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Modem Pooling

Many of the integrated remote access servers now have shared dial-out—or modem pooling—capabilities. Modem pooling, as illustrated in Exhibit 2-7-3, allows the workstations on the network to share the same modems that are used for incoming access. These modems, attached or enclosed in the server, are managed by the server software and accessed through requests from the LAN workstations. Any of the authorized workstations can then gain access to a shared modem when needed.


Exhibit 2-7-3.  Modem Pooling

Any workstation on the LAN can be loaded with a program that connects it to a modem attached to the server. This virtual connection made between the LAN workstation and the remote access server uses one of a few standard methodologies. Interrupt 14 is the most common methodology. Others include Interrupt 6B and NASI. Remote access products that support Interrupt 14 include Novell's NetWare Connect, DCA's RLN, and Microdyne's LAN Expanders.

Many commercial programs support these connection standards, including Data Storm's Procomm, DCA's Crosstalk, and WRQ's Reflections. These programs run at the workstation and are configured to emulate various terminal types. Through these configurations, the workstation can emulate terminal types such as DEC VT100, IBM 3270, or a standard ANSI terminal. Terminal emulation is required so that host-based applications can be properly displayed at the LAN workstation through the modem pool.

Although dial-out is not always required by every organization, it is a great economical feature to have in a remote access or communication server. Many workstations might have their own modem attached, but with client/server networks, only that workstation can use the modem. Besides the extra cost for the additional modems, there is also the cost of all the additional telephone lines required. Modem pooling is a highly effective means of controlling communications costs.

SECURITY OPTIONS

Although each LAN operating system has its own security system, most of the remote access software and server products have additional security functions. There are several options to be considered, including encryption, dial-back, audit logs, and authentication.

Encryption and Dial-back

Password encryption and dial-back methods are the most common security methods used by today's products. Dial-back allows remote users to call in, enter a password, hang up, and wait for the remote access device to verify their access and then call them back. This technique prevents intruders who have learned someone's password from calling in from a different location. Passwords are usually encrypted so that eavesdroppers cannot intercept the call and record the password for their own use alter. Data Encryption Standard (DES) is the most popular method for password encryption.

Audit Logs and Authentication

There are several authentication protocols including Kerberos, PAP (password authentication protocol), CHAP (challenge handshake authentication protocol), RADIUS (remote authentication dial-in user service), and others. These systems can check various incoming items to verify their authenticity. Recording each access and all its transactions in an audit report can monitor any illegal access activity that might occur.

Of course, there is a trade-off between the amount of security that is used and the ease of access desired. The more layers of security that are added, the more difficult the access.

SUMMARY

As communications technology continues to improve and costs continue to drop, more people will adapt their activities around these tools for increasing productivity. In the 1960s, only large institutions could afford mainframe computers. In the 1970s, most medium-size companies acquired minicomputers. In the 1980s, most organizations acquired some type of computer equipment, ranging from mainframes to personal computers. By the early 1990s, most organizations networked their computers to share data and programs. Now, most organizations allow remote computers to access their networks.

There are many remote access server options to consider, including:

  Which networking technology—Ethernet or Token Ring?
  Which network operating system/and or protocol—NetWare, Windows NT, TCP/IP, or other?
  Which access method—remote control or remote node?

Most of the available products support both NetWare (IPX or ODI) and Ethernet, because they are the most common configurations installed.

Another important decision is the remote access connection required. Choices include ISDN, wireless, or standard asynchronous. If an asynchronous link is chosen, then the user must choose either an internal or external modem and the speed of modem desired. The level of security must also be considered and compared with the ease of access needed. Finally, it is important to ensure that the network operating system has tested and approved the chosen products.

The easier the products are for workers to use, the more likely it is that their productivity will increase. If remote users can plug their computers into a telephone jack, turn on the machine, click on an icon or enter a command, and quickly see the network's logon prompt (just like at the office), they will use the system. The more people at all levels use the network, the more informed and productive everyone—from field force personnel to the organization's management—will be.


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