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The February 23, 2003 Issue Provided by System Dynamics Inc.
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Broadband Home Labs - Vonage DigitalVoice Broadband VoIP Service

We believe SIP will dominate digital telephony in many markets, and we've been evaluating several approaches to SIP telephony for home use. We've been using a low-cost SIP-based telephone service from Vonage for most of our phone calls during the past few months.

We've had different reactions to using the Vonage service:

  • Dave thought it was pretty good -- much better than cellular and almost as good as regular service. He experienced a few "funnies" like unexpected "network busy" tones and some calls that got cut off, but is happy to keep using it for most calls.
  • Sandy found it more annoying. Frequent clipping of words led to the tendency of two people to "step on" or talk over one another -- because they thought there had been a pause, but there really wasn't. She likes the idea of paying less for phone calls but does not use the service for critical calls or those where nuances and emotional content may be present.
  • It's clearly pretty subjective: Getting off the same phone call, Dave would think it had been fine but Sandy had found it less than satisfying.

In this article, we'll describe IP telephony and especially the role of SIP. We'll describe our experience with the Vonage service, and mention two other SIP tests we're conducting from our home. Several readers have already participated in our tests and we invite you all to call us.

IP telephony, H.323 and SIP

As many readers know, "IP telephony" or "VoIP" refers to the technologies and services for telephone services using IP protocols. These come in many forms and include creating voice connections between PCs, standard PSTN phones, and special "IP phones". Some services operate purely over the public Internet, some over managed IP networks, and some connect through "gateways" to the PSTN.

There are two main standards-based approaches to packet-switched telephony. The older is the H.323 protocol suite from the ITU and is most common in Europe. The newer is the SIP protocol suite from the IETF and is most common in North America. SIP is entirely based on IP, while H.323 has many roots in earlier PSTN protocols.

SIP is solely a signaling protocol, while H.323 includes much more. The key differences between H.323 and SIP are in the methods used for signaling: locating users, setting up calls between them, and then tearing the calls down. Once a call is in progress, voice (and possibly also video) are encoded with a common set of media compression protocols.

IP telephony is increasingly used in enterprises around the world; systems based on H.323 and SIP are available in many markets. In consumer markets, simple PC-to-PC IP telephony has been available for many years. In the Windows world, Microsoft NetMeeting has always been based on H.323. The newer Windows Messenger is based on SIP. These have mostly been used by enterprises and to a limited extent by more technical users.

With the rapid growth of broadband users, VoIP is starting to reach the mass market.

The Vonage DigitalVoice Service

Vonage is a privately-held company founded in early 2001. Its DigitalVoice service is currently available in many major US markets and is expanding each month. The basic service includes unlimited local and regional calling, with 500 long-distance minutes anywhere in the US and Canada, for $25.99/month; the premium service offers unlimited long distance in the US and Canada for $39.99. Vonage says they now have close to 15,000 customers and should have 100,000 at the end of this year.

Cisco ATA186 phone adapter --> Click for larger pictureThe Vonage customer uses a standard analog telephone to place and receive phone calls. When we signed up to test the service, Vonage sent us a Cisco ATA 186 Analog Telephone Adaptor -- "a handset-to-Ethernet adaptor that turns traditional telephone devices into IP devices".

The ATA 186 is an example of what is called a "multimedia terminal adapter" (MTA). In the home, the MTA is connected to a broadband router and a standard phone is plugged into the MTA. No PC is used to make phone calls - the MTA does all the work. The ATA 186 supports both H.323 and SIP; Vonage uses SIP.

4-line phone, using Vonage --> Click for larger pictureWe set up and tested the service with a single phone plugged into the ATA 186. When that seemed to be working fine, we connected the 186 into the patch panel for our telphony wiring so that the Vonage service appears as "Line 4" on all our analog multi-line phones. When we pick up a phone and select line 4, we get a dial tone from the ATA 186, rather than from the phone company. We then dial a number (we have to use 11 digits for all calls) and soon hear a phone ring at the other end. Except for having to dial a "1" before local calls, it's exactly the same as making calls on our analog lines. When we're done, we hang up as usual.

Vonage assigned us a phone number 973-447-0929 for incoming calls. When someone calls that number, our phones ring on "line 4". Again, it works just like our analog lines.

Our Evaluation

We've used DigitalVoice for both personal and business calls, local and long distance, and for calls to "800" numbers. We've used it to place most of our calls, and have received a few.

Over the Web, Vonage provides users with a log of all the calls they've made and received. It shows that over the past 30 days we've placed 60 calls and received 6, for a total of 566 minutes.

The two of us reacted somewhat differently to using DigitalVoice:

(Dave) I found it quite acceptable - not quite as good as our analog lines, but much better than our cell phones. Most calls connected without a problem, although a few got a repeated "fast busy" indicating network congestion while the same call placed on an analog line went through without a problem. On three calls, the initial voice quality was very poor and I had to hang up and place the call again - it worked fine the second time. I was cut off twice without warning in the middle of long calls. I found the voice quality very acceptable; none of the people I called noticed any difference in voice quality. A few times in long conversations, I and the person at the other end started talking at the same time, and had to start the sentences again. I have continued to use it for most of my calls though I'd still want to have an analog line for lifeline calls to "911" which aren't supported by DigitalVoice.

(Sandy) I frequently found calls made thru Vonage annoying. There often seemed to be subtle clipping of words which led myself and the other party to talk at the same time. I really like the idea of paying less for phone calls but have made the conscious decision not to use the Vonage service for critical calls or those where nuances and emotional content are important. That said, however, calls in the "emotional/critical" category are the minority of my calls.

How it Works

Setting it up

To set up the service, you first plug a phone into the ATA 186 and connect it to your broadband router through a home network. It's easy to use a phone somewhere else if you have an Ethernet network in the house (as we do). You can also use a Wi-Fi or HomePlug network, or you can plug a portable phone into the ATA 186. If you don't have a router, Vonage will sell you one at a discount.

When you connect the power adapter to the ATA, a red button starts blinking. After it stops, you pick up the phone and dial 80#. You then hang up and again wait for the button to stop blinking - while you're waiting, the ATA is activating the Vonage account. When it stops blinking, you make a phone call - this proves that everything is working. Then you use a Web browser on a PC to configure your DigitalVoice account online.

This was all very easy and worked without a hitch.

Making calls

Each time you pick up the phone, the ATA 186 gives you dial tone and you dial a phone number. The ATA then uses SIP to communicate with a Vonage server over the Internet; the Vonage server tells the ATA how to connect to the most cost-effective media gateway connected to the PSTN, and is no longer involved. The ATA connects over the Internet to the media gateway, typically located in the same city as the called party, or close by.

Vonage does not have its own network. All connections between the ATA and the selected media gateway operate over the public Internet.

There are many ways calls could be impaired with this approach - by delays over the broadband connection (cable or DSL), and especially by delays over the Internet. But our experience was that few calls were badly impaired.

Try VoIP

This is one of three SIP telephony trials we are currently working on from our home. Please visit our web site at for more information about these trials. That includes our phone numbers so you can try the SIP-based VoIP services either from analog or SIP phones.

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