Explanation

Scenario: Business Requirements
Litware identifies business requirements include: meet an SLA of 99.99% availability for all Azure deployments.
Box 1: Cloud witness
If you have a Failover Cluster deployment, where all nodes can reach the internet (by extension of Azure), it is recommended that you configure a Cloud Witness as your quorum witness resource.
Box 2: Azure Basic Load Balancer
Microsoft guarantees that a Load Balanced Endpoint using Azure Standard Load Balancer, serving two or more Healthy Virtual Machine Instances, will be available 99.99% of the time.
Note: There are two main options for setting up your listener: external (public) or internal. The external (public) listener uses an internet facing load balancer and is associated with a publicVirtual IP (VIP) that is accessible over the internet. An internal listener uses an internal load balancer and only supports clients within the same Virtual Network.
Reference:
https://technet.microsoft.com/windows-server-docs/failover-clustering/deploy-cloud-witness
https://azure.microsoft.com/en-us/support/legal/sla/load-balancer/v1_0/