Networking / Beginners

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Letting your channels be your guide

When you open a trouble ticket, it's always helpful to ask the carrier for a circuit snapshot. A snapshot of the circuit is the disposition of each channel on your circuit. Even if you think you have a DS-1 level issue, it's always a good practice to ask for this information. You might believe that your entire circuit is being affected, but a snapshot could reveal that only half of the channels are impaired. With basic facts from the PMs and a circuit snapshot, you can begin setting realistic expectations for resolution of your service. Additionally, you can isolate individual DS-0 issues to the specific channels experiencing the problem. To solve your problem, you might be able to reboot your phone system to bring the channels back into service, or have your phone system deselect them as available lines. The key is using every available bit of information your circuit provides. Taking in the disposition of your individual DS-0 channels on your DS-1 circuit is a quick and easy way to glean what is happening to your circuit.

Idle: IDL

Your channels are in an idle state when they have access to your carrier's network, but don't have an active call. This is the state you expect your channels to be in when everything is working fine and the circuit is waiting to process a call.

Remember The circuit must be considered idle by both your carrier's technology and your own phone system in order for a call to come through on the line. If, according to your carrier, the channels are idle, but your hardware is unable to seize the channels for some reason, one end of the circuit isn't speaking to the other. Open a trouble ticket. The problem might be between your phone system and your multiplexer, or your multiplexer and your CSU. If your carrier sees the circuit as active and you can't seize a channel, there must be a piece of hardware interacting with your carrier to make the carrier think everything is fine.

Call processing busy: CPB

Call processing busy or CPB is the healthy state of a channel with an active call on it. Under normal circumstances, your active circuit has several channels in the CPB state, indicating active calls on the specific DS-0s. The rest of the channels are idle, waiting to accept a call. A circuit with channels in CPB is obviously connected to the carrier, because only a call that is connected to the network can establish the channel in this state.