The use of load balancers is crucial for ensuring both high availability and the smooth running of operations in the event of an emergency.

Azure offers four distinct kinds of load balancers.                             

 Azure Load Balancer 
Azure Application Gateway
Azure Traffic Manager
Azure Front Manager

In Azure, load balancing services can be broken down into two broad categories: global and regional,
and HTTP(S) and non-HTTP(S)
                                                                                                                                                                                                                                                                                                                     Global vs Regional

In this section, we will understand the difference between Global and Regional categories of load balancers.

Global

• Distributes traffic across regional backends,clouds,or hybrid on-premises services.
• Route end-user traffic to the closest available backend.
• React to changes in service reliability or performance in order to gain high availability and performance.

Regional

• Distribute traffic within virtual networks across VMs or zonal and zone-redundant service endpoints within a region.
• Load balance between VMs, containers or clusters within a region in a virtual network.

HTTP(S) vs non-HTTP(S)

Now, let us look at HTTP(s) and non-HTTP(s) categories of load-balancers.

HTTP(S)

• Layer-7 based load-balancing services.
• Accepts only HTTP(S) traffic.
• Intended for web applications or other HTTP(S) endpoints.
• Includes features such as SSL Offload, Web Application Firewall, path-based load-balancing, session affinity.

non-HTTP(S)

• Recommended for non-web workloads.
• Handles non-HTTP(s) traffic.

Now, let us understand about the different types of Load balancers.

Azure Load Balance

• It is Layer-4 load-balancing service.
• It supports UDP and TCP Protocol.
• It supports Network Address Translation (NAT).
• We also have Zone-redundant load balancers.
• We have two categories of Load Balancers:
  • • • External (Public) Load Balancer and,
      • Internal (Private) Load Balancers
• It is used to distribute traffic between VMs,containers or clusters within a region in a Virtual Network.
• It does not support SSL Certificate and No support for custom domain.
• It is Regional + non-HTTP(S) service.

Azure Application Gateway

• It offers Layer-7 Load-balancing capabilities.
• Application Gateway supports only HTTP(S) traffic.
• Intended for web applications or other HTTP(S) endpoints.
• Core features of Azure Application Gateway are SSL Offload, Web Application Firewall, path-based load-balancing and session affinity.
• It is heavily used for path-based routing and optimize web-farm productivity by SSL offloading.
• It is Regional + HTTP(S) service.

Azure Traffic Manager

• It is a Layer-7 load-balancer which Implements DNS based load-balancing for traffic.
• It is used to distribute traffic globally – across the region.
• It load-balances only at the Domain level.
• Azure Traffic manager supports various routing methods such as Priority, Weighted, Performance, Geographic, Multivalue and Subnet.

It takes time to fail-over because of common challenges around DNS caching and request  time to leave.

• It is Global+non-HTTP(S) service.

Azure Front Door

• Azure Front Door acts as an Application Deliver Network and works at Layer-7.
• Along with ADN it also serves Dynamic Site Acceleration.
• The key capabilities of Azure Front Door is Anycast mechanism to deliver the responses faster from the nearest Point of Presence or edges and implementation of Split-TCP to have the shorter response time.
• Azure Front Door is a global service like Azure Traffic Manager and offers SSL Offloading, URL Path based routing and session-affinity like the offerings of Application Gateway.
• Unlike Azure Traffic Manager, it supports HTTP(S). Unlike Application gateway, it is Global.
• It is Global + HTTP(S) service