- Contexts 3 3 1 – Fast Window Switcher Systems Diagram
- Contexts 3 3 1 – Fast Window Switcher Systems Inc
- Contexts 3 3 1 – Fast Window Switcher Systems Installation
- Contexts 3 3 1 – Fast Window Switcher Systems System
- Both types involve handing control over to the operating system kernel to perform the context switch. The process of switching in and out of the OS kernel along with the cost of switching out the registers is the largest fixed cost of performing a context switch. A more fuzzy cost is that a context switch messes with the processors cacheing.
- SystemContext Switches/sec counter reports system wide context switches. Thread(Total)Context Switches/sec counter reports the total number of context switches generated per second by all threads Context switch overhead is low but if you see a much higher number at the same time as% processor time spikes then you can start troubleshooting.
In the above figure, you can see that initially, the process P1 is in the running state and the process P2 is in the ready state. Now, when some interruption occurs then you have to switch the process P1 from running to the ready state after saving the context and the process P2 from ready to running state.
An OpenGL context represents many things. A context stores all of the state associated with this instance of OpenGL. It represents the (potentially visible) default framebuffer that rendering commands will draw to when not drawing to a framebuffer object. Think of a context as an object that holds all of OpenGL; when a context is destroyed, OpenGL is destroyed.
Contexts are localized within a particular process of execution (an application, more or less) on an operating system. A process can create multiple OpenGL contexts. Each context can represent a separate viewable surface, like a window in an application.
Each context has its own set of OpenGL Objects, which are independent of those from other contexts. A context's objects can be shared with other contexts. Most OpenGL objects are sharable, including Sync Objects and GLSL Objects. Container Objects are not sharable, nor are Query Objects.
Any object sharing must be made explicitly, either as the context is created or before a newly created context creates any objects. However, contexts do not have to share objects; they can remain completely separate from one another.
In order for any OpenGL commands to work, a context must be current; all OpenGL commands affect the state of whichever context is current. The current context is a thread-local variable, so a single process can have several threads, each of which has its own current context. However, a single context cannot be current in multiple threads at the same time.
- 1Context types
- 2Context information queries
- 2.4Extension list
- 2.6Shading language version
Context types
Until version 3.0, all versions of OpenGL were fully backwards compatible with earlier ones. Code written against OpenGL 1.1 could execute just fine on OpenGL 2.1 implementations.
OpenGL version 3.0 introduced the idea of deprecating functionality. Many OpenGL functions were declared deprecated, which means that users should avoid using them because they may be removed from later API versions. OpenGL 3.1 removed almost all of the functionality deprecated in OpenGL 3.0. This includes the Fixed Function Pipeline.
However, since many implementations support the deprecated and removed features anyway, some implementations want to be able to provide a way for users of higher GL versions to gain access to the old APIs. Several techniques were tried, and it has settled down into a division between Core and Compatibility contexts.
There are other context variations as well.
OpenGL 3.1 and ARB_compatibility
A new extension, ARB_compatibility, was introduced when OpenGL 3.1 was revealed. The presence of this extension is a signal to the user that deprecated or removed features are still available through the original entrypoints and enumerations. The behavior of such implementations is defined with a separate, much larger, OpenGL Specification. Thus, there was a backwards-compatible specification and a non-backwards compatible specification.
OpenGL 3.2 and Profiles
When OpenGL 3.0 was introduced, a new context creation mechanism was introduced as well. Since later versions could remove functionality, it was important that the user be able to ask for a specific version of OpenGL, one that they had written their code against.
However, the ARB_compatibility extension posed a problem: the implementation decided whether to define it or not. A user could not request to deactivate ARB_compatibility; it was forced on them. This also meant that the core specification had to be a proper subset of the compatibility specification; the core specification couldn't provide functionality that the compatibility one did not provide.
Thus, another change was made to context creation.
