I want to draw an architecture diagram for a general ERP application. In that I have…

I want to draw an architecture diagram for a general ERP
application.
In that I have come across a confusing point: where should I
place the SSL and Firewall?
I tried to figure out exactly where the SSL and Firewall fit in
the OSI Model. I know we can use Firewall in Application Layer,
Network Layer, Transportation Layer, etc.