Of all the hot networking technologies, none is more so than virtual private LAN service (VPLS) just now. In fact, VPLS may be the most important transport protocol to come along since MPLS; so much so that the two WAN VPN technologies have sometimes been cast as adversaries, or at least rivals. Some even ask, “Is VPLS the new MPLS? Like, on steroids?"
The answer for agents and VARS is both "yes" and "no" (c’mon, you didn’t expect an easy answer, did you?). But for those who can determine when to deploy the service in conjunction with other VPN options and how to layer business services and applications on top, it could be a golden opportunity.
VPLS is the fastest growing WAN Ethernet service, according to Vertical Systems Group, largely because it’s the enabling technology for the large enterprise’s “endgame," as Erin Dunne, Vertical Systems Group’s director of research services, puts it; a long-haul mesh service that combines the best of Layer 2 (switching) and Layer 3 (routing) technology. Think of it as Layer 2.5 which, like MPLS, provides deterministic connectivity for protocols that are inherently connectionless. Whether using pseudowires (as with VPLS) or label switch paths (MPLS), these allow providers to provision and manage WAN paths with the QoS and security of a dedicated ATM connection, but with greater and more flexible bandwidth and simplicity. Running pseudowires over MPLS creates a transport path that can support any access technology, such as private line, LAN Ethernet, ATM and frame relay, while at least partially addressing the scalability and connectivity issues of Ethernet switching as it moves from the MAN to the WAN.
Since it’s based on Ethernet and MPLS, VPLS brings a number of advantages over most IP MPLS VPNs to the table. Besides feeds and speeds, VPLS makes all endpoints look like nodes on the same LAN, no matter how geographically dispersed. Thus, customers can control their own switching tables in-house rather than be forced to turn over routing chores to an IP MPLS provider. While this can impose some complexity on internal IT staff, many businesses, particularly in the financial or public sector, are more comfortable extending their Ethernet LAN across the WAN and don’t want to risk turning their routing tables over to a provider, believing it could compromise the logical or physical security of their data. This also generally allows customers to control the switching path more precisely than with IP MPLS. This approach recalls the old network administrator maxim, “Switch when you can, route where you must."
