Networking / Beginners

---

Identifying the Level of Your Problem

Dedicated circuits come in many sizes, and the first order of business is to isolate the level of the issue within the circuit. Here's a rundown of the basic levels of circuitry you might be dealing with:

• OC-12 or OC-3: Problems at these levels are usually related to large optical circuits. A problem at this level affects everything on the circuit. Alternatively, you may have a problem that just affects part of the circuit (one or two DS-1s on a specific DS-3), thus eliminating the OC-3 or the larger OC-12 (in which the OC-3 rides) as the possible source of the issue.
• DS-3: Problems at this level affect all the lower-level DS-1s and DS-0s. If red lights or alarms are flashing on your DS-3 multiplexer where the coax cable enters, and all of your DS-1s are down, you can trace the source to the DS-3 level.
• DS-1 (also called T-1): Problems at this level affect the entire DS-1 circuit and all the individual calls running on the circuit. If you have any individual DS-0 channel that is unaffected, your problem is not at the DS-1 level.
  Tip Don't get tripped up if someone uses the term T-1. T-1s and DS-1s are two names for exactly the same thing, like Bobby and Robert.
• DS-0:Problems at this level affect the individual call channel. These problems are either isolated to individual DS-0 level interfaces on your phone system, the DS-0 level hardware at your carrier, or somewhere within the public switched telephone network (PSTN). You know you're dealing with a DS-0 problem if the problem only affects specific calls; it won't affect the entire DS-1 circuit.
  Tip The good news is that troubleshooting anything above the level of a T-1 (DS-1) circuit involves the same carriers and quantity of hardware. The greatest change in variables occurs when troubleshooting issues at the T-1 level and individual channel (DS-0) level.

If your local carrier provides your dedicated circuit, be sure to include the carrier in your troubleshooting process. Most dedicated circuits for voice calls terminate at your long-distance carrier, and because of that, the local carrier has only a supporting role in the circuit. As you isolate dedicated circuits from the DS-3 or DS-1 level down to the individual DS-0 channel level, take note of the variables at work and who is responsible for each one.

Beware the misdiagnosed problem

Remember Begin troubleshooting your dedicated circuit only after you confirm that your issue doesn't exist anywhere else. Your dedicated circuit only involves a few miles of cabling and a few pieces of hardware between your company and your carrier. If calls that don't use the dedicated circuit also experience the same problem, you need to report it to your carrier as a switched problem.

In fact, you may have a brand-new problem on your hands if you open a trouble ticket for your dedicated circuit and the problem could be effectively resolved as a switched issue. Put simply, troubleshooting the dedicated circuit places your circuit at unnecessary risk; you may end up taking down the circuit entirely, leaving your business without phone service for the duration of testing.

If your issue affects a variety of your long-distance calls, from switched outbound calls to dedicated inbound calls, I advise you (nay, I entreat you) to open your trouble ticket on the switched outbound issue, because it provides the greatest focus for your carrier.