LECTURE 1

Question 1

What is circuit switching?

Answer 1

Circuit switching is a connection-oriented network switching technique. Here, a dedicated route is established between the source and the destination and the entire message is transferred through it.

Question 2

What are the phases of circuit switching?

Answer 2

Circuit Establishment : In this phase, a dedicated circuit is established from the source to the destination through a number of intermediate switching centres. The sender and receiver transmits communication signals to request and acknowledge establishment of circuits.

Data Transfer : Once the circuit has been established, data and voice are transferred from the source to the destination. The dedicated connection remains as long as the end parties communicate.

Circuit Disconnection : When data transfer is complete, the connection is relinquished. The disconnection is initiated by any one of the user. Disconnection involves removal of all intermediate links from the sender to the receiver.

*see doc for pic

Question 3

What are the advantages and disadvantages of circuit switching?

Answer 3

Advantages

It is suitable for long continuous transmission, since a continuous transmission route is established, that remains throughout the conversation.

The dedicated path ensures a steady data rate of communication.

No intermediate delays are found once the circuit is established. So, they are suitable for real time communication of both voice and data transmission.

Disadvantages

Circuit switching establishes a dedicated connection between the end parties. This dedicated connection cannot be used for transmitting any other data, even if the data load is very low.

Bandwidth requirement is high even in cases of low data volume.

There is underutilization of system resources. Once resources are allocated to a particular connection, they cannot be used for other connections.

Time required to establish connection may be high.

Question 4

What is multiplexing?

Answer 4

Multiplexing is the technology that is able to combine multiple communication signals together in order for them to traverse an otherwise single signal communication medium simultaneously.

Question 5

What is FDM?

Answer 5

Frequency Division Multiplexing or FDM is used when multiple data signals are combined for simultaneous transmission via a shared communication medium.It is a technique by which the total bandwidth is divided into a series of non-overlapping frequency sub-bands,where each sub-band carry different signal. Practical use in radio spectrum & optical fiber to share multiple independent signals.

Question 6

What is TDM?

Answer 6

Time Division Multiplexing : Divides into frames
Time-division multiplexing (TDM) is a method of transmitting and receiving independent signals over a common signal path by means of synchronized switches at each end of the transmission line. TDM is used for long-distance communication links and bears heavy data traffic loads from end user.
Time division multiplexing (TDM) is also known as a digital circuit switched.

Question 7

What is FDM?

Answer 7

Divides into multiple bands
Frequency Division Multiplexing or FDM is used when multiple data signals are combined for simultaneous transmission via a shared communication medium.It is a technique by which the total bandwidth is divided into a series of non-overlapping frequency sub-bands,where each sub-band carry different signal. Practical use in radio spectrum & optical fiber to share multiple independent signals.

Question 8

What is bursty internet traffic

Answer 8

Unexpected or sudden network traffic volume peaks and troughs based on seasonal factors.

*Circuit switching is unsuitable for bursty internet traffic

Question 9

What is a queue in networking and what do they introduce during packet switching?

Answer 9

a collection of data packets collectively waiting to be transmitted by a network device
They introduce variable delay and losses (when packets arrive to a full queue they are dropped)

Question 10

What does variable delay constitute of in a network?

Answer 10

Delay = Queuing delay + propagation delay + transmission delay + processing delay

Question 11

What is packet switching?

Answer 11

a mode of data transmission in which a message is broken into a number of parts which are sent independently, over whatever route is optimum for each packet, and reassembled at the destination.
* mostly for dats

Question 12

What are the advantages and disadvantages of packet switching?

Answer 12

Advantages

• There is no delay in the delivery of the packets as they are sent to the destination as soon as they are available.
• There is no requirement for massive storage space as the information is passed on to the destination as soon as they are received.
• Failure in the links does not stop the delivery of the data as these packets can be routed from other paths too.
• Multiple users can use the same channel while transferring their packets.
• The usage of bandwidth is better in case of packet switching as multiple sources can transfer packets from the same source link.

Disadvantages

• Installation costs of packet switching are expensive.
• The delivery of these packets becomes easy when complicated protocols are used.
• High-quality voice calls cannot use packet switching as there is a lot of delay in this type of communication.
• Connectivity issues may lead to loss of information and delay in the delivery of the information.

Question 13

What are the differences between circuit switching and packet switching?

Answer 13

1. CS-A circuit needs to be established to make sure that data transmission takes place. PS-Each packet containing the information that needs to be processed goes through the dynamic route.
2. CS-A uniform path is followed throughout the session. PS-There is no uniform path that is followed end to end through the session.

3CS-It is most ideal for voice communication, while also keeping the delay uniform. PS-It is used mainly for data transmission as the delay is not uniform.

4. CS-Without a connection, it cannot exist, as the connection needs to be present on a physical layer. PS- A connection is not necessary, as it can exist without one too. It needs to be present on a network layer.
5. CS- Data to be transmitted is processed at the source itself. DS-Data is processed and transmitted at the source as well as at each switching station.