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{{Mergefrom|KVMoIP|date=September 2006}} |
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[[Image:Computers-kvm-switch-amoswolfe.png|right|thumb|A diagram of how a KVM switch functions.]] |
[[Image:Computers-kvm-switch-amoswolfe.png|right|thumb|A diagram of how a KVM switch functions.]] |
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A '''KVM switch''' (with KVM being an [[Acronym and initialism|initialism]] for '''Keyboard, Video, Mouse''') is a hardware device that allows a user to control multiple [[computer]]s from a single [[Computer keyboard|keyboard]], [[Computer display|video monitor]] and [[Computer mouse|mouse]]. Although multiple computers are connected to the KVM, typically a smaller number of computers can be controlled at any given time. This is referred to as the '[[Blocking Factor]]'. Modern devices have also added the ability to share [[Universal Serial Bus|USB]] devices and speakers with multiple computers. |
A '''KVM switch''' (with KVM being an [[Acronym and initialism|initialism]] for '''Keyboard, Video, Mouse''') is a hardware device that allows a user to control multiple [[computer]]s from a single [[Computer keyboard|keyboard]], [[Computer display|video monitor]] and [[Computer mouse|mouse]]. Although multiple computers are connected to the KVM, typically a smaller number of computers can be controlled at any given time. This is referred to as the '[[Blocking Factor]]'. Modern devices have also added the ability to share [[Universal Serial Bus|USB]] devices and speakers with multiple computers. |
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Remote KVM devices are also available that allow multiple computers to be controlled remotely across a [[wide area network]], [[local area network]] or [[telephone|telephone-line]] using the [[Internet protocol suite|TCP/IP]] protocols and a [[web browser]] or specially designed viewer software. A big advantage of this viewer software over a browser based application is the belief that ActiveX or Java security issues are eliminated creating a safer KVM over IP access method, although this may not always be true, given that the viewer software provided by many manufacturers is also reliant on ActiveX or Java. In addition, some manufacturers charge additional licensing fees for this software. In comparison to conventional methods of remote administration (for example [[Virtual Network Computing]] or [[Terminal Services]]), a KVM switch has the advantage that it doesn't depend on a software component running on the remote computer, thus allowing remote editing of [[BIOS]] settings and monitoring of the entire booting process. |
Remote KVM devices are also available that allow multiple computers to be controlled remotely across a [[wide area network]], [[local area network]] or [[telephone|telephone-line]] using the [[Internet protocol suite|TCP/IP]] protocols and a [[web browser]] or specially designed viewer software. A big advantage of this viewer software over a browser based application is the belief that ActiveX or Java security issues are eliminated creating a safer KVM over IP access method, although this may not always be true, given that the viewer software provided by many manufacturers is also reliant on ActiveX or Java. In addition, some manufacturers charge additional licensing fees for this software. In comparison to conventional methods of remote administration (for example [[Virtual Network Computing]] or [[Terminal Services]]), a KVM switch has the advantage that it doesn't depend on a software component running on the remote computer, thus allowing remote editing of [[BIOS]] settings and monitoring of the entire booting process. |
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Modern KVM over IP gateways or switches use 128-bit data encryption securing the KVM configuration over a WAN or LAN. |
Modern KVM over IP gateways or switches use 128-bit data encryption securing the KVM configuration over a WAN or LAN. |
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== KVM over IP == |
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'''Keyboard Video Mouse over Internet Protocol''' ("KVMoIP" or "KVM over IP") is very similar to remote graphical console access software such as [[PCAnywhere]], [[Virtual Network Computing]] (VNC) and Microsoft [[Remote Desktop Connection]]. The main benefit of KVM-over-IP is to make traditional KVM functionality available without the associated cabling limitations. |
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=== Similarities === |
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In each of these remote graphical console applications a user is able to see a local copy of the remote graphics display and to perform most of the keyboard and mouse related tasks that he could if he were in front of the actual system. In fact, some of them even redirect the audio channel to the remote console. Some of the main limitations of these software based implementations are the inability to access the [[BIOS]] setup screen and the inability to redirect the graphical console in [[safe mode]]. This is because software based remote graphical console applications require the operating system to boot and to load a driver before the graphical console can be redirected. Also, software is inherently difficult to trust because much of the quality is currently tested in, not designed in. The remote graphical console software providers have no way of knowing the configuration of the system that it's being loaded on, and testing with every permutation and combination of 3rd party driver and application software is not practical. |
