IP cameras on ring topology, not star

Uh... they HAVE broken-ring IP cameras??? AFAIK, all IP cameras are ethernet-based.

A hub on each pole? Are you planning to have multiple cameras on each pole?

A little more detail would be helpful...

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

The ring connects all poles and provides a path for the video traffic from each camera to flow around the ring and out through a point on the ring to the DV recorder(s).

IBM sells token ring routers, but they are physically wired as a star (every device has a physical connection back to the router), which does work for this application.

These routers also have a maximum bandwidth of about 30 Mbit/s, which may not be enough for 100+ cameras.

I've seen some gigabit LAN gear which supports a r> Pat Coghlan wrote:

I saw your reply to Matt and still don't know what you're looking for. Are you trying to wire to 100+ cameras up in a daisy-chain fashion rather than home-running each wire?

You DON"T want token-ring, that as an antiquated technology that requires each network device to have an electronic "token" before it can talk to the network.

If your application is spread over 1-2 KM than how about wireless? There are good 102.11 based systems that can do what you need provided you have line-of-sight (up to 10 miles). You possibly could create a hybrid system of wireless transmitters for the further out cams and wired for the closer cams to the head-end.

Look at this data sheet for an example:

Please provide more information on the application.

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.

Token ring is an entirely different networking protocol from ethernet. To use a token-ring hub, you have to have token-ring devices; you can't just plug ethernet devices into a T-R hub.

Token-ring being an essentially obsolete technology in a world of dirt-cheap 10/100 switches (T-R data rates are 4 and 16 megabit), I really doubt you'd ever find IP cameras that support it, and a token-ring NIC for your DVR will be bloody expensive, as well as very rare. And despite the network's "ring" protocol design, 99.9% of wiring designs use the same "star" topology as ethernet, which for your purposes, completely eliminates any benefits there may be to T-R.

Frankly, I think you've been misled by the "ring" designation - it refers to the way packets are distributed around the network, rather than the physical cabling of the network.

Given the other considerations you'll have with 100 cameras - most notably, processing power and storage issues with the DVRs themselves - you need to go back to the beginning in your design concept. Particularly: you're almost certainly going to need multiple DVRs to handle the amount of data 100 cameras are going to be outputting. That alone means breaking the network up into segments. At that point, you can segment groups of cameras, each to a switch central to that group, with that switch feeding back to a main switch with the DVRs.

Example: break camera locations down into seven groups of 14-15 cameras that are nearest each other. Locate a 16-port switch near the center of each group. Run a network feed from each camera to its assinged switch. Then locate a 16-or-more port switch in your "server room" (or wherever your DVRs are located). Run a network line from each of the outlying switches back to the central room.

Again, your other option would be a low-cost 4- or 5-port switch mounted with each camera, as described above - D-Link sells a 5-port gigabit switch for around $60 - but in the long run you'll find that an excessive cost-per-port figure (that's $6000 right there) and it allows too many potential points of failure: one switch goes down, and your whole camera network from that point outward goes down.

Without a lot more application detail, it's hard to offer specific advise. You can use a network of switches where each switch adds a camera to the network and then loops to the next pole thus forming a ring. This isn't a Token Ring network.

The applications we've done that sort of sound like what you've done have used either wireless ethernet (SmartSight for the small systems and Marconi for the larger ones) or we've pulled fiber and used analog cameras.

I agree with John. Use fiber.

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I dunno... from this guy's idea of token-ring, I'd expect him to start stuffing the cameras with bran flakes on this suggestion...

Bob La L> I agree with John. Use fiber.

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.

A couple of people mentioned wireless, but the customer does not feel that wireless is secure enough.

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

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

I haven't been misled by anything. The "ring" designation is a hard requirement. 200 cameras can't be wired back to a common switch/panel. They must operate as drops on a ring/loop and be wired to two other poles.

...as long as they go back to the main switch via the ring they are physically wired to.

No can do. In addition to this being a wide perimiter configuration, it's also a temporary project. Everything needs to go in with pre-cut cables etc. You're pretty much looking at going pole-to-pole to set up and take down.

Cost is not an object.

What goes on each pole, add/drop fibre mux of some kind? Cost?

Are you thinking of Sonet? DWDM?

Real world examples of this type of setup?

Bob La L> I agree with John. Use fiber.

The main problem with token ring - as I said - is that most gear (MAUs etc.) still require devices to be plugged in to a common switch/panel.

They > I dunno... from this guy's idea of token-ring, I'd expect him to start

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.

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.

You're talking about an ethernet to token-ring bridge, something like this:

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

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.

How about putting a little platform on each pole and just have a security guard sit there with a handycam?

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).

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 r> Pat Coghlan wrote:

I'm not an optical expert, but a technology like FDDI, Sonet or DWM could provide the ring.

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.

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

Agreed.

We tried that. Won't fly.

Out of curiosity, what's a reasonable limit on how many can be daisy-chained together?

The optical ring approach might fit the bill.

Let me start by saying that I am not a data network guru, and some of the stuff you are talking about is way beyond my skill level. However, if cost is not an object, there may be an alternative that will do the job for you.

I consider your ring topology to be a very bad idea from an engineering standpoint, because a cable fault will wipe out some or all of your cameras. However, if you insist, then perhaps the solution is to think of this as a cable television system.

Cable systems, especially fiberoptic systems, routinely carry hundreds of television channels on a single backbone. They can also handle lots of cable modems, if two-way data communication is needed. For an analog video system, RF modulators could place each of your cameras on a different channel, and for 1-2 km, coax should be adequate. I'm guessing something comparable would be possible for fiber and/or network cameras, but that is beyond my level of expertise.

Just something to consider.

- badenov

May be a cable company can come up with all the hardware and software for such a setup.

That's a possibility as well, but you'd need a modulator for each camera, each putting signal on a different channel. The "cheap" ones only work on channels 3 and 4; the ones that give you a wider option of higher channels (like this one:

are more in the range of $300. Each. I guess if cost is no object, the $30,000 worth of modulators is a viable option...

That might work for fixed cameras, but what if some are PTZ's?

I wonder where the client got the idea wireless is not secure? The US Government uses encrypted 802.11a for at least one Homeland Security application that I personally worked on.

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.

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

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

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.

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.

Not at all. You're forgetting to consider the cost savings of using analog cameras compared to the substantially more expensive network cameras. The cost of RF modulators can be further reduced if it is possible to place two cameras on one pole and use one two-channel modulator.

I'm not saying this is the optimal solution, but if one-way video is all that's required, this might be cost-effective.

- badenov

Well, within reason, but it's not a major consideration.

Rings are typically self-healing, with a loopback occuring at the break.