Packet sequence problems...

My broadband has always appeared a little flaky and any application that requires a consistent fast connection struggles.

Until recently I thought it was the actual throughput of the line and have been jumping through hoops to improve the router connection/sync speed. After much rewiring and assorted other changes this has seen the downstream connection increase slowly from 4xx kbps to 1472 kbps.

ADSL Link Downstream Upstream
Connection Speed 1472 kbps 448 kbps
Line Attenuation 63.5 db 31.5 db
Noise Margin 11.1 db 14.0 db

There is still some noise on the line and the latest BT speed test showed an actual transfer rate of 1147 kbps downstream and 256 kbps upstream.

Download speedachieved during the test was - 1147 Kbps
For your connection, the acceptable range of speeds is 400-2000 Kbps.
Additional Information:
Your DSL Connection Rate :1472 Kbps(DOWN-STREAM), 448 Kbps(UP-STREAM)
IP Profile for your line is - 1250 Kbps

I am still, however, having problems with certain applications that struggle yet work fine when connected to wifi elsewhere.

I have been unable to find any software to run on the Mac OS X that will give me more information other than to confirm that packet loss is almost always 0%. I eventually stumbled upon the Second Life application which provides some useful debugging data. I can run Windows XP software under emulation but obviously native Mac stuff would be preferable.

It appears that a significant number of packets are arriving out of sequence and many require that they are resent. So whilst no packets actually get lost many do get overtaken along the way.

This problem has existed even back in the days when I was getting a download sync speed of 448 kbps or less so the new profiles that are allowing me to physically connect faster don't seem to be causing any additional problems.

Unfortunately I am at a loss as to how to proceed to better understand the problem or obtain some data to try to persuade my ISP to investigate further.

Any suggestions?

I had a new Master Socket installed recently and replaced almost all the wiring internally.

The wire from the telegraph pole to the side of the house is less than five years old but the cable from there down the side of the house to the Master Socket must be at least 45 years old but, alas, it belongs to BT and not to me...

In reply to a post by asanyfuleno:

..... but, alas, it belongs to BT and not to me...

If the matter is important, you can still get it moved - for a fee (as you would for a house extension, say)

You are on a VERY long line there

Where you say things work fine on wifi elsewhere - I'm guessing you're getting a faster/better connection than your home line ?!

RouterStats is great for monitoring your line but again not for MACs I'm afraid...

Edited by b4dger (Wed 02-Dec-09 18:39:07)

Try a different router. What router do you have now?

I have tried the current NetGear DG384G and a couple of old Linksys WAG300N models.

Problem seems fairly consistent so far.

Try wireshark on your Mac. I'd be interested in seeing if it thinks packets are being delivered out of sequence.

http://www.wireshark.org/

I did a couple of TCP Dumps and looked at the results in WireShark.

Dump contained a selection of what appear to be warnings or errors including:

TCP Previous Segment Lost
TCP Dup Ack
TCP Out Of Order
TCP Retransmission
TCP Window Update

I assume this suggest that things are not working particularly well.

How do you know the issue is nothing to do with the ADSL? It may be congestion elsewhere.

I have no clue about anything hence the random questions...

Is there anything I can do to investigate further?

One concern is the impact of the 45 years old wire that runs down the outside wall of the property to the master socket which should be a relatively easy fix if there are issues I can prove to get BT to do some investigation.