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Circuit Switching in Computer Network

Creating and maintaining a dedicated communication connection between two devices in a computer network is done through the use of circuit switching. In contrast to packet switching, which is more frequently used in contemporary computer networks like the Internet, this technique was previously utilized in telephony networks.

Circuit switching is a communication technique in which two devices establish a dedicated and continuous communication path (referred to as a circuit) for the duration of the communication session. This circuit stays open and is only used by the parties conversing, ensuring a steady and uninterrupted flow of data. The Public Switched Telephone Network (PSTN), one of the more well-known traditional telephone networks, made heavy use of circuit switching, which was initially created for voice transmission.

Characteristics of Circuit Switching

1. Dedicated Communication Path:

Circuit switching establishes a dedicated and continuous communication link or circuit between two devices (such as telephones) when they desire to connect with one another for the duration of the discussion. This route is set up specifically for their communication and is available throughout the whole exchange.

2. Resource Reservation:

Network resources, including bandwidth and routing information, are reserved throughout the full path from the source to the destination in order to construct a circuit-switched connection. By doing this, a constant and guaranteed level of resources is made available throughout the communication.

3. Fixed Bandwidth:

Even if there are brief pauses or periods of inactivity during the conversation, the reserved bandwidth is fixed and stays allotted for the duration of the call. This can result in an ineffective use of the network's resources, particularly for discussions with irregular traffic patterns.

4. Low Latency:

Due to the dedicated path, circuit-switched networks often have low latency since data may be transferred without interruptions from packet routing or network resource competition.

Circuit Switching in Historical Context

  • Traditional Telephony:

The PSTN and other classic telephone networks were built around circuit switching. A dedicated circuit was created between the caller and the recipient when a user dialed a number, ensuring a clear and continuous speech connection.

  • Limited Data Applications:

Circuit switching was also utilized for data communication in the early days of computer networking. b. Limited Data Applications. However, it worked best for applications that required constant data streams, such as mainframe computer connections and early videoconferencing systems.

Phases in Circuit Switching

In computer networks, circuit switching entails a number of discrete steps to create and maintain a dedicated communication connection between two devices. These steps guarantee consistent, dependable communication over the course of the session. The main steps in circuit switching are as follows:

1. Call Establishment Phases:

  • Request for Connection:

The conversation starts with one device (the caller) asking the other (the callee) to connect. The user often initiates this request by picking up the phone and calling a number for example.

  • Resource Reservation:

In response to the request, the network sets aside the bandwidth and switching hardware required along the whole communication line to accommodate the call. These resources have been set aside specifically for the connection.

2. Call Setup Phases:

  • Path Establishment:

From the caller to the callee, the network creates a specialized communication path (or circuit). This route often entails a number of logical and physical connections made via switches and other network components like transmission lines.

  • Path Verification:

After the path has been constructed, the network checks to make sure it is functioning and prepared to transmit data. This check makes that the circuit is clear of flaws or problems that can obstruct communication.

3. Data Transfer Phase:

Data can be sent continuously between the caller, and the callee once the dedicated circuit is established and authenticated. Since there is constant data flow throughout this phase, it is appropriate for real-time applications like voice calls.

4. Call Termination Phase:

  • User Request:

A call termination request is made when one of the parties (often the caller or callee) desires to discontinue the contact. For instance, hanging up the phone on someone signifies the end of a phone call.

  • Resource Release:

The network releases the reserved resources connected to the circuit after receiving the termination request. By doing this, network resources and bandwidth are made available for use by other calls or data transmissions.

5. Call Release Phases:

  • Deactivation of the Circuit:

The call's dedicated circuit is deactivated by the network. The resources are no longer solely dedicated to the ended call thanks to this deactivation.

  • Connection Closure:

When the circuit is turned off, the communication is deemed to be finished, and the devices go back to their idle state where they are prepared for incoming calls or other communications.

6. Connection Maintenance (optional):

Periodic maintenance may be necessary in some circumstances, especially for calls with longer durations or connections that transmit data continuously. The quality and integrity of the circuit are inspected during this maintenance phase to guarantee ongoing, dependable communication.

