Voip Blog

Mandatory Dialing for 505/575 New Mexico Area Code Split

2008-09-16T17:22:00.000-07:00

Approved by the New Mexico Public Regulation Commission (NMPRC) the final phase of the New Mexico 505/575 Area Code Split begins on October 5, 2008.

On the start date, mandatory dialing takes effect - meaning that callers must use the correct area code to complete their calls. When a 505 area code call is placed to the affected area codes callers will hear a recorded announcement for numbers that moved to the new 575 area code. Callers will be directed to hang up and redial using the new 575 area code.

The NMPRC divided the state into two regions. The southern and eastern portions of the state will be served by the new 575 area code. The northwestern region of the state, including Albuquerque, will remain with the 505 area code. Local calling areas will remain the same; the price of a call, coverage area, or other rates and services will not change. Users' 7-digit telephone numbers will remain the same.

If you live in the affected 505 area code make sure you notify you family members, friends and business associates - as well as update your speed dialing and call forwarding settings if necessary.

How Do You Tax VoIP?

2008-07-23T21:55:00.000-07:00

Telephony over IP, wireless service, and traditional landlines all provide the same service--a voice channel over which to communicate. Why is each service taxed differently?

Part of this can be explained this way: while telecommunications is global in nature, it is regulated locally--down to the city level! I pay city taxes on my landline bill, in addition to all the state and federal taxes.

Internet telephony service providers like voip.com are not subject to the same regulations as a local telephone company. Due to their interstate nature, they are specifically exempt from state telecommunication regulations!

That being said, companies like voip.com do have to collect money to pay for certain things mandated by the federal government. Your voip.com bill has three fees on it:

E911 Fee: By law, voip.com and other Internet telephony service providers must provide you access to E911 emergency services. This fee covers the cost of providing that service. Traditional telephone bill will have a similar charge.

Regulatory Recovery Fee: This is a generic fee that covers the cost of complying with the various state and federal regulations. Many wireless phone companies charge a similar fee.

Universal Service Fund (USF): The USF was created in 1997 to comply with the Telecommunications Act of 1996. It was established to ensure that consumers in all regions of the Nation have access to quality telecommunications and information services at affordable rates. While not explicitly required, voip.com and other providers currently pay into the USF as it is expected to be required in the near future.

To the question at hand: how to tax VoIP. I don't really have the answer for that. However, there are some good ideas discussed on the 15 July 2008 episode of the Alec Saunders Squawk Box podcast. Jim Kohlenberger, Executive Director of the VON Coalition and Brita Strandberg, Partner at Harris Wiltshire and Grannis discuss these issues with guest host Carl Ford.

Mobile Phones On Planes

2008-05-31T00:00:00.000-07:00

There has been a lot of controversy around the topic of using mobile phones on an airplane. The objections raised include interference with aviation equipment, problems with the terrestrial mobile phone networks when using your handset in the air, and simply annoying your fellow passengers. Here's the skinny on each of these points:

Interference With Aviation Equipment: Aviation equipment is generally well-shielded, making the possibility of interference small. Despite bans, people either accidentally or purposefully leave their phones on during flights with no ill effects. I am unaware of any flight disasters that can be attributed to someone using a mobile device in-flight.

Terrestrial Phone Networks: One issue with using your mobile phone in-flight is that the phone can see way more towers than usual. The mobile phone networks were designed to handle handoffs with handsets moving at highway speeds, not airplanes at subsonic speeds. Due to the distance between the ground and the towers, the phone will have to work that much harder to get signal to those towers as well, which does increase the risk of interference and decrease overall battery life.

Annoying Your Fellow Passengers: There's no question that yakking on the phone in-flight is likely to annoy your fellow passengers to no end. This takes a rather voice-centric view of the mobile phone into account. While I personally wouldn't want to talk to someone on the phone while in the air, I would love it if SMS and data service were available. None of these things would be disturbing to other passengers in the least and would give me the functionality I really want.

Of course, the downside of allowing data service is: you can do voice over IP using that data connection! A friend of mine did just that when Lufthansa offered WiFi Internet service over their flights. With airlines in the U.S. also considering adding WiFi service to their flights, the issue of telephony on planes is going to have to be dealt with one way or the other, whether we like it or not.

The Pros And Cons Of Calling Party Pays

2008-05-30T14:49:00.000-07:00

People outside the U.S. and Canada find it odd that we pay for both incoming and outgoing calls on our mobile phones. Conversely, we find it odd that it costs, say, 1.6 cents a minute to call a U.K. landline using voip.com's low rates, but it can cost up to 33.5 cents a minute to call a U.K. mobile phone!

The main reason for this difference comes from the calling party pays system that is prevalent throughout the rest of the world. There is no such thing as "free local calls" as there is in the U.S., which means the person calling must pay for the privilege of doing so. Incoming calls, whether you have a landline or mobile phone, are free.

