Azure Load Balancer Part- 1

Load balancing provides a higher level of availability by spreading incoming requests across multiple virtual machines. 

A public load balancer can provide outbound connections for virtual machines (VMs) inside your virtual network. These connections are accomplished by translating their private IP addresses to public IP addresses. Public Load Balancers are used to load balance internet traffic to your VMs.

An internal (or private) load balancer is used where private IPs are needed at the frontend only. Internal load balancers are used to load balance traffic inside a virtual network.

Azure Load Balancer SKUs

SKU is short for 'Stock-keeping-Unit'.In terms of the Microsoft Azure cloud, they basically signify a purchasable SKU under a product. It has a bunch of different shapes of the product. Azure Load Balancer has two SKUs.

SKU comparison

Load balancer supports both Standard and Basic SKUs. These SKUs differ in scenario scale, features, and pricing. Any scenario that's possible with Basic load balancer can be created with Standard load balancer.

To compare and understand the differences, see the following table. 

                                    Standard Load Balancer                                         Basic Load Balancer           

Backend pool size	Supports up to 1000 instances.	Supports up to 300 instances.
Backend pool endpoints	Any virtual machines or virtual machine scale sets in a single virtual network.	Virtual machines in a single availability set or virtual machine scale set.
Health probes	TCP, HTTP, HTTPS	TCP, HTTP
Health probe down behavior	TCP connections stay alive on an instance probe down and on all probes down.	TCP connections stay alive on an instance probe down. All TCP connections end when all probes are down.
Availability Zones	Zone-redundant and zonal frontends for inbound and outbound traffic.	Not available
Diagnostics	Azure Monitor multi-dimensional metrics	Azure Monitor logs
HA Ports	Available for Internal Load Balancer	Not available
Secure by default	Closed to inbound flows unless allowed by a network security group. Internal traffic from the virtual network to the internal load balancer is allowed.	Open by default. Network security group optional.
Outbound Rules	Declarative outbound NAT configuration	Not available
TCP Reset on Idle	Available on any rule	Not available
Multiple front ends	Inbound and outbound	Inbound only
Management Operations	Most operations < 30 seconds	60-90+ seconds typical

Limitations of SKU

• SKUs aren't mutable. You can't change the SKU of an existing resource.
• A standalone virtual machine resource, availability set resource, or virtual machine scale set resource can reference one SKU, never both.