Before you get too deep into this page - you should check out the page on T1 technology. |
Good - you did. Are you still awake?
If you are awake and are prepared to continue - let me take a moment to remind you:
Folks who work in telco are responsible individuals - not morons.
They understand the concept of personal responsibility.
Trust is essential especially when you enter the world of Wide Area Trunking.
Every time traffic hits the Wide Area Network, the meter is running.
Hopefully, the meter is ticking on a legitimate business call and not putting money in the pocket of Hackers or irresponsible Insiders out to make a quick buck.
When I say the meter is running - a Hacker or another might be able to make $20,000 over a weekend using your company's outbound trunks.
$20,000 may seem like peanuts to a major corporation but in reality the $20,000 made by the Hacker or Insider could translate into $500,000 tacked on the company's telephone bill. With the addition of legal and internal costs - rack up another $100,000.
Somewhere down the line - the financial cost becomes a human cost.
Companies may not be able to make payroll. Your brother, sister, father, mother or your best friend could be given a pink-slip because the money is simply not there to cut their check.
Okay, so you've gotten this far - hopefully you've gotten my drift and understand that while I want you to understand basic trunking - I want you to be aware that you must understand the full consequences in case temptation raises it's ugly head. Simply put it is not worth it, period.
Alright, you know everything you need to know about T1 technology but how to get a voice path from a PBX through the CSU - into the Westel/Smart Jack and out over copper to the Local-Loop and then on to the Wide Area Network?
Two words: Trunk Group.
Let's use a T1 as an example.
What have we got - yip, 24 channels @ 64 kbps per channel configured for B8ZS - (clear channel signalling).
We know that each channel can be configured for Inbound, Outbound and Bothway voice traffic and we can even throw in a few data channels.
For simplicity - let's say we go with:
- 8 Channels inbound.
- 8 Channels outbound.
- 8 Channels 800 inbound.
Altogether we have 24 channels @ 64 Kbps for a total of 1.544 mbps.
- Channels 1 through 8 dedicated to Inbound calls.
- Channels 9 though 16 dedicated to Outbound calls.
- Channels 17 through 24 dedicated to 800 Inbound calls.
So we create three Trunk Groups to handle voice traffic to and from this T1.
Let's call the first Trunk Group: T1_In; the second: T1_Out; and the third: T1_800.
Each Trunk Group may have unique characteristics that can be modified within the PBX Software. Stuff like Wink - fasy busy forward number - error return rates - whether the trunk is Inbound/Outbound or Bothway - Frame Drops and so on.
So, with the Trunk Groups created - we return to the T1 Card within the PBX where we can modify the individual channels on the Card.
The channels are converted to unique Trunks assigned to a particular Trunk Group.
So for example: Channel 9 may become circuit XXX0 within Trunk Group T1_Out.
It doesn't take a giant leap to figure out through internal routing within a PBX that if someone dials an access code - (9 is an access code but it's not the only one) - that all outbound calls can be targeted to Channel 9 plus the other seven channels above it.
This is a real simplification of the scenario. You should be aware that there are quite a few internal controls (steps) that are in place to prevent anyone abusing this process.
But don't ever make the mistake that it is difficult and reason that no-one could really pull it off.
The most important thing is to understand how it is done.
What Hackers are looking for is dial-tone. If they can't find it - can they create it??
If you make it easy - hey, they'll come back again and again until you finally check your phone bill or the Carrier cuts off your Long Distance service.
So, how do you stop it?
Become familiar with how your Phone System works.
Understand routing, COS, feature codes, translation tables.
Most importantly - just who has access to your Switch? Do you really know? When was the last time you changed the password? How secure is the maintenance port?
Who has privileges to modify Hunt Groups, Trunk Groups, Class of Service (COS) and so on?
Also, if you pick up a phone handset and dial a few digits - are you likely to get unrestricted dial-tone back? Better check out maintenance dailing, pronto.
And, of course - don't ignore Voice Mail. Is Zero # an option? If it is - how many other variables will this function allow?
Make sure that your Carrier monitors the usage on your Outbound Trunks. Flags can be thrown up at your request based on your parameters.
If you're in El Paso and most of your business is conducted in California - it might seem a little unusual if you were receiving telephone bills with calls to Alaska buried on the 10th page.
The bottom line. You must understand Trunking if you want to make it in telecommunications.
Finally, two things:
If you're an aspiring Hacker and laughing quietly to yourself - consider this:
You're reasonably intelligent, employable, computer literate and on the fast-track to nowhere. So you can make a few bucks. Big deal.
Come into the fold and put your little gray cells to better use.
Don't sell your friends, family and yourself out. Dollars are one thing - human life is another. Think about the human cost associated with your actions.
If you're an aspiring Telecom Manager - understand Trunking or find another career.
I spent about 5 years in telco before I even got near a Trunk Group. Don't take it personally if you don't have privileges to make changes or even view the setups. It takes time. However, that doesn't mean you should ignore the concepts. Prepare for future personal growth each and every day.