Disadvantages of VPNs

With the hype that has surrounded VPNs historically, the potential pitfalls or "weak spots" in the VPN model can be easy to forget. These four concerns with VPN solutions are often raised.

1. VPNs require an in-depth understanding of public network security issues and taking proper precautions in VPN deployment.

2. The availability and performance of an organization's wide-area VPN (over the Internet in particular) depends on factors largely outside of their control.

3. VPN technologies from different vendors may not work well together due to immature standards.

4. VPNs need to accomodate protocols other than IP and existing ("legacy") internal network technology.

Generally speaking, these four factors comprise the hidden costs of a VPN solution. Whereas VPN advocates tout cost savings as the primary advantage of this technology, detractors cite hidden costs as the primary disadvantage of VPNs

What Exactly Is A VPN?

A VPN supplies network connectivity over a possibly long physical distance. In this respect, a VPN is a form of WAN.

The key feature of a VPN, however, is its ability to use public networks like the Internet rather than rely on private leased lines. VPN technologies implement restricted-access networks that utilize the same cabling and Routers as a public network, and they do so without sacrificing features or basic security.

A VPN supports at least three different modes of use:

Remote access client connections
LAN-to-LAN internetworking
Controlled access within an intranet

VPN Pros and Cons

Like many commercialized network technologies, a significant amount of sales and marketing "hype" surrounds VPN. In reality, VPNs provide just a simple few clear potential advantages over more traditional forms of wide-area networking. These advantages can be quite significant, but they do not come for free.

The potential problems with the VPN outnumber the advantages and are generally more difficult to understand. The disadvantages do not necessarily outweigh the advantages, however. From security and performance concerns, to coping with a wide range of sometimes incompatible vendor products, the decision of whether or not to use a VPN cannot be made without significant planning and preparation.

Technology Behind VPNs
Several network protocols have become popular as a result of VPN developments:

PPTP
L2TP
IPsec
SOCKS

These protocols emphasize authentication and encryption in VPNs. Authentication allows VPN clients and servers to correctly establish the identity of people on the network. Encryption allows potentially sensitive data to be hidden from the general public.

Many vendors have developed VPN hardware and/or software products. Unfortunately, immature VPN standards mean that some of these products remain incompatible with each other.