A lot of attention gets paid here and elsewhere to VPNs based on equipment that sits on corporate sites. These VPNs are largely under the control of corporate IT staff but they can also be managed by service providers.An alternative that is growing in popularity is managed VPN services that are based on equipment within the carrier's network. Customers buy an access line to the network and the VPN is handled there.These services have advantages that should not be ignored, especially since many of these providers now support DSL access to their services, meaning they can be affordable to relatively small companies and companies with many small sites.The downside is that customers lose a certain amount of direct control over the VPN, but that is an issue with any network-based service.Factors on the upside can be many. Cost of the VPN is very predictable - whatever the agreed upon rate is. Many providers offer tools that give customers control over aspects of their VPN such as changing who has access rights and monitoring network performance. Plus, there is less administration and maintenance required of the customer, which can eliminate the need for additional staff.Many providers can also offer QoS. This is important as VoIP becomes more and more popular because it demands high service quality to work well. Turning up a higher QoS with relatively little effort offers flexibility to businesses toying with VoIP but that have not yet committed. For those that ultimately choose VoIP, a VPN with QoS options can make for a smoother transition.These are just highlights of possible benefits of managed VPN services, and future newsletters will take a closer look.