Background:
Azure ExpressRoute is a networking service that allows you to securely and reliably connect your on-premises network to Azure cloud virtual networking. ExpressRoute extends your on-premises network into the Microsoft Cloud over a private and dedicated connection using a connectivity provider. This dedicated connection offers faster speeds, consistent latencies, and higher security compared to typical connections over the public Internet. Additionally, ExpressRoute ensures that your data does not travel over the public Internet, which helps to reduce the risk of security breaches and data theft. With ExpressRoute, you can enjoy a faster, more reliable, and more secure connection to Azure cloud virtual networking.
An ExpressRoute circuit comprises two connection links—one between Microsoft Edge routers and Partner or Customer Edge (CE) routers. Please refer to the above diagram. Each link can carry up to the circuit bandwidth set by the customer. For example, a circuit set to 1 Gbps can distribute traffic evenly across both links and reach up to 2*1 (that is, 2) Gbps.
What does the rate-limiting feature improve?
Rate limiting is a powerful and valuable feature designed to help control the network QOS, which regulates the traffic volume between your on-premises network and Azure via an ExpressRoute Direct circuit. This feature applies to traffic that traverses either private or Microsoft peering off the ExpressRoute circuit and is incredibly useful for ensuring network stability and averting network congestion.
The primary purpose of rate limiting is to help you evenly distribute the port bandwidth across the circuits, fortifying your network’s stability and ensuring it remains free of any performance issues. This is particularly important when dealing with high traffic volumes, as it helps ensure your network remains responsive and doesn’t become bogged down by excessive traffic.
By using rate limiting, you can easily control the volume of traffic that flows through your network, which helps ensure that your network remains healthy and responsive. This feature is handy if you have much traffic flowing through your network regularly, as it helps prevent your network from becoming congested and ensures that your users can access the resources they need with minimal delay.
Configuration:
It enables you to exercise enhanced control over your network’s bandwidth usage. Without this feature, all circuits can burst up to the port pair’s bandwidth, irrespective of their configured bandwidth. Such uncontrolled bursting can significantly impact the network’s performance and reliability.
You can activate this feature during or after creating the ExpressRoute Direct circuit. Moreover, you can enable rate-limiting for each circuit individually, allowing you to prioritize specific circuits over others. In addition, the express route circuits can turn rate limiting on or off.
Suppose you exceed the express route’s set bandwidth over private or Microsoft peering on either of the links by more than 20%. In that case, your throughput will be reduced to the configured bandwidth. You can keep track of the rate-limiting status in the Azure portal. On the ‘Circuits’ pane of your ExpressRoute Direct port, you will find all the circuits set up over the ExpressRoute Direct port and their corresponding rate-limiting statuses. In addition, we can monitor the express route traffic under the monitoring of each circuit.
Final Thoughts:
Quality of Service (QoS) is crucial as it provides better control over bandwidth usage. Without QoS, all circuits can burst up to the port pair’s bandwidth, regardless of their configured bandwidth. This can negatively impact the performance and reliability of your network. However, Rate Limiting can help you throttle traffic throughput to align with the configured bandwidth of your circuits.
Rate limiting allows you to manage and restrict the data transfer rate over your ExpressRoute Direct circuits, thus optimizing network performance and reducing costs. This feature has been available for all the Azure public cloud regions since the last week of March 2024.
Santhosh has over 15 years of experience in the IT organization. Working as a Cloud Infrastructure Architect and has a wide range of expertise in Microsoft technologies, with a specialization in public & private cloud services for enterprise customers. My varied background includes work in cloud computing, virtualization, storage, networks, automation and DevOps.