TN invoke from java client to submit document takes long time

In our environment, multiple users access weblogic to create documents that are submitted to TN (webMethods). The TN recieve service is configured to asynchronously initiate relevant IS service for processing.

The time taken for webMethods connection and submission of xml found to take long time (for each document from 9 to 17 seconds).
How can we reduce the time for submission?
Is there anyway to avoid authentication for each submission?

We intend to achieve submission within 3 seconds. Systems used are webLogic6.1, webMethods TN & IS 6.0.1.

I searched and find a thread (Calling Trading Network from Java classes) in which Reamon mention ā€œIā€™d encourage that the Java program not submit documents directly to the service. There are threads on the forums that cover the whys and whatfors.ā€

Your advice to reduce the connection time or alternate method that can result in our expected result (submit within 3 seconds) is appreciated.