Module Three

Extranet n extranet can be accessed by users outside

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Extranet n Extranet can be accessed by users outside of the company, (i.e. vendors and partners) but not the general public. n Includes some type of authentication or encryption
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Asynchronous vs. Synchronous Communications n Asynchronous is basis of modems and dial up remote access. Must operate at same speed. n Start and stop bits mark the beginning and the end of each transfer. n Synchronous is very high speed, governed by electronic clock timing signals. Common Data Network Services: Files Services – Share data files and subdirectories on file server Mail Services – send and receive mail internally and externally Print Services – Print documents to shared printers Client/ Server Services – Allocate computing resources among workstations Domain Name Service – Matches Internet Uniform Resource Locator (URL) with the actual IP address of the server providing the URL. Maps host names to IP Addresses. The Domain Name System (DNS) is a global network of servers that provide this service. Data Networking Technologies: LAN Cabling Types: Twisted Pair Cable n Relatively slow speed n Two insulated wires can be shielded (STP) or unshielded (UTP) n UTP is a four-pair medium comes in several categories n UTP can be easily tapped by eavesdroppers than the other cable types. n Category based on how tightly wound the wires are, tighter the wind the higher the rating and resistance to interference. n Cat 1 UTP– was used for telephone lines not good for data. n Cat 2 UTP – up to 4 MBps n Cat 3 UTP – Used for 10BaseT networks up to 10 MBps n Cat 4 UTP – Used in Token Ring Networks up to 16 MBps n Cat 5 UTP - Current UTP standard for new installations up to 100 MBps n Cat 6 UTP – up to 155 MBps n Cat 7 UTP – up to 1 GBps Coaxial Cable n Hollow outer conductor surrounds inner wire conductor. Currently two types in LANs n 50-ohm Cable for digital signaling n 75-ohm Cable for analog signaling and high speed digital signaling n Coax is more expensive but is more resistant to Electromagnetic Interference (EMI). n Used rarely except in Broadband communications n Comes in two types: n Thinnet – (RG58) n Thicknet – (RG8 or RG11) n Two common types of coaxial transmission methods: n Baseband – The cable carries a single channel n Broadband – cable carries several channels such as data, voice, audio, and video Fiber Optic Cable n Conducts modulated light transmission n Light waves are faster and travel greater distances n Difficult to tap
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n Resistant to EMI n Usually connects backbones in larger networks n Can be used to connect workstations to the network. n Expensive to install and to terminate. LAN Transmission Protocols: n Rules for communication between computers on a LAN n Formatting of the data frame, the timing and sequencing of packet delivery, and resolution of error states. Carrier Sense Multiple Access (CSMA)
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Extranet n Extranet can be accessed by users outside of the...

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