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#1 ThoughtPhreaker

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Posted 12 October 2010 - 03:40 AM

So let's get one thing out of the way first.

I'm not opposed to packetized telephony. There's reasonable ways to do it, and it's been done semi-frequently in the past. An employee of a major long distance company tells me a large number of their links to different cities use ATM rather than TDM. Verizon has installed a number of intra-LATA tandems that rely on an ATM technology. Even the 5ESS uses ATM in it's internal switching matrix. When you think about it, this makes sense. ATM packets are small enough for minimal overlay to be applied to the call, it has fairly elaborate QoS built into the protocol, and it's even designed with the idea of real-time transport in mind.

IP is not. In fact, RTP, the packet format for real-time data over IP, wasn't even standardized until 1996, 16 years after UDP was developed. As much as companies love to tout the efficiency of an all IP network, it seems to work in quite the opposite direction. The overlay causes a SIP call with uLaw to chew up a little more than 90 kbps of bandwidth, as opposed to 64 kbps, plus the ~500 bytes of call setup data transmitted via SS7. While this sounds relatively tiny, imagine it on a carrier-grade network that processes hundreds, if not thousands of simultaneous calls. The only way to get IP voice to be "efficient" is to compress the called audio, largely to the point to where we've had to introduce out of band DTMF standards to even reliably transmit two sine wave frequencies. This also introduces lookahead delay in the case of CELP codecs (read: almost every low bandwidth telephony codec that wasn't folded into g.726) into a call already riddled with considerable delay, assuming there hasn't been more introduced by a server relaying a stream instead of using a technique such as media bypass. If I can find where I put the recordings, I'll see if I can show how this works in practice. Back when Sprint sold STi their prepaid card platform in 2008, the very same platform was put onto an IP network. Shortly afterwards, the card platform pissed itself with delay. 

So can someone please tell me why this protocol has even touched the PSTN? It makes about as much sense to me as the IRS having a facebook account.

Oh, wait... http://www.facebook....107968832558644

#2 10nix

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Posted 12 October 2010 - 02:34 PM

Well, I think that was one long setup for a facebook joke...

I'm not actually sure why there are attempts to utilize VoIP in the PSTN. I think at some times it must be modernization for modernization's sake. Perhaps the equipment is cheaper? I really couldn't tell you.

Is the press to implement IP in the PSTN really that great? I was under the impression that the few forays into that area were ill fated marketing gimmicks.

#3 JmanA9

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Posted 13 October 2010 - 07:00 PM

I think the entire thing comes down to the fact that most people don't notice the difference. I'd say that about half half of the people I ask, of all ages, can't tell the difference between a modern GSM or CDMA cell phone and a land line. The same people are the type that can't tell the difference between an MP3 encoded at 96kbps and one encoded at 320kbps. If I point it out to them, if they then notice, it usually doesn't bother them. I like to ask my friends/family/coworkers weird questions.

Savings to the carrier is a second priority here. If 1 out of 2 customers complained, I doubt major carriers would pull this stuff. However, if nobody notices, nobody can complain.

#4 nyphonejacks

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Posted 13 October 2010 - 07:49 PM

I think the entire thing comes down to the fact that most people don't notice the difference. I'd say that about half half of the people I ask, of all ages, can't tell the difference between a modern GSM or CDMA cell phone and a land line. The same people are the type that can't tell the difference between an MP3 encoded at 96kbps and one encoded at 320kbps. If I point it out to them, if they then notice, it usually doesn't bother them. I like to ask my friends/family/coworkers weird questions.

Savings to the carrier is a second priority here. If 1 out of 2 customers complained, I doubt major carriers would pull this stuff. However, if nobody notices, nobody can complain.

perhaps my ears are too tuned when it comes to telephone lines being a phone tech to hear the differences...

while IP for voice is usually fine.. when it comes to data/fax transmissions that is where the real trouble starts... for the most part the subtle audible differences are not a major problem when dealing with voice... but i have had many service calls where customers attempted to fax either on a VoIP line, or long distance/international on a POTS line that was at least partially being routed by the LD carrier over some form of IP... circuit switching still has a place in society...

