Networking

A terminal server (sometimes called a serial server) is a hardware device that enables you to connect serial devices across a network.

Terminal servers acquired their name because they were originally used for long-distance connection of dumb terminals to large mainframe systems such as VAX™. Today, the name terminal server refers to a device that connects any serial device to a network, usually Ethernet. In this day of network-ready devices, terminal servers are not as common as they used to be, but they’re still frequently used for applications such as remote connection of PLCs, sensors, or automatic teller machines.

The primary advantage of terminal servers is that they save you the cost of running separate RS-232 devices. By using a network, you can connect serial devices even over very long distances—as far as your network stretches. It’s even possible to connect serial devices across the Internet. A terminal server connects the remote serial device to the network, and then another terminal server somewhere else on the network connects to the other serial device.

Terminal servers act as virtual serial ports by providing the appropriate connectors for serial data and also by grouping serial data in both directions into Ethernet TCP/IP packets. This conversion enables you to connect serial devices across Ethernet without the need for software changes.

Because terminal servers send data across a network, security is a consideration. If your network is isolated, you can get by with an inexpensive terminal server that has few or no security functions. If, however, you’re using a terminal server to make network connections across a network that’s also an Internet subnet, you should look for a terminal server that offers extensive security features.

Remote access is the ability to access a network, a personal computer, a server, or other device from a distance for the purpose of controlling it or to access data. Today, remote access is usually accomplished over the Internet, although a local IP network, telephone lines, cellular service, or leased lines may also be used. With today’s ubiquitous Internet availability, remote access is increasingly popular and often results in significant cost savings by enabling greater network access and reducing travel to remote sites. Remote access is a very general term that covers a wide range of applications from telecommuting to resetting a distant server. Here are just a few of the applications that fall under the remote access umbrella:

Remote network access
A common use for remote access is to provide corporate network access to employees who work at home or are in sales or other traveling positions. This kind of remote access typically uses IPsec VPN tunnels to authenticate and secure connections.

Remote desktop access
Remote desktop access enables users to access a computer remotely from another computer and take control of it as if it were local. This kind of remote control requires that special software—which is included with most operating systems—be installed and enabled. It’s often used by those who travel frequently to access their “home” computer, and by network administrators for remote server access. This remote access method has some inherent security concerns and is usually incompatible with firewalls, so it’s important to be aware of its limitations and use adequate security precautions.

Remote KVM access
A common application in organizations that maintain servers across multiple sites is server administration through an IP-enabled KVM switch. These IP-addressable switches support one or more servers and have an integral Web server, enabling users to access them over the Internet through a Web browser. Because they’re intended for Internet use, these switches offer authentication and encryption for secure connections.

Remote power management
Anyone who’s ever had to get out of bed in the middle of the night to go switch a server off and back on again to reset it can appreciate the convenience of remote power management. Remote power managers have a wide range of capabilities ranging from simple power switching to reboot a device to sophisticated power monitoring, reporting, and management functions.

Remote environmental security monitoring
Remote environmental and security monitoring over the Internet is increasingly popular, largely because of the cost savings of using existing network infrastructure rather than a proprietary security system. This application requires IP-addressable hubs that support a variety of sensors ranging from temperature and humidity to power monitors. Some models even support surveillance cameras.

A terminal server (sometimes called a serial server or a console server or a device server) is a hardware device that enables you to connect serial devices across a network.

Terminal servers acquired their name because they were originally used for long-distance connection of dumb terminals to large mainframe systems such as VAX™. Today, the name terminal server refers to a device that connects any serial device to a network, usually Ethernet. In this day of network-ready devices, terminal servers are not as common as they used to be, but they’re still frequently used for applications such as remote connection of PLCs, sensors, or automatic teller machines.

The primary advantage of terminal servers is that they save you the cost of running separate RS-232 devices. By using a network, you can connect serial devices even over very long distances—as far as your network stretches. It’s even possible to connect serial devices across the Internet. A terminal server connects the remote serial device to the network, and then another terminal server somewhere else on the network connects to the other serial device.

Terminal servers act as virtual serial ports by providing the appropriate connectors for serial data and also by grouping serial data in both directions into Ethernet TCP/IP packets. This conversion enables you to connect serial devices across Ethernet without the need for software changes.

Because terminal servers send data across a network, security is a consideration. If your network is isolated, you can get by with an inexpensive terminal server that has few or no security functions. But if you’re using a terminal server to make network connections across a network that’s also an Internet subnet, you should look for a terminal server that offers extensive security features.