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IP Telephony Drives in Power over Ethernet
GuitarNeophyte writes "The Channel Register states that although the idea for Power Over Ethernet has been around for a long time, the stage may finally be set for it to become an essential factor in our technical lives. One of the main reasons is because of the emergence of ip telephony. 'Telephones need to work in an emergency including when there is a power failure. Traditional telephones do, but IP phones will only do so if there is an uninterrupted power supply (UPS). The only practical way of guaranteeing power supply to a large number of IP phones is PoE.' Will IP telephones bring in PoE?"
I work for a school system in Maryland (Charles County) and we're implementing system-wide IP telephony at all 30-something of our schools (20 elementary, 7 middle, 7 high, plus several education centers and other facilities.) All our IP phones use PoE, so half the ports in each school are PoE capable.
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Apparently, my cousin has Ethernet over Power, that was installed by The Internet Service Guy...
...or maybe they would cancel each other out, and you'd just get regular ethernet? ...or maybe it would be like a divide-by-zero, and your NIC would explode? :P
It would be interesting to see what happens if you ran Ethernet over Power on a system powered by Power over Ethernet... who would win? an epic battle, to be sure!
That'll be great when there's a storm, and trees bring down the power lines.
Or you could just plug the switch into a UPS...
Smoke much?
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I'd say that we will eventually have PoE, but I don't think it will be a necessary consequence of VoIP or telephony. I have VoIP, but I use it exclusively for the three hours a day I work as a call desk support monkey for my company. If I had an emergency, I have my cell phone on me as well.
This is something I've wondered about a lot: how many slashdotters out there use VoIP as their primary telecommunications resource? How many would use telephony once x gets improved?
#define CLUE 0
I imagine we'll be seeing plenty of useless (but pretty) little blinkinlites and other silly gadgets built on RJ45 plugs, for keeping the dust out of unused router ports.
I remember a while back there was an article on Slashdot about how PoE can become an universal power standard. While there are different plugs and voltages used around the world, PoE has a standard jack. Sure PoE is low powered but with miniaturization, many of our devices can be powered off of PoE. With VoIP driving the spread of PoE, I hope this will build momentum in making the prediction come true. Imagine going to another country and needing to bring just a CAT 5 cable instead of a power adapter.
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We were facing the same problem and found it cheaper to inject POE right at the phone untill we found that you could buy a 24 port power injector for a couple hundred dollars off of ebay. Put these things next to your switch and inject it there.
Something is wrong with the math currently because a 24 port switch with POE is almost three times as expensive than a 24 port switch & a 24 port POE injector.
At my office we've already switched over to new Cisco VoIP phones, which are powered via the ethernet cable. There is an optional DC plug for a wall wart if it can't power up via the ethernet cable. On a related note, when I called my parents today my call was dropped because their VoIP connection was too busy. So I still don't entirely trust the technology to be reliable, especially in emergencies, not to mention power outages in rural areas where when the power goes out, the ISP provider's (cable company's) equipment also goes down. If you have VoIP, I suggest a cellphone as a backup. But if you have cellphone with a reasonable plan, do you even NEED VoIP?
Yeah, I've had a wireless phone for years, never a single problem during a blackout, it works fine. So tell me again why we need to reinvent the cell phone?
I worked for a large company, during my time there we made the switch to VOIP, with the nice Cisco phones. The whole deal was set up with POE to all the phones, which was great for a couple reasons: Power outages we could still use the phone (as mentioned in the article), one fewer cord on our desk (no power cord), one less stolen slot on the power bar.
/LOVE/ to see is POE being used on the desktop to maintain power to your RAM during a power outage. Obviously there is a chain of things that would need to support this in order for it to work, but on an enterprise level I think it sounds like a good investment. Once the power is restored everyone's machine turns on to it's previous state.
The server room manager guy was a big fan of this system because it allowed him to reduce the number of UPS protected outlets outside of the server room (some models of the desk phones used at the help desk required their own power supply), and since it was now his problem a boost to his budget.
Something I would
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My office just completed moving to a new office building, and one of the things planned from the beginning was VoIP phones.
For VoIP phones to be useful in any way they had to be no more intrusive than a regular phone, but provide benefits. Power over Ethernet keeps the requirements for the phone down to a single CAT-5e cable, and a capable backend switch (we ended up going with an end-to-end Cisco solution for both phones and general network switching, which has worked out perfectly.) That and the system provides an on-phone phonebook for numbers as well as advanced message logging and voicemail abilities, all managed through a PoTS bridge, and the Cisco server.
This let us put only ethernet jacks in the majority of offices, and lets us plug the phone into ANY port and it works instantly.
So you might say that VoIP and PoE go hand in hand; PoE needs VoIP to justify itself, and VoIP needs PoE to make the devices unintrusive compared to regular phones.
