Success with VoIP Depends on Many Factors

October 16, 2007

In a recent article, Robert Mitchell expressed his frustration with VoIP running on Windows. It might be Windows to blame, but it might just be a poorly written soft client, which appears to be the case since he mentioned that it crashed frequently.

Whatever the case, Mr. Mitchell is not alone with his problems. Users have faced lots of challenges with VoIP, and the success has a lot to do with, well, the whole system!

If voice quality sounds poor, it might be due to use of a lower-quality voice codec. In general, VoIP calls sounds just find using G.729, which requires a mere 8Kbps to encode and 24Kbps on the wire. G.729 should work well even if you do not have a lot of bandwidth. G.711, on the other hand, which is the standard used on PSTN, requires 64Kbps to encode and 80Kbps on the wire. Still 80Kbps is nothing, really, when you have a 5000Kbps cable connection. Or does it?

What many people forget is that when service providers sell bandwidth, you generally have a slow upload speed than a download speed. In the United States, it's quite common for a cable company, for example, to offer up to 5000Kbps down, but a mere 384Kbps up. If you are only uploading 80Kbps, then out of the 384Kbps, you are still left with 304Kbps. However, there are almost always other applications running somewhere on the network that are consuming a little bandwidth here or there. Don't forget that when you are making a VoIP call and uploading a big file at the same time, both of those applications are competing for the same limited bandwidth. It is not unusual to see file transfers consume nearly all of the available bandwidth!

One should also consider the network inside the home or enterprise. If your VoIP application is running on your laptop connected to the network using Wi-Fi, perhaps other applications on the local network are consuming bandwidth, preventing a smooth flow of voice packets onto the public Internet.

People who have had the best success with VoIP generally use ATA devices. Is it because the hardware devices are better than the PC for VoIP? Probably not. The benefit of the hardware devices is that, in many cases, the hardware can be physically placed closer to the router that connects to your service provider. The voice application inside the hardware device will, quite literally, give priority to the voice traffic over any data traffic, thereby reducing or eliminating problems where a person uploads a file and consumes all of the bandwidth.

Another common problem is the network hardware. What kind of hardware do you use in your home or office? Quite likely, you went to the store and purchased the cheapest product on the shelf and/or you took what your cable or DSL provide gave you for free. That's not always the best product for the job, especially if you need something that is robust enough to handle a continuous stream of data packets. Just like anything else, you get what you pay for. If you want a really reliable firewall and router, consider getting a small enterprise-class firewall device like the Cisco ASA 5505 (50 or 10 user licenses). That is a solid firewall platform that will both protect your network and provide you with excellent packet transmission throughput. If your wireless access point acts a little flaky, perhaps consider getting the Cisco Aironet 1100, which will provide excellent Wi-Fi service in your home or office, can sit on a table, mounted on a wall, or hung on a cubicle. We cannot stress enough how important solid hardware is for ensuring good quality VoIP functionality.

We invite readers to provide us with suggestions on other things to consider when trying to get VoIP working at home or in the office. We could update this article with such entries or append your comments to the end of this article.