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The company I work for has roughly 45-55 simultaneous users (local and remote/VPN) logged in at a given time. We currently subscribe to an ADSL connection but we have been experiencing slower upload/download speeds as our number of users increase. So, I have a few questions with regards to upgrading our connection to a t1 line.

I am aware that the number of channels on a t1 line are much greater then that of our current ADSL connection, but I have heard that the number of active users on a t1 line should be no greater than ~30 for optimal performance. I would think this statement is dependent on what each user was using the connection for and could change depending on this variable. That being said, I have tried to break down how the line would be used in our organization based on our major departments:

Sales (~60% of total users) - Everyday surfing, email, research, occasional streaming media

Marketing (~15% of total users) - Heavy reliance on uploading/downloading, streaming media, file sharing

Other (~25% of total users) - email, rare use of any connection intensive activities.

I have considered keeping the ADSL for our local users and dedicating the t1 to our remote users (or vice versa) but the cost is significantly higher then what we had hoped for.

All factors being equal (# of users, frequency of downloads/uploads from our current activities) Would you suspect a significant performance increase in making the transition to a t1 line from our current ADSL line?

What are your thoughts or recommendations?

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up vote 2 down vote accepted

I have a similarly sized office, and I addressed the limitations of our 1.5Mbps DSL by bringing in a business class cable modem (16down, 2up). It's hooked to a dual WAN router, where I customized the iptables so that the highest traffic protocols (http/https, RDC, FTP) go out the Cable, all other traffic hits the default route of the DSL.

As to whether or not the T1 speed is > ADSL, we don't know how fast your ADSL is. As long as they both perform properly, 1.5Mbps is the same over either connection. Biggest difference is that a T1 is usually provided with a higher availability SLA.

BTW,when you're looking at IP traffic, the # of T1 channels isn't part of the consideration. The channels are about voice calls only.

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T1 is slow.

Unless you have a specific reason for wanting T1, such as voice functionality, or you're sick and tired of your local provider's being incompetent, you don't want T1.

You should ask your ADSL provider for more bandwidth, look into cable modem or some other metro area service like wimax, or call around for metro ethernet.

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+1 T1 is about 1.5Mbps but is synchronous whereas ADSL is not. As suggested, check with other providers for something faster and possibly synchronous. T1 will alos have some QoS attached but you may not need that. Hre in Canada T1 is very expensive and there are many great options. – Dave M Feb 11 '10 at 14:49
The symmetric vs asymmetric speeds may be an issue, but mostly office traffic is just like home traffic, more in than out. If you're running servers, colocating them in a hosting site is a better option than having the servers share bandwidth for most needs. And lastly, the T1s can have their backhaul oversubscribed just like any other service. This tends not to happen, but it certainly can. T1 is for voice these days. (and it'll be called ISDN in any case.) – chris Feb 11 '10 at 16:02

Instead of replacing ADSL, why not compliment it with another ADSL line from another provider? You'll have limited redundancy (to the exchange at least), and you can stick a load balancing router in to provide failover and double your throughput.

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if your looking at doing anything professional, fibre is the only choice. ADSL suffers many problems. Tcp doesn't really like or understand asymmetric connections.

I've diagnosed many problems with ADSL physical layer. Here in the UK we get slower sync speeds at night due to interference from street lighting!. This causes errors, retransmits , high latencies and lower throughputs. Depending on the length of your adsl line to the exchange will effect bandwidth and day to day reliability.

I've had customers that loose half their speed during wet weather, somewhere in the path of the line, the copper cable is exposed, and is being shorted by water!!! Sure they can move you to another line, but it means downtime. Usually the copper cabling is barely enough to support a phone call.

ADSL is okay for domestic broadband, however it's not the solution for business networks supporting services such as vpn's. If you have no alternative to adsl, then try for sdsl, it's symmetric nature will make things at the tcp layer run a bit smoother.

If your ADSL line is syncing at a high rate, force it to sync at a lower rate, thus reducing the number of error's you'll be getting.

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