Re: IP cameras on ring topology, not star

T-splice is a good description of what I need to do atop each pole.

I think this should be possible, in that it's kind of a miniature version of a metropolitan area network (MAN). In this case, though, I'm connecting a single host (camera) at each add/drop location on the ring rather than a "building".

Even if the traffic from each camera had to flow around the ring independent of the other cameras back to a large switch, that would be okay. In other words, all cameras use the ring purely as a medium to connect them back to a switch.

Matt Ion wrote:
Pat Coghlan wrote:
Matt Ion wrote:

Pat Coghlan wrote:

By hub on each pole I mean a device connected to the ring, with an ethernet port for 1 camera.


Umm, okay... what you're basically talking about then, is a three-port hub on each pole: one port for the camera, one to uplink to the previous pole, one to uplink to the next pole. It's do-able (4-port 10/100 ethernet switches are fairly cheap these days) but rather convoluted.


I'm not suggesting daisy-chaining up to a couple of hundred of these devices around 2 km ring.

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.


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.

I kinda wondered if there might be adapter hubs that do this, especially whether they buffered traffic etc. until the token arrived.

You're talking about an ethernet to token-ring bridge, something like this: http://www.ringdale.com/products/st/asp/control.wizmoreinfo/id.227/po./en/default.html


However, token-ring wiring is STILL PHYSICALLY done as a home-run.

Yeah, that's appears to be the deal killer with token ring.

The advantage of token ring would be that it resolves the collision issue that occurs with CSMACD.

That it does, but when you're talking 100 IP cameras, I don't think you'll find it has enough bandwidth. And again, it doesn't solve the desire for a physical ring layout.

Agreed.

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.

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?

The optical ring approach might fit the bill.

--

-Pat
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Relevant Pages

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  • Re: IP cameras on ring topology, not star
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