Contents
1 Introduction
This document describes how to configure the Network Application Server (NW AS) Forking Interworking Function (F-IWF) service in MTAS.
1.1 Prerequisites
It is assumed that the user of this document is familiar with the Operation and Maintenance (O&M) area, in general.
1.1.1 Licenses
To enable the F-IWF function, the Forking Interworking Function license must be installed. The NW AS Capacity license with the desired capacity value is also required to enable NW AS.
For more information about the F-IWF and NW AS licenses, refer to MTAS Licenses.
1.1.2 Documents
Before starting any procedure in this document, ensure that the following documents are available:
1.1.3 Conditions
Before starting any of the procedures described in this document, ensure that the following condition is met:
- An Ericsson Command-Line Interface (ECLI) session in Exec mode is in progress.
2 Overview
The NW AS F-IWF service provides interworking between a caller endpoint lacking support of multiple early dialogs and the IMS network.
The F-IWF service aggregates multiple early dialogues to a single dialogue, keeps track of the media state on multiple-dialog-side, and maps the authorized media towards the single dialog.
Originating UE/network are expected to support reliable provisional responses and SIP UPDATE. F-IWF rejects the session establishment attempt if any of the following occur:
- 100rel is missing in both the Require and Supported header.
- There is no UPDATE in the Allow header.
F-IWF propagates the caller precondition fulfilled to all remote ends.
F-IWF can be configured to be executed on all traffic, or have a flexible invocation mechanism to trigger its execution based on the presence of a SIP header or an attribute in a SIP header in the initial INVITE.
3 Forking IWF Service Configuration
The NW AS F-IWF service is controlled by the MtasFoIw Managed Object Class (MOC).
The Managed Object (MO) structure of the NW AS F-IWF service is shown in Figure 1.
For configurable MOs and attributes related to the NW AS F-IWF service, refer to Managed Object Model (MOM).
3.1 Forking IWF Administrative State Configuration
The F-IWF service is enabled by setting the mtasFowAdministrativeState attribute in the MtasFoIw MO to 1 (Unlocked).
If the mtasFoIwAdministrativeState attribute is set to 0 (Locked), no F-IWF service is provided by the NW AS.
3.2 Forking IWF Invocation
The F-IWF service can be started from two levels: Initial Filter Criteria (IFC) and CM parameters within MTAS.
The top-most route header must have an "as" parameter with value set to the configured CM attribute mtasNwFoIwAsName.
When the IFC has no rule (except "as" to trigger the FoIwf AS), the control is within the CM parameters as follows:
- If the CM attribute mtasFoIwMode is set to ORIGINATING, the P-Served-User header must be present with parameter "sescase=orig".
- If the CM attribute mtasFoIwMode is set to TERMINATING, the P-Served-User header must be present with parameter "sescase=term".
- If the CM attribute mtasFoIwMode is set to ORIGINATING_AND_TERMINATING, the P-Served-User header can have "sescase=orig" or "sescase=term".
- If CM attribute mtasFoIwMode is set to DYNAMIC, the value configured in the
CM attribute mtasFoIwInvocationHeaderValue must be the substring of the parameter in the header configured
in the CM attribute mtasFoIwInvocationHeaderName. No extra IFC condition is recommended when the DYNAMIC value is set.
For example: attribute mtasFoIwInvocationHeaderName is set to "Request-Disposition" and mtasFoIwInvocationHeaderValue is set to "no-fork".
If there is a "Request-Disposition:no-fork" header in the initial INVITE, then the F-IWF service is started.
When there are several IFC rules, the configuration of CM attributes must not conflict with the IFC rules, it is thus recommended to configure the CM attribute mtasFoIwMode to ORIGINATING_AND_TERMINATING.
F-IWF also supports to combine the IFC and CM parameters within MTAS.
3.3 Service Data Configuration
This service does not require any service level subscription from operator or user.
4 Performance Management
For information on measurements, related to the NW AS F-IWF service, refer to MTAS Performance Measurements.