Slow ADSL CQM

Using our CQM graphs can give you a good idea as to what could be causing a line to be slow.

You can take a look at your graph and compare it to the examples below to see if there is a match.

Lots of traffic on the line

Here is an example of a CQM Graph with lots of upload traffic,

Lots of upload in the morning - a backup without any traffic shaping on the client end

This line is doing a large backup from just before 6am. The dark red horizontal line shows the traffic, during this time there is lots of packet loss (red) and the light blue at the bottom is showing high latency. So, whilst the backup is happening the line has about 50% packet loss and around 300ms of latency. Using the line for things like web browsing at this time will be slow and sluggish. However, this is not a fault per-se. It is normal for a line to appear slow when it's being filled with traffic. However, this traffic may be unknown, it may not be a backup, but could be a virus or peer-to-peer traffic. You can do a Traffic Capture to see what the traffic is, or ask Support to Help.

Sync rate has been capped or lowered

You can check the linerate of your line - this is the speed of the line as reported to us by the back-haul provider.

Examples:

Line rate as shown on the control pages, ie 39.8M - Good!

This one has a rate of 338k - something is wrong!

1. Log in to the Control Pages
2. The line rate is usually shown on the front page, as per the image above

Packet loss on the line

Packet loss is shown as dripping red from the top on the graph. Here are some examples:

Packet loss when a downloading but not filling the line

This is a rather strange one. There is packetloss when downloading, however the download is not filling the link, but there is still loss, this is unusual. This turned out to be congestion on the Virtual Path within BT, or it may have been miss-configured. It took our escalation staff 3 months to convince BT that the fault was within their network.

In this case, talk to Support.