While this sounds great in theory, what has happened is that the mobile network operators in the various countries have jacked up the termination rates to their network. This can make it expensive to call across the mobile/landline boundary, or even between mobile networks!

Because of these expensive termination rates, some people in calling party pays countries rarely make a voice call. They may, for instance, signal to someone based on the number of rings rather than complete a call. Or they may bypass the voice channel altogether and just use SMS, which is a lot cheaper than making a call.

In the U.S. and Canada, we have a wireless subscriber pays system, where inbound and outbound calls are paid for, in some way, by the wireless subscriber. While these rates were initially high, competition has driven the cost down to the point where the cost-per-minute is fairly low--low enough that it most cases, it is simply a non-issue. The cost to call landline to mobile or mobile to landline is the same. Unlike in calling party pays countries, the cost of calling a particular number rarely enters into the equation.

The end result? According to the CTIA, the lobbying group for the mobile network operators, mobile phones are used more in the United States for voice calling. See their filing with the FCC for more details (warning: PDF link).

Why Mobile Phones In The U.S. Are Geographic

2008-05-29T14:01:00.000-07:00

One of the fundamental tenets of the Bell System that survives today is the concept that local calls are free. What's local? The rough guideline I remember was "anything within a 12 mile radius." In some cases, particularly in more rural locations, local calls may cover a wider area, sometimes at a higher local line cost. When I lived in Hawaii, all calls within the same island were considered local.

The telecom laws in the U.S. require that mobile phones have a "home" in a geographic region. From a practical point of view, it means that all mobile phones are "local" calls from somewhere. In other words, it does not cost any extra money to call a mobile phone than it does to call a landline. The converse is true, mobile-to-mobile minute plans notwithstanding.

Since mobile network operators do not maintain points of presence in every community, your mobile phone number will frequently come from a nearby community. While this generally results in your mobile phone being a local call from your landline, in rare cases, your mobile phone number may be long distance.

One major problem with requiring mobile phones to be associated with a particular geography became readily apparent with the Hurricane Katrina disaster. Anyone who had a mobile phone with a New Orleans telephone number--even though they were physically elsewhere--were unable to receive telephone calls. This is because the New Orleans telephone exchanges were not available.

The downside, of course, to landlines and mobile phones being treated equally in the eyes of the public switched telephone network is that users of mobile phones are charged for both incoming and outgoing calls in the U.S. and Canada. The good news for mobile phone users is that competition has driven the cost of minutes down to the point where the pain of paying for an incoming call is minimal.

Dial Telephones, ANI, and Caller ID

2008-05-28T14:21:00.000-07:00

It's funny that we still use the phrase dialing the phone when most people under the age of 30 have never used a dial telephone. I was using rotary phones well into high school. If you've never used one of these phones, this instructional movie short from 1927 should help:

Back then, you typically only dialed telephone numbers in your local area. If you needed long distance, you called the operator and they connected you. Most people didn't know the area codes of distant cities, nor did they need to.

By the time I was born, direct distance dialing, as it was referred to in old telephone instruction manuals, was fairly common. Even with direct distance dialing, there were some locations that required operator intervention.

Here's a crazy fact about dialing long distance calls: you had to supply your own telephone number to the operator! I'm sure this was taken advantage of by nefarious individuals, not to mention a source for billing errors! There wasn't automatic number identification (ANI) back then. One direct distance dialing became more prevalent in the 1960s, ANI simply came along for the ride.

ANI is something that is used within the telephone company trunks. Caller ID is a consumer-level manifestation of ANI, i.e. the transmission of caller information, but it's a completely different system from ANI. ANI is typically not seen by a consumer--and can't be blocked. Caller ID is seen by the consumer--assuming this service is enabled on your handset.

Caller ID can be communicated in a number of different ways, based on the local telco standards. In the U.S. and Canada, it is communicated as a short burst of modem data between the first and second ring. In the case of Call Waiting Caller ID (i.e. caller ID while you are on a call), your phone handset has to go quiet for up to 100ms in order to capture and decode the Caller ID!

Personalizing Your Telephony Experience

2008-05-27T13:24:00.000-07:00

Image via Wikipedia

Back in the early days of telephony, the phone company was the arbiter of what telephones you could hook up to the network. That meant only a few models of phones were available--in whatever color they wanted to sell it in. In the early part of the 20th century, the phones were black, like the model T.

This remained the state of affairs until the 1968 Carterfone ruling by the FCC. In short, it permitted any device to be connected to the public telephone network, so long as it did not interfere with it's operation. This single ruling opened up not just the market for telephones and telephony devices of all shapes, sizes, and colors, but opened up new uses of the conventional telephony network, e.g. modems that eventually evolved into high-speed data connectivity.

Back to telephony devices. There are a number of landline and mobile phones available from a variety of manufacturers. Landline phones tend to be, by their very nature, fixed in one location. The fact that you and your neighbor might have the exact same telephone handset is almost a non-issue.

