Stephen Kingston

The Internet is not something you just dump something on. It’s not a truck.

It’s a series of tubes.

American Senator Ted Stevens (Alaska)

Full story.

In CS35110 lecture one today, we briefly looked at the network stack. Particularly this diagram:

At each level the protocol module at that level communicates only with the layer above and the layer below. Thus the network layer may received data from the transport layer that it must enclose in a network packet (like an envelope) before passing that packet down to the link layer.

the protocol layers are thus stacked on top of each other in the protocol suite.

Bear in mind that packets are really just sequences of data, and all that is really transmitted over the physical medium (the wires or wireless medium of the internet) are long strings of binary data.

Next lecture we will look particularly at issues such as why packets are used, and we will look at the network layer in more detail. However, if there are specific issues you want to raise, add comments here and we can discuss those issues in the next lecture.

We have Sky satellite at home. Sky like to monitor their satellite boxes through the telephone line using a clever little feature that BT developed called “silent signalling”.

The idea is that any piece of data terminal equipment (DTE) can be plugged into the phone line and called up from a central system from where it can be interrogated over the phone network. The signalling is silent, so the phone does not ring and the householder need not be aware a call is in progress. As I understand it, taking a phone off the hook immediately interrupts this process, and no calling line identification (CLI) is ever presented, so it is as if the call did not happen.

Except that theory is not always the reality. It seems that some lines are configured (or misconfigured) in such a way as to cause a telephone to “chirp” briefly when the silent signalling takes place.

Caller line identification is also presented by silent signalling, so it is possible the phone will chipr briefly before all calls for users who have CLI presented on their lines.

Phones will also ring if the BT exchange is carrying out routine testing to your line. This may present as a regular short ring at about the same time each night.

So solutions?

We tried raising a fault with BT. As usual, BT faults told us that they had never heard of such a thing, they could book an engineer for us, but they would charge us if they decided our equipment was at fault. (But the problem is at the exchange, I told them – to no avail).

We tried asking Sky to stop calling us. They suggested unplugging our box from the wall (but the problem is your equipment raising the call, I told them – to no avail. Apparently Sky cannot stop their equipment from contacting you).

Next we tried the BT nuisance call bureau. They tried to convince us to sign up for a service that stops calls from a given number. (But hey – this is silent signalling. No number is presented!)

Finally we found someone at the nuisance call bureau who passed us onto someone at the exchange who knew what was what. He took our line off the regular testing schedule. Hooray!

And then that very night, Sky called and the phones chirped just as my daughter was falling asleep. Grrr.

Last attempt with Sky – I shall tell them we have changed telephones and give them a new number to call. Now if I knew Rupert Murdoch’s number, I would give them his. But I don’t, so I’ll just have to send the chirping phone to work!

If anyone else has found a way to convince BT to fix the line to stop this happening, please let me know. In the meantime, I offer my solutions above as the best way to avoid those annoying calls at 5 AM and the children’s bed time.