WCF Session - ASP.Net Session

I have a WCF service using netTcpBinding (so the default is InstanceContextMode = PerSession).
The service is called from an ASP.Net web application using code similar to:

ServiceClient service = new ServiceClient();
service.ServiceMethod1();
service.Close();

So, we create a proxy instance here - call the required method and - close the service.

Request -
When do we say that a WCF session has been created?
This corresponds to one ASP.Net session ... so suppose that one user having an ASP.Net session, regardless of what this user calls for service from his session, will also mean a WCF session?

Thank!