VoIP test drive

The asymmetric nature of the ubiquitous ADSL broadband technology means that uplink speeds are very limited, causing problems when trying to combine multiple voice calls with concurrent data activity.

The asymmetric nature of the ubiquitous ADSL broadband technology means that uplink speeds are very limited, causing problems when trying to combine multiple voice calls with concurrent data activity.

Despite voice compression techniques taking bandwidth requirements down to a mere 8Kbps for each call, in reality the overheads involved in packaging the voice mean that each call uses at least five times this bandwidth. At more than 40Kbps per call, a typical ADSL uplink cannot support many calls.

With no Quality of Service (QoS) available, any data transfer activity has a huge impact on voice calls, making true concurrent voice and data activity impossible beyond very low call/data levels. Even with standard QoS enabled, at typical ADSL uplink speeds, the impact of the QoS parameters is negligible. Worse still, some operators do not support QoS across all links and inherent limitations mean that the maximum number of concurrent calls that can be made is very low.


However, UK start-up Voipex claims to have a solution to these issues in the form of its ViBE technology tested here. With ViBE, Voipex has created an alternative QoS technology that is designed to operate successfully at much lower bandwidth availability rates than standard QoS mechanisms.

Using intelligent header compression and other optimisation techniques, Voipex claims that by handling voice as a very specific application, it really can minimise bandwidth usage down to the 8Kbps that a G.729 (compression standard) voice call technically requires and not the 40Kbps+ normally found in practice.

The ViBE technology is also very flexible in that it can be deployed in a very broad range of environments, such as point-to-point, hub-spoke, private/public network, managed service, internal service.


ViBE put to the test

To test Voipex's claims, we created a testbed, based on a typical configuration - effectively a branch office or small business (Birmingham) connecting to a hosted ViBE server via a DSL Max service (Docklands), in turn connecting to an Asterisk server via a second ViBE appliance at a remote site (Milton Keynes). On our live network we were able to generate in excess of 40 calls on a 448Kbps (as measured by ourselves) ADSL uplink, with concurrent data traffic and recorded zero packet loss. As more voice calls are brought up, the bandwidth made available to the data traffic is automatically reduced to allow bandwidth for the extra voice calls, but data applications were maintained throughout testing, with no failures.

We confirmed voice call quality with live calls as part of the test and heard no sound degradation whatsoever, even with more than 40 concurrent calls up.

The technology itself is also very flexible. It is available in a low-cost, small form factor appliance, as well as in rack-mount format for enterprise, ISPs, hosting companies etc, so is both inexpensive and scalable. Note that the appliance is a full-function router, so is a true technology replacement option, not simply an additional "black box".

We also saw the ViBE technology working as an integrated, additional application on a standard Netgear ADSL router. Integration of the ViBE code with any Linux-based appliance is not only possible, but very uncomplicated.

ViBE supports the ability to duplicate call packets down the same or alternative bandwidths. This does eat into the overall bandwidth saving that ViBE delivers, but at the destination point the fastest arriving packets are used thereby eliminating any ad-hoc latency or interference that does occur in certain markets. This means that a service provider, for example, can offer very real service level agreements while still benefitting from a significant bandwidth saving - at least two or three times - using ViBE. Resilience is dramatically improved.

Should for any reason the bandwidth fail then the call will continue completely uninterrupted with the user not even aware that a problem has occurred. In practice this means you can deliver a real E1 replacement capability over a pair of cheap broadband circuits, maybe even from two different suppliers.

In summary

With ViBE, Voipex has finally given meaning to VoIP in providing a real, cost-effective and technically superior alternative to classic voice that isn't just hype. Realistically, this is technology that should be sitting on every router in the world.

As an ISDN 30 replacement - yes there are still huge numbers of ISDN users out there - ViBE makes obvious sense. From a service provider or even supplier standpoint, to not take advantage of the ViBE technology would be a criminal offence in that it denies the user base serious economies. Can we make it a chargeable offence not to deploy it?

The advantages and disadvantages of ViBE


Makes VoIP a commercial reality for the masses by giving you real cost savings - five VoIP calls for the price of one effectively

Improves QoS and resilience when combining voice with data across any network connection

From a service provider perspective it means that offering SLAs across even ADSL connections is a reality

The technology is pure software so it can be deployed on any kind of platform as well as in the form of a "shrink-wrap" range of appliances.


Technology needs to be deployed at both ends of the connection, or in a hub-and-spoke architecture; an obvious point yes, but still worth nothing

Would be a far easier buying decision for an IT manager if it had a major supplier's "badge" on the product - a no-brainer actually.


Head-end appliances

SPS-501 (supports 3,000 simultaneous calls): £3,500

SPS 503 (supports 200 simultaneous calls): £450

CPE appliances

P2PB-202 (supports 200 simultaneous calls) two Ethernet port version: £299

P2PB-203 (supports 200 simultaneous calls) three Ethernet version: £349



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