It's significant to remember that circuit switching is frequently related to speech communication, like conventional phone conversations. For a clear and continuous speech connection in this setting, the steps mentioned above are crucial. Many of these phases, however, are no longer relevant because modern computer networks are moving toward packet switching, which dynamically routes and transmits data in smaller, discrete packets rather than allocating a continuous circuit.

Types of Circuit Switching in Computer Networks

Circuit-switched networks and circuit-switched virtual circuits are the two main Traditional voice communication systems like the Public Switched Telephone Network (PSTN) are frequently linked with circuit-switched networks. A dedicated physical circuit is formed for the whole communication period in this kind of circuit switching. The following are the main traits:

1. Circuit-Switched Networks:

  • Dedicated Physical Circuit:

During the whole connection, a physical communication line is set up between the calling and receiving parties. In order to maintain a connection, this dedicated circuit is only used for the continuing conversation.

  • Resource Reservation:

Network resources, such as bandwidth and switching hardware, are reserved from the beginning to the end. This booking ensures a constant and unbroken connection line, making it perfect for voice calls. varieties of circuit switching used in computer networks, which creates a dedicated communication path for the duration of a session.

  • Inefficiency for Data:

Circuit-switched networks are excellent at delivering a dependable and clear voice connection, but they are less effective at communicating data, particularly when the data transfer patterns are irregular or contain bursts of activity.

Example:

A well-known illustration of circuit-switched networks is the use of traditional landline telephone networks. A dedicated physical circuit is created from your phone to the recipient's phone when you make a call, and it remains in place throughout the conversation.

2. Circuit-Switched Virtual Circuits:

Circuit-switched virtual circuits, which offer some flexibility and efficiency gains over conventional circuit-switched networks, combine aspects of circuit switching and packet switching. Here is how they function.

  • Virtual Circuits:

In a packet-switched network, circuit-switched virtual circuits build logical pathways as opposed to establishing a dedicated physical circuit. These "virtual circuits," also known as logical routes, imitate the behaviour of dedicated circuits without consuming physical resources for the duration of the session.

  • Resource Allocation:

Just like traditional circuit switching, virtual circuits also entail resource allocation, but they do so in a more flexible and effective manner. Dynamic resource allocation minimizes the inefficiencies associated with maintaining fixed bandwidth during the session.

Example:

Asynchronous Transfer Mode (ATM) and Frame Relay are two examples of circuit-switched virtual circuit technology. In the past, they were employed for data communication, allowing devices to communicate with one another without a specific physical circuit being required.

Comparison

Circuit-switched networks are ideal for real-time applications like phone conversations because they provide a high level of reliability and minimal latency. However, they are less effective for transmitting data, particularly when there are fluctuations in traffic patterns.

The efficiency of packet switching and the dependability of circuit switching are balanced by circuit-switched virtual circuits. They offer logical communication pathways within a packet-switched infrastructure, which increases their adaptability to various data kinds and traffic patterns.

In computer networks, there are two basic types of circuit switching: virtual circuit switching, which creates logical routes within packet-switched networks, and classic circuit switching networks with dedicated physical circuits. The decision between each type depends on the particular requirements of the communication and the network architecture being used, and each has advantages and cons of its own.

Advantages of Circuit Switching

Despite, its declining use in contemporary networks, dominated by packet switching, the older technique of circuit switching for establishing communication in computer networks still has numerous advantages in some circumstances. For the duration of a session, circuit switching offers a dedicated and continuous communication connection between two devices. We shall examine the benefits of circuit switching in computer networks in this essay.

1. Reduced Latency

Low latency is a well-known characteristic of circuit switching. Data may be sent with little delay once the dedicated circuit is in place. This qualifies it for real-time applications like audio and video calls where low latency is essential. Low latency guarantees that discussions are natural and clear in applications like telephony, free of observable delays that could impair communication.

