Explanation
With the Premium plan the max outbound connections per instance is unbounded compared to the 600 active (1200 total) in a Consumption plan.
Note: The number of available connections is limited partly because a function app runs in a sandbox environment. One of the restrictions that the sandbox imposes on your code is a limit on the number of outbound connections, which is currently 600 active (1,200 total) connections per instance. When you reach this limit, the functions runtime writes the following message to the logs: Host thresholds exceeded:
Connections.
Reference:
https://docs.microsoft.com/en-us/azure/azure-functions/manage-connections
https://docs.microsoft.com/en-us/azure/azure-functions/functions-scale#service-limits