The 3.0 form of context creation did not have the concept of profiles. There was only one form of OpenGL: the core specification. In 3.2, OpenGL was effectively split into two profiles, core and compatibility. An implementation was only required to define core, so compatibility is not guaranteed to be available. However, on most implementations, the compatibility profile will be available.
Platform Issue (MacOSX): When MacOSX 10.7 introduced support for OpenGL beyond 2.1, they also introduced the core/compatibility dichotomy. However, they did not introduce support for the compatibility profile itself. Instead, MacOSX gives you a choice: core profile for versions 3.2 or higher, or just version 2.1. There is no way to get access to features after 2.1 and still access the Fixed Function Pipeline.
The 3.2 wording also changed what kind of contexts can be returned, allowing 3.0 and higher versions to be given when not directly asked so long as they support ARB_compatibility or are the compatibility profile of that version of OpenGL. So if you ask for 2.1, the implementation is free to give you 3.2 compatibility; it was not previously free to do this.
Because of the change in wording, the way to detect the changed functionality is to check the extension string. If WGL_ARB_create_context_profile is present, then it uses the 3.2 wording. Otherwise it uses the 3.0/3.1 wording.
Forward compatibility
A context, of version 3.0 or greater, can be created with the 'forward compatibility' bit set. This will cause, for the given profile, all functionality marked 'deprecated' to be removed. You can combine the forward compatibility bit with core and compatibility contexts.
Contexts 3 3 1 – Fast Window Switcher Systems Diagram
For 3.0, this means that all deprecated functionality will no longer be available. This simulates the 3.1 experience.
For 3.1, this means that any remaining deprecated functionality (things deprecated in 3.0 but not removed in 3.1) will be removed. Basically, wide-lines. Also, you're not likely to see implementations offer ARB_compatibility if you pass forward compatibility.
For 3.2+ compatibility, it should mean nothing at all. Games turtle odyssey 2 crack. Since no functionality is marked deprecated in the compatibility profile, the forward compatibility bit removes nothing.
For 3.2+ core, it again means that all functionality that is still deprecated (wide-lines) will be removed.
Recommendation: You should use the forward compatibility bit only if you need compatibility with MacOS. That API requires the forward compatibility bit to create any core profile context.
Debug contexts
A context can be created in debug mode. This allows, among other things, debug output functionality to work more effectively.
No error contexts
V · E
Core in version | 4.6 | |
---|---|---|
Core since version | 4.6 | |
ARB extension | KHR_no_error |
An OpenGL Context can be created which does not report OpenGL Errors. If the context bit GL_CONTEXT_FLAG_NO_ERROR_BIT is set to true, then the context will not report most errors. It will still report GL_OUT_OF_MEMORY_ERROR where appropriate, but this can be delayed from the point where the error actually happens. No other errors will be reported.
This also means that the implementation will not check for errors either. So if you provide incorrect parameters to a function that would have provoked an error, you will get undefined behavior instead. This includes the possibility of application termination.
Contexts cannot have the no error bit and the robustsness or debug bits.
Robust access context
Normally, many buffer memory access operations that access data outside of the bound range of storage have undefined results (potentially including program termination). However, if the program doesn't crash, this can lead to being able to read values that were written by other applications, which is a security concern.
Robust access means that out-of-bounds reads will provide well-defined results (usually zero). And such accesses will never cause program termination. It provides better process isolation.
Context information queries
There is a lot of information about an OpenGL context can be queried.
OpenGL version number
To get the OpenGL major and minor version numbers, you can call these functions:
These are available on OpenGL version 3.0 and above contexts. If those are not available, you can use this instead:
The string returned starts with '<major version>.<minor version>'. Following the minor version, there can be another '.', then a vendor-specific build number. The string may have more content, which is completely vendor-specific (thus not a part of the OpenGL standard).
For example, the returned string may be like '2.0.6914 WinXP SSE/SSE2/SSE3/3DNow!'. 2.0 is the actual version number of GL supported. 6914 is a driver build number. WinXP is the OS. SSE/SSE2/SSE3/3DNow! are CPU features that the driver can use.