Savings to the carrier is a second priority here. If 1 out of 2 customers complained, I doubt major carriers would pull this stuff. However, if nobody notices, nobody can complain.

i do not think the savings is a second priority, i think that it is the main motivational factor, if carriers can converge their voice and data networks it reduces hardware costs, labor costs, and for telecom providers, provides a way to get around interconnect fees to other carriers for routing thru the interconnect companies equiptment...

i think you might have meant 1 or 2 customers, because if 1 out of 2 customers complained, that would be half of their customers, and a 50% satisfaction rating is not acceptable for any companies bottom line... so, assuming that you mean only 1 or 2 customers, i would have to disagree with the amount of complaints being so low... perhaps on the voice end of things yea, but there are still many dial up lines, and fax machines that businesses rely on, and using a dial up or fax over a line being switched by IP is not perfect... so i would tend to believe that the amount of complaints are far higher than just a hand full of customers, and the ones that are complaining are the business accounts that have multiple lines - the customers that you do not want to churn....

#5 InsaneAutomata

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Posted 14 October 2010 - 02:11 AM

while IP for voice is usually fine.. when it comes to data/fax transmissions that is where the real trouble starts... for the most part the subtle audible differences are not a major problem when dealing with voice... but i have had many service calls where customers attempted to fax either on a VoIP line, or long distance/international on a POTS line that was at least partially being routed by the LD carrier over some form of IP... circuit switching still has a place in society...


You're right about that. Fax machines and mail machines need a pure Analog line. You might not realize it but mail machines big or small are in virtually every office in America. It is one of those "hidden" items that everyone forgets about. An immediate switch would destroy most mail systems at small and medium size businesses.

So yeah a big caveat to this is that if you switch to a packet network, as opposed to a circuit switched network you also by definition turn it into a digital setup since the packets everyone is taking about are TCP/IP based packets. Fax machines, Mail machines, Kiosks, ATMS (depends though on the setup), and other devices that are not in everyones common vision would break.

I personally think that the POTS infrastructure is a marvelous piece of engineering and it is far more efficient system than most people realize. I think that the big telcos don't have the appropriate vision to use key advantages of circuit switched networks. Take DSL for instance. Yeah, yeah, it is technically slower than many of the cable based systems, but if you are an internet junkie like me as all of us hackers are then you've definitely experienced, especially if you live around large numbers of people, bandwidth problems with your cable service. That is because as everyone knows large numbers of people are sharing one "trunk." Cable companies do very little to ensure your paid for "best of service" bandwidth. So you are stuck waiting until everyone gets off. With DSL I have consistent speeds with almost no interrupts primarily due to the circuit switching infrastructure that I'm a part of. That is why I prefer DSL over cable...I rather have good speeds that are consistent than miraculous speeds that are inconsistent.

Another concern is hacking. Future wars will be like those in Iraq/Afganistan and one country hacking another. If you switch to packet based networks using existing technology like TCP/IP, the hacking vectors increase substantially. Look at the culture of Phreakers. It is very hardware based and physical. To be a good Phreaker requires proximity and localization (such as finding codes for a particular telco, conference, etc.). With packet switched networks, packet injection at foreign locations is will be a major problem.

I think too that the slow down in the process is partially because the FCC is getting its ass kicked right now. The major internet providers were able to prevent the FCC from implementing Net neutrality rules like they did with the phone system. They are also experiencing some resistance from the telcos and other big industry players for the switch. I think that the FCC knows that its going to have to really fight it out and so has made the decision to regroup or actually quit on the issue size they may not believe that they have the strength to win.


#6 nyphonejacks

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Posted 14 October 2010 - 07:16 PM

I am REALLY going to have to disagree with your argument of DSL being better than cable modem service... and will go one further, and say that FiOS is not as good as DoCISS 3.0 cable modem service...

what is DSL topping out at now-a-days? 8.0? with most users opting for 3.0 or less, and upload speeds are even more pathetic...

cable modem service starts out at around 5mbps... i got 30/5 on my internet connection, so my upload is much faster than most DSL customers download speeds... I live in NYC and have yet to notice that whole problem of the node being overcrowded and slowing my speed or performance - especially not to that of the speed of DSL, or worse....

DSL was a stop gap product that was outdated the day that it came out... it only arrived on the scene because they could not afford to sit back and allow the cable companies to come in and take over all of the high speed internet lines...

and as for FiOS vs. DoCISS 3.0 - can FiOS offer 101/15 for $100 per month??

and as for the phone companies earlier advertising campaigns that touted DSL as better than cable because DSL was a dedicated line, and cable was shared... where are those claims now? doesn't FiOS share a connection with up to 32 users from the tap (or whatever verizon is calling the FiOS terminal)_

but other than that... i agree with the rest of what you said =)

#7 InsaneAutomata

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Posted 14 October 2010 - 08:16 PM

To each his own...but I am an internet hog. I have terrabytes worth of data downloaded off the web. I've been doing this for years so my experience I guess comes from that. I go to work and suck the internet dry with a consistent speed and I'm never throttled. I have a 6 Mb service for about 40 bucks a month. When I used to behave this way with cable, everything was always throttled. Whether torrent traffic, Netflix, or Hulu. Maybe things have changed. I also don't have to bundle it with another 100 bucks cable charge. I don't have cable service because I get everything I watch off the Web. Trunk jam was always a spotty issue, some areas better than others and so if you are in a great area you have it sweet.

