Loop Loss?

Hi,

Im with plusnet, and have a 512k ADSL line. I gather this means I am on
RADSL?

Anyhow, I've noticed recently, or perhaps more over, that when Im trying
to connect to my server (a Linux box, for private access only of email
and such, not a full dedicated server), the speed is horrendously slow.

I'll try and explain the technical side of it first before I mention
what my ISP has said.

Some research over the past weeks indicate that the connection is
freezing due to TCP exponential backoff's. Essentially, my computer is
sending two packets out at a time, but they aren't getting to their
destination, so my computer waits x seconds before resending the first
packet, which does then get through to the remote end and is then acked
accordingly by the remote end. Unfortunately, then the cycle continues,
two more packets get sent, and each time, this timeout (x) is multiplied
by 2. So 1, 2, 4, 8, 16 etc...

This means my connections freeze. I only notice it with other ADSL
users, since mostly, these will not be behind Linux computers, being
Windows XP machines and such, and therefore will not use TCP timestamps.
If the remote end employs timestamps for TCP then the problem is less
noticable, the connection completes, all information is downloaded, but
packetloss is still present. Turning off timestamps on my end, results
in the same problems. Reducing my MTU to 910 (max) also alleviates the
issues of freezing (but packet loss is still there).

Anyhow, I've filed a speed report to my ISP.

They've got back to me with the following information:

ADSL Status Check
OK
Circuit Information
Circuit In Sync
Upstream ADSL Link Info
Loop Loss 9.5 dB
Cell Count 150957
Downstream ADSL Link Info
Loop Loss 24.5 dB
Cell Count 350057

So what's that showing? Is that particularly good loop loss? Should I be
seeing so much packet loss on my end, and all this freezing?

The result reads as follows:

Major Findings Suspect Test OK - No ADSL faults found
Conclusions Inconclusive

They've added:

"Your line has been checked out with no problems found. You have rate
adaptive DSL which means upstream speeds are compromised to ensure full
downstream speed - BT do not guarantee upstream bandwidth for this reason. "

What does all this mean? Am I too far from the exchange? Is that line
loss incredibly bad? What should it be to get around these issues? 0db???

I understand that this isn't a networking newsgroup, I just wanted to
post some background. Im more interesting in what those ADSL tests
indicate. With tests like that, should I really be experiencing that
many problems upstream?

Cheers
Simon





Simon Dean

"Simon Dean" <(E-Mail Removed)> wrote in message
news:bqcobk$kpp$(E-Mail Removed)...
>
> Im with plusnet, and have a 512k ADSL line. I gather this means I am on
> RADSL?

Yes.

> ADSL Status Check
> OK
> Circuit Information
> Circuit In Sync
> Upstream ADSL Link Info
> Loop Loss 9.5 dB
> Cell Count 150957
> Downstream ADSL Link Info
> Loop Loss 24.5 dB
> Cell Count 350057
>
> So what's that showing? Is that particularly good loop loss? Should I be
> seeing so much packet loss on my end, and all this freezing?

That shows that your ADSL line is fine - any problems are either with your
computer/your ISP or the internet somewhere...

>Downstream ADSL Link Info
> Loop Loss 24.5 dB

That is quite good and RADSL will not kick in until its more than about
55dB. The 2MB line test (non RADSL) is 45dB...

> The result reads as follows:
>
> Major Findings Suspect Test OK - No ADSL faults found
> Conclusions Inconclusive

It means your ADSL line is fine - the problems you are having are not to do
with your physical line..

> They've added:
>
> "Your line has been checked out with no problems found. You have rate
> adaptive DSL which means upstream speeds are compromised to ensure full
> downstream speed - BT do not guarantee upstream bandwidth for this reason.
"

As above - this isn't relevant in your case (though its true)

Regards
Sunil

>>They've added:
>>
>>"Your line has been checked out with no problems found. You have rate
>>adaptive DSL which means upstream speeds are compromised to ensure full
>>downstream speed - BT do not guarantee upstream bandwidth for this reason.
>
> "
>
> As above - this isn't relevant in your case (though its true)


Thanks for the reply. As I suspected, Im feeling that my problem is
being brushed aside with a "Its not our fault, go away".

Cheers
Simon