Chapter 2

 Types of Network  Circuit Switched & Packet Switched  Signaling Techniques  Baseband & Broadband  Interference  Transmission Medium  Wired & wireless Prepared by Saher H. Mohammed2

 There are two kinds of networks over which data can be transmitted.  Circuit switched network  Packet switched network 3Prepared by Saher H. Mohammed

 In a circuit switched network, there is a dedicated and a direct physical connection between the sender and the receiver.  No other transmission can take place while the connection is active.  Once the current transmission is ended, other connections can be made.  Ideal for voice communication as no interruption from other devices. 4Prepared by Saher H. Mohammed

 This network requires data transmission be broken into smaller units called packets.  Each packet is sent independently through the network.  It is used for data transmission because data is not as time- sensitive as voice communication.  It allows multiple devices to share one line or frequency.  It facilitates error correction. 5Prepared by Saher H. Mohammed

 There are two ways to send a signal over a medium.  Baseband signaling  Broadband signaling 6Prepared by Saher H. Mohammed

 Sends one data signal across the network media.  Entire capacity of the media is used for the one data signal.  Signals are transmitted in a digital format.  Many devices can send and receive across the medium, but only one at a time.  Used for computer network data transmissions. 7Prepared by Saher H. Mohammed

 Divides the cable into several different channels.  Signals are transmitted at different frequencies in an analog mode.  Allows many different signals to be sent simultaneously on a single cable.  Signal sent in only one direction. 8Prepared by Saher H. Mohammed

 The flow of a signal down the network media can become distorted.  Common types of distortions are attenuation and interference. 9Prepared by Saher H. Mohammed

 Attenuation is the loss of signal power.  Measured by the decrease in decibels (db) over a specific distance. 10Prepared by Saher H. Mohammed

 Interference is caused when a strong external signal interferes with a signal.  Radio frequency interference (RFI) is an interference caused by broadcast signals from a radio or television transmitter.  Electromagnetic interference (EMI) when motor or source of intense electrical activity creates an electromagnetic signal that interferes with a data signal.  Near end crosstalk (NEXT) and Far end crosstalk (FEXT) - interference from another data signal being transmitted on adjacent wire. 11Prepared by Saher H. Mohammed

 Media is the base for communication between devices.  Coaxial cables (coax).  Twisted Pair cable.  Fiber optic cables.  Wireless. 12Prepared by Saher H. Mohammed

 Coaxial cables are very common in connecting TV’s to cable services or satellite.  It is used in these areas because of its high bandwidth and shielding capabilities.  Coax cables are less prone to the external interferences, but very costly to run. 13Prepared by Saher H. Mohammed

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 Twisted-pair cables have replaced the coax cables in the Ethernet networks.  Twisted-pair cables use the same technology used by the phone company for the movement of electrical signals.  Twisted-pair cables come if two forms,  Unshielded Twisted-pair cables  Shielded Twisted-pair cables 15Prepared by Saher H. Mohammed

 Shielded twisted-pair Cable (STP) has a foil shield around the pairs to provide extra shielding from electromagnetic interference.  Unshielded twisted-pair Cable (UTP) has no such foil around it. It uses the actual twists to eliminate interference.  STP provides better communication, but it is expensive compared to UTP. 16Prepared by Saher H. Mohammed

 The standard method of connecting twisted-pair cables is via a 8-pin connector called RJ-45 connector.  Twisted-pair cables are divided into three categories depending upon their transmission speed. DesignationCategoryDescription 10BaseTCategory 310 Mbps baseband Ethernet over twisted pair cable with a maximum length of 100 meters. 100BaseTCategory 5100 Mbps baseband Ethernet over twisted pair cable. 1000BaseTCategory Mbps baseband Ethernet over four pairs of category 5 unshielded twisted pair cables. 17Prepared by Saher H. Mohammed

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 Fiber optic cable uses a beam of laser light to connect devices over a thin glass wire.  The biggest advantage of fiber optic cables is the higher bandwidth. These cables are used as a backbone to all the large networks and internet.  The biggest disadvantage of fiber optic cables is the cost. 19Prepared by Saher H. Mohammed

 Making connection to a fiber optic cable is very difficult/ impossible.  It is very difficult to splice a fiber optic. Making the precise connections on the end of fiber optic line is a highly skilled job and is done by a specifically trained professionals.  Once the connector is fitted on the end, several forms of connectors and blocks are used to make new connections. 20Prepared by Saher H. Mohammed

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 Transmission is sent and received through invisible waves.  Unguided media is a phrase used to cover all transmission media not guided by wire or fiber.  Unguided media includes radio frequency (RF), infrared (IR) and microwave methods. 23Prepared by Saher H. Mohammed

 Unguided media have one attribute in common, that they are unguided and can travel to many machines simultaneously.  Allows the user to move freely around the office or campus and still remain connected to the network.  Fastest-growing segment of network media today.  Less expensive than copper or fiber optic lines. 24Prepared by Saher H. Mohammed

 Radio Frequency (RF) is the most common and widely used method of wireless communication.  RF waves uses variety of frequency bands, each with special characteristics.  Microwave is used to describe a specific portion of the RF spectrum that is used for communication as well as other tasks such as cooking. 25Prepared by Saher H. Mohammed

 Advantages of Microwaves  Microwaves can penetrate through thick walls  Microwaves can propagate through rough terrain  Microwaves have broadcast capability  Microwaves provide cost-effective solutions 26Prepared by Saher H. Mohammed

 IR is a band of electromagnetic energy just beyond the red end of the visible spectrum.  IR is commonly used in remote control devices, wireless devices like printers, keyboards, mice and PDA’s.  Drawbacks of IR  Slow  Cannot penetrate thick walls 27Prepared by Saher H. Mohammed

 The NIC serves as the connection between the personal computer and the network media.  It connects to the computer on its base by plugging into an expansion slot of the computer.  Another connection is accessible from the outside of the computer and has connections for the cables to plug into the network. 28Prepared by Saher H. Mohammed

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