North American Network Operators Group

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Re: London incidents

  • From: Michael.Dillon
  • Date: Mon Jul 11 07:35:31 2005

> A hospital using up "emergency mode" GSM capacity doesn't make much 
> sense to me. You're not supposed to use cell phones in many places in 
> hospitals, and the ones that I've seen have an ample supply of fixed 
> lines that are cheaper, more reliable and pose less risk of 
> interference with the equipment.

This was just a guess on my part because the congestion
in this suburban area lasted well into the evening. The
only time I was able to make phonecalls on my mobile was
when I took a bus out of the area. I planned to travel 
away from the city to get away from mobile congestion
but the phone started working again before I had gotten
any further from the centre. However I had moved a km or
two from the hospital. Later, I returned home and lost the
ability to use the mobile even as late as 11:30 p.m.

> It's probably just congestion. Cellular networks don't come close to 
> being able to absorb the burstiness of the (potential) usage patterns 
> in situations like this.

This, I understand. But it doesn't explain why this area
would have suffered such a prolonged problem.

> When it gets 
> really bad the random access channel gets clogged and all mobile- 
> intiated communication, including SMS, is dead in the water.

I never had a problem sending or receiving SMS other than
the long delays. The people on the other end were near
Aldgate on the edge of central London so even there, SMS
was still functioning.

It was an interesting experience which seems to show that
it is better to have several completely different communications
channels to choose from. In my case I had lost landline and
DSL Internet access due to moving house, and I lost mobile 
voice access due to congestion. But SMS still functioned.
I haven't heard of any Internet outages caused by the attacks
although everyone who has travelled on the tube knows that there
are lots of cables in the tunnels. Presumably, there are so
many tunnels with cables that breaks in three places are easily
covered by protection switching.

--Michael Dillon