I agree with what you are saying about some of the DSL technology. But I'm not up on some of the standards that you mentioned to talk about it any better. I used to be very pro cable modem in the early days...late 90's early aughts, but my above experiences ruined me and perhaps rightfully so since my behavior is not very saintly. :tongue:


#8 nyphonejacks

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Posted 14 October 2010 - 08:50 PM

i think that it really all depends on the cable company, and their policies...

i have cablevision/optimum online... so i have it pretty good.. i have heard the opposite argument against cable modems from people in other areas, because of their cable companies policies... i don't even think that TWC can touch cablevision...

and my cable company provides some pretty awesome fiber optic service (lightpath), that i can only dream about getting cause of its price... it is more for enterprise customers - and provides redundant fiber optic links so that if one drop goes out, traffic is transferred to the other fiber drop...

i canceled TV service about 2 months ago.. it went unwatched with hulu, and other less than legit sources for filling my hard drive with movies, etc... (especially since i have a PC connected to the HDTV in the living room)

#9 InsaneAutomata

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Posted 14 October 2010 - 09:14 PM

... (especially since i have a PC connected to the HDTV in the living room)


Almost ditto...I use my Xbox for that...I can give up cable but not Gaming!! The xbox if connected to a network that also has a Windows 7 machine with the media client installed can link up with it. So through the same router that I download about 3TB a year I can also link up with my 10 external usb 2.0 hard drives...lol...and watch it on my HD t.v.

Love technology.

Edit. BTW, on your browser (doesn't matter which) do you see the text in the dialog boxes? They are all whited out for me.

Edited by InsaneAutomata, 14 October 2010 - 09:16 PM.


#10 InsaneAutomata

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Posted 14 October 2010 - 09:21 PM

Oh, another thing for this discussion in general. Priority. Is it me or is it the local loop that is the bottleneck in the system no matter which switching technology you use. Maybe they should be working on upgrading the local copper so that the phone network can really compete with the cable and wireless infrastructure. Most telcos are fiber internally, right, so there is a big mismatch in potential. I know it would be expensive but if they are to thrive they need to start thinking in this direction.

#11 nyphonejacks

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Posted 14 October 2010 - 09:47 PM

the blanked out quote box has been a common problem on this forum that was supposed to have been being worked on with the default skin... if you change the skin to a different theme then you can see the text in the boxes... personally i find the white background theme better looking than the black background anyway...

as for upgrading the copper network? lol i doubt that will ever happen... there is still plenty of lead sheath cable out there, and the phone companies are not investing capital into the copper network, they are spending all of their money on FTTH (FiOS, Uverse, or whatever the local teleco brands it as)

land line phone service with good copper cable is superior to other forms of wired phone service.. but, it is also expensive to install and maintain... fiber does not tend to have the same issues as copper as far as weather related troubles... but then again, i guess we will see, when the outer sheaths of these FTTH cables get chewed by squirrels and the moisture begins to distort the light in the fiber...

the problem with FTTC and Litespan2000 has been defective cards in the CEV, and power outages taking out the entire terminal, so compared to copper the chances of everything in a terminal going down at the same time are greatly increased, even if rare... unfortunately my employment with verizon terminated several years ago, so i will not have much hands on experience in knowing if these same problems can/will find their way into FTTH installations... for some reason i would tend to not think so, since the ONT is at the customer premise with a back up battery, but i guess time will tell...

#12 ThoughtPhreaker

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Posted 15 October 2010 - 06:49 AM

 Woah, looks like this discussion has sparked quite a bit of activity.

perhaps my ears are too tuned when it comes to telephone lines being a phone tech to hear the differences...


For the benefit of clarity, would you mind defining what you mean by "phone tech"? Installing a subscriber line is a lot different than maintaining a switch, or sitting in a NOC provisioning long distance routes.

i do not think the savings is a second priority, i think that it is the main motivational factor, if carriers can converge their voice and data networks it reduces hardware costs, labor costs, and for telecom providers, provides a way to get around interconnect fees to other carriers for routing thru the interconnect companies equiptment...


