Understand Azure Load Balancer, Traffic Manager and Application Gateway

Understand Azure Load Balancer, Traffic Manager and Application Gateway

Understand Azure Load Balancer, Traffic Manager and Application Gateway

Azure is fast caching up with Business requirements and have released number of services in the past to meet the diverse Business requirements across globe. Important one being effective support of Azure workloads when they are load balanced in different regions within Country, Country separated regions and Servers that are made highly available with in Azure Region. The Azure Offerings that cater to this business need are – Azure Load Balancer, Traffic Manager and Application Gateway

Load Balancer Differences

Azure Load Balancer – works at a transport layer (Layer 4 in the OSI) Is an External / Internal Services that load balances the Incoming TCP/UDP traffic targeting to Azure Resources within Azure data center

Traffic Manager – is a DNS based service that redirects traffic to globally separated endpoints based on the rules configured

Application Gateway – works at a application layer (Layer 7 in the OSI) that supports SSL offloading, session based affinity, WAF, round robin distribution, URL based redirection and many more

Purpose Azure Load Balancer Traffic Manager Application Gateway
Supported Protocols Any HTTP endpoint HTTP and HTTPS
Endpoints Azure VMs / Cloud Services Azure VMs / Cloud Services / external endpoints Internal / External IP Address
Load Balancing Mode Destination IP / Port Round robin, Cookie based (Session affinity)
SSL Offloading Not Supported NA Supported
Endpoint Monitoring via Probes HTTP / HTTPS Get responses via Probes

Detailed Explanation and Use Cases

Azure Load Balancer is used to –

  • forward incoming traffic to internal machines running same application for example web-servers
  • use a single public (or external) IP address and range of ports (e.g. 8100 to 8200) to internal servers running service on standard port (e.g. 3389/RDP). This allows to expose all 100 internal servers expose their RDP services using same public IP address. Also called as PAT (Port Address Translation)
  • Forward traffic to a specific Virtual Machine

Traffic Manager is a DNS service that uses traffic-routing methods to route traffic to desired endpoint by the Administrator. It is a DNS based service and does not see the traffic between Client machine and actual server delivering the content

Traffic Manager traffic routing methods –

  • Priority – This methods routes traffic to a primary server for content delivery and other servers are used as backup in case Primary goes down. This is good option for Primary and DR location based servers where Primary server is closest to other Infrastructure servers such as Database, File servers etc., and are sized appropriately for Performance
  • Weighted – This method distributes load across servers either evenly or according to weight as configured by the Administrator. Good option where Servers are of different configurations and therefore have different Performance metrics
  • Performance – This method is best from Performance point of view, where servers are geo-located and based on the Client location the “closest” server is selected to avoid network latency and best content delivery experience. This option is good for Static content websites and for Applications that have consistency in the n-tier Infrastructure in all locations including databases

Application Gateway is used to provide multiple features that are not provided by Azure Load Balancer as explained above. Application Manager uses Azure Load Balancer to distribute load across servers but provides below added features –

  • SSL Termination
  • Round robin distribution of Incoming traffic
  • Cookie based session affinity
  • URL path based routing (/location1 goes to Server 1, /location2 goes to Server 2)
  • Contains Web Application Firewall
  • Can host upto 20 websites in a single Application Gateway
  • Support HTTP and HTTPs traffic
  • End-to-end SSL
  • Health Monitoring and Diagnostics


Representation Diagram – Traffic Manager, Load Balancer & Application Gateway

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