Re: Some newbie questions about T3's

cscott · ‎05-03-2004

I've got some questions concerning T3 technology that I haven't been able to find a clear answer about anywhere.

1) What is the difference between Clear Channel and Channelized? I've heard that Clear Channel (B8ZS? I know what this, is Clear Channel the same thing?) is one single channel; Channelized is, of course, multiple channels.

2) If I wanted to get a fractional T3, would I need a Clear Channel or Channelized T3 WIC? Does it matter?

3) What is the minimum Cisco chassis that supports a fractional T3? 2600?

Thanks in advance, and sorry if these are relatively 'newbie' type questions.

-Chris

bolds04 · ‎05-04-2004

The answer to:

1) Clear Channel (I think) refers to Voice but could be wrong on this one.

2) you would want a Channelized T3 WIC - Part number NM-1A-T3 if you are ordering an ATM DS-3 (T3).

3) 2610 Series - 12.1(2)T - I would suggest adding additional RAM if you go with anything lower than 3640. Then again it depends on how you are using it.

micah · ‎05-04-2004

Chris,

1. Channelized refers to whether or not the provider will provide multiplexing on the circuit. A T3 can be divided into 28 channels (28 T1's). If the provider puts a multiplexer on the circuit and you put a multiplexer on the circuit (or use a multichannel card) then you can service multiple T1's on that DS-3 up to 28. This basically gives you a way to order T1's and have them cross connected in the CO to your DS-3. Essentially you would order your T1's and provide Circuit Facility Assignment (CFA) to the telco on the order to have them install it on your DS-3. You would only want the channelized DS-3 if you are planning on installing T1's back to a main location and it would probably take 10 or more to make it cost effective. If you wanted to run T1's into your PBX and router then you would require an external multiplexer.

2. You are looking at the NM-1TE3 if you are talking about the 2600 platform. There is no option for channelized T3 on the 2600 platform.

3. 2650 and up. If you plan on going with a full T3 at some point I would get the 3725 or 3745 chassis now.

HTH

-Micah-

cscott · ‎05-04-2004

Thanks for the input. That's the kind of technical explanation I was looking for!

So, if I do a clear channel T3, the provider just subrates it on their end based on how many timeslots we buy?

micah · ‎05-05-2004

You got it!

Craig Norborg · ‎05-05-2004

Clear channel and channelized are talking about different things. You got a pretty good explanation on the channelized vs. unchannelized, so here is an explanation about "clear channel" or "B8ZS".

To put it simply there are two common ways to configure a DS0, they are known as "ANI/SF" or "B8ZS/ESF" (also known as "clear channel"). The ANI and B8ZS are the encoding they do on the frame, the "SF" and "ESF" are "Super Frame" and "Extended Super Frame" respectively. "ANI/SF" is commonly used for voice-grade circuits and gives you 56K of data and the other 8k is used by the telco. So, if you have a T1 (which is known as a DS1), which consists of 24 DS0's, if you have them as ANI/SF, you get 24*56 = 1344Kbits of bandwidth. While with a T1 that is B8ZS/ESF, you get 24*64 = 1536Kilobits of bandwith.

Now, translate that into a T3 which is 28 T1's I believe and you can see that little 8K of bandwidth that having a circuit "clear channel" gets you adds up to quite a bit of bandwidth...

Almost forgot, with most telco's I've dealt with there is no difference in monthly costs of a "clear channel" or non-"clear-channel" circuit, but they will usually charge you a one-time fee of maybe $3-500 to get the circuit provisioned as clear-channel. Well worth the money over time!!

HTH!!

micah · ‎05-05-2004

Hey Craig...

Good explanation of how the bandwidth works out... I believe you meant AMI, not ANI (Alternate Mark Inversion).

I have never heard of a charge for setting up a circuit with b8zs/esf in all of the hundreds of circuits I have ordered. In P2P configurations this will be the optioning that is used by default.

Craig Norborg · ‎05-06-2004

Ah yes, I did. Spending too much time working with Ciscoworks 2000 and its ANI server... 8-)

It very well might have changed, but I do know that all the circuits I used to order from Ameritech (not SBC if that tells you how long ago it was) had a $350 one time charge for doing clear channel.