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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 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
paul reinheimer
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.
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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Yes, but with PoE built into the switch, you can run at Gigabit speeds because it uses phantom power. Power injector patch panels use pins 4,5,7,8, therefore taking the possibility of gigabit away. This may not seem significant, but most IPT deployments end up with the PC plugging into the back of the phone, the PC may need gig speeds (CAD stations).
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.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
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.
There are 4 boxes to use in the defense of liberty: soap, ballot, jury, ammo. Use in that order. Starting now.
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?
I strongly disagree! Standard telephone quality is 8kHz 16-bit linear PCM (or 8-bit G.711). G.729 gives a VERY noticable reduction in sound quality. I have long wished for some sort of wideband standard for phones (16kHz would be great!). It would make the speech quality far better and would allow us to differentiate easily between f/s sounds and d/p sounds.
the Speex codec allows high quality wideband speech starting around 14 kbit/s - not much more than standard G.711. There's just no support from the various vendors (yet)...
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.
Mea navis aericumbens anguillis abundat
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
Til a contractor doesn't get a locate and hits the line. Or, a car runs into a padmount xfmr. Also, the ground doesn't exactly stay still. Problems occur during the summer especially, and locating and repairing bad underground cable takes a lot longer than repairing an overhead service line. Additionally, underground service is ridiculously more expensive to put in existing areas. Overhead service just makes more sense in some parts of the system. (Also, the hi-lines are going to be overhead no matter what you do..)
Nice thing about PoE in the switch is that you have the ability to remotely power cycle a device.
I have 135 wireless access points and 100+ IP telephones in this hospital. If one freaks out and becomes non-responsive, I can shut the port down and bring it back up for a cold start. Doesn't happen very often, but I live 45 miles away, and it's a lifesaver in the middle of the night.
Also, the switch will auto-detect whether the device needs power or not. The injector panels I've seen are dumb, and will happily provide enough juice to fry your NIC if you happen to plug into the wrong jack.