Q. I understand VMs in Azure have an SLA for their availability but what about an SLA for the ability to communicate with them via IP?
A. Actually the SLA of the Azure VMs is based around the ability to communicate with them as documented at https://azure.microsoft.com/en-us/support/legal/sla/virtual-machines/v1_6/. Specifically the SLAs all refer to "Virtual Machine Connectivity" where that connectivity is defined as:
""Virtual Machine Connectivity" is bi-directional network traffic between the Virtual Machine and other IP addresses using TCP or UDP network protocols in which the Virtual Machine is configured for allowed traffic. The IP addresses can be IP addresses in the same Cloud Service as the Virtual Machine, IP addresses within the same virtual network as the Virtual Machine or public, routable IP addresses."
This means the SLA is not just the VM is running, but the ability to actually communicate to it.