Slashdot Mirror
Cable VoIP Sounds Better Than Some Landlines
A. G. Bell writes "A recent study that looked at the quality of phone calls came up with some surprising results. Ars Technica reports that while 'traditional' VoIP call quality lagged behind landlines, service from cable ISPs was much better because of their use of PacketCable: 'VoIP from the cable companies actually surpassed the traditional phone network in reliability, meaning that the service was more often available and connected calls without dropping them. Cable providers also led the way in audio quality; the top firm in Keynote's study actually turned in an MOS of 4.24, above most real phone networks.'"
In my little hometown they still use the original ancient phone lines that leak signal like crazy. In fact, you could easily hear other conversations if you paused while talking on the phone. I'd guess that a majority of towns are using lines that are at least 30-50 years old still.
The idea behind PacketCable is that the call stays on the cable providers backbone for as long as possible, and only then does it go to the normal phone system. If any phone company tried to block or deblieratly degrade the service of phone service, I fully expect them to be on the recieving end of a lawsuit quickly.
"Useless organic meatbag" -HK-47
I have a Cisco 7960 at home and a polycom 601 at work and they both toast landlines. We sell voip systems based on asterisk and a lot of it depends on whether the phone is full duplex, half duplex, if you use a switch or a hub, your isp. My isp is time warner and is very good. My same phone on my moms comcast would suck at 6pm when it is congested. VOIP on a pri definitely rules though if you have a full duplex phone. even on speakerphone.
Contrary to popular belief, Unix is user friendly. It just happens to be particular about who it makes friends with.
...anecdotal evidence for you:
I'm using a Cogeco* VoIP phone, and it's awesome. It's clear as a bell, whereas the Bell POTS connection that I had previously had enough static on the line that it made it tremendously hard to hear the conversation. For the longest time I thought it was the handset...You can imagine my surprise when I switched over, used the same handset, and found that all that static had disappeared.
* - I don't work for Cogeco and frankly couldn't care less if they survived or went belly-up tomorrow... but they're a cable company and it fits with TFA...
Oh god, that woman is John Romero!
-William Brendel
I forgot where I saw it (it might've been here), but not too long ago I read a minirant where the person was comparing the phone service of yesterday to the service expectations of today. Admittedly it's two different types of service (landline vs. cell), but we've gone from advertising phone service so clear where you can supposedly hear a pin drop to making a big deal out of being able to hear the person at all. Just a little food for thought...
This seems to me like the ISP gets an advantage because of this PacketCable thing -- something I'm sure they will not be licensing to their VoIP competitors like Vonage. Not surprisingly, these 'other' VoIP providers fared worse then the ISP-provided VoIP service.
That's the point. When a VOIP call is made from a cable ISP, the call stays on the cable ISP's backbone(but not the regular net. A wicked huge Intranet would be a better analogy) for as long as it can. Some cable providers created additional plant lines just for this. With Vonage and friends, they hop on the normal internet and do the 20 + jumps of fun. Think of PacketCable as an express lane for the Cable ISP's calls.
"Useless organic meatbag" -HK-47
This matches my experience. We have Vonage via cable modem. Our neighbors who have POTS have had a number of lengthy service outages within the last yeur or two, whereas we've never had any. As far as audio quality, it just sounds normal to me.
The only problems we've had have been with integration among the various parts of the system, and I guess that's not surprising, since it is multiple systems working together, rather than a monolithic system like Ma Bell used to be. The big problem we had was that every time someone would leave a voice mail on Vonage's system, our internet connection would die, and we'd have to power cycle to get it back up. The solution was simply to stop using Vonage's voice mail (which was klutzy anyway), and switch to using the answering machine that was already built into our phone anyway.
A lot of people express concern about the 911 issue. Vonage now has automatic address recognition (if you set it up with them, which they try very aggressively to make sure you do), and from what I understand, there's no real data on reliability of Vonage's 911 versus reliability of POTS's 911. It's apparently quite common for POTS's automatic address recognition to fail, and for that reason, the first thing they always do when you call 911 is ask for your address anyway. The thing that does bother me a little about the 911 issue, regardless of the service provider, is that you can't test it without making a false 911 call. I don't like the idea of an important safety system that you can't test.
