Question

7. CIR is the actual frame relay network throughput realized at times of low usage. True or False?

a. True

b. False

8. Which of the following factors might influence the use of a frame relay network over a T1 mesh network?

a. Number of endpoints (networks) that need to be connected

b. Types of computers being used

c. Type of router being used to connect the network

d. Physical circuit being used

9. A PAD serves what purpose on an X.25 network?

a. It assigns frames locally significant DLCIs as they traverse the network switches

b. It accepts byte streams from synchronous DTE and assembles them into X.25 packets

c. It provides an interface between the PSTN and the packet network

d. It accepts data from an asynchronous DTE and assembles that data into X.25 packets

10. Which are the X.25 virtual circuit stages? (Choose three.)

a. Call setup

b. Call cancel

c. Data transfer

d. Call clearing

Answer 1

7.CIR is the actual frame relay network throughput realized at times of low usage. False

Explanation :

• CIR is the maximum bandwidth at which data will be delivered guaranteed.
• Suppose two networks purchase speed 64 KB and 128 KB respectively with effective CIR 64 KB over the same leased line.
• At times of high usage, both networks will get the same speed as CIR i.e 64 KB.
• At times of low usage, the first network will get speed as CIR i.e 64 KB and the second network will get a speed between 64 KB to 128 KB. (CIR<speed<=PIR)
• If the first network is not using the leased line, the second network will get its maximum speed i.e 128 KB.
• The reason behind this is that the second network gets better speed is EIR ( excess information rate) in addition to CIR that is peak information rate (PIR = CIR + EIR)

8.Which of the following factors might influence the use of a frame relay network over a T1 mesh network?

Ans: a. Number of endpoints (networks) that need to be connected.

Explanation :

• The type of computers and routers used does not affect the performance of the frame relay.
• Frame relay makes use of virtual circuits instead of physical to remove errors and redundancies.
• The number of links required depends on the number of endpoints that need to be connected.
• For n nodes, we require (n - (n - 1)) / 2 which is less than usual links required in mesh topology without frame relay. This influences the use of frame relay in the T1 mesh network.

  9. A PAD serves what purpose on an X.25 network?

Ans: d.It accepts data from an asynchronous DTE and assembles that data into X.25 packets.

Explanation :

• PAD is a communication device which provides multiple asynchronous terminal connectivity(DTEs) to an X.25 network.
• During assembly, it accepts data from these asynchronous DTEs and assembles into X.25 packets.
• During disassembly, it accepts data from the packet-switching network and returns it in a character stream to transfer to the terminals.

10. Which are the X.25 virtual circuit stages?

Ans :

a. Call setup

c. Data transfer

d. Call clearing

Explanation :

• Call setup Stage is used to establish SVCs between DTE devices.
• Data Transfer Stage is used for transferring data between two DTE devices across a virtual circuit after establishing a virtual circuit.
• Call Clearing Stage is used to end communication sessions between DTE devices and terminate SVCs.
• There is no Call Cancel Stage.