SIP 182 Queued Message

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.

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.

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.

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

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

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

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.

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).