384k actual speed

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pretdsl

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Hi everyone

I am curious to find out what actual speeds you are getting on your 384k lines.
The theoretical max is of course 48kB/s and for the first 1.5 years I was able to get this speed. The last few months however, the highest I ever get is 38.
I know it isnt my hardware or PC, no spyware issues etc, and I also had a Telkom technician check my line a few weeks ago and he said this was pretty normal.

So, my question is, what connection speeds are you folks experiencing on your 384k lines ?

Thanks, cheers
 
Actually 48kB/s is more than the theoretical limit.

48kB/s is only possible if :
1 . There are no protocols in use (each byte is pure data and no handshaking)
2. There are zero errors (no retransmits)

You might see 48kB/s if some of the data is compressed and being expanded as it comes out of the modem since compression protocols are used on ADSL as far as I know.
I've never seen a sustained transfer rate of more than 40kB/sec on my 384 kbps line - it typically hovers around 38 kB/sec on a good day.

If you want to know the real theoretical limit I could haul out my TCP/IP networking book and start counting all the header sizes and add all handshaking packet overheads but it's a very tedious process so I'll leave that up to you.
 
You shouldn't be able to get any speeds higher than 40kb/s because of TCP overhead. So... whatever you used to check your download speeds previously was wrong, or you mistakenly had a 512kbps line and Telkom merely corrected the error.
 
try www.gamco.co.za under support, bandwidth meter. Test it a few time a day for a few days. true speed normally is lower than ur advertised speed - eg: 384 would tipically run @ 340 more or less. if ur speed tests much lower phone telkom again. they sometimes need to reset ur speed to 512 en then back to 384. For some reason it sometimes changes to a lower speed. my 4meg ran @ 512 for a week after telkom told me a few times my line is fine. eventually some cleaver guy at secondline support fixed it and told me they are suppose to test for this at first line (helpdesk) support. good luck
 
Armizael said:
You shouldn't be able to get any speeds higher than 40kb/s because of TCP overhead. So... whatever you used to check your download speeds previously was wrong, or you mistakenly had a 512kbps line and Telkom merely corrected the error.
Click to expand...

LOL thought of the same thing. I wish for 64kb/s on my 512 line. :D:p
 
384k lines used to sync at 512/256. Since August last year they sync (correctly) at 384/128
 
The norm is usually about 40 or so, sometimes it might spike higher than that for a few seconds but its not sustainable.
 
It will never actually go more than 40kB/s for a sustainable period of time, it will only go higher for a few seconds before normalising. This is most evident at the beginning of a download where the speed always starts off high and starts slowing down.

Think of the following analogy: You have a water pipe that is capable of a certain flow rate. If the pipe becomes clogged, the water is held back under a higher pressure. As soon as the pipe becomes unclogged, all the water that was being held back suddenly rushes through before it starts flowing again at a steady rate.

Same principle applies - you're getting the same data, but not exactly at a higher rate because you still have to take into account the amount of time that it was "clogged" up. So in effect, it all averages out.

gora said:
Telkom states a upload of between 64 and 128. How can I determine my average?
Click to expand...
You could try a few speed tests to determine more or less what it is.
 
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Grabit is strange, im on 384, and when i download from the IS News server, it reports 56, or 50kb/s, and behaves that fast too... :S
 
On my 384 I get between 38 & 40 from the saix servers and sometime triple that on the news servers and this is constant for hour and hours... Any ideas how that works?
 
Thanks for your replies.
The explanation about the Telkom 384 accounts synching at 512k sounds possible to me, and was probably the reason why I was experiencing about 10kBps higher speeds before.
My measurements werent made with any program, just what I saw on ftp downloads, I would get sustained 46-48kBps. But as you correcly say, there are packet overheads to consider too, so a 384 would not normally be expected to get this amount unless you are gaining from v.bis type hardware compression.

Well, I'm glad my speed is normal, having more would be nicer of course :)
But in ZA ADSL scene, beggars cannot be choosers. :P

Thanks to all for your help.

Cheers
 
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