Mobile phones, on the other hand, are a different story. It's not only possible for multiple people to have the same mobile phone, but there are circumstances where figuring out whose phone is who might be a problem. I actually attended an event where a number of people were carrying Nokia N95s around. Yes, there are four different models of the N95, but many of the phones looked alike!

One way you can differentiate your handset from someone else's is to change it's outer appearance somehow. My Nokia N95 actually has a strap from an old digital camera hanging off of it. It makes sense for me because I actually use the phone as my primary digital camera. If you have a different phone or want something different, you can go and buy cell phone accessories such as a new faceplate, keypad, or a "bling kit." Whatever it takes to make your phone look the way you want.

Is The VoIP Market Growing?

2008-05-26T14:38:00.000-07:00

The folks over at the VoIP Supply blog have asked a rather important question--at least for a service provider such as voip.com--is the VoIP industry growing or shrinking? The numbers show some pretty clear trends:

Number of landlines are decreasing: The three biggest local exchange carriers--AT&T, Verizon and Qwest—have lost 17.3 million residential telephone lines in 2007.
Number of subscribers to telephony provided by cable company is rising: The number of net adds as reported by the cable companies over the past two quarters is trending upward.

Of course, voice over IP is not the only thing driving landline defections. Mobile telephony is also on the rise as well. Reports are that as teens are turning into 20-somethings and moving out on their own, getting a landline is just not something they consider anymore. Their mobile phone is their only phone.

So what does all this mean for independent providers like voip.com? It means that one can't focus on just replacing the conventional landline, but provide service that can be useful anywhere. voip.com does exactly that by providing the following features:

Softphone: Maybe your mobile phone needs a charge or doesn't have any signal. A softphone allows you to make a call from your computer to the regular phone network. All of voip.com's plans includes this feature at no extra cost, or you can purchase it as a standalone feature.
VoIP calls from any phone: Using the web-based calling features of voip.com--also available with any plan at no extra cost--you can make a call over VoIP using any telephone, even a landline!
VoIP-enabling your mobile: voip.com offers an add-on service that gives your mobile phone a second telephone number and makes it possible to make cheaper international calls.

And, of course, all of this is available for cheaper than your cable company will charge for the privilege, even at their "temporarily" discounted prices.

How Many Calls Over A WiFi Access Point?

2008-05-25T13:31:00.000-07:00

A couple of years ago, a friend of mine wrote an article that answers the question: how many voice over IP calls can you realistically have over a standard WiFi access point? The answer actually depends on a number of factors, and the article can give you an answer depending on the exact deployment. Here are the factors that affect these numbers:

Shared Bandwidth: Unlike an Ethernet switch, WiFi is more like an Ethernet hub. In particular, that means all users of a given WiFi access point share bandwidth. With an older 802.11b WiFi access point, each user is effectively sharing 11mb (really 5.5mb as the 11mb accounts for both directions). 802.11g and 802.11a offer a bit more bandwidth, and the 802.11n specification offers even more.

Codec Choice: How the call is encoded makes a big difference in the amount of bandwidth the call takes. It not only affects how good the sound is, but it affects how much data is transmitted.

Effective Bandwidth: Partially because of the shared bandwidth situation, partially because of the fact that WiFi uses unlicensed spectrum and thus is subject to interference, and because 802.11g and 802.11n offer backward compatibility modes, the bandwidth that is available for all clients can fluctuate radically. It is possible for an older device to effectively reduce the throughput for the entire network by attempting to connect--if the access point is configured to allow it!

Certainly in a home environment, unless you have a bandwidth hog in your midst, or serious interference issues, you're unlikely to run into any serious problems. The upper-limit even for the old 802.11b WiFi access points is 23 concurrent connections. Certainly one or two WiFi phones--or calls that happen on a WiFi-enabled laptop--aren't going to break the bank.

Even a small business should not have too many issues with this. These issues generally pertain to larger deployments in enterprise environments where there many more users per square inch. Unfortunately, there are no easy--or cheap--answers to these questions.

Do Area Codes Really Matter Anymore?

2008-05-24T13:23:00.000-07:00

About 9 months ago, I moved from the 360 area code to the 253 area code. It meant a lot of changes for our household. Every aspect of our utilities and fixed telecommunications changed. With the exception of gas service, every connection was with a different, unrelated company from the one before. It also meant a new fixed line number for the house.

The one thing neither of changed was our mobile numbers. Enough people had our respective mobile numbers that it would have been more of a pain to change it than to simply leave it alone. The mobile operator, quite frankly, doesn't care where we are. The same thing is true at voip.com. We don't care where you are in the country, you can have a number in any location you want. Just ask and chances are, we can give you a number there or in a nearby town

Given that we opted for unlimited long distance for our home telephone, the fact that it is "long distance" to call our mobile phones from home doesn't even enter our consciousness. It's long distance for other people in the local area to call our mobile phone, but they too either have unlimited long distance or the minutes are cheap enough as to not be a concern.

