Is isupplier module REQUIRED to make the supplier able to enter response for negociation in Sourcin

Hi Group,

I have a urgent issue.

I'm implementing Sourcing module R11.

The client wabt suppliers to access negociation and enter their own responses by theirselves. 

I know weel about sourcing supplier and user supplier.

But is iSupplier module required to that ?? Do iSupplier module must be installed ? implemented ??

Regards.