VoIP – Reliability, Performance & Security

In this article, we will discuss VoIP reliability, performance and security in a candid manner, offer reassurance, and advise as well as some tips that may mitigate the worse of the problems.

When considering VoIP as a telephony solution many potential adopters fail to make the commitment even after months of pilot testing due to their concern over the troublesome threesome – Reliability, Performance & Security.



Hosted VoIP providers and equipment Vendors measure reliability on the availability of the service or product. Usually they present this figure as an availability percentage of the proportion of time that the service was available over a period. Typical vendors market their products and services as being five nines. What this means is that the product or service was available for 99.999% of the time. The time is usually a year. Therefore 99.999% translates to about five minutes of downtime a year.

Customers however also measure reliability though usually less formally but effectively none the less of the times that the VoIP service was not available – and it was certainly longer than 5 minutes!

This is the classic problem of the difference in perception of what is the VoIP service. Customers rarely read the contract to get the definition of the service provided and even if they did it wouldn’t change anything, their belief would be that if they couldn’t place a VoIP call, when everything appeared to be functional at their end, then the service was unavailable.

The service provider however will point to their availability figures and politely disagree. The reason for this misunderstanding is that they are both measuring different things. The service provider will be measuring the availability of its servers and applications sending heartbeats and URLs to the test the applications and web-server responses. They will undoubtedly have their private wire Internet connections monitored 24/7 by their Telecom supplier and have the availability and performance statistics to prove it. They will be confident in the reliability of their service.

The customer however knows that several times during the last month they were unable to make calls. Sometimes when they did manage to connect, calls were dropped, were poor quality, perhaps had echo or they could hear but not be heard at the other end. The problem here though is that there could be other parties involved that the service depends on but are not under the control or the responsibility of the VoIP service provider.

These third parties and their products provide the infrastructure and transport that the overall VoIP service rides on. They are typically the customer’s local ISP and internet connection and the local Telecom and their phone lines. Then there are the same issues at the other end with the called party. These are the usual suspects when intermittent poor quality issues arise and the most difficult to troubleshoot.

Complaints of missed calls are all too common but often these are due to the technology not the hosted service. Again customers perception is that their PSTN landline works in a power cut so why can’t the VoIP service. That is down to the Teleco providing the power down the telephone lines to the phone. However, it is still a common complaint especially as there will be no emergency calls available. The only thing that the customer can do to mitigate this issue is to keep the ADSL modem and computer connected to a UPS or better still use the UPS only for the modem and use it a Smartphone, laptop or Tablet with a Wi-Fi connection.

If you do experience reliability issues, then taking an end-to-end approach is the only way to isolate the problem. Unfortunately, there are many parties involved, such as transit ISP’s, who have no actual financial interest or desire to get involved. Try to explain the issues that you are having and avoid the blame game or jumping to conclusions and pointing the finger without reasonable cause. The trouble is though there isn’t a lot you can do if it is a poor quality ISP in the internet path, or worse it is down to the aging copper telephone line in the local loop.

So how can a consumer or SMB get reliability and availability figures? Well, the forums can give a good insight into how other clients view the service, though make sure to try a few to get a balanced viewpoint.



One of the most common complaints regards VoIP from those who have piloted a hosted service or just used Skype is how unpredictable the call quality is. This is a very frustrating issue as it always seems to happen when you least need it too. That of course compounds the problem even though it only happened twice during a six-month trial period – that was twice too many. However, again like when discussing reliability the underlying fault may not be with the VoIP service provider but much closer to home.

So, what things can we check that are not the responsibility of the service provider. Well, there are several key performance indicators that you can check which though not directly related to the VoIP service are related to the underlying services, media and protocols. The first thing to do is to check your own connection to your ISP, are you happy with the predictability of your internet service? Of course, it will vary but is it still on a bad day, reasonably good or is it barely acceptable or even unusable. If your own internet connect isn’t reliable then the VoIP solution will also be unreliable as it is dependent on it. If however your local internet is great then that also absolves your local loop telephone connection as it rides atop of it.

So what can I do if I get poor voice quality on a call?

Well the first thing to do should you have the presence of mind and be on the computer soft-phone, is to check the computers task manager for processes, performance and networking. Often you can find processes running, greedily consuming resources and CPU cycles that you didn’t know about. Again, check the monitor for networking to see the input/output from the computers network card, you can also check this on the ADSL router, which is even better if you have several computers on a home network or in the office.

If it’s a Wi-Fi router check to see who is all connected, and make sure that the Wi-Fi router is protected by WPA-PSK and not WEP. Again, if file downloading is taking place or there is video streaming on another device then bandwidth contention may well be the problem in this instance.

For the SoHO (small office / home office) or SMB it is best to try and separate the data internet from the voice, consider getting a second internet connection that will be used only for voice traffic. Likewise, inside the home or office run a second cable or if you know how and your switch supports the feature then configure your switch for Vlans. The same goes for WiFi configure separate Vlans and dedicate one for voice.

You might also want to take a look at your firewall settings and check there isn’t double NAT taking place on your router and modem, this is a very common problem caused by daisy chaining devices.


VoIP Security

The security concerns that prospective customer have with a VoIP phone system tend to question whether VoIP will make the data network less secure. If that is your concern consider segregating the networks and running VoIP on a separate infrastructure. If the VoIP platform is on-premises and you host your own service then the PBX-server can be incorporated behind the usual security equipment just like any other server. The VoIP infrastructure and protocols will not make the network less secure, however the security devices might well degrade the VoIP performance and quality.

Firewalls and intrusion protection devices and applications that do deep packet inspection do add latency, jitter and delay to IP traffic, which VoIP is sensitive too. Vendors always claim that their firewalls work at wire speed and have minimal delay, but in practice, that is nonsense. You only have to by-pass one to see a noticeable decrease in the delay. Encryption and decryption such as when running VPN’s can sometimes cause unacceptable delay, but usually only if the service was hovering just below the thresholds for latency, jitter and packet loss anyway.

Improving and introducing robust security measures may well make the network tougher to break but it can also have a negative effect on performance and quality. However, this is not something VoIP specific, it is the same for data and video, and results in the same trade-off.


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