So why do we have area codes, still? It's definitely part of the Ma Bell legacy, and for some, it is an important indicator of location. Despite the fact that services like voip.com erase the concept of domestic long distance from your thinking, there are still people out there that use the legacy telcos for their voice service--and don't have unlimited long distance. It's the reason voip.com offers the ability to have numbers in most any part of the country.

7 Digit Versus 10 Digit Dialing

2008-05-23T13:40:00.000-07:00

7 digits versus 10 digits. How can three little digits be so problematic? When you're trying to write dial plans, of course!

A traditional telco Central Office only has to worry about crafting a dial plan for a specific community. For example, in the Central Office my landline connects to, it's possible for me to dial--via 10 digit dialing--two different area codes: 253 and 360. Other area codes would be considered "long distance."

On a VoIP analog terminal adapter or IP phone, there are four possible types of dial plans you could do for North America. Assume all dial plans below also permit 11 digit dialing, X11, and 011 for international calls. The inter-digit timeout--the time allowed between button presses on your touch tone keypad--is 4 seconds.

The dial plans are:

7 Digit Dialing Required: If the first digit is not one or zero, the VoIP device will expect 6 more digits to be dialed before the call is connected.
10 Digit Dialing Required: If the first digit is not one or zero, the VoIP device will expect 9 more digits to be dialed before the call is connected,
10 Digit Dialing with 7 Digits Permitted: If the first digit is not one or zero, if you dial 6 more digits and wait for the inter-digit timeout to expire (4 seconds), the call will be connected. Otherwise, if you dial 10 digits in total, the call will be connected. This is how voip.com handles both 7 and 10-digit dialing.
7 Digit Dialing with Smart 10 Digit Dialing: In areas where 7 and 10 digit dialing is permitted, in reality, only a few area codes can be dialed with 10 digits, others will require 11. In my example above, only 253 and 360 can potentially be dialed 10 digits. If the first three digits I dial are either 360 or 253, expect 7 more digits. Otherwise, assume only 7 digits will be dialed.

While the last method is perhaps the most clever, it creates the most overhead in terms of management.

What's Your Dial Plan?

2008-05-22T13:17:00.000-07:00

When you dial a telephone number, you probably don't think about it too much. You know that as long as you dial a valid number, the call will go through and connect you to your destination. However, the network has to take what you dialed and do something with it. What it does depends on what you dialed.

If you use an analog telephone adapter or an IP telephone, it is important that they emulate--as much as possible--the traditional telephony experience. Unlike in a traditional telephony environment, where the endpoints don't actually know anything about how to dial telephone numbers, VoIP-enabled endpoints do. In fact, they need to know in order to do their job of emulating the traditional telephony experience.

Dial plans for VoIP devices are simply rules that tell the VoIP device when it should considered the dialed number complete and ready to attempt to connect. It also does some gross-level filtering to ensure that the numbers dialed are a valid phone number.

For example, if you dialed 031795443 on a North American dialing plan, that would be considered an invalid number. The VoIP device would likely issue a reorder tone when it saw the first three being dialed as the only digit valid after dialing a zero is a one (as in 011 for an international call).

The other reason for needing to know what's valid is so that the call can be connected as quickly as possible. For example, when I dial 911, or any other X11 number for that matter, it needs to know to send those digits NOW! If I dial 1 as the first digit, the VoIP device should expect 10 more digits to be dialed before attempting to connect the call.

Where it gets tricky is supporting 7 versus 10 digit dialing, which we will get into next time.

How Quickly Calls Are Connected

2008-05-21T14:00:00.000-07:00

Hunting around on the Bell Memorial site, I found a recording of a typical long distance call from 1949. The call originated from Los Angeles and being made to Murphy, Idaho. Granted, it's an excerpt from the radio version of Dragnet, but given how Jack Webb was a stickler for getting the details right, I have no reason to believe this call wasn't a representative sample of long distance calling of the day.

What I like about this audio clip is that you get to hear how the call was manually routed from one place to another. There were a number of human operators involved in the process. You could hear the entire routing process, from initial call to a pickup at the other end.

So how long did it take before the call was connected? Almost 2 minutes. There was even an offer by the operator to call him back once the call was connected! That is simply unheard of in this day and age, but it was very common with long distance calls back in the late 1940s.

Why were manual operators needed? Because even the automated switches of the day were only used to process local calls. Long distance calls needed help from manual operators to, quite literally, connect a series of cords between the caller and the recipient. Because there was no direct route between Los Angeles and Murphy, Idaho, it required a series of operators to be involved to cross-connect circuits so the two parties could communicate.

Today, calling long distance is as quick--and inexpensive--as calling down the street. Calls are routed in just a few seconds--automatically. Even International calls are routed with only a few seconds delay! And with voip.com's low rates, you can call a lot more often than you did in the older days!

