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T1 Internet

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by john

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I have a client who is installing T1 internet in his office. He is ordereing it through Mcleoud USA. They tell me that the loop for the DMARK is on the first floor and his office is on the fourth. They said that it needs to then be extended to the fourth and they asked me if I wanted to do it or if they should. Is this a difficult task? I have a lot of experience with networking. Is it something that could be figured out on-site?

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by oz_media

If the DMARK needs to be extended to the fourth, let McLeoud do it. If they have a router on the first, you can run the Cat or fibre youself if you are confortable with it.

The problem with T-1 is that bandwidth is easily dropped if not cabled properly, you may notice great throughput and the customer is happy but it may also be functioning at 60%.

My thoughts would be to have the telco or line provider extend the DMARK to the fourth floor or simply install a new DMARK point on the fourth and run a new line in.

If running T-1 from fl.1-4 you may even want to look at fibre if cost allows it. Once the bandiwdth is in the office, they can waste it as they please but with the extremely high cost of T-1 and the endledd bandwidth usage costs, you'd want to make sure not a single bit is dropped before the office.

by oldefar

My recommendation is that you let them extend the circuit to the fourth floor. This way, it gets tested from your connection point back to the CO.

The applicable standard is ANSI T1.403-1995, Standard for Telecommunications,
"Network-to-Customer Installation--DS1 Metallic Interface". SBC has a pdf file you can download that gets into installing the extension. You can find this at http://tinyurl.com/393pq

As for how it works - depends on whether the circuit is channelized for DSO or not, and also which circuit encoding is used. This has to match between your CSU and the CO. The detailed explanation is beyond the 2000 word limit, but you can email me for an overview or go to the ANSI site for all the specifications.

You will NOT see a degraded performance situation. The circuit will be up or down. Install that extension incorrectly and the errors will alarm at one or both ends. Mismatch the CSU settings and the circuit may work end to end but fail to loop for testing. If you have to much signal loss in the extension, and you will fail to come up but telco will test clean to the demarc via smart jack and you will be on your own to resolve the problem.

Now, if this is in fact a T1 internect connection and includes a router, your extension will be ethernet and you will face the ethernet issues instead. Again, having the router on site with your customer instead of 4 floors away makes problem resolutiion simpler.

Your client can expect 1.544 Mbps full duplex over a T1. Of that, 1.536 is usable for data, less whatever routing overhead you have. The data will of course include its own IP overheads, so you lose a bit more there.

by oldefar

Mcleod USA was light on their service description for dedicated Internet. They are reselling SBC and MCI circuits, so the SBC description should be fairly applicable.

The fractional services (128 up to the full T1) uses channelized service. The T1 is configured as 24 DS0 64Kbps channels, and the terminating DSU/CSU bundles the assigned channels into one router connection. A 128 Kbps would be 2 DS0. The circuit still operates at the full 1.544 Mbps between site and CO, and the channels are pulled of at either end.

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