daverea.com

Intro

Ever since the mainstream voice-over-IP (voip) services started rolling out their products, I’d been intrigued with the prospect of trading in a twisted-pair copper telephone connection for a spiffy new Internet-enabled phone line. However, I received my Internet connection via DSL, so adding a net-phone would have been an exercise in redundancy – albeit a fun geeky adventure at the same time!

I’m glad I waited, because the ensuing years have given voip technologies a chance to mature, and have created a competitive landscape among hardware and service providers that can really save you some substantial coin.

A few months ago, we decided to investigate switching from a phone+Internet package from the phone company to a cable+Internet package from the local cable provider. Fortunately for my geeky side, the only way this would end up saving us money is if we opted out of the cable company’s Internet phone offering, and rolled our own solution instead.

After doing a lot of research, and spending a lot of time cruising around the Voip-Info wiki, I proposed a solution: Purchase our own voip analog telephone adapter, sign on with a bulk provider of voip minutes, and give it a try before shutting off our trusty old copper phone line.

The service

The most familiar voip services out there offer monthly service plans between $10 and $30 per month, including some quantity of minutes and a certain level of long-distance service. You rent an analog telephone adapter (ATA) from them as part of this fee, and you usually receive all the same services you would from a traditional phone company (caller ID, voice mail, call waiting, etc).

Going with this route wouldn’t have saved us any money, since we do very little long distance calling, and those long distance calls we do make can usually be placed via cell phone or our dial-in access long-distance provider. So instead, I checked out the Cheapest service providers page at Voip-Info.org, and found a few gems:

Junction Networks was the first place I checked out. They have great per-minute rates, no monthly fees for outgoing calls, and adding a local number (or “DID” for direct-inward-dial) is under two clams per month. Unfortunately, they don’t offer 911 service, and it costs $50 to port your existing number over to them.

SellVoip was the next find. They looked more promising – even better per-minute rates and per-month charges for a local phone number, and porting your existing number was only $8. But still no 911! I started thinking this wouldn’t be a problem – we could just use our cell phones for 911 service – but if we have guests or someone housesitting who isn’t familiar with the system, I wouldn’t want them to be stuck without 911.

Vitelity proved to be the winner. They have the same great rates as SellVoip, a nicer user interface, and they offer both e911 service and a voicemail system that e-mails you your messages as WAV files! What more could a geek want?

The analog telephone adapter (ATA)

After reading about the various protocols out there to carry voip traffic, I settled on using the “new kid on the block”: the IAX protocol. The main reason for this decision was because IAX is very good at traversing the NAT firewalls that are commonly found in home Internet routers and wireless routers, and doesn’t require any fiddling with port forwarding and finicky STUN servers. A big advantage of this is that it allows you to tuck as many ATAs behind your NAT router as you want, so adding lines doesn’t require port mangling.

Update 2006-11-05 – As it turns out, some of the features of IAX ATAs are only usable if you have a local IAX server, such as Asterisk. Unless you’re a geek of formidable fortitude, you probably won’t want to set that up. So, despite the benefits of IAX, SIP might be a better protocol to use if you don’t want to set up a local PBX.

There are only a handful of IAX-capable ATAs on the market, so selecting was relatively easy. I went with the GlobeTelX IAD-200X (made by GlobeTel) for a variety of reasons. For one thing, it offered the best bang-for-the-buck with two lines and a built-in NAT router. It’s also nice to know that there’s a US-based, English-speaking support operation in Florida.

I bought my IAD-200X from The Voip Connection and it arrived well-packed and on-time a week later. Upon opening the box, I was delighted to see that it included a non-wall-wart (desktop-style) wide-input-range switching power supply, as well as beefy, well-constructed plug adapters for EU, UK and Austrailian power jacks. I was a little less-than-delighted to find that it didn’t include a user’s manual or CD-ROM containing one, but a quick visit to The Voip Connection’s web site netted me a digital copy. (Update 2006-11-05 – TheVoipConnection has since also published the installation manual for IAD-200X, as well.)

When I initially powered-up the ATA, it grabbed an IP address from my routing server via DHCP immediately, and I was able to navigate to the management web page. Unfortunately, the password wasn’t set to the default as prescribed in the user’s manual. A quick call to The Voip Connection fixed that problem, and later I found out that their online forum also includes a sticky posting containing the password for those who receive locked ATAs.

Setting up the ATA proved challenging, since neither the web GUI or manual provide much description for what the different configuration parameters do. After connecting an old phone to the telephone port, I spent about half a day trying to get the ATA to place a call to my existing phone line. No luck – every time I tried, I just got a fast-busy signal.