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=== Differences === |
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KVMoIP is different from the above because it is hardware based, requiring no software to be installed on the remote system. Instead, a dedicated microcontroller and potentially specialized video capture hardware work to capture the video signals, compress and packetize them, and send them over an [[Ethernet]] link (which may include very remote connections over the Internet) to a remote console application that unpacks and reconstitutes the dynamic graphical image. This KVMoIP subsystem is typically connected to a system's standby power plane so that it's available during the entire BIOS boot process. Thus one can see all the BIOS messages occur and even cause the remote system to enter BIOS setup to make any required adjustments. KVMoIP is considered by many to be a valuable tool in the support of Service Level Agreements for commercial servers. |
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=== Implementation details === |
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There are many potential ways of implementing KVMoIP. For the graphics capture portion, [[Peripheral Component Interconnect|PCI]] based KVMoIP cards used a variation of a technique known as [[screen scraping]] where the PCI [[bus master]] KVMoIP card would access graphics data directly from the graphics memory buffer. In these cases, the PCI card had to know which graphics chip it was working with, and what graphics mode this chip was currently in so that the contents of the buffer could be interpreted correctly as picture data. Newer techniques such as those used by [[OPMA]] management subsystem cards and other implementations obtain the video data directly from the graphics chip using the industry standard [[DVI]] bus. There are also a variety of ways to emulate the keyboard and the mouse remotely, but newer implementations emulate [[USB]] based keyboards and mice using the management controller. |
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==The KVM market== |
==The KVM market== |
Revision as of 19:22, 12 November 2006
A KVM switch (with KVM being an initialism for Keyboard, Video, Mouse) is a hardware device that allows a user to control multiple computers from a single keyboard, video monitor and mouse. Although multiple computers are connected to the KVM, typically a smaller number of computers can be controlled at any given time. This is referred to as the 'Blocking Factor'. Modern devices have also added the ability to share USB devices and speakers with multiple computers.
Use
A user connects a monitor, keyboard, and mouse to the KVM device, then uses special cables to connect the KVM device to the computers. Control is switched from one computer to another by the use of buttons on the KVM device, with the KVM passing the signals between the computers and the keyboard, mouse and monitor depending on which computer is currently selected. Most devices also allow control to be switched through keyboard commands (such as hitting a certain key, often Scroll Lock, rapidly two or three times). Some KVM devices also provide peripheral emulation - they send signals to the computers that are not currently selected to ensure that they do not think that the keyboard, mouse and monitor are disconnected.
Devices differ in the number of computers that can be connected, with anywhere from two up to 64 computers possible. Enterprise-grade devices can also be daisy-chained to allow even greater numbers of computers to be controlled from a single set of a keyboard, video and mouse.
A KVM switch is useful where there are multiple computers, but no need for a dedicated keyboard, monitor and mouse for each one. They are frequently used in data centers where multiple servers are placed in a single rack with a single keyboard, monitor and mouse. A KVM switch then allows data center personnel to connect to any server in the rack.
Software alternatives
There are software alternatives to a hardware KVM switch such as Synergy, Kavoom![1], Virtual Network Computing (VNC), teleport or the non-free Multiplicity and PC Anywhere, which do the switching in software and forward input over standard network connections. This has the advantage of reducing the number of wires needed, and the screen-edge switching it provides makes it easier to forget that you are using two computers. However, there are some disadvantages. Software alternatives typically require additional software to be pre-loaded onto each one of the target servers or computers to allow clients to remotely attach to. They also can not be used when the host Operating System is not installed yet or has not started: operating system installations are thus not possible nor is access to a computer's BIOS or other built-in configuration areas. Finally, the software alternatives can be difficult or impossible to access if the computer is very busy or stopped responding to network connections.
