What advantage does a circuit switched network has over a packet switched network list the advantages of TDM over FDM in a circuit switched network?

Circuit switching is a type of network configuration in which a physical path is obtained and dedicated to a single connection between two endpoints in the network for the duration of a dedicated connection. Ordinary voice phone service uses circuit switching. This reserved circuit is used for the duration of a call. As long as the call lasts, the circuit cannot be used for anything else.

In circuit switching, the bandwidth and data transmission rate are fixed. Circuit switching is connection-oriented, meaning a physical connection between hosts is required for it to work.

What is circuit switching used for?

Examples of where circuit switching is used include the following:

• Continuous connections. Circuit switching is used for connections that must be continuous for long periods of time, such as long-distance communication. Traditional telephone systems -- i.e., landlines -- are an example of a technology that uses circuit switching.
• Dial-up network connections. When computers connect to the internet via a dial-up service, it uses the public switched network. With dial-up, Internet Protocol (IP) data packets are carried over a circuit-switched telephone network.
• Optical circuit switching. Data center networks also use circuit switching. Optical circuit switching is used to scale traditional data centers and meet growing bandwidth requirements.

What are the phases of circuit switching?

These are the three main phases of circuit switching:

1. Connection establishment. Also called call setup, this phase establishes a dedicated circuit between two communicating endpoints. The parties send a message back and forth acknowledging the established connection. There are usually intermediate links or switches between the two parties.
2. Data transfer. Data -- usually voice -- is transmitted from the source to the destination. The connection remains intact for the length of the interaction.
3. Connection relinquishment. This is also called the teardown phase. At the end of the interaction, one of the two endpoints sends a message initiating a disconnection. The communication path, including the intermediate links, is terminated.

How do packet-switched and circuit-switched networks differ?

The main difference between packet-switched vs. circuit-switched networks is that circuit-switched networks are connection-oriented and packet-switched networks are connectionless. Voice over IP is a telephony protocol that uses packet switching.

In packet switching, information is broken into data packets that are sent through the network independently of one another. There is no fixed, dedicated channel as there is in circuit switching. Instead, packets are sent over a network that other hosts share. Transmission also is not continuous.

Some packet-switched networks, such as X.25, have switched virtual circuits. Virtual circuit switching establishes a dedicated connection using packet-switching technology. A virtual circuit-switched connection is a dedicated, logical connection that enables multiple virtual circuit connections to share a physical path.

Packet switching does not reserve all the bandwidth for a connection in advance. Because of that, it is more energy-efficient. One drawback to packet switching is that transmission quality can be poor because there can be lost or dropped packets.

What are the advantages of circuit-switched networks?

The advantages of circuit-switched networks include the following:

• Dedicated channel. Circuit-switched networks reserve a dedicated communications channel circuit that only the two endpoints can access.
• Reliable. A dedicated circuit between two hosts for the duration of that connection decreases the potential for data loss or other reliability problems.
• Security. Circuit-switched networks are more secure than packet-switched networks due to having only two communicating parties on a dedicated circuit.
• Quality. Once a connection is established, this type of network generally has a consistent connection quality without delays in data flow.

What are the disadvantages of circuit-switching?

The drawbacks of using a circuit-switched network include the following:

• Limited use. Circuit-switched networks can only be used for voice communication and aren't available for other types of connections.
• Inefficient. When a circuit is continuously reserved even when it's not in use, network bandwidth is wasted.
• Inflexible. A dedicated channel can only be used for circuit-switched network traffic and nothing else. And, if there aren't enough dedicated channels, calls can fail.
• Higher cost. A dedicated channel costs more per use.
• Latency. Extra time is required to establish a connection before data is sent.

The takeaway

Circuit switching is the foundation of traditional telecommunication systems and landlines. Packet switching is the basis of the modern internet. Each has advantages and disadvantages. And, sometimes, they overlap -- for example, when a packet switching network emulates circuit-switching technology and establishes a connection-oriented method of data transfer.

Today, the internet and most phone services rely on packet switching. But most legacy networks were designed for circuit-switched traffic. New optical routing architecture could help close this gap.

In circuit switching network resources (bandwidth) are divided into pieces and bit delay is constant during a connection. The dedicated path/circuit established between sender and receiver provides a guaranteed data rate. Data can be transmitted without any delays once the circuit is established. 

Telephone system network is one of the example of Circuit switching. TDM (Time Division Multiplexing) and FDM (Frequency Division Multiplexing) are two methods of multiplexing multiple signals into a single carrier. 

• Frequency Division Multiplexing : 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 fibre to share multiple independent signals.
• 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.

Advantages of Circuit Switching: It has the following advantages : 

1. The main advantage of circuit switching is that a committed transmission channel is established between the computers which give a guaranteed data rate.
2. In-circuit switching, there is no delay in data flow because of the dedicated transmission path.

Disadvantages of Circuit Switching: It has the following disadvantages : 

1. It takes a long time to establish a connection.
2. More bandwidth is required in setting up dedicated channels.
3. It cannot be used to transmit any other data even if the channel is free as the connection is dedicated to circuit switching.

Formulas in Circuit Switching : 
 

Question on Circuit switching – These questions will help you understand circuit switching  

Example 1 : How long it takes to send a file of ‘x bits’ from host A to host B over a circuit switched network that uses TDM with ‘h slots’ and have a bit rate of ‘R Mbps’, circuit establish time is k seconds.Find total time? 

Explanation : Transmission rate = Link Rate or Bit rate / no. of slots = R/h bps 

Transmission time = size of file/ transmission rate = x / (R/h) = (x*h)/R 

Total time = transmission time + circuit setup time = (x*h)/R secs + k secs  

Example 2 : If a link transmits F frames/sec and each slot has B bits then find the transmission rate? 

Explanation : Since it is not mention how many slots in each frame we take one frame has one slot. The transmission rate is the amount of data sent in 1 second. Transmission rate = F * B bits/sec 

To know the difference between Circuit Switching and Packet Switching refer – Difference b/w Circuit switch & packet switch 
 

References : 
https://en.wikipedia.org/wiki/Circuit_switching 
https://en.wikipedia.org/wiki/Frequency-division_multiplexing 

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