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SIP 182 Queued Message

Overview

One usage of the 182 Queued message is as follows: the called party is temporarily unavailable but the server decides to queue the call rather than reject it.

When the called party becomes available, it returns the appropriate final status response.

The reason phrase might give further details about the status of the call for example, "5 calls queued; expected waiting time is 15 minutes."

The server might issue several 182 (Queued) responses to update the caller about the status of the queued call.

With this feature, the SIP stack is enhanced to allow the host to:

• generate the 182 Queued message

• report the receipt of the 182 Queued message to the host

This feature is supported in Call Agent and Non-Call Agent calls.

Pertinent Specification

RFC 2543/3261

Description

When the CSP receives a 182 Queued message for a call in a pre-answered state, the CSP reports it to the host as a PPL Event Indication message. The PPL Event (0x002E) in SIP component 0x00A7 reports this information.

Reporting 182 Queued Message

When the CSP receives a 182 Queued message for a call in a pre-answered state, the CSP reports it to the host as a PPL Event Indication. The PPL Event (0x002E) in SIP component 0x00A7 reports this information.

See Call Flow for the format of this PPL Event Indication. The PPL Event Indication message contains the SIP Response Reason Phrase (0x2949) TLV if the Reason phrase is present in the received 182 message and if it is less than 250 bytes in length.

NACK Values

The PPL Event Request that generates the 182 Queued message has the following NACK Values.

Nack Values | Name | Description
--- | --- | ---
0x1303 | Invalid PPL Event | PPL Event not expected at this point
0x1304 | Invalid Data | Check the date in the API
0x1305 | Network Error | Unable to send the message

Generating 182 Queued Message

You do not configure the CSP to generate the 182 Queued message.

The SIP Stack allows the host to generate outbound 182 Queued message using PPL Event Request (0x0026) in SIP UA component (0x00A7).

See NACK Values for the format of this message.

The SIP Response Reason Phrase (0x2949) TLV is supported in this PPL Event Request.

API Messages Used

• PPL Event Indications (0x0043)

• PPL Event Request (0x0044)

PPL Information

PPL Event Request (0x0026) in SIP UA component (0x00A7).

Configuring

This functionality is disabled by default. Set bit 7 in the PPL Event Notification Mask TLV in the VoIP Protocol Configure message to enable this feature.

Call Flow

The following call flow shows messages involved with the reporting and generating SIP 182 Queued message.

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.
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.
Tag-Length-Value block. A standardized block that allows data to inserted in a standard way into API messages.
Negative acknowledgement to a message.
Voice over Internet Protocol. The delivery of voice information in digital form in discrete packets rather than in the traditional circuit-committed protocols of the public-switched telephone network (PSTN).