How We Dial Phone Numbers In The U.S.

2008-05-20T13:00:00.000-07:00

Surprisingly, after all these years, we still do not have a consistent method for dialing telephone numbers in every U.S. location. In some areas, you need 7 digits, in others, you need 10 or 11 digits. Why can't we be the same?

Remember that in the last article, I talked about area code splits and overlays. In areas where overlay codes exist, 10 digit dialing is mandatory. In areas where there isn't overlay codes, 7 digit dialing is usually ok. 10 digit dialing may be allowed in these areas--particularly if the areas are preparing for overlay codes.

And then, of course, there's 11 digit dialing--dialing a 1 plus the area code and number. The 1 historically signified dialing long distance, which is why the first digit of either an area code or a prefix cannot be a zero or a one. In some areas--San Francisco Bay Area comes to mind--you have to dial 11 digits if you're calling a different area code even if the call ends up being a local call.

Back when I was a kid in the San Francisco Bay Area, I would occasionally call numbers that were long distance, but within the same area code. I had to dial a 1 first so that I knew--and the system knew--I was dialing long distance. Now the 1 is dropped from calls within the same area code--even if the call is long distance, and yes, I've unknowingly been billed for these calls!

Of course with voip.com, you don't have to worry about where a call is long distance or not--calls anywhere in the U.S., Canada, and Puerto Rico are included! Also, voip.com allows you to dial your numbers however you want: 7 digit, 10 digit, or 11 digit. Just dial as normal, and your call will connect.

Area Code Splits and Overlays

2008-05-19T13:00:00.000-07:00

Last time, I got into how telephone numbers evolved. This time around, I'm going to get into a perennial problem as telephone usage increased: area code splits.

Reviewing from last time, we settled on 7 digit telephone numbers back in the 1960s. The first three digits of that number are considered the exchange. The first digit of the phone number can be 2 thru 9, the other two digits in the exchange can be anything.

There are some exceptions. X11 refers to special service numbers (211 used to be how you reached long distance, 411 for Directory Assistance, 911 for Emergency Services), thus they cannot be telephone prefixes. We also exclude the 555 exchange for a variety of reasons I will get into in a future post.

With that in mind, there are 791 possible exchanges in a given area code, or 7.91 million possible phone numbers. With the proliferation of phone lines in their various forms, the phone companies have had to implement either area code splits or overlays.

An area code split is taking a large area code and splitting it up, giving a new area code to another part of that area. For example, all of Washington State used to have the area code 206. In 1957, the Eastern half gained the area code 509. 206 has split again two other times since then, largely around geographical boundaries.

The other strategy that's been employed--particularly in larger metropolitan areas--is the idea of an area code overlay. This means there are two or more area codes co-exist in the same area. For example, the city of Atlanta has two area codes: 404 and 770.

The main reason overlay codes are considered problematic is that they require changes in dialing patterns. Dialing patterns, as you might have guessed, is a whole different article.

Telephone Exchanges and Numbers

2008-05-18T13:00:00.000-07:00

One of the fascinating things I've uncovered digging around in Ma Bell's history is how telephone numbers have changed over the years. Up until the 1950s, numbers could be anything up to 6 digits long, depending on where you live. This didn't matter so much since, in some cases, it was not possible to directly dial, a human operator had to connect the line.

The other funny thing phone numbers had were these "exchange" names. Things like PEnnsylvania, GRamercy, DUpont. Notice that the first couple of letters were capitalized. This was to indicate which "letters" to dial on your rotary dial, which of course corresponded to numbers.

As exchange names were based on pronounceable names, it meant that some of the possible numbers ones could use for telephone numbers weren't usable. In particular, it eliminated the use of one or zero as the second digit in the exchange number. Even after converting to 7 digit telephone numbers starting in the early 1960s, it became necessary to institute all number calling.

All number calling phased in the replacement of the exchange names with numbers, meaning everyone got a 7 digit telephone number. That's what they had all along, but they lost the name that went with it. It was apparently fought against in the cities where the exchange names gave a sense of community.

Due to the growth of the phone system, they also had to change a rule about area codes. Originally, they were 3 digits of the following form: first digit could not be a one or zero, second digit had to be either a zero or one, and the last digit could not be a one or zero. Now the second and third digit can be anything!

Even with all these changes to the allowable telephone numbers, there were some other challenges we'll cover next time.

What's VoIP Like On A T1?

2008-05-17T13:00:00.000-07:00

Several months ago, I was lucky enough to have three broadband lines coming into my house--cable Internet, DSL and a Covad T1. The Covad T1 was for their blogger relations program that I was in at the time. Pity I moved out of their service footprint, because it's difficult to go back to DSL and cable once you've had a taste of a T1.

Nominally speaking, DSL and Cable can be faster than a T1, which tops out at 1.544 megabits per second upstream and downstream. However, what a T1 lacks in raw speed--particularly on the downstream--it more than makes up for in latency. A T1 provides a consistent, low-latency connection to the Internet--something that's critical for high-quality VoIP calls.