But, one other detail, there will probably need to be a warning on the box, for use only by folks that have already HAD thier children.
My phone line has rarely gone down if ever. I can't come close to saying that about my internet connections, cable or DSL. The fact that we have two small children means when I pick up that phone in an emergency, I want it to work. I don't want to be mucking around rebooting computers and routers. That's why I've stayed away from VOIP over my existing internet connection.
Any thoughts on the reliability of this? Will VOIP ever be as solid as good old copper? I mean, you have issues (DDOS) with VOIP you just don't have with traditional PSTN service.
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and what do you think will power those access points? oh right POE
Bah, I can't wait for POWF - Power Over WiFi. Now that would be pretty darn cool!
Telephones need to work in an emergency including when there is a power failure. Traditional telephones do
The majority of phones today are cordless and practically none work without power.
I used to buy cordless phones that had a speaker on the base unit for this very reason, but alas, those also don't work anymore without power, on most modern phones.
With the proliferation of cordless telephones in the 80s and 90s, most people today don't even remember that a phone can work without power. And those that do probably don't even have a regular corded phone around the house anymore. I don't think telephone service during a power outage is important to that many people..
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The standard seems to be around 220v @ 50 or 60hz AC. I'm not sure I want that kind of load on four twisted pair of cable (CAT5). Besides, being the RJ45 connection could be standard eithernet, what's to prevent your casual user from making a BIG mistake. Jokes aside, it could cause one's battery in a laptop to explode with the force of a stick of TNT.
For power ratings around the world, check out http://kropla.com/electric2.htm
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Even with PoE a few well placed and clearly marked land lines combined with near ubiquitous cell phones add an extra layer of insurance for 911 and for more mundane VoIP issues.
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A cisco 6509-E chassis can supply ~1,000 devices with the full 350mA input power @ 42V described in the 802.3af spec. In other words you can fully populate the chassis with 8x96 port blades and it will provide full power to all of them. Info obtained from here which also has some useufull primer info on how 802.3af works as well a cisco pre-spec PoE.
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Panduit also is marketing a PoE patch panel. That way you can make use of existing switches and just add PoE at the patch panel level. Then you'd just UPS the patch panel.
PoE (802.3af) is incredibly useful in for business deployments of video cameras and wifi access points, not to mention mini-switches and outdoor wireless bridge equipment. You can even power a laser link with PoE. It makes life easier for those averse to paying out huge amounts of cash to have an electrician come in and put in new outlets. I've been playing with PoE splitters recently to power non PoE gear at 5 & 12V DC - the splitters are $35 ea and are switchable between voltages.
Hmm, hate to reply to myself but Cisco says a max of 571 devices can be supported by dual 6KVA power supplies in the 6509-E, not sure where the descrepency between the numbers comes in. Still that's 72 ports per blade, which means you can fully populate the chassis with 48 port blades.
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Nothing on the horizon that will drop the price of solar cells? Understatement, mate.
And yes, you're damn right, PoE is cheaper. Wireless is really handy, but I don't think there's any point in ditching cable because of it. I can usually go further, it can go practically anywhere, through nearly everything, and transmit power!
PoE is excellent, anything that gets rid of bulky transformers that are designed to fail early and cover three electrical outlets has got to be. It's 48V isn't it? What's the maximum current draw allowed? Or does that depend greatly on the switch?
There were major improvements in the audio quality of radio broadcasts from remote locations, like sports, when they switched from POTS to custom codecs over one or more ISDN B channels.
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Few things. 802.3af has nothing to do with CDP. CDP is used with Cisco pre-standard inline power, which is ever-so-slowly being phased out (802.3af is more widely supported, delivers more power, and, well, doesn't rely on the ever so patented CDP).
Also, the power reporting in both pre-standard inline power and 802.3af doesn't save power, it just allows the switch to manage its own power and not be overloaded.
Anyway, I'm having fun. This is one of those topics I actually know things about.
--
Phil
Yeah, there are solar cell price drops on the horizon. Well I guess it depends on what you define as the horizon. There's now a room-temperature nano-self-assembly spray that turns itself into solar cells in the lab. Made, I might add, by the co-author (Warner) of "green chemistry" who is into all sorts of really cool stuff and worth keeping track of. Saw him speak a while back and he was very entertaining.
e re-it-dont-belong." But the standard was surprisingly thorough, and I very much look forward to a wider range of PoE products becoming available 1) because they will make it easy to power from renewable sources (48-56V DC, no 120V 60HZ invertor needed) and 2) because I really hate USB and it would be nice if PoE took a shot at it's market niche.
