KVM hardware developed as a console switching technology long before smart thin client tools such as ICA, RDP and VNC were developed. These graphical desktop software tools are now standard components of the operating system platforms, and they offer high-quality low-bandwidth graphical transfer. External digital KVM converts analogue video into digital, introduces errors/noise, jitter and so on. It cannot make use of the screen transfer intelligence - a feature that is built into ICA / RDP/ VNC clients. And into the KVM found in the service processors like Dell's DRAC and HP's iLO, which are built into today's server platforms.
As a result the market is rapidly moving away from legacy external hardware KVM solutions, and on to a mix of embedded KVM in service processors, and virtual KVM software solutions. With virtual KVM, software is used to route the operator's Keyboard output, Video input, and Mouse output to/from the targeted computer - over the IP network.
Virtual KM solutions
There are "virtual KVM" software products that route just the keyboard and mouse outputs. With these "virtual KM" solutions an operator can control multiple computers, each having its own display, from the one keyboard/mouse interface.
Synergy2 is the virtual KM open source project. With Synergy, all the computers on a desktop can be operated form the mouse and keyboard of only one of the computers. You tell Synergy how many screens you have and their positions relative to one another, and Synergy then detects when the mouse moves off the edge of a screen and jumps it instantly to the neighboring screen. The keyboard works normally on each screen; input goes to whichever screen has the cursor.
You can download Synergy from http://sourceforge.net/projects/synergy2/. There's also a number of commercial virtual KM utilities:
Virtual Network Computing - Virtual KVM
Virtual Network Computing (VNC) is an open source tool designed so users and administrators can remotely access and control Windows 98/NT/2000/XP/2003, Linux, Macintosh, Solaris and UNIX computers. The open source version of VNC has been freely available since 1998, and more than 50 million copies of the software have been downloaded. VNC transmits the Keyboard depressions and Mouse movements from one computer to another; and relays the Video screen updates back in the other direction, over a network.
VNC has two parts, a Viewer client and a server. The server is the program on the machine that shares its screen, and the Viewer is the program that watches and interacts with the server. VNC is truly platform-independent so a VNC Viewer on any operating system can connect to a VNC server on any other operating system. There are Viewers and servers for almost all operating systems and for Java. Also multiple clients may connect to a VNC server at the same time.
VNC uses a simple protocol where the server sends small rectangles of the video frame buffer to the client. This protocol allows the client and server to negotiate which encoding will be used to optimize the bandwidth used for the video transfer.
There’s a range of popular freeware and commercial VNC software available:
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RealVNC is fully cross-platform, so a desktop running on a Linux machine may be displayed on a Windows PC, on a Solaris machine, or on any number of other architectures. There is a Windows server, allowing you to view the desktop of a remote Windows machine on any of these platforms using exactly the same viewer. RealVNC was founded by members of the AT&T team who originally developed VNC.
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TightVNC is an enhanced version of VNC. It has added features such as file transfer, performance improvements, and read-only password support. They have just recently included a video drive much like UltraVNC's. TightVNC is still free, cross-platform (Windows Unix and Linux) and compatible with the standard (Real) VNC.
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UltraVNC is easy to use, fast and free VNC software that has pioneered and perfected features that the other flavors have consistently refused or been very slow to implement for cross platform and minimalist reasons. UltraVNC runs under Windows operating systems (95, 98, Me, NT4, 2000, XP, 2003) Download UltraVNC from Sourceforge's UltraVNC file list |
Microsoft's Remote Desktop - Virtual KVM
Another excellent in-band network console technology is RDP (Microsoft's Remote Desktop Protocol). As with VNC, it enables a user or administrator to connect to a computer and have access to all of its applications, files and network resources - so security is imperative. With the RDP feature, an administrator can remotely control a client computer or server from another location. RDP is included in all Windows 2003 servers and in Windows XP Professional clients; and the RDP client software is freely available for earlier Windows versions. And there is an open source RDP client rdesktop for UNIX based platforms. In earlier Windows NT and Windows 2000 servers, RDP was available as part of Terminal Services.
RDP provides the remotely connected user or administrator with a graphical interface connection to the computer being accessed. A remote user can connect to the computer, and have access to all of the applications, files, and network resources, as though they were in front of the computer screen at work. Administrators can manage remote servers from the application layer down through the operating system (reconfiguring and upgrading the Windows OS, rebooting the machine etc). Also RDP is embedded inside the managed server so the communication is optimized to minimize the latency and the bandwidth requirements. RDP mainly targets Windows server management, however it is based on an ISO standard and it is permeating. Tarantella (now Sun Microsystems) unveiled its RDP client for Linux in late 2004 and ships it to thin client OEMs, providing Linux thin client terminal vendors with standard RDP-based access to Windows applications. However Remote Desktop currently only controls Windows computers, and the RDP protocol at this stage is not robust enough to use on its own across the public network - so its scope for remote control is limited.
Secure Tunneling
Opengear's console server families all now offer Secure Tunneling (SDT) which provides secure VNC and RDP access using SSH tunnels. However SDT is not limited to using virtual KVM applications to gain secure graphical console access to servers and desktops. SDT can connect to the server's service processors with IPMI and SoL. And it can then access the KVM console embedded there. SDT can also provide secure access to routers, LAN switches, Wireless access points, power reboot switches. This is all done securely using SSH tunnels and whatever native management scheme the devices use; be it HTTP/HTTPS, custom applications or telnet/SSH text screens. In addition it can log and alert on access or data patterns, so that issues can be identified early, reducing downtime or avoiding costly outages.
SDT leverages the compact screen transfer of RDP, VNC etc so it can be used out-of-band quite successfully over modems (if the main network path is down). In fact SDT can also access graphical based PC systems that are not network connected and only have a serial port available (which is of use in factory automation, medical equipment and point of sale, where Ethernet cable access is not always available).
So Opengear's IM4200, SD4000 and CM4000 servers enable managers to take control of their remote computers and networks just as though they were attached to a local computer screen. SDT delivers secure remote management from the applications layer, through the operating system and BIOS layers; right down to the embedded service processors and power switch hardware, without the high costs of installing legacy external KVM over IP solutions.
