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How to fix common causes of disconnections

There are of course many reasons for disconnections when using Sky Broadband but experience over the last few months has highlighted three main areas:

« The UPnP “bug” (frequent and regular disconnections)

« A low noise margin (certain times of the day)

« An equipment fault (random)

The UPnP “bug”.

This isn't the most common reason but it seems to be common enough so we'll start with this.

UPnP stands for Universal Plug ‘n Play. This is a set of computer network protocols which allow computer devices to communicate with each other. In principle, w hen devices incorporating UPnP technology are physically connected to a network, they'll connect automatically to one another, without the need for user configuration.

Is this a good thing or a bad thing? Well, many IT professionals would say that this is a security risk because with UPnP active, malware on a PC may be able to operate more or less unhindered. However, that's not the issue concerning us now. The problem some Sky BB users have is that with the current Sky supplied Netgear router, UPnP can cause regular disconnections. The symptoms for most affected systems are very regular disconnections every 15 minutes or so though sometimes the disconnections may appear more random.

The fix is simple: turn off UPnP in the router.

To get access to the router admin pages you simply type 192.168.0.1 in your browser and at the prompt type admin for the user name and sky for the password. On the screen that opens you will find a menu on the left and at the bottom UPnP. Click this and then untick “turn UPnP on”. Click apply then reboot both the PC and the router.

What's the downside? Well, if you are a user of torrent or P2P clients that use UPnP then you will have to set up port forwarding manually for these applications. You'll find a guide in the tutorial section.

A low noise margin.

This is a little more complex to explain but also fairly simple to resolve. A background guide to this issue can be found at:

Sky router stats (speed, noise, attenuation) explained

In brief, your router uses all the available bandwidth of your phone line other than that required for voice calls. Whilst copper phone wires are excellent conductors of these signals they are also rather susceptible to “noise” (interference) - and noise is the enemy of a good ADSL connection.

However, a certain degree of noise is acceptable and the router and exchange equipment cleverly monitor and set a threshold level when they first communicate each time the router is powered up or rebooted. This threshold is translated into what is known as the noise margin. This figure can also be found in the router admin pages (see above) by going to “router status” and then pressing “show statistics”.

The Sky supplied router can operate perfectly well with a noise margin of about 6.2db or greater. In fact when the router syncs with the exchange it will usually negotiate a speed that allows it to have a noise margin of 6.9db (greater if this will not suppress speed).

The problem arises because noise varies through the day, typically getting higher in the evening then dropping back; the same cycle day after day.

If you have connected or rebooted at a “quiet” time of day then the router will have happily synced at a noise margin of at least 6.9db. However, if the noise increases later in the day (and it usually will) then this will cause the noise margin, the amount of slack the router has given itself, to fall . Once it falls to around 6.2db browsing may seem to stutter. Much below about 5.5db and the connection will be lost.

The fix for this issue is to boot the rooter at the time of highest noise (lowest noise margin) and then leave the router connected.

The best way to do this would be to open the “show statistics” in a separate browser window and watch from time to time during the evening. If the noise margin drops below 6.5db immediately reboot the router. When the connection comes back it will be at 6.9db or thereabouts. Continue to reboot whenever the noise margin drops below 6.5db until it starts to rise (you may have to do this several times). You will now have “locked” your router to the right noise margin for the noisy time of day and it will stay this way unless you power off or unplug it from the socket.

An equipment fault.

This is a bit of a catch all as there are so many potential things that could have failed and only so many that are within the control of the user. However, equipment failure is easily the least cause of disconnections.

If your connection is dropping randomly and you have already excluded UPnP and a falling noise margin then the first thing to look at is your cables. The two key ones are the RJ11 (the one that connects the router to the phone socket) and the Ethernet cable (the one that connects the router to the PC, if not wireless). If the RJ11 cable is faulty then you will be able to access the router but you will see that you have no internet connection shown. If it is the Ethernet cable then you will not be able to connect to the router. Either of these however does not conclusively point to the cable as the cause; you must exclude other causes first.

There have been a small number of cases where the socket in the router is faulty giving an intermittent connection. If it is the socket then one trick is to wrap a rubber band around the router pinning the cable in place so it can't move, if this fixes it then contact Sky for a new router.

If that's not the problem then consider whether the router is overheating.

The Sky supplied router is rather prone to this and really must be supported on its side by use of the supplied feet. Electronics will play up when they get too hot.

If it is not the cables, the socket or overheating, then really it is likely to be something outside of your control and needs to be passed to Sky for diagnosis and resolution.