Slashdot Mirror
Do-It-Yourself VOIP Telco
DamnYankee writes "Robert X. Cringley predicts the coming demise of the landline telco monopolies from the grassroots encroachment of VoIP and Linux on the latest generation of Wifi routers. According to Bob, 'The result is a system with economics with which a traditional local phone company simply can't compete'. With Linux capabilities and builtin VoIP any Mom and Pop can become the local equivalent of a cellular phone company for the price of $79 Wifi router. Now how is Verizon going to compete with that? Get the full scoop from the man himself."
Take care!
Erick
http://www.busyweather.com/
You need more bandwidth than you think.
Remember, ADSL and cable are asymmetric. That upstream bandwith is usually 256-384k. Each VoIP call is going to take anywhere between 24 and 64k of that just for the audio. Add on to that the administration overhead (UDP/IP and whatever stream management protocol you're using), and it starts to chew away at your bandwidth.
Additionally, the connection you've got is designed for bursty traffic. VoIP is most definitely NOT bursty (unless you use silence suppression, which I've yet to see a vendor get right). If you packet delay gets over 150ms, you're going to be upset. Jitter larger than about 50-80ms is going to screw with your call quality. I've done VoIP networks, and can attest to the catestrophic effects of just a small amount of jitter when you start to get near your 150ms limit.
Don't get me wrong: VoIP is here and going strong. But it's doing so in high-quality networks that can afford to supply fixed-bandwidth reservation, , not commodity broadband products.
Already happening....recently, New York state classified Vonage as a phone company.
I'd settle for forcing VOIP companies to provide the same reliability.
This all reminds me of a Grou Telecom outage a couple years ago. They lost a core IP router. Guess what happened to all of their VOIP stuff? That's right.. all down.. We had to contact our sales rep by her cell phone because their helpdesk was dead.
Right now I'm not seeing VOIP as anything more than a way to cut down on my long distace bills.
*sigh*
:-)
First off, the minute you go from a VOIP endpoint to the POTS phone system (you know, to route calls to legacy landline equipment) you are then classified as a phone company. This is where the tarrifs come in. This might not be the case if you just went from VOIP to Cellular, not 100% positive.
Next up, while the Vonage/Packet8 endpoints work well, it can be a pain deploying a reliable VOIP network. Qualtiy of service is a must, because a large email with an attachment can totally take out audio in one direction for a few seconds.
VOIP is neat, I think it will seriously cut into the long distance profits, but *I* firmly believe wireless phones are more of a threat to landline POTS service. I think the phone companies need to replace the legacy ESS5a switches with something newer, capable of dropping 50mbps to each copper customer.
Personally I plan to move my phone lines to a message rate service, it's incoming only landline. I believe it is about $10 a month. This supports the excuse to have a PBX at home
Southeastern Virginia REPRESENT!
The telephone network has been packet-switched for decades. Do you own or work for a small business? You don't have phone lines. You have a T-1.
Sounds like you're confusing digital with packet-switched. A T1 is a 1.544Mbps digital circuit, often chopped up into 24 64kbps voice-grade circuits. That T1 that serves your local business is a dedicated circuit from your location to your telco office. Even if you're using that T1 for Frame Relay, or ATM, or TCP/IP, it's still a dedicated circuit from the point it leaves your premise to the point it hits the packet-switching equipment on the other end.
Plain Old Telephone Service (known as POTS in the industry) gets digitized after it leaves your handset and before it gets far into the local telco central office. For a business system, the digitization could be in the PBX. For a home, it might be in a box on the corner of the neighborhood. The usual conversion is to a 64kbps data stream. No compression, no packetization. When you make a call, it rides on a 64kbps channel all the way until it gets to the final digital-analog jump-off point. If you're calling cross-country, you are the sole user of that 64k channel for the entire time you're on the call. A given T1 will carry 24 of them simultaneously, a T3 will carry 672.
One of the biggest advantages of packetized voice (be it VoIP, VoATM, VoFrame Relay or whatever) is that using compression, silence supression and a couple of other tricks, an acceptable voice channel can use as little as 8kbps. You get much more efficient use of the bandwidth. But the general Public Switched Telephone Network doesn't do this - it's circuit switching all the way.
Hm. This is new information for me. I thought a vox T-1 was muxed at the packet level. Now you're telling me that it's muxed in some other way?
Yup. The term you're looking for is "Time Domain Multiplexing" - TDM. Each channel gets a time slice of the circuit, just under 1/24th of the total. There's a bit of overhead. This 1/24th, or 64k is allocated *whether that channel is in use or not*. And while it's in use, the "user" gets all 64k of it. Even if the mouthpiece of the phone is disconnected and nobody's talking the other way - no use on the 'line' whatsoever - the call is still using the 64k channel.
Cell or packet switching is a different animal altogether. A given channel may have a certain bandwidth guaranteed, and may be able to use well over that guaranteed amount, depending on the technology and lots of other stuff. Your average cell/packet circuit is only firing cells about 10% of the time.
The TDM part of a data circuit puts a hard limit the overall bandwidth. If you've got a T1 connection to your ISP, you can't send/receive more than 1.544Mbps, even if the ISP's router can switch hundreds of Mbps and they have an OC12 to their next peer. And if the site you're communicating with depends on an even lower bandwidth connection - such as when a dial-up user hits your ftp server - then *their* circuit is the limiting factor.