2. Predictable Quality of Service (QoS)

Throughout the communication session, circuit switching ensures a predictable and consistent degree of service quality. There is no competition for resources because network resources, including bandwidth, are reserved in advance. This implies that regardless of other network activity, the communication's quality remains consistent. For services like mission-critical communications and emergency services that demand guaranteed QoS, this predictability is extremely significant.

3. Assurance of Bandwidth

A predetermined amount of bandwidth is promised via circuit switching for the duration of the connection. This is especially helpful for applications like high-definition video conferencing and uncompressed audio transmission that demand a steady and high data flow. Due to changes in network demand, the communication will be kept as uninterrupted as possible thanks to the reserved bandwidth.

4. Basic Routing:

In order to switch circuits, a dedicated path must be established between the source and the destination. This path, once defined, does not change during the communication session. The reliability of circuit-switched connections is increased by this routing's simplicity while the complexity of network management is decreased.

5. Efficient for Continuous Data Streams:

Circuit switching performs best in situations like voice and video calls where data transmission is sustained and constant. It is a good option for these applications because it reduces the overhead of packetization, addressing, and routing.

6. Security:

Circuit switching already offers some degree of security. Less prone to eavesdropping and interception than packet-switched networks, where data is split up into separate packets that can be intercepted, because the communication line is dedicated to the session.

7. Legacy Support:

The PSTN and other conventional telecommunications networks are heavily reliant on circuit switching. Circuit switching is still necessary for legacy maintenance even if these networks are rapidly converting to packet switching. It guarantees compatibility with earlier communication technologies and apparatus.

8. Deterministic Behavior:

Circuit switching provides predictable behaviour. Given that the dedicated circuit is established and maintained throughout the call, users may predict the network's behaviour with reliability. In crucial applications like air traffic control and financial trading, where network behavior needs to be accurately managed, this predictability is advantageous.

9. Simplicity of Implementation:

In some circumstances, implementing circuit switching can be less complicated than implementing packet switching, particularly where resource reservation and real-time traffic control are crucial needs.

Disadvantages of Circuit Switching

1. Inefficient Resource Utilization

Circuit switching uses network resources, especially bandwidth, inefficiently, which is one of its biggest downsides. Even if there are times of inactivity or quiet throughout the conversation, the bandwidth in a circuit-switched network is allocated and allotted only for the duration of the communication. Resources are wasted as a result, which may be better applied to other forms of communication.

2. Unsuitability for Bursty Traffic

For traffic patterns that feature bursts of data transmission followed by idle times, circuit switching is not a good fit. Such circumstances could result in an inefficient use of network resources since a dedicated circuit with a set bandwidth allocation may not be fully utilized during inactive times. Circuit switching is less able to adapt to the changing and unexpected data traffic patterns present in contemporary computer networks as a result of this constraint.

3. Scalability Challenges

It can be not easy to scale circuit switching effectively, especially in big networks with many simultaneous connections. It is expensive and difficult to manage network expansion as the need for dedicated circuits and resources grows along with the number of users and sessions. The scalability of packet-switched networks, which may dynamically assign resources as needed, contrasts with this restriction.

4. Lack of Flexibility

Circuit switching is not flexible enough to accommodate various data and application kinds. It performs best with continuous data streams like audio and video calls but is less effective with applications that need fluctuating bandwidth and sporadic data delivery. Its usefulness in the various network contexts of today is constrained by this rigidity.

5. Extended Setup

There are multiple steps involved in establishing a circuit-switched connection, including call establishment, path configuration, and verification. In contrast to packet-switched connections' almost immediate setup time, this process may take a while. The setup time may be a significant disadvantage for applications that require quick responses or short-term connections.

6. Unsuitability for Data Networks

Although circuit switching was once employed for voice transmission, it is unsuitable for usage in contemporary data networks. Due to its effectiveness and versatility, packet switching, for instance, is heavily utilized on the internet. Circuit-switched networks and data networks thus frequently need complicated interworking protocols and infrastructure, which causes problems with compatibility.







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