Sometimes glGetString(GL_VERSION) also returns also the bus type used, such as AGP or PCI or PCIEx.
Vendor string
The OpenGL implementations have a vendor string associated with it that is used for identifying the maker of the implementation.
It could be 'ATI Technologies', 'NVIDIA Corporation', 'INTEL' and so on. Note that there's no guarantee that the string for a specific vendor will remain the same in future implementations. On Windows, if it says 'Microsoft' then you are using the Windows software renderer or the Windows Direct3D wrapper. You probably haven't installed the graphics drivers yet in that case.
Renderer name
This names the renderer used by the implementation.
This string is often the name of the GPU. In the case of Mesa3d, it would be i.e 'Gallium 0.4 on NVA8'. It might even say 'Direct3D' if the Windows Direct3D wrapper is being used.
Extension list
Extensions can be queried one by one. To do this, first use glGetIntegerv(GL_NUM_EXTENSIONS, *) to get the number of extensions supported by the implementation. Then iterate over each one with this:
Where k is less than the GL_NUM_EXTENSIONS value.
Legacy extension list
A string containing a space-separated list of extension names can be queried as follows:
Context flags
There are multiple kinds of OpenGL contexts.
You can detect which profile the context supports with this query:
This can contain the bits GL_CONTEXT_CORE_PROFILE_BIT or GL_CONTEXT_COMPATIBILITY_PROFILE_BIT, but not both at the same time.
Other features of contexts can be detected via context flags:
The available context flags are:
- GL_CONTEXT_FLAG_FORWARD_COMPATIBLE_BIT
- The context is a forward compatible context.
- GL_CONTEXT_FLAG_DEBUG_BIT
- The context is a debug context.
- GL_CONTEXT_FLAG_ROBUST_ACCESS_BIT
- The context supports robust memory access functionality.
- GL_CONTEXT_FLAG_NO_ERROR_BIT
- The context does not report OpenGL errors.
Shading language version
The primary version of GLSL supported by the implementation can be queried:
The version string has almost the same format as the context version string. The difference is that the minor version always has two digits.
Supported GLSL versions
Core in version | 4.6 | |
---|---|---|
Core since version | 4.3 |
Support for specific versions of GLSL can be queried via an indexed get. The number of supported GLSL versions is queried with glGetIntegerv(GL_NUM_SHADING_LANGUAGE_VERSIONS, *). Each individual version can be queried from an indexed string:
https://solid-converter-2-1-7640-67-download-free3.peatix.com. Where k is on the range 0 to GL_NUM_SHADING_LANGUAGE_VERSIONS - 1.
These strings use the formatting of GLSL's #version declaration. This has the following forms:
or
The profile is only present for versions of GLSL that have this distinction.
Note that GLSL only gained the #version declaration in version 1.10; if an implementation exposes support for GLSL 1.00 (through ARB_shading_language_100), then it will return an empty string (').
Versions of the GLSL for OpenGL ES can also be supported. If an implementation returns '100', this does not refer to GLSL 1.00. It instead refers to support for OpenGL ES's 2.0's GLSL ES version 1.00. The profile can also be 'es', which represents a version of OpenGL ES's shading language. So version '300 es' represents GLSL ES 3.00. GLSL ES 1.00 does not use the 'es' profile name.
Retrieved from 'http://www.khronos.org/opengl/wiki_opengl/index.php?title=OpenGL_Context&oldid=14586'
Contexts 3 3 1 – Fast Window Switcher Systems Inc
(Redirected from Network Switch)
AvayaERS 2550T-PWR, a 50-port Ethernet switch
A network switch (also called switching hub, bridging hub, and by the IEEEMAC bridge[1] Adobe photoshop cs2 paradox keygen indir gezginler. ) is networking hardware that connects devices on a computer network by using packet switching to receive and forward data to the destination device.
