Load shedding

Load Shedding in the network layer refers to the practice of selectively discarding packets when the network or device is overwhelmed by too much traffic. The purpose of load shedding is to prevent network congestion and ensure system stability by reducing the load, thus avoiding complete failure or a significant drop in performance.

Key Points:

Definition and Purpose:

• Load shedding is a congestion control technique used to reduce the volume of traffic when a network or device (like a router or switch) cannot process all incoming packets due to overload.
• It aims to maintain the overall network performance and prevent system crashes or excessive delays by prioritizing important data and discarding lower-priority traffic.

How Load Shedding Works:

• When a network or device becomes congested, it may drop less important packets while prioritizing high-priority traffic, such as real-time communications (VoIP) or critical data.
• Load shedding can be applied based on different policies:
• Selective Packet Dropping: Some packets are discarded based on certain criteria (e.g., traffic type or priority).
• Priority Queuing: Higher-priority packets are processed first, and lower-priority packets are dropped or delayed.

Techniques Used:

• Congestion Awareness: Devices monitor the load and buffer usage to detect when they are near capacity, triggering load shedding.
• Random Early Detection (RED): A technique where devices start dropping packets before the queue is completely full to signal congestion early.
• Priority Scheduling: Ensures that high-priority traffic (e.g., emergency services or VoIP) is handled even during congestion.

Example of Load Shedding in the Network Layer:

• Scenario: Load Shedding in a Router during Network Congestion
• Imagine a router in a large corporate network that handles traffic for both internal communications and internet access. The router is designed to handle up to 1 Gbps of data, but during certain peak times, such as the start of the workday, traffic spikes to 1.5 Gbps due to increased usage from employees.

How Load Shedding Works:

• As the router’s buffer fills up and congestion builds, it detects that it can no longer handle all the incoming packets efficiently.
• To prevent network delays or a complete system failure, the router drops less important packets, such as non-urgent email data or large file transfers.
• The router can apply Selective Packet Dropping where low-priority traffic (like background file transfers) is discarded, while high-priority packets (such as VoIP calls or video conferencing data) are kept and processed to ensure that real-time communications are not disrupted.
• Random Early Detection (RED) can also be employed. The router starts dropping packets early (before the buffer is full), signaling to the source devices to slow down the transmission rate, preventing more serious congestion later.

Outcome:

• Network Stability: The router prevents overload and ensures that essential traffic continues to flow smoothly without significant delays or packet loss.
• Fair Resource Allocation: By shedding low-priority traffic, it ensures that the most important services (e.g., VoIP or critical business applications) are given priority during peak times.
• Improved User Experience: Users experience minimal disruption in important services like voice calls or video conferencing, while non-critical services experience some delay or packet loss.