ADFS for Multple AD Domain

Hi,

I have situation where I have a set of application in the perimeter network.

I have an internal AD in corporate network for our internal users.

I have to maintain a separate AD in perimeter network for external users /customer who need access to the perimeter applications.

How many ADFS instances I need?

Can I configure ADFS instance in corporate network and a ADFS proxy in perimeter network.

Is it possible to add internal AD and perimeter AD in the internal ADFS instance to serve both internal and external user to access the perimeter applications. without a trust between internal AD & perimeter AD.

Or I need to setup 2 different ADFS instances one for perimeter and one for internal? and in this case how to configure the application redirect to multiple ADFS instances to get STS for internal users from internal ADFS and for external users from perimeter ADFS?

Also, what should be the proxy server placement?

Thanks,

Soumen Ghosh