A network switch is a multiport network bridge that uses MAC addresses to forward data at the data link layer (layer 2) of the OSI model. Some switches can also forward data at the network layer (layer 3) by additionally incorporating routing functionality. Such switches are commonly known as layer-3 switches or multilayer switches.[2]
Switches for Ethernet are the most common form of network switch. The first Ethernet switch was introduced by Kalpana in 1990.[3] Switches also exist for other types of networks including Fibre Channel, Asynchronous Transfer Mode, and InfiniBand.
Unlike less advanced repeater hubs, which broadcast the same data out of each of its ports and let the devices decide what data they need, a network switch forwards data only to the devices that need to receive it.[4]
Overview[edit]
Cisco small business SG300-28 28-port Gigabit Ethernet rackmount switch and its internals
A switch is a device in a computer network that connects other devices together. Multiple data cables are plugged into a switch to enable communication between different networked devices. Switches manage the flow of data across a network by transmitting a received network packet only to the one or more devices for which the packet is intended. Each networked device connected to a switch can be identified by its network address, allowing the switch to direct the flow of traffic maximizing the security and efficiency of the network.
A switch is more intelligent than an Ethernet hub, which simply retransmits packets out of every port of the hub except the port on which the packet was received, unable to distinguish different recipients, and achieving an overall lower network efficiency.
An Ethernet switch operates at the data link layer (layer 2) of the OSI model to create a separate collision domain for each switch port. Each device connected to a switch port can transfer data to any of the other ports at any time and the transmissions will not interfere.[a] Because broadcasts are still being forwarded to all connected devices by the switch, the newly formed network segment continues to be a broadcast domain. Switches may also operate at higher layers of the OSI model, including the network layer and above. A device that also operates at these higher layers is known as a multilayer switch.
Segmentation involves the use of a switch to split a larger collision domain into smaller ones in order to reduce collision probability and to improve overall network throughput. In the extreme case (i.e. micro-segmentation), each device is located on a dedicated switch port. In contrast to an Ethernet hub, there is a separate collision domain on each of the switch ports. This allows computers to have dedicated bandwidth on point-to-point connections to the network and also to run in full-duplex mode. Full-duplex mode has only one transmitter and one receiver per collision domain, making collisions impossible.
3d chess game full version. The network switch plays an integral role in most modern Ethernet local area networks (LANs). Mid-to-large sized LANs contain a number of linked managed switches. Small office/home office (SOHO) applications typically use a single switch, or an all-purpose device such as a residential gateway to access small office/home broadband services such as DSL or cable Internet. In most of these cases, the end-user device contains a router and components that interface to the particular physical broadband technology. User devices may also include a telephone interface for Voice over IP (VoIP).
Role in a network[edit]
Switches are most commonly used as the network connection point for hosts at the edge of a network. In the hierarchical internetworking model and similar network architectures, switches are also used deeper in the network to provide connections between the switches at the edge.
In switches intended for commercial use, built-in or modular interfaces make it possible to connect different types of networks, including Ethernet, Fibre Channel, RapidIO, ATM, ITU-TG.hn and 802.11. This connectivity can be at any of the layers mentioned. While the layer-2 functionality is adequate for bandwidth-shifting within one technology, interconnecting technologies such as Ethernet and token ring is performed more easily at layer 3 or via routing.[6] Devices that interconnect at the layer 3 are traditionally called routers.[7]
Where there is a need for a great deal of analysis of network performance and security, switches may be connected between WAN routers as places for analytic modules. Some vendors provide firewall,[8][9] network intrusion detection,[10] and performance analysis modules that can plug into switch ports. Some of these functions may be on combined modules.[11]
Through port mirroring, a switch can create a mirror image of data that can go to an external device such as intrusion detection systems and packet sniffers.
A modern switch may implement power over Ethernet (PoE), which avoids the need for attached devices, such as a VoIP phone or wireless access point, to have a separate power supply. Since switches can have redundant power circuits connected to uninterruptible power supplies, the connected device can continue operating even when regular office power fails.
