Remote access refers to a temporary link—usually a phone connection—and does not include permanent LAN-to-LAN connections. These temporary links can be made over a number of different kinds of media including Public Switched Telephone Network (PSTN), Integrated Services Digital Network (ISDN), wireless, and Digital Subscriber Line (DSL).

Remote access enables remote users to dial into your LAN over the phone by using either land lines or a cellular connection. Typically, remote users plug their laptop modems into a hotel phone jack, call your LAN’s phone number, and then access the LAN as if they were on-site and connected directly to the network—albeit at a slower speed.

The most common use for remote access is to provide network access to remote employees who are “on the road” in sales or other traveling positions. Remote access can also enable LAN users to dial out to remote locations or to the Internet, although this is less common today with the availability of inexpensive “always up” broadband connections.

PSTN
An ordinary analog modem over an ordinary dialup telephone line is still the most inexpensive and common method of remote network access. But conditions on the Public Switched Telephone Network (PSTN) are often less then ideal, so connections may be slow—even for a 56-kbps modem—and the average connection delay of 12 to 25 seconds is too long for some network applications. But for occasional connections where slow connect times are acceptable, regular phone lines can be a good, inexpensive choice.

ISDN
Integrated Services Digital Network (ISDN) is a digital data service provided by most phone companies. With ISDN you can transmit large amounts of data, voice, and video signals up to 128 kbps over a single phone line. ISDN is waning somewhat in popularity with the advent of faster technologies, but it can still be an effective solution.

Wireless
Wireless remote access gives remote users flexibility—they don’t have to be near a phone connection. Wireless connections have recently become affordable and fast enough to be a practical alternative for remote access. Most wireless access is via a service provided by a cellular phone network. The options currently available include: circuit-switched cellular, cellular digital packet data (CDPD), ARDIS, PCS, and digital cellular. For greater geographical coverage, satellite networks such as Iridium, Inmarsat, and MSAT can handle basic services such as e-mail.

DSL
Digital Subscriber Line (DSL) generally refers to any of a number of ways to send data at high speeds across standard copper phone lines. For more information about DSL, see FaxBack #26451.

Remote Access Servers
The device that takes calls from remote users and connects them to the network is known as a remote access server (RAS). A RAS is generally a standalone device that attaches directly to a network via Ethernet or Token Ring. A RAS may feature internal modems or be attached to external modems via RS-232 cable. Many remote access servers also support ISDN with either internal ISDN circuitry or through external terminal adapters.

The remote access server enables remote users to dial into the LAN via a modem connection and use it as though their workstations were directly connected to it. Once linked to the LAN, any application programs the user executes will run on the remote PC.

The type of remote access server you select depends on the size of your LAN, the amount of remote traffic it handles, and how many operating systems you run in your LAN/WAN environment. Although the most common remote access solution is a dedicated remote access server, other devices such as network file servers, remote access routers, and remote node software, are sometimes used to provide remote access.