When I had my Covad T1, given that I was the only one using it, VoIP was a dream. Many of the problems I had on my cable and DSL at the time--random increases in latency, jitter, and dropped packets--simply went away. I experienced the true power of voice over IP. And video? Even better. I did some tests with a couple of different video calling services over the Covad T1 and it worked absolutely fabulously.

Is a T1 shared? A dedicated like between you and the telco central office. You're sharing with everyone else at the Central Office once you're there, but a telco central office has enough bandwidth. Even so, you're much farther up the food chain than you are with a cable headend or a remote DSLAM, which are often connected with far less bandwidth.

I am lucky that my T1 was paid for as part of my participation in this blogger relations programs, because the T1 would have cost nearly $600 a month, and it varies greatly on location. When cable or DSL costs less than a tenth of that, and you're a consumer, and you tend to get more bandwidth with DSL or Cable, it's obvious which choice you'll make.

In all honesty, in my current house, both DSL and Cable provide very good voice over IP service. Your house is probably in the same boat. A T1 would likely be overkill, but in specialized applications, it may be just the thing you need.

Cable? DSL? It's All Shared, Part 2

2008-05-16T13:00:00.000-07:00

In my last post, we were discussing the difference between cable Internet and DSL provided by a local exchange carriers. Cable has a couple of places where the bottleneck can occur: in the neighborhood due to the shared bandwidth, and at the headend where the cable signals are turned over the Internet.

DSL is deployed a bit differently. Although people old enough to remember party lines might disagree--and I remember them as a child--but there is a dedicated pair of copper between you and the central office. If you happen to be close enough to a central office with a DSL access multiplexer (DSLAM)--18,000 feet by wire--you're very lucky and might be able to get the best speeds DSL has to offer.

However, with suburbia continuing to spread, people have gotten farther and farther away from the central offices. Voice is relatively easy to extend past 18,000 feet, DSL requires more specialized equipment than voice. Remote DSLAMs became available, making it possible to deploy DSL deeper and deeper into the neighborhoods.

Up until about two years ago, my previous house was unable to get DSL because of the lack of a DSLAM in my neighborhood. Once that changed, I was able to get DSL--at a pokey 1.5 megabits down and 864 kilobytes up. Even two years ago, cable modems were faster in my neighborhood.

While DSL could do better--and I was close enough to the DSLAM that I could do it--the main problem was that the DSLAM was connected to the outside world by multiple T1 lines versus being fed by a fiber link. This meant that the available bandwidth by all the people on my DSLAM was limited by those T1 lines--how many T1s, I don't know, but each one gives you 1.544mb/s of symmetrical bandwidth. I don't know how many subscribers they had hooked up to that DSLAM, but I'm sure it didn't take many before that DSLAM didn't have enough bandwidth!

So when the DSL folks tell you that your bandwidth isn't shared, remember that depending on how it's deployed in your neighborhood, it could be even worse than the sharing that goes on with cable!

Cable? DSL? It's All Shared, Part 1

2008-05-15T13:00:00.000-07:00

Chances are before you got VoIP, you got a broadband connection. And chances are, you had to choose: cable or DSL? Which do you choose?

This commercial from Pacific Bell in the 1990s pokes fun at the fact that cable is a shared line versus DSL, which is not, or so they say:

In some respects, this Pacific Bell commercial is correct: cable is a shared line. However, what they aren't entirely honest on is the fact that DSL is also shared. The sharing just happens at a different point in the network.

Cable TV lines run from house to house to house. Depending on the neighborhood, the lines go in a sort of daisy chain, or it can be a star topology. No matter how the local, physical plant is laid out, it ultimately all comes from or goes to the headend, or the cable modem termination system (CMTS). The CMTS is responsible for routing traffic between the cable modems and the larger Internet.

Each cable modem in a network is given a time slice during which they can speak using a technique called time division multiple access (TDMA), so they do not all try and speak at once. They are all speaking to--and can only be heard by--the CMTS. For packets coming the other way, there's only one speaker--the headend. There is only one intended recipient for a given packet, but the CMTS broadcasts that data to all the cable modems. Only the one it is intended for forwards the packet onward to the subscriber.

There are a couple of different bottlenecks here: the "shared" bandwidth to the CMTS--particularly in larger neighborhoods--and the bandwidth the CMTS has to the larger Internet. Which ones causes cable Internet slowdown? Depends on the area, but given the amount of bandwidth available even in a shared network, I'd be willing to bet the CMTS is having issues.

So is DSL the way to go? We'll talk about that next time.

Video Transmission In 1927

2008-05-14T13:00:00.000-07:00

The Bell System was doing a lot more than telephones. That's part of the reason they experienced anti-trust and breakup orders twice in its history, once in 1956 and again in 1984 when the Bell System was effectively broken up and declared dead.

