Re: IP cameras on ring topology, not star

[Matt Ion <soundy@xxxxxxxxxxxxxxx>]

Pat Coghlan wrote:

>>> Let's get back to the main requirement: cameras must be connected in
>>> a ring rather than home-running (to borrow Morgan's description) each
>>> camera back to a switch.  I'd like to find out what the best way to
>>> do this would be.
>>
>>
>> That's just the point: I don't think there is one, short of a "faux"
>> ring as I desscibed above.  What you're basically looking for is some
>> way to "tee-splice" each camera into a single wiring ring... you can't
>> do that with video OR network, period.  The closest would be as I
>> desrcibed above, using a small switch at each pole as the "tee"
>> connector.
>
>
> I'm not an optical expert, but a technology like FDDI, Sonet or DWM
> could provide the ring.

Sure, but you still need a module of some sort to tap each camera into
the ring... essentially the same thing you'd be looking at with a small
ethernet switch on each pole.  So... KISS principle.  IP camera and
5-port gigabit switch on each pole.  Simple, and by far the more
cost-effective option.

>> The only type of network that would PHYSICALLY resemble this would be
>> a 10base-2 setup (the old ethernet-over-coax), but then you'd have to
>> find IP cameras with a 10base-2 interface (non-existant, as 10base-2
>> is even more obsolete than token-ring), and you'd also be limited to
>> 10 megabits, which would not be nearly enough bandwidth.
>>
>> The important question is, WHY *must* they be in a ring, rather than
>> home-run?  Perhaps the customer has unrealistic requirements or
>> expectations.
>
>
> The reason is, of course, the fact that if the poles were, say 50m
> apart, there would be a 50m run to camera #1, a 100m run to camera #2
> etc.  It was suggested that cameras be grouped together, but the team
> looking at setting up/tearing down this project essentially want to
> drive up with a truck loaded with pre-cut cables and go pole-to-pole.

A bigger consideration then would be that 100m is the maximum defined
length for reliable ethernet operation.

>>> Cost is not an object.
>>
>>
>> How about putting a little platform on each pole and just have a
>> security guard sit there with a handycam?
>
>
> We tried that.  Won't fly.

Of course not - you have to give them ladders or something :)

>> Again, I think you're looking at a small ethernet switch mounted on
>> each pole to act as a "tee" to a daisy-chained pole-to-pole ethernet
>> run.  If you're going gigabit, make sure to use AT LEAST Cat-5e
>> cabling (Cat-6 preferable, since cost is not an object).
>
>
> Out of curiosity, what's a reasonable limit on how many can be
> daisy-chained together?

Shouldn't be any limit to the number of them.  Gigabit should provide
the requisite bandwidth, especially if the cameras are set to transmit
on motion-sense instead of constant output.  The main consideration
would be that ethernet isn't reliable beyond a 100m cable length, so
distance from switch-to-switch (including the runs up and down the
poles, if they're transiting across the ground) can't be more than 100m
without potentially introducing problems.

> The optical ring approach might fit the bill.

Once again, you'd be looking at pretty much the same concept/setup, just
using more expensive components.  Optical fiber also tends to be a lot
more delicate than copper, so it's probably not something you want a
couple of mooks slinging around.



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