Bridging[edit]
A modular network switch with three network modules (a total of 24 Ethernet and 14 Fast Ethernet ports) and one power supply.
A 5-port layer-2 switch without management functionality
Modern commercial switches use primarily Ethernet interfaces. The core function of an Ethernet switch is to provide multiport layer-2 bridging. Layer-1 functionality is required in all switches in support of the higher layers. https://ameblo.jp/20confcanci-ba8i/entry-12635519399.html. Many switches also perform operations at other layers. A device capable of more than bridging is known as a multilayer switch.
A layer 2 network device is a multiport device that uses hardware addresses, MAC address, to process and forward data at the data link layer (layer 2).
A switch operating as a network bridge may interconnect devices in a home or office. The bridge learns the MAC address of each connected device. Bridges also buffer an incoming packet and adapt the transmission speed to that of the outgoing port. While there are specialized applications, such as storage area networks, where the input and output interfaces are the same bandwidth, this is not always the case in general LAN applications. In LANs, a switch used for end-user access typically concentrates lower bandwidth and uplinks into a higher bandwidth.
Contexts 3 3 1 – Fast Window Switcher Systems Installation
Interconnect between switches may be regulated using spanning tree protocol (STP) that disables links so that the resulting local area network is a tree without loops. In contrast to routers, spanning tree bridges must have topologies with only one active path between two points. Shortest path bridging is a layer 2 alternative to STP that allows all paths to be active with multiple equal cost paths.[12][13]
Types[edit]
A rack-mounted 24-port 3Com switch
Form factors[edit]
Switches are available in many form factors, including stand-alone, desktop units which are typically intended to be used in a home or office environment outside a wiring closet; rack-mounted switches for use in an equipment rack or an enclosure; DIN rail mounted for use in industrial environments; and small installation switches, mounted into a cable duct, floor box or communications tower, as found, for example, in fiber to the office infrastructures.
Rack-mounted switches may be standalone units, stackable switches or large chassis units with swappable line cards.
Configuration options[edit]
- Unmanaged switches have no configuration interface or options. They are plug and play. They are typically the least expensive switches, and therefore often used in a small office/home office environment. Unmanaged switches can be desktop or rack mounted.
- Managed switches have one or more methods to modify the operation of the switch. Common management methods include: a command-line interface (CLI) accessed via serial console, telnet or Secure Shell, an embedded Simple Network Management Protocol (SNMP) agent allowing management from a remote console or management station, or a web interface for management from a web browser. Examples of configuration changes that one can do from a managed switch include: enabling features such as Spanning Tree Protocol or port mirroring, setting port bandwidth, creating or modifying virtual LANs (VLANs), etc. Two sub-classes of managed switches are smart and enterprise managed switches.
- Smart switches (aka intelligent switches) are managed switches with a limited set of management features. Likewise, 'web-managed' switches are switches that fall into a market niche between unmanaged and managed. For a price much lower than a fully managed switch they provide a web interface (and usually no CLI access) and allow configuration of basic settings, such as VLANs, port-bandwidth and duplex.[14]
- Enterprise managed switches (aka managed switches) have a full set of management features, including CLI, SNMP agent, and web interface. They may have additional features to manipulate configurations, such as the ability to display, modify, backup and restore configurations. Compared with smart switches, enterprise switches have more features that can be customized or optimized and are generally more expensive than smart switches. Enterprise switches are typically found in networks with a larger number of switches and connections, where centralized management is a significant savings in administrative time and effort. A stackable switch is a type of an enterprise-managed switch.
