Support REFER Request in Call Agent

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This feature allows the CSP to process an inbound REFER request and to generate an outbound REFER request in Call Agent Mode.

Whenever there is an incoming REFER request, the REFER-TO header is reported to the host in the PPL Event Indication (Event 0x0021; Component 0x00A7). The host can propagate the REFER request to the outbound leg using the PPL Event Request message (Event 0x0027; Component 0x00A7).

The status of the reference is reported to the SIP component in the NOTIFY messages. This status is reported to the host in the PPL Event Indication (Event 0x0028; Component 0x00A7).

• Success REFER request and NOTIFY message in Call Agent Mode (Includes sample API and SIP message traces.)

This call flow assumes that the Referrer and Referee are in the answered state. The second PPL Event Request (0x0020) to generate the NOTIFY message is not supported as of now, but will be supported in a future release.

The PPL Event Indication (0x0043) message includes the NPDI SIP Response Code TLV - 0x2915 as follows:

The PPL Event Indications now supports this existing TLV within the NPDI Universal ICB (0x0033).

This TLV provides the response code received for any SIP message generated by the CSP.

Used in:
0x0033 NPDI Universal ICB in:
Channel Released with Data message
Release Channel with Data message
PPL Event Indication message
Request for Service with Data message

0x0027 - Allows the CSP to generate an outbound REFER request with the refer target URL filling in the TLV.

0x0027 - Informs the host about the result of the sent REFER request (Success - 2xx or Failure - 4xx-6xx).

0x0028 - Informs the host that sent the REFER request about the status of the reference (Trying, Success, or Failure). The value in the SIP Response Code TLV (0x2915) reports the exact response code.

See Programmable Protocol Language.

A condition that, when met, drives a state machine from one state to another. A condition that drives a Component out of its current state by invoking an associated primitive.

Session-Initiation Protocol. A signaling protocol used for establishing sessions in an IP network. A session could be a simple, two-way telephone call, or it could be a collaborative multi-media conference session.

Network Protocol Data Intelligence. Also called “Interworking,” it is a software product that operates within Excel’s Call Control (Layer 4) and Services (Layer 5) call processing layers. NPDI is meant to enhance Excel’s call processing product offering by allowing call processing layers (specifically Layers 4 and 5) to perform advanced analysis, generation, and conversion of Network Signaling (NS) Layer 3 information.

A computer, attached to the Excel platform through an RS-232 or Ethernet link, from which you run the telecommunications application that controls the Excel platform.

The point in the Excel platform where a DS0 connects to a network. Also known as a "socket."

Tag-Length-Value block. A standardized block that allows data to inserted in a standard way into API messages.

A group of data bits in a specific format, with a flag at each end to indicate the beginning and the end of the frame.

See Address Information Block.

A programmable software component that uses PPL state machines that can be modified with the PPL Tool.

See Information Control Block.

In PPL, a condition that, when met, drives a state machine (PPL Component) from one state to another, by invoking an associated Primitive. In PPL files, an Event is marked by an arrow and text.

MESSAGE (White)		RESPONSE (Gray)
Byte	Field Description	Byte	Field Description
0	Frame (0xFE)	0	Frame (0xFE)
1, 2	Length (0x00NN)	1, 2	Length (0x0005)
3, 4	Message Type (0x0043)	3, 4	Message Type (0x0043)
5	Reserved (0x00)	5	Reserved (0x00)
6	Sequence Number	6	Same Sequence Number
7	Logical Node ID	7	Logical Node ID
:	AIB Channel (0x0D)	8	Checksum




:	PPL Component ID - 0x00A7
:	PPL Event 0x0027/0x0028
:	Number of ICBs to follow - 0x01
:	ICB Type (0x03) - Extended Data ICB
:	ICB ID - NPDI Universal ICB - 0x0033)
:	Data Length - 0x0008
:	Number of TLVs - 0x0001
:	NPDI SIP Response Code TLV -0x2915 (See format below.)
:	Checksum

Byte	Description
0, 1	Tag 0x2915
2, 3	Length 0x0002
4, 5	Value SIP Response Code (2 Bytes) This TLV, when reported in the PPL Event Indication for Event (0x0027/0x0028), will have any valid SIP Response value. The response code to be interpreted for event 0x0027 is as follows: 202 - Accepted (The REFER request is successful) 405 – Method Not Allowed (REFER request failed) 408 – Request Timed Out (REFER request failed) The response code to be interpreted for event 0x0028 is as follows: 100 – Trying 200 - OK (The reference is successful) 503 - Service Unavailable (The reference failed) 603 - Decline (The reference failed)