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The correct CHOICE is (a) FRAD assembles and disassembles the frames COMING from other protocols

Easy explanation: FRAD stands for Frame Relay Assembler/Disassembler. It converts packets into frames that can be transmitted over Frame Relay NETWORKS. It operates at the physical layer.

Correct answer is (a) to INCREASE the RANGE of data link connection identifiers

Best explanation: Extended address is indicated by the last bit of every address byte in the DLCI. It specifies whether the byte is the last in the ADDRESSING FIELD. It is used to increase the range of data link connection identifiers.

Right OPTION is (c) PHYSICAL layer and data link layer

Explanation: The physical layer is guided by the protocols recognized by the ANSI and PROVIDES CONVERSION to frames. The data link layer supports the simplified core functions specified by the OSI model like ERROR detection.

Correct CHOICE is (a) data link CONNECTION identifier

To explain I WOULD say: The Data Link Connection Identifier is 10-bit VIRTUAL circuit identifier. It is used to assign frames to the specified Permanent Virtual Circuits or Switched Virtual Circuits.

The correct OPTION is (b) data link LAYER

The best I can explain: Frame relay PROVIDES error detection using CRC in the data link layer. The transport layer then provides the error correction features if an error is detected.

Correct ANSWER is (d) SONET

Explanation: Frame Relays uses carriers such as SONET (for fiber-optic CONNECTIONS) to PHYSICALLY TRANSMIT DATA frames over a Frame Relay network. SONET is cheaper and provides better network reliability than other carriers.

The correct choice is (c) Upper Level Protocol

Explanation: Frame relay only provides error detection using CRC. If ERRORS are detected, the upper-LAYER protocols, such as TCP are expected to provide error CORRECTION FEATURES. Network layer provides flow control.

The correct CHOICE is (c) Nine

To explain I would say: Frame relay is a WIDE area network technology used to transmit information over a network in the form of FRAMES using relays. The frames are of variable size. It is CHEAPER than other WANs and it’s SIMPLE to configure user equipment in the network.

Correct option is (b) WANs

Explanation: Frame relay is a standardized wide area NETWORK TECHNOLOGY and is popularly used because it is CHEAPER than leased line WANs. It is ALSO very simple to configure user equipment in a Frame Relay network.

The correct OPTION is (a) FRAD assembles and disassembles the frames coming from other protocols

The best EXPLANATION: FRAD stands for Frame Relay Assembler/Disassembler. It converts packets into frames that can be transmitted over Frame Relay Networks. It operates at the physical layer.

The correct option is (a) to increase the range of data link CONNECTION identifiers

Explanation: Extended ADDRESS is indicated by the last bit of every address BYTE in the DLCI. It SPECIFIES whether the byte is the last in the addressing field. It is used to increase the range of data link connection identifiers.

The CORRECT answer is (d) both physical and data link LAYER

The best I can EXPLAIN: The physical layer is guided by the protocols recognized by the ANSI. The data link layer supports the simplified CORE functions specified by the OSI model.

Correct answer is (a) data link connection identifier

The best I can explain: The Data Link Connection Identifier is 10-bit virtual CIRCUIT identifier. It is USED to ASSIGN frames to the SPECIFIED PERMANENT Virtual Circuits or Switched Virtual Circuits.

Correct option is (b) data LINK layer

To explain: The Frame Relay header contains an 8-bit Header ERROR CONTROL field (HEC). The HEC field contains an 8-bit CRC which is used for error control.

Correct choice is (b) 48 bytes

For explanation: An ATM field CONTAINS a header and a payload. The header is of 5 bytes and the payload is of 48 bytes. The SIZE of the header REMAINS FIXED.

Right option is (d) networks covering any range

The explanation: ATM is a connection oriented network for cell relay which can be implemented for networks covering any area. It USES TIME Division Multiplexing and supports voice, video and DATA COMMUNICATIONS.

The correct choice is (B) 3

The best I can explain: The three layers are physical LAYER, ATM layer and application adoption layer. The physical layer corresponds to the physical layer, ATM layer corresponds to the DATA link layer and the AAL layer corresponds to the NETWORK layer of the OSI MODEL.

The correct CHOICE is (b) asynchronous time division multiplexing

The BEST explanation: ATM uses a constant data stream consisting of TRANSMISSION cells to transmit information in a fixed division of time. The packet size remains fixed.

Right ANSWER is (a) virtual circuit networks

To EXPLAIN: ATM and frame relay are transmission MODES in which information is transferred through ELECTRIC circuit layer as PACKETS. ATM has fixed packet size and frame relay has variable packet size.

