CS2302-COMPUTERNETWORKS

17. Define Aggregation points?

            It collects and processes the data they receive from neighboring nodes, and then transmit the processed data. By processing the data incrementally, instead of forwarding all the raw data to the base station, the amount of traffic in the network is reduced.

18. Define Beacons?

            Beacon to determine their own absolute locations based on GPS or manual configuration. The majority of nodes can then derive their absolute location by combining an estimate of their position relative to the beacons with the absolute location information provided by the beacons.

19. What is the use of Switch?

            It is used to forward the packets between shared media LANs such as Ethernet. Such switches are sometimes known by the obvious name of LAN switches.

20. Explain Bridge?

            It is a collection of LANs connected by one or more bridges is usually said to form an extended LAN. In their simplest variants, bridges simply accept LAN frames on their inputs and forward them out on all other outputs.

21. What is Spanning tree?

            It is for the bridges to select the ports over which they will forward frames.

22. What are the three pieces of information in the configuration messages?

1.      The ID for the bridge that is sending the message.

2.      The ID for what the sending bridge believes to the root bridge.

3.      The distance, measured in hops, from the sending bridge to the root bridge.

23. What is broadcast?

            Broadcast is simple – each bridge forwards a frame with a destination broadcast address out on each active (selected) port other than the one on which the frame was received.

24. What is multicast?

            It can be implemented with each host deciding for itself whether  or not to accept the message.

25. How does a given bridge learn whether it should forward a multicast frame over a given port?

            It learns exactly the same way that a bridge learns whether it should forward a unicast frame over a particular port- by observing the source addresses that it receives over that port.

26. What are the limitations of bridges?

·         scale

·         heterogeneity

27. Write short notes on CRC.(NOV/DEC 2007)

The third and most powerful of the redundancy checking techniques is the cyclic redundancy checks (CRC) CRC is based on binary division. Here a sequence of redundant bits, called the CRC remainder is appended to the end of data unit.

28. Define HDLC.(NOV/DEC 2007)

It is a bit-oriented data link protocol designed to support both half-duplex and full duplex communication over point to point and midpoint links.

29. List the types of stations is HDLC.

HDLC differentiates between 3 types of stations.

a) Primary

b) Secondary

c) Combined

30.Give the examples of common packet mode multiple access protocols for wired multi-drop networks are:

• CSMA/CD (used in Ethernet and IEEE 802.3) (NOV/DEC 2007)
• Token bus (IEEE 802.4)
• Token ring (IEEE 802.5)
• Token passing (used in FDDI)

31. Define HUB.

• HUB is a repeater which is a OSI model device. Hubs are common connection point for devices in a network and are commonly used to connect segment of a LAN.