VPN Basics

G. I. Papadimitriou, Aristotle University

M. S. Obaidat, Monmouth University

C. Papazoglou and A.S. Pomportsis, Aristotle University


Types of VPN Services

Intranet VPNs

Extranet VPNs

Remote Access VPNs


Security Concerns


Integrity Checksums


Access Management

VPN Implementations

Hardware Components

Protocols Employed by VPNs

Point-to-Point Tunneling Protocol

Layer-2 Tunneling Protocol (L2TP)

IP Security

SOCKS v5 and SSL

Multiprotocol Label Switching

Quality of Service Support



Cross References


Further Reading


The best way to come up with a definition of the term virtual private network (VPN) is to analyze each word separately. Having done that, Ferguson and Huston (1998) came up with the following definition: A VPN is a communications environment in which access is controlled to permit peer connections only within a defined community of interest and is constructed through some form of partitioning of a common underlying communications medium, where this underlying communications medium provides services to the network on a nonexclusive basis. Ferguson and Huston also provided a simpler and less formal description. A VPN is a private network constructed within a public network infrastructure, such as the global Internet. Others define a VPN as a network that allows two or more private networks to be connected over a publicly accessed network. It is similar to wide area networks ...

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