Question about different connection types: T1, T3, etc.

[Mike2002]

T1s are 1.544 Mbps so does that mean that mean if two users are sharing that connection then the speed for each user will drop to around 768 Kbps?? There are many businesses that I've seen that use just a T1 for around 30 people. Can a T1, T3, or the higher bandwidth lines allow say 20 people to run at 1.544 Mbps and if there are more then the speed will drastically decrease. Or is it that each person gets a cut of the 1.544 Mbps of bandwidth. Hope you can understand this and thanks to anyone who can help me with my question.

 

[RangerJoe]

if you use a switch to network people, then effectively each person will have 1.544Mbps, of course everyone cant have that much, but instead of being maxed at 768kbps, depending on usage, you can have 1Mbps, or whatever.

from what i have heard, T1 is basically beefed up cable (as far as transfer goes) a known problem with cable is upload speed, download is great, but upload is crap. this is where T1 makes up for it. download is about the same as most cable accounts, but upload is doubled, or tripled.

 

[9mmCensor]

YEah What RangerJoe said about the Diff Between Cable nad T1. Except that cable is also a helluva a lot cheaper.

If you are running a server or something that needs alot of upload then get T1, otherwise a beefed up cable line is fine.

Cable is simply a T3 line for a specific area, divided and capped and run into peoples homes.

 

[su root]

Compared with cable, T1 and T3 have a "Guaranteed Rate", you can go as fast as 1.544 any time you want, but they can also go faster than that speed, depending on how busy the network is. (but at all times 1.544 Mbits/s per subscriber on the network is set aside, where others cannot touch it). Also compared with Cable, your upload is the same as your download, 1.544Mbits/s. A lot of companies prefer this guaranteed download and guaranteed upload speeds to run websites and mission-critical internet access off of. They're usually guaranteed in the 99.999% uptime range.

They also have a "Burst Rate", which means that for a second or two, the traffic to or from you may burst up to a certain rate higher than your regular connection speed.

You can also get Fractional-T1's in 64kbps channel incriments:
A full T1 is 23 * 64kbps channels = 1,472kbps
plus one signalling channel, at 64kbps (which, after call setup, can be used as a data channel.)
=1,536kbps (the missing 8k is for framing = not usable).

You can also take the individual channels and use voice or data over each of them, so when you buy a T1, you could hook up 23 phone lines, or 23 data pipes, or any combination you want. You can also connect T1 between two locations (instead of to the internet), so you can connect phones or data through that connection to the other location (great for offices with multiple locations).

As for the per-person question, the full bandwidth is available to everyone, it doesn't split in half when another host enters the network, they just have access to it. In the situation where they all used it equally, then yes, it would be HostA has half the bandwidth, HostB has the 2nd half (in theory). In reality, you have to measure in the activities of each host, burst speeds, and extra speeds granted to you.

 

[Smokeys]

This math of $bandwidth / $users = bandwidth per user is factually wrong. Just because you have a pipe of say 1.544mbit and you have two users it does not mean that each user only get 768kbits, you have to think of the nature of how bandwidth is normally used in a client side setting.

When web surfing, bandwidth is used in very sharp spikes, IE when a user loads a page, then sits idle for a period of time, the user reads the page, then repeats, the chances of two people actively web surfing hitting a page at the EXACT same time would be rare, and even rarer is a page that would fill even a T1. This can be applied to 20 users and even upwards.

 

[jajmon]

To add to what SU Root said 'guaranteed rate' is referred to as CIR, certified information rate.

 

[Supchaka]

Just to throw something out there for you... I owned an ISP from 95-2000' With a single T1 and 140 56k dial-ups. Never a complaint about the system lagging, although common math would look like I didn't have enough bandwidth for the number of ports.

One thing not mentioned as well, you can have frame relay versus point to point conectivity. Frame relay was alot cheaper, your pipe goes into a shared cloud, but the CIR was much lower. Even on the PPP T1, I wanna say that my CIR was only 60-70% on the frame it was like 40%. Then again I was out in the sticks and maybe things have changed now.

 

[chuckerants]

T3 or DS3 is 28 T1s.

 

[Motley]

CIR = Committed Information Rate

DS3 = 24 T1s

 

[AMD Phreak]

24 T1's = 576 DS0's.... lots of phone lines!