Confused about T1 bandwidth? No need to be any longer. Here's some of the most commonly asked questions .... with practical answers to set you straight and on your way to confidently utilizing this backbone of business voice and data networks.

1. If T1 data rate is 1.5 Mb, why isn't a cable service "equal or better" which offers 6MB down/768 Kb up? What are the fundamental differences between T1 and Cable?

Basically T1's are business connections. Cable/DSL services are usually residential.

T1's normally have:

* unlimited throughput

* a guaranteed uptime per month

* no port blocking, allowing servers

* upload 2-5x as high as cable/DSL

* faster repair times, as in the company will most likely take priority repairing them

* a dedicated line

Cable/DSL usually has an AUP or TOS that disallows servers, and may have high downtimes. Plus when there is no internet, there might be no business either.

Cable/DSL have high download speeds, but in a business setting, you might only be checking email/browsing the web/updating database records, so you don't need so much download. However you may be running a server that uploads a lot, or you might be updating a website and need to send files often. The upload of a T1 helps in this setting.

Raw peak speed it not all there is to a connection. T1 is marketed as a business class service. That means it is symmetrical, making is easy to run servers and comes with a service level agreement that guarantee minimal acceptable performance and mean time to repair (MTTR). These are critical components in the marketing of different services. If you are a business the cost of a network outage could be dramatic.

That being said the widespread availability of extremely low cost residential services is putting tremendous price pressure on traditional business class services. With that you see the cost of T1 lines (as well as DS3 even OC3) dropping steadily over the last year.

2. Is T1 more than just raw bandwidth? Is voice T1 fundamentally different than data T1 for Internet access or "integrated T1" for voice and Internet access? If you need voice, do you have to go with a telco-type T1 provider who can provide you DIDs and local and long-distance service, etc? When people talk about "integrated T1" which can be used for Internet access (data) and telephone service (voice), how does the provider handle data side and voice side?

Simply put T1 is a point-to-point link. T1 was developed in the late early 1960's to carry 24 digitized phone calls between telephone switching offices. Think of T1 as a simple pipe, between you and the service provider. That service provider may be the phone company delivering voice service over the T1 pipe, or an ISP delivering Internet access. To the T1 line how the bits are used does not matter, bit-is-bits. If you want DID trunks you need to make sure the remote end of the T1 connects to a service provider capable of delivering them.

Remember the history of T1.

It was designed to carry digital phone calls. Total capacity is divided into 64 kbps channels. That is ideal for voice but is makes no sense for data, so data uses unchannalized T1. In the middle is that ability to mix and match data and voice. Thus the birth of "integrated T1" lines.

3. In "integrated T1", voice calls get priority. In the absence of any voice calls, all the bandwidth is available for Internet access. How is "dynamic and automatic" bandwidth allocation done? Do you need special edge equipment to do this?

T1 is just a pipe. It is a simple matter to have equipment at each end of the T1 dynamically allocate voice as high priority and data on a best effort basis over a single T1 pipe, the common term is Integrated Access Device (IAD).

There you go. You're now armed with the basic knowledge needed to make the initial educated decisions on installing a T1 line for your business voice/data network. For more complex applications I strongly suggest using the services of a no-cost consultant to guide your business through any potential minefields.