ACN Sample Paper 1 (1).docx

MODEL TEST PAPER 1 Subject: Advance Computer Networks Q1 (a) What is Hidden and Exposed problem? Ans. The exposed node problem occurs when a node is prevented from sending packets to other nodes due to a neighboring transmitter. The hidden node problem or hidden terminal problem occurs when a node is visible from a wireless access point (AP), but not from other nodes communicating with that AP. This leads to difficulties in media access control. (b)Explain the advantages and disadvantages of Fiber Distributed Data Interface?

Ans.     

Advantages:

FDDI supports real-time allocation of network bandwidth. This allows you to use a wide array of different types of traffic. FDDI has a dual ring that is fault-tolerant. The benefit here is that if a station on the ring fails or if the cable becomes damaged, the dual ring is automatically doubled back onto itself into a single ring. The FDDI compensates for wiring failures. The stations wrap within themselves when the wiring fails. Optical bypass switches are used that can help prevent ring segmentation. The failed stations are eliminated from the ring. Disadvantages:

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There's a potential for multiple ring failures. As the network grows, this possibility grows larger and larger. The uses of fiber optic cables are expensive. This has kept many companies from deploying FDDI in a widespread manner. Instead, they have been using copper wire and the similar method of CDDI. (c) Explain the following term in respect to ATM technology:Virtual Path:- The bandwidth of the transmission path is logically divided into separate virtual paths and identified using the VPI in the ATM header. Each virtual path is allocated a fixed amount of bandwidth. Virtual paths do not dynamically vary their bandwidths beyond what has been allocated. Virtual Connection:- The bandwidth of a virtual path is logically divided into separate virtual channels using a virtual channel identifier in the ATM header. Unlike virtual paths, virtual channels share the bandwidth within a virtual path dynamically. UNI:- UNI is the interface between the ATM end user and a private ATM switch. It also can represent the interface between a private ATM switch and the public carrier ATM network. SVC:- An SVC is an on-demand connection that is dynamically established by end devices through the Network-Network Interface (NNI) signaling method. There must be an ATM switch between the end-devices that dynamically route the call through the ATM cloud. Network operators do not have to manually configure every ATM switch in the path. If there is a link failure, the end-device must reinitiate the SVC call.

(d) Differentiate between Wi Fi and Wimax. Ans. Freature

WiMax (802.16a)

Wi-Fi (802.11b)

Wi-Fi (802.11a/g)

Primary Application

Broadband Wireless Access

Wireless LAN

Wireless LAN

Frequency Band

Licensed/Unlicensed 2 G to 11 GHz

2.4 GHz ISM

2.4 GHz ISM (g) 5 GHz U-NII (a)

Channel Bandwidth

Adjustable 1.25 M to 20 MHz

25 MHz

20 MHz

Half/Full Duplex

Full

Half

Half

Radio Technology

OFDM (256-channels)

Direct Sequence Spread Spectrum

OFDM (64-channels)

Bandwidth Efficiency