Correct answer is (d) 4

Easiest EXPLANATION: The SWITCH maintains a table for each Virtual Circuit Network. In the data transfer phase, it maintains 2 columns each for INCOMING data and outgoing data. The columns are in the following order: SOURCE port, Source VCI, DESTINATION port, Destination VCI.

Correct option is (a) 1 and 1

To EXPLAIN I WOULD say: There is one-time delay for both setup and teardown phase. The one-time delay in setup phase is for resource ALLOCATION and the one-time delay in teardown phase is for the de-allocation of the RESOURCES.

The correct ANSWER is (d) different for each PACKET

Best explanation: If a resource is to be allocated on demand during the data transfer phase, the delay for each packet WOULD be different depending upon the resource REQUIREMENT of the PACKETS.

The CORRECT choice is (c) same for each PACKET

For EXPLANATION I would say: If a resource is allocated during SETUP phase, delay is same for each packet as there is only one-time delay during the setup phase and no delay during the DATA transfer phase.

Right CHOICE is (b) TEARDOWN request

Explanation: The source, after sending all the FRAMES to destination sends teardown request to which, destination sends teardown RESPONSE. The switches then DELETE the corresponding table entries.

Right choice is (a) SETUP request and ACKNOWLEDGEMENT

Explanation: Setup request (sent by a source) and acknowledgement (sent by the DESTINATION) are the STEPS in the setup process. Both the ENDS’ switches make table entries during the setup process.

Correct option is (C) Termination PHASE

To ELABORATE: There are three phases in a virtual circuit network: setup, data transfer and teardown phase. There is no termination phase in it.

Correct option is (B) VIRTUAL circuit identifier

The best I can explain: A virtual circuit identifier is a TYPE of numeric IDENTIFYING address that is used to distinguish between different virtual circuits in a circuit-switched network. It is used for data transfer and has a switch scope.

The correct CHOICE is (a) Global address

For EXPLANATION: Global address is a NETWORK address that is unique internationally and is used as a common address by all the USERS of the network. It is used to create a virtual circuit IDENTIFIER.

Right option is (b) ADDITIVELY

To EXPLAIN: In the congestion avoidance algorithm, the SIZE of the congestion window increases additively until congestion is detected. Once congestion is detected, the size of congestion window is DECREASED once and then the packets are transmitted to achieve congestion avoidance.

Correct answer is (a) exponentially

Best explanation: In slow-start algorithm, the size of the congestion window increases exponentially until it reaches a threshold. When it reaches the threshold, it stops increasing and CONTINUES sending PACKETS through the threshold window thus PREVENTING congestion.

Right option is (c) Choke

The explanation is: Choke packet is sent by a NODE to the source to inform it of CONGESTION. TWO choke packet techniques can be used for the OPERATION called hop-by-hop choke packet and source choke packet.

Right option is (d) Virtual circuit NETWORKS

The BEST I can explain: In Virtual circuit networks, each node knows the upstream node from which a flow data is COMING. So, it makes possible for the congested node to track the source of the congestion and then INFORM that node to reduce the flow to remove congestion.

The correct option is (b) Backpressure

To EXPLAIN I would say: In this closed loop congestion control TECHNIQUE, the congested node propagates in the opposite direction of the data flow to inform the predecessor node to reduce the flow of PACKETS. This is why this technique is CALLED a node-to-node congestion control technique.

The correct option is (a) Remove after CONGESTION occurs

Explanation: In closed LOOP congestion control, METHODS are implemented to remove congestion after it occurs. Some of the methods used are BACKPRESSURE and choke packet.

Correct choice is (c) Router

For explanation: The discarding policy ADOPTED by the routers mainly states that the routers DISCARD sensitive or corrupted packets that it receives, thus controlling the integrity of the PACKET flow. The discarding policy is adopted as an open loop congestion control TECHNIQUE.

Right option is (b) Only those packets which are lost or corrupted

Explanation: In Selective REPEAT, the sender SIDE uses a searching algorithm to find the packets which NEED to be retransmitted based on the negative ACKNOWLEDGEMENTS received and then resends only those packets thus saving bandwidth.

The correct option is (d) Packet is error-free

The best I can explain: Retransmission refers to the sender having to RESEND the packet to the RECEIVER. It NEEDS to be DONE only when some anomaly OCCURS with the packet like when the packet is lost or corrupted.

Correct CHOICE is (a) Open-loop and Closed-loop

The explanation is: Open loop congestion CONTROL TECHNIQUES are used to prevent congestion before it even happens by enforcing certain POLICIES. Closed loop congestion control techniques are used to treat congestion after it has HAPPENED.