Typical management features[edit]
A couple of managed D-Link Gigabit Ethernet rackmount switches, connected to the Ethernet ports on a few patch panels using Category 6patch cables (all equipment is installed in a standard 19-inch rack)
- Enable and disable ports
- Link bandwidth and duplex settings
- Quality of service configuration and monitoring
- MAC filtering and other access control list features
- Configuration of Spanning Tree Protocol (STP) and Shortest Path Bridging (SPB) features
- Simple Network Management Protocol (SNMP) monitoring of device and link health
- Port mirroring for monitoring traffic and troubleshooting
- Link aggregation configuration to set up multiple ports for the same connection to achieve higher data transfer rates and reliability
- VLAN configuration and port assignments including IEEE 802.1Q tagging
- Network Access Control features such as IEEE 802.1X
- IGMP snooping for control of multicast traffic
Traffic monitoring[edit]
It is difficult to monitor traffic that is bridged using a switch because only the sending and receiving ports can see the traffic.
Methods that are specifically designed to allow a network analyst to monitor traffic include:
- Port mirroring – the switch sends a copy of network packets to a monitoring network connection.
- SMON – 'Switch Monitoring' is described by RFC 2613 and is a protocol for controlling facilities such as port mirroring.
- RMON[15]
These monitoring features are rarely present on consumer-grade switches. Other monitoring methods include connecting a layer-1 hub or network tap between the monitored device and its switch port.[16]
See also[edit]
Notes[edit]
- ^In half duplex mode, each switch port can only either receive from or transmit to its connected device at a certain time. In full duplex mode, each switch port can simultaneously transmit and receive, assuming the connected device also supports full-duplex mode.[5]
Contexts 3 3 1 – Fast Window Switcher Systems System
References[edit]
- ^IEEE 802.1D
- ^Thayumanavan Sridhar (September 1998). 'Layer 2 and Layer 3 Switch Evolution'. cisco.com. The Internet Protocol Journal. Cisco Systems. Retrieved 2014-08-05.
- ^Robert J. Kohlhepp (2000-10-02). 'The 10 Most Important Products of the Decade'. Network Computing. Archived from the original on 2010-01-05. Retrieved 2008-02-25.
- ^'Hubs Versus Switches – Understand the Tradeoffs'(PDF). ccontrols.com. 2002. Retrieved 2013-12-10.
- ^'Cisco Networking Academy's Introduction to Basic Switching Concepts and Configuration'. Cisco Systems. 2014-03-31. Retrieved 2015-08-17.
- ^Joe Efferson; Ted Gary; Bob Nevins (February 2002). 'Token-Ring to Ethernet Migration'(PDF). IBM. p. 13. Archived from the original(PDF) on 2015-09-24. Retrieved 2015-08-11.
- ^Thayumanavan Sridhar (September 1998). 'The Internet Protocol Journal - Volume 1, No. 2: Layer 2 and Layer 3 Switch Evolution'. Cisco Systems. Retrieved 2015-08-11.
- ^Cisco Catalyst 6500 Series Firewall Services Module, Cisco Systems,2007
- ^Switch 8800 Firewall Module, 3Com Corporation, 2006
- ^Cisco Catalyst 6500 Series Intrusion Detection System (IDSM-2) Module, Cisco Systems,2007
- ^Getting Started with Check Point Fire Wall-1, Checkpoint Software Technologies Ltd., n.d.
- ^Peter Ashwood-Smith (24 February 2011). 'Shortest Path Bridging IEEE 802.1aq Overview'(PDF). Huawei. Archived from the original(PDF) on 15 May 2013. Retrieved 11 May 2012.
- ^'IEEE Approves New IEEE 802.1aq Shortest Path Bridging Standard'. Tech Power Up. 7 May 2012. Retrieved 11 May 2012.
- ^'Tech specs for a sample HP 'web-managed' switch'. Archived from the original on December 13, 2007. Retrieved 2007-05-25.CS1 maint: BOT: original-url status unknown (link)
- ^Remote Network Monitoring Management Information Base, RFC 2819, S. Waldbusser,May 2000
- ^'How to Build a Miniature Network Monitor Device'. Retrieved 2019-01-08.
External links[edit]
Wikimedia Commons has media related to Ethernet switches. |
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