How much bandwidth does a T1 typically give?

Question

We're about to move into a new apartment which has a T1 for $35 a month. How much bandwidth does a T1 usually supply?

Right now we are with Comcast cable which theoretically gives us 14mb down / 7mb up, but I haven't really seen any download or upload speeds going at more than 1mb in all the time we've been using it.

Solution 1

By definition, a T1 provides 1.544 Mbps, full duplex. (The equivalent European specification is the E1, which provides 2.048 Mbps.)

However, it is divided into 24 channels, and they can be aggregated in any number, so you can get a "partial" T1 in many different bandwidths.

And sometimes multiple T1s are sold aggregated together in what tends to be called "bonded" T1s.

Also, sometimes "T1" is used incorrectly to mean a full-duplex business-class (which usually means "better bandwidth guarantee") circuit, or possibly even something else. You need to make sure what you're getting from your vendor.

Solution 2

A T1 is a data circuit with 24 channels. Depending on the provisioning, it can provide different bandwidths and you won't get the full 1.544Mbps for your use. B8ZS/ESF "clear channel" uses 64k channels while AMI/D4 uses 56k channels (8k is used for control). Sometimes you'll use fewer channels, such as a fractional T1.

• 24*64k = 1.536 Mbps (slightly less due to signaling codes)
• 24*56k = 1.344 Mbps

A lot of T1s are now HDSL circuits and use a single pair instead of two pair.

Other things also use T1s like a PRI circuit. For a PRI, you often see 23 B channels to carry calls or data and 1 D channel for control.

Solution 3

According to Wikipedia T1 provides 1.544 Mbits/s of bandwidth both directions.

Comments

[MDMarra]

Absolutely wrong about a speed increase. It is common to have 10/3 from cable internet nowadays. Having an increased upload speed and reduced download speed will absolutely not increase performance, especially with such a drop in download speed. Not to mention that a standard cable internet service from most major providers exceeds 1.544Mbps up and down anyway.

[quack quixote]

+1 for "check what you're getting from the vendor". good tip.

[Josh K]

I've never gotten 10 up 3 down on any cable provider, even when I had a 16Mbs plan I still capped at 1Mbit up. A T1 line is dedicated, cable broadband connections are a shared "best effort" line. You won't get what you pay for, at best 80% of the advertised bandwidth.

[MDMarra]

Regardless of your individual experience, an 80% reduction in download speed is going to give a noticeably slower experience than a (possible) marginally increased upload speed.

[Josh K]

Where do you get an 80% reduction? My point is that a cable connection is a party line, you [strong]will[/strong] different speeds at different times of the day, and it depends on the number of people on that line and the connection to the ISP. A T1 line is a dedicated line you have all to yourself. You can host off of a T1 line, not a cable line. Static (or dedicated) IP address with a block of bandwidth.

[MDMarra]

From your answer "A T1 line will give you a noticeable speed increase because you can send data at the same rate as you receive it." That's misleading. Even on a shared trunk like DOCSIS, any modern day connection will give you better performance for a home user than a T1. The question didn't involve anything about hosting at all.

[Franz Wong]

Keep in mind that if you get a real T1 trunk direct to your wall, you can't use a normal modem/router and you'll need to get a T1 device, which are quite a bit more expensive than a Cable/DSL device usually.

[wfaulk]

Most ISPs will provide the requisite equipment and bill you for it.

[David Harris]

I just want to point out there is a difference between Mb and MB - superuser.com/questions/301015/…