Download speed

Hi
I have just moved house and have come to the end on my 10 day stabilisation period. I have just done a speed check on the BT speed test page and got the following results:

Your DSL connection rate: 8128 kbps(DOWN-STREAM), 448 kbps(UP-STREAM)
IP profile for your line is - 7150 kbps
Actual IP throughput achieved during the test was - 6571 kbps


Now are these speeds expected for a line syn'd at 8128kbps?

Cheers,

Chris

Yes.

To explain more, you are connected at the maximum possible speed. The connection speed determines an IP Profile, which is basically a grouping of speeds into bands to make network management simpler.

The IP Profile is what actually determines your maximum download speed (throughput).

The drop from 8128 to 7150 looks big, but it isn't as bad as it sounds.

In the transmission of data there are several overheads to do with packaging the information. It is split into small packets with routing information, and the small packets are sent out mixed in with packets for other users. It would be impossible to send a continuous stream of data unpackaged to you, as you would monopolise a number of high capacity circuits (working in 100s of megabytes or more per second) for your 8 megabits per second of traffic. One byte is 8 bits.

The two main overheads are TCP/IP and ATM. TCP/IP is the basic packaging on the digital bit of the network. This takes up 10%-12% of your line's capacity. Then there are ATM overheads of about 5% between you and the exchange, because that is an analogue circuit, so the TCP/IP packets have to have an ATM wrapper.

The TCP/IP overheads are accounted for inside the loss due to the IP Profile. So nearly all the difference between your connection speed and your profile is TCP/IP overheads. Edit - The maximum between you and the exchange is about 95% of the profile because of the ATM wrappers.

So your throughput speed is pretty good.

For more information see this table and the explanations above and below it.

Edited by RobertoS (Sat 11-Jul-09 09:17:47)

They are about right, as I sync at the same speed and have the same ip profile.
The max download speeds i get are around 840-60 KB/S.

Edited by Anis (Sat 11-Jul-09 14:47:27)

Thanks for the replys guys, much appreciated.

Chris