What is Congestion Control in Computer Networks?

Sometimes, we have faced the situation when our data does not get transferred properly or takes a lot of time to get delivered. To resolve this difficulty, a congestion control process is followed. In this article, readers will get a brief understanding of congestion control in computer networks. This article will define what congestion means in the context of Computer Networks. The article will also explain the negative effects of congestion, including degraded network performance, increased latency, and packet loss.

What is Congestion Control in Computer Networks?

Congestion control in computer networks refers to the set of techniques, mechanisms, and protocols designed to manage and regulate the flow of data traffic within a network to prevent congestion. It is a vital aspect of network management, aimed at ensuring the efficient and reliable transfer of data while avoiding the degradation of network performance due to overload.

When the demand for network resources exceeds its capacity, congestion occurs. Similar to traffic congestion on busy roads, network congestion leads to delays, increased latency, packet loss, and reduced throughput. This can severely impact the overall user experience, hinder critical applications, and result in a loss of productivity and revenue for businesses.

The primary goal of congestion control is to balance the usage of available network resources, preventing any single component from becoming overwhelmed. It achieves this by actively monitoring network conditions, detecting congestion indicators, and taking appropriate actions to alleviate congestion or prevent it from occurring in the first place.

Effects of Congestion in Computer Network

• Improved Network Stability: It helps keep the network stable by preventing it from getting overloaded. It manages the flow of data so the network doesn’t crash or fail due to too much traffic.
• Reduced Latency and Packet Loss: Without congestion control, data transmission can slow down, causing delays and data loss. Congestion control helps manage traffic better, reducing these delays and ensuring fewer data packets are lost, making data transfer faster and the network more responsive.
• Enhanced Throughput: By avoiding congestion, the network can use its resources more effectively. This means more data can be sent in a shorter time, which is important for handling large amounts of data and supporting high-speed applications.
• Fairness in Resource Allocation: Congestion control ensures that network resources are shared fairly among users. No single user or application can take up all the bandwidth, allowing everyone to have a fair share.
• Better User Experience: When data flows smoothly and quickly, users have a better experience. Websites, online services, and applications work more reliably and without annoying delays.
• Mitigation of Network Congestion Collapse: Without congestion control, a sudden spike in data traffic can overwhelm the network, causing severe congestion and making it almost unusable. Congestion control helps prevent this by managing traffic efficiently and avoiding such critical breakdowns.

Types of Congestion Control in Computer Network

Various types of congestion control mechanisms are employed in computer networks (CN) to manage and mitigate network congestion. Here are some notable types:

• Open Loop Congestion Control: This approach employs preset, static methods to control congestion. It doesn’t rely on real-time feedback or dynamic adjustments. Examples include traffic shaping and admission control.
• Closed Loop Congestion Control: In this type, the network continuously monitors its state and adapts congestion control strategies based on real-time feedback. TCP (Transmission Control Protocol) is a classic example of this type.
• End-to-End Congestion Control: This approach involves end systems, such as computers and servers, in the congestion control process. They adjust their behavior based on signals from the network. TCP’s congestion control is an example of end-to-end congestion control.
• Network-Assisted Congestion Control: In this case, network elements (routers, switches, etc.) play an active role in controlling congestion. They provide feedback and assist end systems in managing congestion. Explicit Congestion Notification (ECN) is an example of network-assisted congestion control.
• Implicit Congestion Signaling: This involves detecting congestion based on observed changes in network performance rather than explicit signals. It might involve monitoring packet loss or delays.
• Explicit Congestion Signaling: This method uses explicit signals to indicate network congestion. One example is the ECN field in IP packets, which routers can use to signal congestion to endpoints.
• Active Queue Management (AQM): AQM mechanisms involve actively managing the length of queues in network routers or switches to prevent excessive queuing and buffer overflows. Examples include Random Early Detection (RED) and its variants.
• Quality of Service (QoS) Congestion Control: This approach prioritizes traffic based on its class or type, ensuring that high-priority traffic is given precedence during times of congestion.

Congestion Control Algorithms

A system called congestion control regulates the flow of data packets into the network, allowing for more efficient use of a shared network infrastructure and preventing congestive collapse. Congestive-Avoidance Algorithms (CAA) are used as a technique to prevent congestive collapse in a network at the TCP layer. The following are two congestion control algorithms:

Leaky Bucket Algorithm

• The leaky bucket method finds applications for shaping or rate-limiting network traffic.
• For traffic shaping algorithms, a token bucket execution and a leaky bucket execution are typically utilized.
• With the help of this method, the network’s transmission rate may be managed, and burst traffic can be turned into a constant stream.
• When compared to the leaky-bucket algorithm, the drawbacks include the ineffective utilization of available network resources.
• The bandwidth and other extensive network resources are not being utilized efficiently.

Token bucket Algorithm

• The output architecture of the leaky bucket method is stiff at an average rate irrespective of the burst traffic.
• When there are significant bursts, certain applications allow the output to accelerate. This needs a more adaptable algorithm, ideally one that never loses data. A token bucket approach is thus useful for rate-limiting or filtering network traffic.
• It is a control algorithm that suggests the best times to send traffic. Based on how many tokens are visible in the bucket, this ranking is generated.
• Tokens are in the bucket. Each token designates a packet of a specific size. To allow the sharing of a packet, tokens in the bucket are erased.
• When tokens are displayed, a flow of transmit traffic also does so.
• If there is no token, no flow will send packets. As a result, a flow transfers traffic in good tokens in the bucket up to its peak burst rate.

Conclusion

Congestion control is essential for keeping computer networks running smoothly. It helps prevent network overloads by managing the flow of data, ensuring that information gets where it needs to go without delays or loss. Effective congestion control improves network performance and reliability, making sure that users have a stable and efficient connection. By using these techniques, networks can handle high traffic volumes and continue to operate effectively.