In deciding whether to use a Virtual Private Network (VPN) or an MPLS architecture, there are several factors to consider and compare.
When it comes to cost, which is often a key part of the decision-making process, VPNs are typically less expensive, and offer various levels of security (which in turn affects cost). Layer 2 VPNs are more secure, while layer 3 VPNs can be deployed faster and are less expensive, but are susceptible to the risks and traffic of running over the public Internet. MPLS offers increased efficiency compared to IP-based routing.
Leased lines are superior in terms of security, since they are limited to a specific user’s traffic. VPNs over the public Internet offer the lowest level of security. MPLS falls somewhere in the middle, relying on shared network elements. MPLS has no inherent encryption, and thus is heavily dependent upon the network core being secure.
Leased lines offer better reliability. VPNs are affected by congestion since it runs on and shares the open Internet, while MPLS enables traffic prioritization and the establishment of service quality levels.
Leased lines have the most difficult scalability, due to the time needed for deployment and also the high cost. MPLS is much more easily scalable.
Finally, one must consider the main operational needs. What type of data is being sent? Does communication need only point-to-point connectivity or multi-point connectivity? Does the network need to cover multiple locations? Leased lines are usually not capable of serving complex network needs, while MPLS offers point-to-point as well as one-to-multi-point capabilities.