As I mentioned in my first post, I'm open to an idea of a new protocol - most companies have been experimenting with all shapes and sizes of packetized telephony throughout the nineties, and if one of the "big three" networks has really made ATM links between cities, I must say, I really am impressed. On domestic calls, the quality pretty much stays within the same standards as the other two with nationwide networks.
To both address 10nix's question and give a good in practice example of how the network could change if we follow through with these new standards, let me introduce you to Excel Communications. Excel, for all intents and purposes, is the closest thing we're going to get at the current moment to a nationwide IP carrier. As far as I've been able to determine, they've actually replaced all their DEX switches with Veraz softswitches, and pretty much rely on IP entirely for their backbone. Not only that, they seem to be _the_ carrier for any form of next generation network. Comcast uses them, Cricket/MetroPCS uses them, Nuvox uses them (though they were recently acquired by Windstream, so this may change), Spoofcard used to, and nearly every VoIP provider that's ever stumbled onto the internet ends up interconnecting with them, whether directly or through another carrier. You get the idea - they're very well recognized, and fortunately for us, they also have a PIC you can dial with; 101-0373. As a rule of thumb, whenever I call over a new carrier, I'll use a pretty simple method of trying to determine roughly how much delay there is; call something that responds to touchtones, press a key, and listen to how long it takes for whatever is at the other end to break. It's not the most precise method, but it's fast, easy, and you can compare the results with anybody else. So that's exactly what I did; 

http://thoughtphreak...ca/audio/delay/


MCI calling card - 250 ms
MCI calling card (x2) - 225 ms
Qwest's 3rd party - 450 ms
Qwest's 3rd party (x2) - 460 ms
Excel (0373) - 550 ms
Excel (0373,x2) - 480 ms


fyi, "Qwest's 3rd party" refers to a mystery carrier Qwest interconnects with when calling the particular CLEC this number got service from. The only thing I'm sure about them as of now is it's some VoIP carrier.

Since this is a call to Maine from the other side of the country (and in the case of MCI, it's routing through their calling card platform. This is because I'm blocked from placing toll calls on 0222), some delay is meant to be expected. Frankly, though, I was a little surprised when I saw this. For something that's supposed to be realtime, 400+ milliseconds is pretty pathetic. It goes without saying that's enough to make people start talking over each other, but this is before - say, radio or transcoding delay, or delivering IP packets to the end user like most of Excel's customers - or maybe everybody if we continue on this path.  The traditional network is engineered to a pretty stringent standard to prevent  unusual or flat out craptastic conditions from completely ruining a call. These two networks we're looking at seem to sorta just halfass their calls under normal circumstances...

So I'd have to say, I agree with most posts as to why IP has become commercially successful. It's both very easy and very cheap to push calls through the internet as so many people with colo spaces have done, and people don't seem to mind the loss in quality. But still, why is the idea of a completely IP telephone network making so much headway in, well, every market that exists? There's probably a reason why Nortel's DMS-10 brochure classifies it as a "carrier-class VoIP solution" (no, seriously), or why Cisco markets IP-PBXes instead of packet or soft PBXes. Is there some incredibly visionary thing I'm overlooking as to why we should rip out machines well into the six figures to lean on a questionable protocol, as opposed to the packetized ones they already support?

as for upgrading the copper network? lol i doubt that will ever happen


I'm not sure how much this is happening within other territories, but the most frequent updates on Qwest and AT&T's wholesale websites seem to be fitting their copper infrastracture with DLC or FTTC.

Edited by ThoughtPhreaker, 15 October 2010 - 06:55 AM.


#13 nyphonejacks

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Posted 15 October 2010 - 08:31 AM

For the benefit of clarity, would you mind defining what you mean by "phone tech"? Installing a subscriber line is a lot different than maintaining a switch, or sitting in a NOC provisioning long distance routes.

im the field tech kind... and seeing some of your posts, you probably have a better ear for things than myself...

you seem to have more specific things that you listen for/to on the line than i normally do as well...

#14 Andrew

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Posted 23 October 2010 - 12:38 PM

So can someone please tell me why this protocol has even touched the PSTN? It makes about as much sense to me as the IRS having a facebook account.


It is cheaper and more cost effective to build one IP network that can be used for other services than build multiple specialized networks. Money, it is the only reason we move forward in technology, makes it cheaper to maintain, less employees to pay and less cost for users. It's the society we live in, as sad as it might be.




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