Find free books.
I should probably give the obligatory "I work for Comcast, but just as a dispatcher" warning, so I know a bit more about this than most people. :-)
Yes, but until any one cable company has coverage to every home in America, a call from NY to CA will most likly traverse another provider's network
Right, unless both sides have (for example) Comcast's VOIP, there will be a hand off between providers. But all phone companies pay when a call transfers to another provider's systems. The amount per call is next to nothing, but considering the number of phone calls made at any one time, it adds up to enough that I know Comcast has laid cable through areas they don't service just to carry their own VOIP calls. Same for cell phones(ever wonder why your phone always homes in on your provider's towers even if another one is closer?). So if Comcast hands off the last bit of a call to say AT&T's network, Comcast would pay AT&T as they would if the call went to Comcast's network.
As for the lawsuit, isn't that the whole debate about the net neutrality issue? What is different from SBC trying to extort more money from Google for data passing over its lines than AT&T trying to extort more money from Comcast or RoadRunner for the same reason?
Different issue. Over Comcast's packetcable thing, the data of the call only goes over Comcast's backbone(and no other part of the net), then it is handed off as a normal phone call.
"Useless organic meatbag" -HK-47
Given the bandwidth of a cable (or any other broadband) connection I don't see why this should be surprising. Since a standard phone line needs to be upgraded for ADSL anyway, clearly the throughput with VoIP should be better than POTS.
The analog bandwidth of a landline is sufficient for decent quality anyway. The most limiting factor is the poor microphone and speaker used in most of these. I've had some great phone calls over VoIP where I couldn't understand what the blazes the other party was saying and it was mostly chalked up to them using some awful little wireless job which picks up interference from everywhere and vox clipping.VoIP on Cable I fully expect to come in 5.1 audio at some point, why the heck not? You've got the bandwidth and then some. The question: does anyone ever really need this will be buried in the relentless pursuit of More Toys.
"Hello, this is sylvia"
"mrs. blechman, this is the gas board. you are 3 months behind in your gas payments when can we expect a payment?"
(ulp) "HELLO? HELLO? Is there anyone there? HELLO?"
A feeling of having made the same mistake before: Deja Foobar
I just got VoIP two months ago through my "local" cable company, and the voice quality has been excellent. And, the bill was even better! So far, so good.
An interesting side not if you're a Verizon phone and DSL customer. Simply mention the fact that you're dropping DSL for cable and they first try and scare you by saying you are on a shared network and will certainly be targeted by intruders. If you can put up with their speach, then they'll offer at least one free month, and in my case, $10 less per month to stay with their DSL.
Then, finally, the second call to cancel phone service they give a speech about unreliable 911 service and dropped calls with VoIP. If you can patiently wait for that speech to conclude, they'll offer another discount to keep you as a land-line customer. In my case, it was $10 again! No rebates on long-distance though...
Bottom line, call up your phone company now, and say you want to cancel DSL and/or land-line service. You will certainly get a free month and a monthly discount.
Cable providers also led the way in audio quality; the top firm in Keynote's study actually turned in an MOS of 4.24, above most real phone networks.
If I recall the DOCSYS standard correctly (that's the one for cable settop boxes), the framing provides the phone company TDM-style 8 kHz synchronized clock, and the phone signals are carried as full-rate uncompressed bytes.
In other words, POTS-over-cable is a 64 kbps synchronized digital signal, identical to what's carried on the phone companies' own ISDN, T, and SONET carriers, and is switched onmodified on and off the rest of the digital network unmodified. The A-D conversion happens in the settop box. It's like having your POTS phone at the switching center within wire-feet of the multiplexer. (The clocking is also good enough to encode analog signals from FAX and 56K computer modems. It has to be, as a side-effect of the need to time the upstream packets properly.)
POTS, on the other hand, is A-D converted at a central office or a "remote terminal" (in a box at the curb) and carried the rest of the way - blocks to miles - in one of a bundle of wires. This is subject to crosstalk, distortion (selective delay and attenuation of higher frequencies), and a number of other pathologies that lower the signal quality.
So it is not at ALL surprising that cable POTS signal quality beats telco POTS. Cable's signal is about as pristine as you can get.
