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Overview
Explicit Congestion Notification (ECN) is a network protocol feature that allows end-to-end notification of network congestion without dropping packets. It is an extension of the IP and TCP protocols, enhancing the way congestion is managed by marking packets instead of discarding them.
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Reduced Packet Loss: By marking packets instead of dropping them, ECN helps in avoiding packet loss, which is particularly beneficial for applications sensitive to packet drops, such as real-time video or voice.
Improved Network Efficiency: ECN allows for more efficient use of network resources by preventing congestion before it becomes severe enough to cause packet drops.
Better Performance: By avoiding packet loss, ECN can lead to better overall performance for TCP connections, resulting in higher throughput and lower latency.
Smooth Traffic Flow: ECN provides a mechanism for more graceful handling of congestion, leading to smoother traffic flow and improved end-user experience.
Restrictions and Guidelines
When you configure ECN, follow these restrictions and guidelines:
To use ECN, both the network devices (such as routers and switches) and the endpoints (such as servers and clients) must support ECN.
Configuring ECN via WRED
On PICOS switches, ECN is used in conjunction with Weighted Random Early Detection (WRED) to provide early signals of congestion to avoid packet loss and improve network performance.
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Monitor the network to ensure that ECN marking and WRED are effectively managing congestion. Adjust the thresholds and probabilities as needed to optimize performance.
Configuration Example
The following commands complete the configurations:
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admin@PICOS# run show interface gigabit-ethernet ge-1/1/3 wred Queue Num Min Thresh Max Thresh Drop Probability ECN Thresh Status ---------- ---------- ---------- ---------------- ----------- ---------- 0 200 400 50% Enabled Enabled 1 0 0 0% Disabled Disabled 2 0 0 0% Disabled Disabled 3 0 0 0% Disabled Disabled 4 0 0 0% Disabled Disabled 5 0 0 0% Disabled Disabled 6 0 0 0% Disabled Disabled 7 0 0 0% Disabled Disabled |
Test Recommended Configuration
Configuring ECN thresholds properly is crucial for ensuring optimal network performance, which helps in managing congestion proactively, leading to improved network performance, reduced packet loss, and lower latency.Testing recommended configurations involves setting specific parameters for ECN to manage congestion effectively and then evaluating the performance outcomes.
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Test Method | Switch Port MTU | Switch Egress Port Link Bandwidth | ECN Min Threshold (Bytes) | ECN Max Threshold (Bytes) | Probability |
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 Three Ingress Port Ports to One Egress Port | 9000 | 99.75G | 80000 | 8000000 | 80 |
 Three Ingress Port Ports to One Egress Port | 4096 | 97.68G | 1000000 | 30000000 | 50 |
Three Ingress Port Ports to One Egress Port | 9000 | 99.75G | 1000000 | 32000000 | 50 |
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