To set up a corporate DSL VPN, a firm would need a DSL connection from each remote office pointing directly back to corporate headquarters and a connection at the corrporate headquarters large enough to handle the traffic coming back to it - possibly a T-1 or T-3. Moyer says such a network is relatively cheap to set up when compared to frame relay VPNs.
"Because you're using DSL, you're using low-cost access mediums to get connected, and you can put together truly private networks for a fraction of what it would have cost you in the old days with frame relay or even dial-up through a remote access server," he says. A DSL connection from a remote office back into a corporate headquarters could cost as little as $60 per month, according to Moyer.
School Administration Unit 29, which represents seven school districts in southwest New Hampshire, is one organization that's taken advantage of DSL to create a VPN between nine of its buildings.
To create the VPN, the administration unit required five circuits - three DSL lines and two T-1s. The circuits run back into a cage owned by Vitts Networks, the provider of the VPN, at a Verizon central office. The VPN is separated from the Internet by a firewall. Each building also has a VPN box to encrypt any data sent over the network.
Dean Hollatz, the administration unit's director of technology, says the T-1s were necessary because one building needed a full 1.5M bit/sec of bandwidth that it couldn't get with DSL, and another building was 1,000 feet outside the three-mile DSL limit of the local central office.
The school district implemented the VPN, Hollatz says, so the buildings could swap sensitive information. The relatively low cost of DSL was what made the VPN possible, he says.
"We couldn't afford to drop a T-1 into our smaller schools, so when DSL and the price point came along it was something we could roll out to our smaller schools," he says.
In addition to software-based VPNs for remote workers and point-to-point VPNs, companies should soon be able to purchase network-based VPNs from service providers. These VPNs would be enabled by devices located within a service provider's network - such as Nortel Network's Shasta boxes, or gear from Cosine and Cisco.
Broadwing, which launched a VPN service for dedicated local loop and analog dial-up users in June, is working on extending the VPN offering to DSL.
Justine Lupul, Broadwing's director of IP services, says the provider should have a network-based VPN-over-DSL service available before year-end once it overcomes technology-related hurdles. Broadwing deploys its VPN service over circuits running frame signaling, and Lupul says most DSL vendors have not yet certified DSL for frame relay interoperability.