1. Circuit Switching
Definition:
Circuit Switching is a method of communication where a dedicated communication path (or circuit) is established between the sender and the receiver for the duration of the transmission. It is typically used for real-time communication where continuous data flow is needed.
Examples:
- Traditional telephone networks (e.g., landlines)
- Early cellular networks
Characteristics:
- Dedicated Path: Once the circuit is established, it remains reserved for the entire duration of the call or session.
- Fixed Bandwidth: The bandwidth is constant and dedicated, meaning no one else can use the circuit during the session.
- Connection Establishment: Before transmission, a connection must be set up between the sender and receiver, which can take time.
- Predictable: Data is sent in a continuous stream without delay, making it ideal for voice and video communication.
- Inefficient in Low Traffic: The dedicated circuit is underutilized if the data flow is sporadic or low.
2. Packet Switching
Definition:
Packet Switching divides the data into small packets, which are transmitted independently over the network. Each packet may take a different path to reach the destination, where the packets are reassembled in the correct order. This method is the basis of the internet and is commonly used for data communication.
Examples:
- Internet
- File transfers (FTP, HTTP)
Characteristics:
- No Dedicated Path: The network does not reserve a specific path. Instead, data is split into smaller packets that are routed independently.
- Dynamic Routing: Each packet may take a different route based on network conditions and congestion.
- Variable Bandwidth: Bandwidth is shared among all users and may vary depending on network usage and congestion.
- Efficient: More efficient than circuit switching in terms of resource usage, especially for bursty or sporadic data transmission.
- Latency and Delay: Data packets may experience delays, especially during high traffic periods or when packets are re-routed.
- Error Handling: Packet switching allows for easy retransmission of lost packets (e.g., in TCP/IP).
Comparison of Circuit Switching and Packet Switching
| Feature | Circuit Switching | Packet Switching |
|---|---|---|
| Path Establishment | Requires establishment of a dedicated circuit before communication. | No need for a dedicated path; packets are sent independently. |
| Bandwidth | Fixed and dedicated bandwidth for the entire session. | Shared bandwidth among all users; bandwidth can vary. |
| Data Transmission | Continuous and predictable data flow. | Data is divided into packets that may take different paths. |
| Efficiency | Less efficient for sporadic or low traffic. | More efficient, especially for bursty traffic. |
| Use Case | Ideal for real-time applications (voice, video calls). | Ideal for data transmission (web browsing, emails). |
| Reliability | Reliable once the circuit is established. | Reliability is ensured through error detection and retransmission. |
| Cost | High, as resources are reserved even when not used. | Cost-effective, as resources are shared. |
| Delay | Low delay (fixed path, no rerouting). | Higher delay due to possible rerouting and congestion. |
Problems with Circuit Switching
- Inefficient Use of Resources:
- If the circuit is reserved but not fully utilized (e.g., during silent periods in a phone call), the bandwidth is wasted.
- Scalability Issues:
- As the number of users grows, the number of required circuits increases, which can lead to network congestion.
- Fixed Delay:
- Circuit switching works well for continuous data streams, but it might not perform well when data flows sporadically.
Example Problem:
A telephone call is made between two users. The connection is established, and the bandwidth is reserved for the entire duration of the call, even if no one is speaking. This leads to inefficient use of network resources, as the dedicated path remains occupied during silent periods.
Problems with Packet Switching
- Variable Latency:
- Packets may experience delays due to network congestion or the different paths they take to the destination.
- Packet Loss:
- If the network becomes congested, some packets may be dropped, requiring retransmission, which can affect real-time communication.
- Out-of-Order Delivery:
- Packets may arrive at the destination out of order, requiring reassembly at the receiver’s end.
Example Problem:
When browsing the internet, a large file is downloaded. Due to network congestion, the packets may arrive at different times, causing some packets to be delayed or dropped. The receiving system must wait for all packets to be received and in the correct order before assembling the file.
Real-World Examples of Circuit Switching and Packet Switching:
- Circuit Switching Example:
- Landline Telephone: When a call is made from one landline phone to another, a dedicated circuit is established between the two phones for the duration of the call. This ensures that the voice data flows continuously without interruption.
- Packet Switching Example:
- Internet Communication: When you visit a website, your computer sends packets of data across the internet. Each packet may travel a different route, depending on the current network conditions. Once all the packets reach the destination, they are reassembled to form the webpage you requested.
Summary
- Circuit Switching is ideal for applications that require constant, uninterrupted data flow, such as voice calls or video streaming. It provides low, consistent latency but is inefficient for low traffic.
- Packet Switching is highly efficient for data communication, especially for applications that involve bursty traffic like web browsing, email, or file transfers. However, it can introduce latency and packet loss, which can be problematic for real-time services.