PoE rocks though. As an EE, I read the spec expecting to be horrified at all the shortcuts, brainfarts, and other cruft you find in other standards associated with ethernet or "lets-jam-everything-over-frame-based-networks-wh
Someone had to do it.
IP phones will only do so if there is an uninterrupted power supply (UPS). The only practical way of guaranteeing power supply to a large number of IP phones is PoE.'
Because POE doesn't require an UPS during a power failure? The Ethernet just keeps on working without power? And the power keeps working because the ethernet is working, right?
Or.... you have a big honkin' UPS in the basement that powers the ethernet and the POE?
Modern FTTP installations require a significant battery to keep your fiber-transported dialtone working during an outage. Now you add some central UPS to keep you IP telephony working? At some point, don't you just start outfitting houses with battery arrays and generators?
So you take the industrial solution already used by the telco and put it in a small package for the individual home.
Personally I would have used cheap non PoE edge switches and installed a separate PoE injection patch panel.
I wanted to make sure that the phones stayed up at all times, so I bout a decent UPS for the wiring/server rack, installed netgear POE switches ($119 for 4port POE, 4port non-POE) and connected up all of the IP phones (polycom IP-500 and sipura 841). Since the cost of the POE switch was so low, I decided to do it this way for the comfort of being able to dial 911 at any time in any room.
Yes, it is overkill for the home, but I like it and my phones have stayed up all of the time. Several of the offices I work for use centrex and there phones are plugged into normal power. They have had several outages since the installations 3-4 months ago.
--Keith
My ISP (Charter) offers a $40/mo phone connection. Why is it worth more than Vonage's $25/mo service? According to the phone rep , because it includes a UPS so it works when the power goes out. Must be a heck of a UPS for $15/mo.
I've had a wireless phone for years, never a single problem during a blackout, it works fine.
By wireless, do you mean cell phones or cordless phones?
Cordless phones definitely "die" during a blackout.
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My own questions about IP for interactive media go at least as far back as the early '90s and the first proposals for RSVP, which introduced a lot of religious debate in the networking community, including what seemed to me to be a lot of circular logic, e.g:
Q."Why do you want to retrofit IP for something it was never designed to do (realtime interactive media)?
A. "Because ATM is too expensive and wastes too much bandwidth."
Q. "How do you plan to upgrade IP then?
A. "By making IP equipment much more expensive, and wasting bandwidth to to prevent dropouts."
I know this grossly oversimplifies the issue, but I never seemed to grasp the theory behind IP as the solution. It always seemed like bandaids on top of bandaids, and no matter how many bandaids are cobbled onto IP, it never seems to be able to deliver the reliability of ATM. Now with cell networks and some broadband providers using ATM, maybe the pendulum is swinging back the other way.
But then again my viewpoint is dated because I've been out of the field for a few years, so any updates to my undestanding would be appreciated.
As an idiot who knows better, your main problem in having more then 20 or so devices on WiFi is that the jitter will go through the roof. Even if there is no data traffic, the probability that more then 2 devices will try to transmit simultaneously and fall back will be sufficient to cause retransmits and even transmit failures. The are two way to fix it:
.11e spec which provides QoS on a more or less good behaviour basis. Well... unfortunately in a realistic environment this spec will not scale to 20+ devices.
1. To use Intel and Co (IIRC)
2. To use the fact that a 802.11 AP can provide a transmit map. There are two sections - a mandatory assignment section which gives an opportunity to a specific device to transmit (usually empty) and a free-for-all section similar to Ethernet. Well, one problem: the last time I looked into it no AP on the market will do mandatory map allocations for you. Further to that, as it is largely unused most clients software and silicon is not tested properly for this part. So if people start deploying it now things are bound to break.
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Have you USED a WiFi VoIP phone? Turn on encryption, have more than one user, and see how good your connection is. Try walking around while on a call. Oh, and they REALLY work well in an office environment with multiple AP's (NOT!)
Due to the fact that WiFi sucks for VoIP, I would rather see a conventional cordless phone that had a VoIP (PoE) base station than a WiFi handset.
But back to the real topic...
WiFi is NOT a panacea for all network challenges. PoE is a damn good solution for powering all sorts of small devices such as WiFi access points, IP security cameras, smart-home touch panels, PHONES etc. The whole point with PoE is that it does away with the wallwart. No need for battery backup at all your devices since the PoE switch is on a beefy UPS. This is what the FA (which you OBVIOUSLY didn't read) is saying.
Spoken like someone who has never tried to deploy WiFi phones. Try it. You will find that it REALLY doesn't fricking work in the "real world" despite vendor hype. Been there, done that. Try taking a call (walking) into another AP zone - BZZZT! call ended (WiFi range in an office environment is actually quite small so you end up needing a lot of AP's.) This is why enterprise users use DECT phones.