Azure Load Balancer v/s App Gateway v/s Traffic Manager
Image Source: Ignite 2017
Summary
Azure has features for some form of load balancing at layer 4, layer 7, and global load balancing. These offerings are Load Balancer, Application Gateway and Traffic Manager. Each offering has a specific use case and it can be confusing at times on which offering is to be used in what scenario. The table below compares the Azure offerings.
Comparison Table
| Sr. No. | Feature | Azure Load Balancer | Azure Application Gateway | Azure Traffic Manager |
| 1 | Technology | Transport Level (At Layer 4) | Application Level (At Layer 7) | DNS Level (used with Azure LB or App Gateway) |
| 2 | Application Protocols Supported |
Any (Layer 4 ports) | HTTP, HTTPS & Websockets | Any (But HTTP endpoint is required for endpoint monitoring) |
| 3 | Load Balancing Mode | 5 Tuple (source IP, source port, destination IP, destination port, protocol type | Round Robin Routing based on URL, Cookie-based affinity |
Traffic Manager routing methods (Priority, Weighted, Performance and Geographic) |
| 4 | Deployment Scenario | L4 Application load balancing within a region (Internal & Internet facing) | L7 Application load balancing within a region (Internal & Internet facing) | Global Load Balancing across multiple regions. |
| 5 | Endpoints | Azure VM and Azure Cloud Services instances | Any Azure internal IP address, public internet IP address, Azure VM, or Azure Cloud Service |
Azure VMs, Cloud Services, Azure Web Apps, and external endpoints |
| 6 | Endpoint Monitoring | Supported via probes | Supported via probes | Supported via HTTP/HTTPS GET |
| 7 | VNET Support | Internet facing and Internal (VNET) facing applications | Internet facing and Internal (VNET) facing applications | Internet facing applications |
| 8 | Scope | Subscription/Region/VNET | Subscription/Region/VNET | Load Balancing Across Regions. Endpoints can span across multiple subscription (except for Azure Web Apps) |
| 9 | SSL offloading | Not Supported | Supported | Not Applicable |
| 10 | Web Application Firewall (WAF) | Not Supported | Supported (except for Small backend instances) | Not Applicable |
| 11 | HA & Redundancy | Automatic Zone Redundancy supported for Standard Load Balancers | Supported when more than 1 instances are deployed | Resilient to failure |
| 12 | Auto Scaling | Not Supported (new VMs can be added manually without impact) | Not Supported (new instances can be added manually without impact) | Not Applicable |
| 13 | Pricing | Basic Load Balancer is free. Standard load balancer will be charged once it is GA | Charged based on Size (Small, Medium and Large) + Charged based on Data Processed + Additional cost for WAF + Outbound Data Transfer Cost (more info here) | Charge per million DNS queries + Charge based on endpoint health check + Charge based on features enabled (more info here) |
| 14 | Throughput | Throughput depends on the backend VM throughput. | Throughput depends on the instance size and backend page size. More details can be found here. | Not officially published by Azure |
Please do leave me a note in case any of the details mentioned above is not accurate.
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