VoIP: Panacea or packet-buster?

Jan. 1, 2003
Remember, being able to do something does not mean something needs to be done.

When I was asked to focus this month's column on Voice over Internet Protocol (VoIP), I was sent the following three inquiries from readers:

Q: Industry "marketeers" are saying that VoIP is not the application of the future—it's the application of the here and now. I manage a LAN with a 100-Mbit/sec backbone and 10-Mbit/sec to the desk, and a traditional PBX for voice, for 200 users. We have two Category 5e ports (one for data and one spare), and one Category 5 port (for voice) at each workstation. I feel like I'm behind the times because I haven't seriously considered using VoIP. What are the pros and cons of VoIP, and how can I determine if it's a good investment for me? Will I have to install new cabling?

A: Yes, the marketeers certainly are pushing "convergence," and tantalizing consumers with promises of lower telecommunications costs, streamlined resource management, and more-efficient use of available bandwidth.

But concerned about the quality of VoIP calls, the reliability of IP networks, and their lack of expertise in the voice-over-data deployment, most consumers who have "seriously considered using VoIP" are not buying into the spiel. Corporate technology decision-makers know from experience that data networks are not as reliable as voice networks. They have had their computers freeze or been told that the network is "down." But this rarely happens with their phones, and they intend to keep it that way.

VoIP pros: Significant cost savings over using the Public Switched Telephone Networks. Remote offices and users can bypass long-distance carriers and their per-minute usage rates and run their voice traffic over the Internet for a flat monthly Internet-access fee. Integrating voice and data network infrastructures and deploying one network that is both modular and scaleable to the needs of users can further reduce costs.

VoIP cons: On data networks, packets collide and get distorted, or even lost. But error-correction mechanisms are in place to compensate for these routine anomalies, and the millisecond delays they cause don't usually affect the applications. This is not the case on voice calls, which require consistent real-time flow of packets from one end of the network to the other. Corporate technology decision-makers believe that if they provide their users with anything less than what they have today, they will not accept it.

Return on investment: You will have to run the numbers and see if the return on investment justifies the additional burden on your network and staff. VoIP looks good if you can get it cheap from multiple vendors and have their expertise and the staff to make it work, but each case is unique.

Cabling: You would not need to install new cabling to support VoIP. The cable you have in place will support even 1000Base-T.

Q: Like most data networks, mine is not "bulletproof." This is most frequently evident to users when they can't gain access some morning, or when their e-mail goes down during the workday. Executives in my company fear that with a VoIP telephone system, our phone service will be down as often as our data network, which they perceive to be often. Are their fears justified, or is there some way I can calm them?

A: Public Switched Telephone Networks provide high-quality voice transmission between two or more parties. VoIP systems digitize and transmit analog voice signals as a stream of packets over a digital data network using standard analog, digital, and IP phones.

But VoIP is a delay-sensitive application. If you are going to run a delay-sensitive application on your existing IP network, it is imperative that you begin with a well-designed end-to-end network, and only then fine-tune it to adequately support VoIP. This fine-tuning will involve a series of steps (consult your network-equipment manufacturer for specifics) to improve quality of service—not just on the router running VoIP, but on all backbone routers and edge routers throughout your network. And since edge routers and backbone routers do not typically perform the same functions and steps necessary to improve quality of service for real-time, voice traffic will also differ.

Your executives are right to worry. The quality of VoIP telephony depends on the network that carries it. If your data network is not reliable, do not add the burden of VoIP traffic. You will only compound the problem. Instead, focus your efforts on resolving your existing network issues. To ignore something this basic is like trying to ride a donkey in a thoroughbred horse race. The pack will go whizzing by and leave you sitting on yourUdonkey. Hee-haw.

Q: You have covered Power over Ethernet technology in some past issues. Often, I hear Power over Ethernet and VoIP in the same breath. Are the two inseparable? What is the relationship between these two technologies?

A: Not only separable, but in some cases even impractical to use together.

Mid-span power, or Power over Ethernet, is used to power and Ethernet device (any device, not just a telephone) over the signal cable. Translation: You would not need a power outlet at the Ethernet device. This is especially handy when installing wireless access points.

Just for the record, I have a VoIP telephone on my desk. It is connected to the same five-port 100Base-T switch as my two laptop computers and network printer. My VoIP telephone is also connected to a power receptacle behind my desk. I could have chosen to mid-span power the set, but that would have required additional equipment in my telecommunications room—not logical in my SOHO environment, but maybe worth considering in a larger installation. Remember, being able to do something does not mean something needs to be done.

Click here to enlarge image

Donna Ballast is BICSI's standards representative, and a BICSI registered communications distribution designer (RCDD). Send your questions to Donna via e-mail: [email protected].

Pause for a hmmmm...

Today, it seems as if everything on the planet will soon have its own IP address. Ever wonder if they will run out of unique addresses to assign? Not likely.

Here is why. There are 340,282,366,920,938,463,463,374,607,431, 768,211,456 128-bit addresses available. (That is more than 340 duodecillion, or 2,128.) That is a really large number. To get an idea of just how large, let's look at it from another perspective. The earth's surface is roughly 511,263,971,197,990 square meters (greater than 511 trillion). You would be able to install 665,570,793,348,866,943,898,599 (greater than 665 sextillion) network devices, all with unique IP addresses, onto every square meter on the planet.

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