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With built-in load balancing for cloud services and virtual machines, we can create highly-available and scalable applications in minutes. But what is Azure Application level routing and load balancing service and how it differs from built-in load balancing for cloud services and virtual machines

nam
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1 Answers1

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I assume you are talking about Azure Application Gateway and Azure Load Balancer.

The primary difference is that AG works at Layer 7, while LB works at Layer 4. AG can be used for HTTP traffic routing, TLS termination, HTTP traffic filtering etc. So you can for example, route requests to the /images path to a different App Service than the rest of the requests.

LB only understands TCP and UDP, and routes packets based on rules to one of the machines in a back-end pool. So for example when a TCP packet arrives on port 80, LB can route it to a random virtual machine in a collection of VMs serving a web app.

What is Azure Application Gateway?

Load balancer documentation

juunas
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  • Probably my question is not very clear. So for example, if we have an Azure Web App that cannot handle more than 100 concurrent user sessions even if we have enabled `Always On` feature and have configured auto-scaling to increase instance counts, should we use `Azure Traffic Manager` or `Azure Application Gateway` to store content close to the application in order to improve performance of the app? – nam Aug 28 '18 at 16:32
  • You mean store content close to the *user*? Traffic Manager works at DNS-level, so can be used as a top-level "load balancer" to divide traffic to different Azure datacenters. Application Gateway works within a datacenter. If app service auto-scale is limiting you, you could setup multiple app service plans and route traffic to them using either TM or AG really. TM could be run in weighted mode so it splits the traffic at random. AG could become a bottleneck since it actually functions as a load balancer, while TM just answers DNS queries. – juunas Aug 28 '18 at 16:42
  • If you need content closer to user, multiple deployments across different datacenters combined with Traffic Manager in performance/geographic mode can be good. Azure CDN is good for getting static content closer to users. – juunas Aug 28 '18 at 16:43
  • I still mean content close to the Application. From your first comment above it seems Traffic Manager is a better choice. In regard to close to user, will `Azure Redis Cache` be a better choice? – nam Aug 28 '18 at 16:51
  • Alright, misunderstood then :) Redis Cache is a cache service, it's pretty useful as a distributed cache; it can be used to share cached data among instances of an App Service within a datacenter. – juunas Aug 28 '18 at 16:56
  • No problem, glad to help :) – juunas Aug 28 '18 at 16:58