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Issue of August 2006 
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The VoIP challenge

VoIP is an excellent way for companies to combine cutting-edge technology and cost efficiency. At the same time, it presents new challenges that need to be met—reliability, resiliency, usability, and security, says Mika Rautila.

The growing trend today is to have voice and data travel through the same network. The potential cost benefit of this convergence is significant and hence the shift to using Voice over IP (VoIP), which in simple terms means making phone calls over the Internet, will be inevitable. The expectations from this new technology are high.

When you pick up your landline phone to make a call, you expect to hear the ringtone within moments. You also expect to be able to talk to the person at the other end without breaks in conversation or delayed voice. We are used to the reliable phone service over traditional lines, with good sound quality, and we take reliability and fault-tolerant phone lines for granted. The telecom industry calls this 99.999 percent availability, which represents the level of service people are expecting. These expectations could be unrealistic when voice is carried over the Internet.

Issues to be overcome

We are all familiar with Internet congestion when we surf on the data highway, but we do not expect that with our phone calls. The way congestion can impact a phone conversation is to introduce latency and jitter. If there is a delay in speech of over 150 ms, a latency of a fraction of a second, the human ear can sense it. On the other hand, jitter results in bad voice quality, as the voice arrives at varying intervals due to the nature of the data networks. Further, data lines are usually not designed to be as fault tolerant as traditional landlines, and therefore service breaks for phone calls over the Internet can be frequent and frustrating.

The challenges may become apparent only after the implementation of the new technology. These challenges are often related to the previously mentioned congestion of the data networks within and outside the company, reliability of Internet connections, and security of these connections. Since these issues require different technologies than what has been used for the actual VoIP implementation, they may not be addressed at all.

The traditional way

The traditional way to handle congestion in the data networks would be to use bandwidth management. What bandwidth management means is that we can determine how much of our capacity can be used for each type of traffic. For instance, we could stipulate that e-mail be designated 50 percent of the line capacity, while Internet browsing could be given 30 percent, VoIP 10 percent, and the rest of the traffic 10 percent. This way you can ensure that each type of traffic gets only its allotted amount and does not take up the whole capacity thereby depriving other traffic their bandwidth.

An alternative solution

An alternative, in some cases it could be more efficient, would be to separate certain traffic onto a private road through the Internet. The earliest implementations of this needed to use dedicated lines from service providers, but today, with modern technology this type of a private road through the Internet can be implemented with little initial investment and no hassle using say DSL lines.

Traditional leased lines cost around 400 pounds per month, whereas with the use of modern technology the cost comes to around 100 pounds per month since you can use regular Internet connections. To reach the reliability of leased lines you would naturally need at least two regular lines so the total cost would be around 200 pounds per month.

Benefits of the Alternative

With voice this type of road privatisation has some interesting benefits. In the traditional implementation of VoIP where all traffic shares the same road, other traffic may have an impact on the voice quality. Not only that but other traffic can impact the line reliability. When there is an accident on the road, other lanes may have to be closed as well. Similarly in the data network, congested Web traffic can impact voice traffic.

Reliability of private lines could be enhanced by using multiple roads (i.e. multiple Internet links) that lead to the same destination. With modern technology this is possible. By having more roads you ensure that when you pick up the phone “the Internet is not down.” We may be used to not being able to surf the Internet or send e-mail at all times due to service breaks, but phone calls are more critical and the expectation is that you are always able to make a phone call.

Security of voice on the Internet

Since voice now uses the same path as other data traffic, it faces the same challenges and threats that are more commonly linked with the Internet. Viruses, worms, trojan horses, Denial-of-Service (DoS) attacks, and connection hijacking are all possible threats for voice. Voice traffic can be attacked, hacked, intercepted, re-routed, and degraded just as any data packet on the data network.

Also, security needs special attention when other traffic is present. In order to avoid most security problems, e.g., malicious eavesdropping conversations, the voice traffic should be at least encrypted. Additionally with a private road for voice, security is increased by the mere fact that you do not have to advertise or let other people know about this road. This also reduces the possibility of someone being able to run a successful DoS attack. So Distributed DoS protection is in fact built into this type of scenario, whereas in the traditional implementation a DoS attack against a company’s Web server can also cause the voice traffic to halt.

Companies have implemented or are planning to implement VoIP solutions where voice, data, and video can travel over the Internet. Today this is already an excellent way for companies to combine cutting-edge technology and cost efficiency. At the same time, it presents new challenges that need to be met—reliability, resiliency, usability, and security.

The author is the Chief Technology Officer of Stonesoft Corporation

 
     
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