Remote KVM devices (KVM/ip)
Remote KVM devices are also available that allow multiple computers to be controlled remotely across a wide area network, local area network or telephone-line using the TCP/IP protocols and a web browser or specially designed viewer software. A big advantage of this viewer software over a browser based application is the belief that ActiveX or Java security issues are eliminated creating a safer KVM over IP access method, although this may not always be true, given that the viewer software provided by many manufacturers is also reliant on ActiveX or Java. In addition, some manufacturers charge additional licensing fees for this software. In comparison to conventional methods of remote administration (for example Virtual Network Computing or Terminal Services), a KVM switch has the advantage that it doesn't depend on a software component running on the remote computer, thus allowing remote editing of BIOS settings and monitoring of the entire booting process. Modern KVM over IP gateways or switches use 128-bit data encryption securing the KVM configuration over a WAN or LAN.
KVM over IP
Keyboard Video Mouse over Internet Protocol ("KVMoIP" or "KVM over IP") is very similar to remote graphical console access software such as PCAnywhere, Virtual Network Computing (VNC) and Microsoft Remote Desktop Connection. The main benefit of KVM-over-IP is to make traditional KVM functionality available without the associated cabling limitations.
Similarities
In each of these remote graphical console applications a user is able to see a local copy of the remote graphics display and to perform most of the keyboard and mouse related tasks that he could if he were in front of the actual system. In fact, some of them even redirect the audio channel to the remote console. Some of the main limitations of these software based implementations are the inability to access the BIOS setup screen and the inability to redirect the graphical console in safe mode. This is because software based remote graphical console applications require the operating system to boot and to load a driver before the graphical console can be redirected. Also, software is inherently difficult to trust because much of the quality is currently tested in, not designed in. The remote graphical console software providers have no way of knowing the configuration of the system that it's being loaded on, and testing with every permutation and combination of 3rd party driver and application software is not practical.
Differences
KVMoIP is different from the above because it is hardware based, requiring no software to be installed on the remote system. Instead, a dedicated microcontroller and potentially specialized video capture hardware work to capture the video signals, compress and packetize them, and send them over an Ethernet link (which may include very remote connections over the Internet) to a remote console application that unpacks and reconstitutes the dynamic graphical image. This KVMoIP subsystem is typically connected to a system's standby power plane so that it's available during the entire BIOS boot process. Thus one can see all the BIOS messages occur and even cause the remote system to enter BIOS setup to make any required adjustments. KVMoIP is considered by many to be a valuable tool in the support of Service Level Agreements for commercial servers.
Implementation details
There are many potential ways of implementing KVMoIP. For the graphics capture portion, PCI based KVMoIP cards used a variation of a technique known as screen scraping where the PCI bus master KVMoIP card would access graphics data directly from the graphics memory buffer. In these cases, the PCI card had to know which graphics chip it was working with, and what graphics mode this chip was currently in so that the contents of the buffer could be interpreted correctly as picture data. Newer techniques such as those used by OPMA management subsystem cards and other implementations obtain the video data directly from the graphics chip using the industry standard DVI bus. There are also a variety of ways to emulate the keyboard and the mouse remotely, but newer implementations emulate USB based keyboards and mice using the management controller.
The KVM market
VDC (Venture Development Corporation) estimates the size of the world-wide KVM market in 2005 to be over $713 million, growing at over 12%.[citation needed]
The largest suppliers of KVM technology worldwide are Avocent, Black Box and Raritan.[citation needed]
Related Technology
- Console server — For managing a command-line driven system through a remote terminal.