Upon seeing that Junction Networks offers 24×7 tech support, I tried giving them a call. The tech was able to determine that the ’200X was indeed talking to their server, but that something was wrong in the voip configuration. Flying blind (he had never heard of an IAX-capable ATA!), I sent him some screenshots of the configuration web site and we tried a few combinations of settings – and after about 10 minutes of tweaking, we found a configuration that worked like a charm.

So far, I’ve been able to get the ’200X working with all three of the voip providers listed above, and all have high audio quality and a delay that’s barely (if ever) perceptible. It’s certainly shorter than the tolerable delay of most terrestrial cell phones. I haven’t had any problems with echos, a big concern of mine since I’d seen so many people posting of echo woes in various voip forums.

Setting up a new incoming number with Vitelity was a snap – just a few clicks and checkboxes, and I was able to call the ATA from my old telephone line. The call quality was the same, regardless of whether the call was incoming or outgoing (see below). Of course, caller-ID is another story – depending on your local phone company, the caller-ID info you enter into the ATA may or may not be displayed properly. In my case, entering my new local number into the ATA resulted in the previous owner’s name showing up on my caller-ID+name local phone. Different ATAs and service providers handle this differently, and I’m going to have to wait to talk to Vitelity’s tech support about it.

My only major complaint about the IAD-200X ATA, so far, is that no explicit “prepend” configuration option exists for 7-digit local numbers. Since voip carriers are location-independent, you have to dial 1 + area-code + number for every call. I don’t really want to dial the 1 + area-code for local calls here, so I’m working on finding a way to have the ATA automatically prepend that string of digits to calls where only seven numbers are dialed. I’ll update this review if I make any progress!

Update 2006-11-05 – After discussing my perplexing prepending puzzler with TheVoipConnection’s tech support, we determined that there’s no way to have the IAD-200X automatically prepend your local area code before 7-digit numbers. What’s more, there’s no way for the carriers to do it either – I checked with all three. So, I bit the bullet, sat down with my friend Jer and set up an Asterisk server. My router/firewall box is filling this role, and even though it’s only powered by a 1.8GHz Celeron, it handles the task, plus traffic shaping (see below) nicely. The prepending is set up in the Asterisk dialplan (extensions.conf) and automatically prepends my area code to any 7-digit numbers that are dialed.

Another complaint I had is that there is no documentation on how to get the debug or logging functions of the ATA working. In the configuration web interface, a “server” address for logging and debug information can be entered – but no information is given on what sort of collection service must be running on that server! It would be cool if it were just an e-mail address, but there’s really no indication given. Again, if I learn anything about this interface, I’ll update this review.

All in all, based on two days’ worth of use, the GlobeTelX IAD-200X ATA seems to be a solid piece of hardware that performs well and isn’t completely impossible to set up. With that in mind, it’s definitely geared toward power-users, as the documentation is sparse and the configuration options are plentiful. As always, there’s some room for improvement, but with this ATA’s $109 pricetag, it’s still a heck of a bargain.

Traffic shaping (added 2006-11-05)

When I first started testing the IAD-200X’s call quality, I did so with no other applications consuming network bandwidth. Later on, however, I tried placing a call with a few (bandwidth-throttled at 4Kb/s) BitTorrent connections running. While the incoming audio quality was not affected (naturally), the outgoing audio developed severe choppyness and delay (upwards of 3-4 seconds). This wouldn’t do!

By the time I discovered this, I was already running a local Asterisk PBX. Since the VoIP traffic bound for my carrier is generated on that machine by Asterisk (after software transcoding), some method of shaping the traffic originating on my LAN was necessary.

Since I was already using a manually-configured (bleck!) iptables setup to route traffic between my cable modem and LAN PCs, I decided to take my firewall to the next level with Shorewall. After a painless install (thank you, Gentoo!) I started by using the Shorewall documentation to get basic NAT routing working again. Following the guide and making my own minor tweaks, this only took about a half-hour.

The challenging part was prioritizing VoIP traffic and de-prioritizing peer-to-peer type traffic. First, I had to get the kernel configured for packet marking and traffic control, the sum of which is casually referred to as traffic “shaping”. Then, I had to get Shorewall configured to recognize the different types of packets, and to allot bandwidth and priority between them according to their type marking. Shorewall provides decent documentation in this vein, but I still ended up going to the shorewall-users mailing list for assistance. After a very helpful thread with another Shorewall user, we managed to get my tcrules.conf file correct – and viola! I had a carpool lane for VoIP traffic!

If you are considering rolling your own VoIP system, be sure you have a router that performs seamless QoS, or otherwise allows traffic prioritization on outgoing packets and connections. This will keep hair on your head, so VoIP can keep money in your wallet…