Computer Network Unit 1 q what are the topologies in computer n/w ?

Destination Address -- Contains a unicast (singular), multicast (group), or broadcast (every station) address. As with Ethernet and Token Ring addresses, FDDI destination addresses are 6 bytes long.
Source Address -- Identifies the single station that sent the frame. As with Ethernet and Token Ring addresses, FDDI source addresses are 6 bytes long.
Data -- Contains either information destined for an upper-layer protocol or control information.
Frame Check Sequence (FCS) -- Filled by source station with a calculated cyclic redundancy check (CRC) value dependent on frame contents (as with Token Ring and Ethernet). The destination address recalculates the value to determine whether the frame was damaged in transit. If so, the frame is discarded.
End Delimiter -- Contains nondata symbols that indicate the end of the frame.
Frame Status -- Allows the source station to determine if an error occurred and if the frame was recognized and copied by a receiving station.
Q 11. Explain X-25 protocol recommended for telephony and telegraphy by CCITT.
Ans: The X.25 protocol, adopted as a standard by the Consultative Committee for International Telegraph and Telephone (CCITT), is a commonly-used network protocol. The X.25 protocol allows computers on different public networks (such as CompuServe, Tymnet, or a TCP/IP network) to communicate through an intermediary computer at the network layer level. X.25's protocols correspond closely to the data-link and physical-layer protocols defined in the Open Systems Interconnection (OSI) communication model.

Configuration Procedures

This section defines the detail for configuring the network displayed in figure,

This configuration shows three routers, the Concentrator router, Remote 1 router, and Remote 2 router. To get XTP up and running on this network, you need to perform the following steps for each of these routers.

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  Set the data-link type
  
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  Configure IP
  
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  Configure X.25
  
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  Configure XTP