Types of Remote Access

Having looked at the protocols required to establish remote access, let's now look at two types of remote access—dial-up remote access and virtual private networking—and how they use remote access protocols. All the major operating systems offer these types of remote access.

Dial-up Remote Access

Perhaps the simplest and most common of all remote access connections is dial-up access. A dial-up connection is established when the modem of one system contacts a modem on another system and communication begins between the two systems. All the major network operating systems support dial-up remote access. To connect to a server via modem, the server needs to be capable of answering and authenticating a remote access client (for example, a RAS server). The server performing this function is known as the remote access server.

Virtual Private Networks

In the mid-1990s, Microsoft, IBM, and Cisco began working on a technology called tunneling. By 1996 more companies had become interested and involved in the work, and the project soon produced two new virtual private networking solutions: PPTP and L2TP. Ascend, 3Com, Microsoft, and U.S. Robotics had developed PPTP, and Cisco Systems had introduced L2F.

From these developments, VPNs became one of the most popular methods of remote access. Essentially, a VPN is an extension of a LAN that establishes a remote connection, using a public network such as the Internet. A VPN is a point-to-point dedicated link over a public IP network.

A VPN encapsulates encrypted data inside another datagram that contains routing information. The connection between two computers establishes a switched connection that is dedicated to the two computers. The encrypted data is encapsulated inside PPP, and that connection is used to deliver the data.

A VPN allows anyone with an Internet connection to use the infrastructure of the public network to dial in to the main network and access resources as if he or she were logged on to the network locally. It also allows two networks to be connected to each other securely.

Many elements are involved in establishing a VPN connection, including the following:

• A VPN client— The VPN client is the computer that initiates the connection to the VPN server.

• A VPN server— The VPN server authenticates connections from VPN clients.

• An access method— As mentioned, a VPN is most often established over a public network such as the Internet; however, some VPN implementations use a private intranet. The network that is used must be IP based.

• VPN protocols— Protocols are required to establish, manage, and secure the data over the VPN connection. PPTP and L2TP are commonly associated with VPN connections.

VPNs have become very popular because they allow the public Internet to be safely utilized as a wide area network (WAN) connectivity solution. (A complete discussion of VPNs would easily fill another book and goes beyond the scope of the Network+ objectives.)