissions.10Communication Basics•How is it possible to measure the capacity of communications links?•Bandwidth –In Digital:Number of bits per second (bps) that can be sent over a link.Wider bandwidth, the more diverse kinds of information can be sent.Simplest is voice, most sophisticated is moving videos.–In Analog:The difference between the highest and lowest frequencies that can be sent over an analog link (like phone lines).Measurement is given in hertz (Hz).–For both: The wider the bandwidth, the more information can flow over the channel.11Communication BasicsTypical cable bandwidths used in local area networks.Cable: Typical Bandwidth:Twisted Pair 10 to 100 MbpsCoaxial Cable 10 to 100 MbpsFiber-optic cable 100 to 200 MbpsThe bandwidths of different services offered by a telephone company:Service: BandwidthISDN 64 KbpsT1 1.544 MbpsT3 44.736 MbpsSTS-1 51.840 MbpsSTS-3 155.250 MbpsSTS-12 622.080 MbpsSTS-24 1.244160 GbpsSTS-48 2.488320 Gbps Mbps = megabits per second (millions) Gbps=Gigabits per second (billions)12Types of Networks•A local-area network (LAN) connects a relatively small number of machines in a relatively close geographical area•A wide-area network (WAN) connects two or more local-area networks over a potentially large geographic distance–Often one particular node on a LAN is set up to serve as a gateway to handle all communication going between that LAN and other networks•Communication between networks is called internetworking–The Internet, as we know it today, is essentially the ultimate wide-area network, spanning the entire globe13Types of NetworksLocal-area networks connected across a distance to create a wide-area network14Intranets and Extranets•Intranet - an organization’s internal private network that uses the infrastructure and standards of the Internet and the WWW•Extranets - private intranets that connect not only internal personnel but also selected suppliers and other strategic parties15Firewalls•A firewall is a machine and its software that serve as a special gateway to a network, protecting it from inappropriate access–Filters network traffic that comes in, checking the validity of the messages as much as possible and perhaps denying some messages altogether–Enforces an organization’s access control policy16Types of LANs•Client/server LAN:–Clients - microcomputers that request data; and–Server - a powerful microcomputer that manages shared devices17Types of LANs•Peer-to-peer LAN–all microcomputers on the network communicate directly with one another without relying on a server18Components of LANs19Components of LANsHub A device that repeats or broadcasts the network stream of information to individual nodes ( usually personal computers) Switch A device that receives packets from its input link, and then sorts them and transmits them over the proper link that connects to the node addressed. Bridge A link between two networks that have identical rules of communication. GatewayA link between two different networks that have different rules of communication. Router A node that sends network packets in one of many possible directions to get them to their destination. Hub A device that repeats or broadcasts the network