(And VoIP isn't in the same ballpark, due to both compression and timing uncertainties.)
Bantam Dominique roosters crow a four-note song. Once you've heard it as "Happy BIRTHday" you can't NOT hear it that way
I'm still going to keep my POTS line. It's my security blanket.
Well, when my power goes out, I'm still on the Internet for hours. Perhaps if you were worried about calls when the power is out, you could spend $100 for a UPS. My cordless phones work great in a power outage. I bought one with a battery in the base. My Internet works great in a power outage. I have a UPS. The runtime is good too, as I have just the minimum data equipment plugged into the UPS and I have a laptop to work off of. I have hours and hours of talk time and Internet usage in a power outage. Oh, and if all those fail, I pull out a cell phone. The only reason a power outage will hurt is if you don't expect it (and you obviously expect it and know the consequences) or you don't think that your uptime is worth the $100. Or, if you are just using it as an excuse to complain about technology you don't like.
Learn to love Alaska
Teamspeak, Ventrillo
Granted, this isn't really a phone replacement, but if all the people I want to talk to are on their computers anyways, then it works great.
There is no mod option "-1: Disagree" for a reason. "Overrated" is not an acceptable substitute. Post something instead.
I lived in 3 different towns in NJ and one in CA and I think the landline has gone down like once in 25+ years. I've never had a landline to landline call dropped, ever. I didn't even think that was possible.
I have had the cable drop off dozens of times though as have most people I know. I'd rely on Verizon for VOIP in a second but I would trust Cablevision to deliver my email. If what they are saying is actually true on a national scale then I'm shocked.
Landlines in most areas are regulated. If their dropped calls/ 1000 rise above a certain level they get fines. Most areas are about 9-15 / 1000 before fines come into play. POTS are rarely fined.
"There are more things in heaven and earth, Horatio, than are dreamt of in your philosophy."
VoIP uses whatever codec it's configured to use, which could be great-sounding G.711 alaw/ulaw (as used on the real phone system) or GSM (not so good).
The problem isn't with bandwidth. Anytime you place a call on a land line (non-local), your signal on the analog POTS line is digited (8KHz, ADPCM, uLaw encoded) at the FXO (foreign exchange office) and transfered over a channel on a T1. 8KHz is plenty of bandwidth to transfer the human voice (Bell labs figured this out in the 50's)... With VOIP, extra bandwidth on one end doesn't give you a thing if you're calling a non-VOIP phone on the other end... eventually the signal gets transfered over a T1, at 8KHz (the lowest common denominator). The real problem is that VOIP is packet switched, without a guarantee of delivery... and as you know with IP, you can also run into issues of packets being received out of order. The real value in VOIP isn't QoS (it won't be for years to come)... the real value is in being able to deploy voice services over an existing IP infrastructure... no more clunky and expensive PBX's!
Now, if you're placing a VOIP to VOIP call (I assume this is what the test was... didn't read TFA), there is no 8KHz constraint and throughtput can theoretically be higher.
# man tar
Before I comment, I'd better post my credentials to say what I'm about to say: I am a co-author on many of the PacketCable specs, wrote the standard text on the subject, and also run a little company that sells PacketCable security software.
So, having said that, I would like to point out that your comment is accurate but may be a little misleading. It may indeed be true that today, and for most cable ISPs, the call stays on their network. But PacketCable was not specifically designed to be that narrow. Its architecture allows lots of things that cable companies have so far mostly not chosen to do. But, for example, there is no reason at all why the service has to be provide by a cable company. Sure, the cable company controls the pipe into the house (and the quality of service on that pipe), but there is nothing at all to prevent an ISP that decides that it doesn't want to get into the telephony business (and telephony could not remotely be described as easy) from contracting with a "real" telephony company so that that company provides service, with all the usual quality of service controls, over the ISP's network.
To give a completely and obviously hypothetical example. Instead of deploying telephony itself, Comcast could have chosen to have Qwest run a Comcast-branded VoIP service over Comcast's network, including the last-mile access network. That service could be given exactly the same quality-of-service guarantees that Comcast has chose to give to itself, and presumably both Qwest and Comcast would receive a cut of each phone call.
