It would depend on where your firewall sits in your configuration, and where your web adaptors are hosted.
If you have a web adaptor in the DMZ (outside the firewall) and the other servers inside the firewall, the the source would be the web adaptor server and your destinations would be Portal, GIS and Image servers.
Users of your services will access the web adaptor server on port 443, and then that server will access the other servers.
GISP