One thing they were doing in the 1920s was experiments with transmitting video. This is before the television was invented, so they had to come up with ways of both capturing and transmitting a video image--synchronized with audio. Not a particularly easy feat in those days, given the available technology.

At the end of the day, the folks at Bell Labs had to convert the video and audio into electrical impulses, transmit them some distance--between Washington D.C. and New York, in the initial demonstration--and reconstruct it and display it on the other end.

The system devices by Bell Labs was electro-mechanical in nature. Specifically, it was a spinning disc with 50 small holes arranged in a spiral. This served to focus a bright light source into a narrow beam and scan the subject 16 times per second. A photoelectric cell received the light reflected off the subject and converted the light into electrical signals, which were then sent over the wire to their destination.

At the receiving end, the electrical signals went to a neon globe tube, which produced a light that changed rapidly with the fluctuation of the electrical impulses. A rapidly spinning disc similar to that used on the sending end was placed between the tube and the viewer. The disc on the receiving end focused a narrow beam to a succession of points 16 times a second.

In order for the sender and receiver to be synchronized, the video was transmitted over one line, a synchronization signal was sent over a second line, and the audio portion was on a third.

The result? A grainy, black-and-white 50-line image about 2 inches by 2.5 inches shown at 16 frames per second. To put that in perspective, standard definition television is 525 lines of resolution shown at 30 frames per second. High definition is either 720 lines of resolution or 1080 lines of resolution, depending on which mode the program is being displayed in.

The initial demonstration in 1927 was one way. By 1929, they had figured out how to transmit video in color. By 1930, there was two-way video phone service between AT&T and Bell Labs respective headquarters.

These days, transmitting video is a lot easier. Heck, you can do it using your mobile phone, complete with live streaming. Two-way video communication can happen much easier--and with much less equipment--than it required in 1927. And you only need one line to do it--your Internet connection.

Can You Still Get An Operator?

2008-05-13T13:00:00.000-07:00

A seeming "relic" of times gone by is the general-purpose operator, reached by dialing zero. I'm willing to bet that most people under the age of 25 probably have no idea that it was even possible, much less what the operator does.

Operators were necessary to complete long distance calls prior to the wide deployment of systems that permitted direct dialing to many destinations. Operators were also needed to make collect calls--calls where the person receiving the call must pay, if they accept. Operators also served as the de-facto emergency response system back in the days before 911 service was available.

With the wide deployment of direct dialing to almost any location worldwide, overall more economical calling costs, and alternatives for almost all services provided by an operator, it doesn't seem that we'd use an operator much anymore. I'd be surprised if it even still worked.

I tried calling zero. From three different lines. Both my land line and mobile phones, dialing zero actually works. In one case I reached a live operator right away. In the other cases, I reached an interactive voice response system that ultimately suggested I dial a number so that I can make a collect call and/or offered me the opportunity to speak to a live operator.

I talked with the live operator briefly as well as a customer service representative at my land line provider. I asked the question "so what do operators do these days?" Surprisingly, the same tasks they've historically done. The technology the operators use is more advanced than it was back in the old days, but the services are more or less the same.

A word of warning: voip.com's terms and conditions state that no operator or operator-assisted calling will be available from a voip.com line. For most everyone I know, this would be a non-issue.

Back Before There Was 911

2008-05-12T13:00:00.000-07:00

Back before there was a 911 system, the way you got help when you need the police or fire was to dial zero for the operator. Of course, back in the 1960s when the particular movie this still was taken from was shot, human operators were required to complete many types of calls and were located in the communities that they served. Traditional 911 service was simply one of many functions local operators performed.

In the 1950s, various parties were pushing for a single number that one could dial nationwide for emergency services. In 1968, AT&T decided on the number 911, which is difficult to dial accidently on a rotary phone, and fit nicely into the pattern of other service numbers (e.g. 211 for long distance operator, 411 for directory assistance, 611 for repair).

Even though 911 service was proposed in 1968, wide deployment of the service was largely delayed in the U.S. by the fact that the operator was still there and still worked. Once AT&T was officially broken up by anti-trust actions in 1984, operator service as we knew it largely disappeared. This created a real need for a dedicated 911 service, though even today, not every corner of the United States and Canada has 911 service!

Surprisingly, dialing zero works on a landline and, even more surprising, from my AT&T mobile phone! On my AT&T phone, the service primarily exists for dialing collect calls. On my land line, I was greeted with a voice menu that allowed me to essentially do the same thing, but offered prompts in English or Spanish. You could speak to an operator, if you wanted to.

Like the operator service of old, 911 service needs to be local to a community. Each community ends up being responsible for implementing it's own 911 service. Each subscriber located within a specific community must pay a monthly fee as part of their phone bill to fund local 911 services. This is why voip.com charges $1.50 per month on applicable monthly rate plans to cover these costs.