The corollary is that third-party providers (the Vonages of this world) do not have agreements and service-level contracts with Comcast. This means that their calls travel over the Comcast network using "best-effort" instead of some kind of guaranteed quality-of-service labelling. In particular, between the subscriber and the cable comapny, Vonage-like services travel over the ordinary standard primary DOCSIS flow from the cable modem, sharing it with all other traffic from that modem; PacketCable calls use special flows that have guaranteed latency-and-jitter limits specially designed for voice. Only the cable company can create and use those flows. (For the gory technical details, look at the DQoS [Dynamic Quality of Service] spec available at www.packetcable.com.)
The first time I connected on Skype (from Shaw in Manitoba to Telus in Alberta), the voice quality was amazing. My father instantly noted that I sounded like I was "right there". Just like watching HD for the first time, other phones (especially mobiles) sound so much worse since we've started runing Skype.
PacketCable calls use special flows that have guaranteed latency-and-jitter limits specially designed for voice. Only the cable company can create and use those flows.
Precisely the point that everybody forgets. (I've done software development on DOCSIS cable modems and a CMTS - although I didn't do any PacketCable work, I've had to read some of the specs and have also configured test systems for use with it.)
The cable company has a huge advantage over DSL when it comes to VoIP, because Vonage et al. share the same logical traffic flow - they just change the priority of the packets within that single stream. With the PacketCable capable modem, you have multiple streams, and the head-end equipment is made aware of this, thus being able to prioritize the streams themselves. It's a kind of super QoS.
Because of this, I feel that cable is the technically superior platform, except that the cable operators just don't want to put any thought, planning or money into the infrastructure. The charges that CableLabs levies for testing don't help either, although they have come down a fair amount since the time I was doing DOCSIS work.
All that said, I'm still waiting for the day when they finally get it right - a single modem/set-top box that can handle a PacketCable stream, an HDTV QAM stream, and a data stream, with PacketCable as top priority, HDTV as second and then the data. From what I've been hearing, companies that are trying to do "triple-play" are finding that they have to install multiple boxes (as many as one for each purpose sometimes), and they don't necessarily work well together.
-- Joe
Well, I worked in the telecom industry for 20 years, and I can tell you that Nortel, for one, engineers its PBX's for exactly the same reliability as its CO switches, and there's no legislation forcing them to do that. (BTW, exactly what piece of legislation subjects Bell Canada to limits on downtime? I've never heard of it.) It's a matter of pride among telecom gear makers that their stuff works all the time.
Of course, there's an economic incentive to make it so. If the network goes down, there's no toll revenue to be had. And service requires expensive people and gear to provide. So you build stuff that works most of the time, degrades gracefully in the event of failure, and then you put lots of redundancy in the network. It makes good business sense.
What was once true, is no longer so
... "VoIP with bandwidth to spare, controlled low latency, and QoS is sometimes almost as good as a dedicated voice network"?
Gee, any telco engineer or high-level tech could have told you that...
Disclaimer: I've been one. From a purely technical POV, VoIP is something of a con. It's attractive to end-users because it offers a chance to break free from the telcos. It's attractive to telcos because it allows them to homogenise their networks onto a single IP-based platform. Technically, though, it's a shitload of kludges to shoehorn something into a transmission platform that was never designed for the requirements of that kind of traffic. Underneath those kludges it's unreliable, inconsistent, and doesn't scale terribly well - though, because it's based on commodity technology, it's relatively cheap to implement/expand.
What part of "a well regulated militia" do you not understand?
Good point. And, we've made something as easy as making a land-line call potentially so complex that the average person can't even do it. For some reason I'm always having to do ridiculous things like unplugging my cable modem, router, and disconnecting the coax from the modem (in some special order that is hard to reproduce) in order to "fix" my internet connection. If I had Vonage for voice on top of all this it would be a real train wreck.
The problem is, people have learned to accept that "the internet is down", but it would be a much bigger deal if the water was off, the electric was out, or the land line was down.
And now that I took time to read the Wiki link, I see that is exactly what it says. So for commercial VoIP, you would specifically NOT use hot-potato routing.
"Hot lesbian witches! It's fucking genius!"