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Saturday, November 24, 2012
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The first commercial application of ALOHA channels was launched in 1976 by Comsat General in the Marisat maritime satellite communications system. At about the same time Metcalfe working with a group from DEC, Intel and Xerox (the DIX Group) formulated an open Ethernet standard based on the Alto ALOHA network. Since 1983 ALOHA channels have been adopted for use in all major mobile telephone standards (1G, 2G and 3G) as the control channel and then for a variety of packet data channels integrated into these voice networks (e.g. GPRS and UMTS). ALOHA has also been adopted for use in a variety of protocols used in wired networks, CSMA/CD and CSMA/CA in single channel local area networks and DOCSIS for commercial cable networks.
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Question 1 [5 Marks]For each Ethernet standard given in the table write each name/value against the titles of the next three columns.
| Ethernet Standards | Ethernet Name | Data Rate | Cable Used |
| 10BaseT | Twisted pair Ethernet | 10 Mbps | Category 5 |
| 100BaseT | Fast Ethernet | 100 Mbps | Category 5E |
| 1000BaseT | Gigabit Ethernet | 1 Gbps | Category 6 |
Question 2 [10 Marks]Write appropriate answer against each technology/requirement.
| Technologies | Access method used |
| Wireless LAN | CSMA/CA - Carrier Sense Multiple Access with Collision Avoidance |
| Ethernet | CSMA/CD: Carrier Sense Multiple Access / Collision Detection |
| Ring networks | Token Passing |
| ALOHA-net | CSMA/CD , CSMA/CA , DOCSIS |
| Requirements | The best cable to be used |
| For Secure and fast delivery | Fiber Optic |
| To make a network of 15 PC’s with low budget | UTP - Unshielded Twisted Pair |
| For cable TV network | Coaxial Cable |
| Requirements | The best topology |
| If using Central hub | Star Topology |
| Provide more security | Mesh topology is the most secure topology because in mesh topology each device has a dedicated link to others . |
| If one system disconnect will disturb all network | Ring Topology |