Telephony And Telegraphy

2008-05-11T13:00:00.000-07:00

This short movie from 1946 explains the opportunities you might have had back then as someone who worked in "wire" communications--either telephone or telegraphy:

The jobs are indeed fairly similar. They involve wires, communication, routing messages, billing customers, and the like. The main difference is the product: one delivers a voice product, the other involves a data product.

Telegraphy predates telephony by at least a century. While electrical telegraphs did not come into existence until the early part of the 19th century, optical telegraphs were used in the late 18th century for message delivery. If you count smoke signals or hydraulic telegraphs, telegraphy goes back much further!

Telegraphy had a long head start in terms of development, but it also has the advantage that it was possible to take the written word and communicate it via a number of different means. Telephony, however, didn't have a feasible way to happen prior to the invention of an electronic system to transmit the human voice in the late 19th century.

In the early part of the 20th century, both telephony and telegraphy had similar problems: the delivery of their product required a lot of people. While automated switching equipment made it possible to make local calls without the assistance of an operator, long distance or other specials services required a human operator.

In the case of telegraphy, people were needed to sort, assemble, and ultimately deliver the telegrams to their proper destination. They also needed to figure out how to send more messages through the same set of transmission lines.

Back in the 1940s, you could have easily had a long career in either field. Today, while telephone is still going strong, telegraphy has been largely replaced by things like the Internet and SMS on mobile phones. You can still send telegrams, believe it or not, though the biggest name in telegraphy service, Western Union, stopped providing the service in January 2006.

Touch Tones and VoIP

2008-05-10T00:00:00.000-07:00

A standard analog telephone line is capable of transmitting all kinds of things, ranging from the human voice to music to data--think fax machines and analog models. The Bell System's focus on audio quality early on in the development of the phone system made this possible.

In the 1950s, AT&T was using specific tones--multifrequency tones--on telephone lines in order to route calls between switching facilities. This practice of in-band signaling was used well into the 1980s, but has since been replaced with much more secure out-of-band signaling.

The Bell System created a derivative system for use by telephone customers called dual-tone multifrequency, or DTMF. They began marketing this service under the trade name Touch-Tone in 1963. This allowed people to push buttons to dial their phone instead of using a rotary dial.

While the touch tone phone could be used to dial a telephone number, it could also be used to signal the remote end of the call in some way-the reason they created the * and # keys. They also created explicit A, B, C, and D keys, but they were never widely used.

While not entirely common back in the 1960s, using your touch tone telephone to navigate a telephone tree is a fairly common occurrence today. Therefore, if your using a VoIP telephone service, touch tone service had better work.

On VoIP, you can signal touch tones one of two-ways: in-band or out-of-band. In-band signaling only works with G.711 and even so, it's generally not recommended. The preferred method is therefore out-of-band signaling for touch tones, and is the only method supported with codecs like G.729.

There are two standards for DTMF signaling out-of-band in VoIP: RFC 2833, which is the common method, and SIP INFO, which can also signal this information. In both cases, they transmit when a particular touch tone has been activated and when the touch tone has been deactivated.

The challenge with both methods is correctly indicating when a particular button has been pressed and, more importantly, when it has been released. Both RFC 2833 and SIP INFO take this into account, but use different methods. RFC 2833 is the most common method and seems to be a bit more reliable than SIP INFO, based on my experience.

G.729 versus G.711

2008-05-09T13:00:00.000-07:00

In the last article, we discussed the G.711 codec, which is often used to give you "toll quality" calling. There are situations where you do not have the bandwidth for G.711 calling. Perhaps you have a restricted upstream speeds on your Internet connection or you need more bandwidth for other applications.

Another common choice for encoding your voice into data is the G.729 codec. Unlike G.711, it is able to transmit voice very efficiently--at about 32 kilobits per second versus 87 kilobits per second for G.711. Unlike G.711, however, the human voice is synthesized by something called a vocoder.

The vocoder uses both a tone generator, a white noise generator, and a filter that shapes the sound as the throat, mouth, tongue, lips, and nasal cavities do. By itself, the vocoder produces intelligible speech, but it sounds like a robot is speaking.

Since that's clearly unacceptable, G.729 also uses samples of the actual human speech to set the vocoder settings properly. It also compares the actual voice from the synthetic voice to come up with a "code." The code along with the vocoder settings are what's sent to the remote end. The remote end takes the code and vocoder settings and plays the sound.

The result of all this work is voice quality that sounds similar to G.711 but at almost a third of the bandwidth requirements. It takes a lot of processing cycles to do all this, too, which is why some voice over IP gear limit the number of streams it is capable of processing G.729 for.

There are some challenges with G.729. While it works great for voice communication, it doesn't do very well for things like faxing, data, and transmitting touch tones. This is because G.729 is designed specifically to translate voice, not data.

So if G.729 doesn't support touch tones, how is it you can do touch tones on a VoIP line? We'll explain that next time.