Obviously you need to fill in the SIP URI of the Application Server. You can use of course parameters, ports, etc.

Then you need to specify what should the S-CSCF do if this Application Server fails to respond to messages. You can indicate that you want the sessions to be terminated or continued based on how critical is your Application Server in your system.

A Service Profile is a group of Initial Filter Criteria, each with an attached priority. Each user can have such a Service Profile attached and this is downloaded from the HSS to the S-CSCF on initial registration, profile changes or when there is a message towards a user that has a Service Profile containing at least an Initial Filter Criteria applicable for the terminating towards unregistered user case.

No, there is no such thing. Subsequent requests can not be filtered or forwarded towards Application Servers.

If you have an Application Server that needs to receive subsequent requests (like a Online-Charging-Proxy), then you should filter the initial request for that dialog and have the Application Server Record-Route.

The Initial Filter Criteria is the grouping between a Trigger Point (the logical expression matching a message) and an Application Server. The absence of a Trigger Point in an Initial Filter Criteria indicates that the message should always be forwarded to the respective Application Server.

The Initial Filter Criteria can only match Initial Requests, like INVITE, REGISTER, SUBSCRIBE, MESSAGE, etc. Subsequent messages (like BYE, NOTIFY, INVITE inside a dialog, etc) are not checked or forwarded.

A Trigger Point is a logical expression of Service Point Triggers. It is composed of groups and each group is formed of the logical atoms, the SPT. It can be of 2 types, based on what logical condition is applied inside the groups and between them:

1. Conjunctive Normal Format (CNF) - (A or B) and (C) and (D or E or F)
2. Disjunctive Normal Forma (DNF) - (A and B) or (C) or (D and E and F)

The Trigger Point is used to build complex message matching conditions.