Resolution:
With Apache:
via modASG(RV-based)
- the message flow would be:: Client--HTTP(s)--Apache--RV--APIX-G
- the /ASG/Channels/modRV_Channel has to be enabled (in asg_core.cdd)
- this also requires an RV installation, which is optional, APIX2.2.0 onwards
- the Apache module(modASG) cannot handle huge payloads
- can propogate client certificate information for Partner identification

in Reverse Proxy Mode
- the message flow would be:: Client--HTTP(s)--Apache--HTTP(s)APIX-G
- RV is not required
- Secure communication can be terminated at Apache

With in-built FacadeHTTP(s) Channel:
- Apache and RV are not required
- Clients can hit APIX-G directly
- can handle huge payloads better then via Apache.
- one can also modify settings for native HTTP Channel from Business Studio, i.e.
DefaultImplementation --> Channels --> FacadeHTTPChannel.channel --> FacadeRequest --> Advanced(tab) --> Tomcat Settings
These settings can be modified and the ear rebuilt as per your requirement.
-- Timeout can be set in asg.properties 2.2.0 onwards.
-- FacadeHTTPSSL Channel can propogate client certificate information for Partner identification 2.2.1 onwards.

Note: THe attached screenshots show how Partner Identification happens in each of the above methods.