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Difference of T1 vs ADSL


Can someone please help me. I am looking to find the technical difference of a T1 connection vs ADSL. I understand most of the technical differences in the technologies themselves, but what I am looking for is a difference a specific case. We have several sites that are spread throughout a small city. There are about a dozen sites that previously were connected to the internet via T1 lines. These sites would connect to a central site where the main servers are located. The decision was made (for cost reasons) to change these connections from T1's to ADSL connections. Now that these changes have been made, the connection speeds at these locations are slower to the central servers.What I am trying to discover is if 2 sites (A and B) are located 5 miles apart, site A is connected to Bellsouth via ADSL and site B is connected by a T1. Would the traffic between the 2 site ever leave the Bellsouth circuits? If not, would the sites run slower on DSL as opposed to T1 simply becasue of the slower upstream speed of the ADSL line.

Thanks for any info you can provide.

Let me know if there is any other information that is needed to help explain the issue.
1 Solution
LucFEMEA Server EngineerCommented:
Hi lowcountrycomputersolutions,

You might want to read an article of wikipedia on T1 and ADSL:

T1 can handle an upload speed of 1536 kbit/s while ADSL is limited at 1024 kbit/s which causes about 30% slowdown in an optimal situation.
As you're probably connecting the sites by VPN or at least using resourses from the other location you're limited by the upload speed and not the download speed. (depending of course which direction the traffic is flowing)
In most locations on this planet the ADSL upload speed is still not even near 1024 kbit/sec, so depending on your location you will be limited even more.

ADSL is mostly used for end-users who will be downloading a lot more than they'll be uploading. Downloading with ADSL(1) can go up to 8Mbit/sec and with ADSL2 it can be 12Mbit/sec. Here in the Netherlands, we've got access to ADSL2+ in the last year being able to handle 24Mbit/sec. You can imagine that especially with the fastest connection the upload speed is way behind.

If available an option for you might be to switch to something like SDSL which can go up till 2320 kbit/s up and download.
The actual distance between the two locations don't matter too much, the distance between the modem and the DSLAM is more interesting on figuring out what the theoretic throughput might be. If the DSLAM is very close to your office, you'll get higher speeds (up and download) than when the DSLAM is further away.


hello lowcountrycomputersolutions, Traffic between 'A'-'B' will be governed by the ADSL speed. Upstream and Downstream speed will never be faster than the physical limit 'A''s ADSL connection permits. Even if 'B' thruputs data from 'A' it can't send info faster than it receives it..Hope this helps...Booda2us
lowcountrycomputersolutionsAuthor Commented:
Thanks guys, I appreciate your help. I understand how ADSL works from the ISP to the site (or rather the differences between ADSL and a T-1 in the last mile connection) what I should have asked was is there a difference in how these methodologies work once the traffic reaches the local carrier. Also, what would be the best method to meassure the speeds between 2 sites. I have run very basic "ping" tests that shows response times, is there a better application to do this with?

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Only tools I am aware of, are privy to the T-1/ADSL provider. Contact tech support and have them run a bandwidth/speed test .
LucFEMEA Server EngineerCommented:

To measure the speed between the two sites, you could equip one computer on each site with AIDA32 Enterprize system information (this software has been discontinued but can still be downloaded from http://www.sofotex.com/AIDA32-download_L9326.html)

After starting the software, go to "Plugin" => "AIDA32 Network Benchmark"
Setup one computer as the Master and the other one as Slave, on that computer type the IP of the master and run the test.
If the server computer is behind a NAT, you might want to put it in DMZ it just for this test.

Once you've finished the test one way, just switch Master and Slave to run the test the other way around.

A simple difference between asdl is $50/month vs T1 $500/month.
Your traffic will leave BS for your ISP at the ISP POP of choice. It may be carried by other networks.
Only if you have a dedicated ptp T1 the traffic will never leave the telco carrier.

A good way to measure throughput is to use ftp and a large file.
LucFEMEA Server EngineerCommented:
Glad to help

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