Circuit Status Query

Overview

The Circuit Query feature allows the host to query the status of a single circuit or a range of circuits using the PPL Event Request message. A Circuit Query Message (CQM) is sent to the remote CSP, which returns a Circuit Query Response (CQR) message containing the status of all the circuits. The local and remote circuit status for each circuit is sent to the host in a PPL Event Indication message.

Recovery Action for ANSI Only

For ANSI only, if the circuit is found in the invalid state by the CQM, a recovery action is taken by CQS. The host can configure the recovery action taken by the CSP using the PPL Configuration Bytes of the CQS component. Recovery actions taken by the CSP are as defined by the ANSI-ISUP T1.113 specification.

Implementation

When a CQM request is received from the host, the CSP sends a CQM message to the network. When a CQR is received from the network, the CSP sends a PPL Event Indication message to the host with an SS7 Data Parameters ICB (0x22) containing the status of the local and remote circuits. If the CQR indicates a maintenance state, the CSP takes appropriate action based on Table 2 in ANSI T1.113.4.

If a CQR is not received before the expiration of T28 (default =10 seconds), a PPL Event Indication of 0x01 is sent to the host indicating the error.

Call Flows

This call flow shows a CQM request from the host and a CQR response from the network.

Status Values

Local and Remote Status

The local and remote status are reported to the host in an SS7 Data Parameters ICB (0x22) in a PPL Event Indication message, where:

Data[0]

Local Status

Data[1]

Remote Status

One of the following values is reported for both Data[0] and Data[1].

0x00

Transient

Maintenance States

0x01

Spare (no interpretation)

0x02

Spare (no interpretation)

0x03

Unequipped

0x04

Incoming Circuit Busy, Active

0x05

Incoming Circuit Busy, Locally Blocked

0x06

Incoming Circuit Busy, Remotely Blocked

0x07

Incoming Circuit Busy, Locally and Remotely Blocked

0x08

Outgoing Circuit Busy, Active

 

Call Processing States

0x09

Outgoing Circuit Busy, Locally Blocked

0x0A

Outgoing Circuit Busy, Remotely Blocked

0x0B

Outgoing Circuit Busy, Locally and Remotely Blocked

0x0C

Idle

0x0D

Idle, Locally Blocked

0x0E

Idle, Remotely Blocked

0x0F

Idle, Locally and Remotely Blocked

0x10 to 0xFF

Spare