The Internet Control Message Protocol (ICMP) is a supporting protocol in the Internet protocol suite. It is used by network devices, including routers, to send error messages and operational information indicating success or failure when communicating with another IP address, for example, an error is indicated when a requested service is not available or that a host or router could not be reached. ICMP differs from transport protocols such as TCP and UDP in that it is not typically used to exchange data between systems, nor is it regularly employed by end-user network applications.
Conventional PCI, often shortened to PCI, is a local computer bus for attaching hardware devices in a computer. PCI is an abbreviation for Peripheral Component Interconnect and is part of the PCI Local Bus standard. The PCI bus supports the functions found on a processor bus but in a standardized format that is independent of any particular processor's native bus. Devices connected to the PCI bus appear to a bus master to be connected directly to its own bus and are assigned addresses in the processor's address space. It is a parallel bus, synchronous to a single bus clock.
Small Computer System Interface is a set of standards for physically connecting and transferring data between computers and peripheral devices. The SCSI standards define commands, protocols, electrical, optical and logical interfaces. SCSI is most commonly used for hard disk drives and tape drives, but it can connect a wide range of other devices, including scanners and CD drives, although not all controllers can handle all devices. The SCSI standard defines command sets for specific peripheral device types; the presence of "unknown" as one of these types means that in theory it can be used as an interface to almost any device, but the standard is highly pragmatic and addressed toward commercial requirements.
In computer programming, an infinite loop is a sequence of instructions that, as written, will continue endlessly, unless an external intervention occurs. It may be intentional.
High-Level Data Link Control (HDLC) is a bit-oriented code-transparent synchronous data link layer protocol developed by the International Organization for Standardization (ISO). The standard for HDLC is ISO/IEC 13239:2002.
In computing, iSCSI is an acronym for Internet Small Computer Systems Interface, an Internet Protocol (IP)-based storage networking standard for linking data storage facilities. It provides block-level access to storage devices by carrying SCSI commands over a TCP/IP network. iSCSI is used to facilitate data transfers over intranets and to manage storage over long distances. It can be used to transmit data over local area networks (LANs), wide area networks (WANs), or the Internet and can enable location-independent data storage and retrieval.
Synchronous Data Link Control (SDLC) is a computer communications protocol. It is the layer 2 protocol for IBM's Systems Network Architecture (SNA). SDLC supports multipoint links as well as error correction. It also runs under the assumption that an SNA header is present after the SDLC header. SDLC was mainly used by IBM mainframe and midrange systems; however, implementations exist on many platforms from many vendors. The use of SDLC is becoming more and more rare, mostly replaced by IP-based protocols or being tunneled through IP. In the United States, SDLC can be found in traffic control cabinets.
In computer networking, cut-through switching, also called cut-through forwarding is a method for packet switching systems, wherein the switch starts forwarding a frame before the whole frame has been received, normally as soon as the destination address is processed. Compared to store and forward, this technique reduces latency through the switch and relies on the destination devices for error handling. Pure cut-through switching is only possible when the speed of the outgoing interface is equal to or greater than the incoming interface speed.
In computing, Serial Attached SCSI (SAS) is a point-to-point serial protocol that moves data to and from computer-storage devices such as hard drives and tape drives. SAS replaces the older Parallel SCSI bus technology that first appeared in the mid-1980s. SAS, like its predecessor, uses the standard SCSI command set. SAS offers optional compatibility with Serial ATA (SATA), versions 2 and later. This allows the connection of SATA drives to most SAS backplanes or controllers. The reverse, connecting SAS drives to SATA backplanes, is not possible.
Key Code Qualifier is an error-code returned by a SCSI device.
A SCSI Status Code is used to determine the success or failure of a SCSI command. At the end of any command, the target returns a Status Code byte which should be one of the following:
SCSI Enclosure Services (SES) devices contains a number of elements, each of which is defined by a one byte SCSI element code. There are many different element codes defined to cover various devices as shown in the list below.
In computer terminology, a Check Condition occurs when a SCSI device needs to report an error.
Parallel SCSI is the earliest of the interface implementations in the SCSI family. SPI is a parallel data bus; there is one set of electrical connections stretching from one end of the SCSI bus to the other. A SCSI device attaches to the bus but does not interrupt it. Both ends of the bus must be terminated.
Tagged Command Queuing (TCQ) is a technology built into certain ATA and SCSI hard drives. It allows the operating system to send multiple read and write requests to a hard drive. ATA TCQ is not identical in function to the more efficient Native Command Queuing (NCQ) used by SATA drives. SCSI TCQ does not suffer from the same limitations as ATA TCQ.
Polling, or polled operation, in computer science, refers to actively sampling the status of an external device by a client program as a synchronous activity. Polling is most often used in terms of input/output, and is also referred to as polled I/O or software-driven I/O.
In a computer or data transmission system, a reset clears any pending errors or events and brings a system to normal condition or an initial state, usually in a controlled manner. It is usually done in response to an error condition when it is impossible or undesirable for a processing activity to proceed and all error recovery mechanisms fail. A computer storage program would normally perform a "reset" if a command times out and error recovery schemes like retry or abort also fail.
The introduction of Serial Attached SCSI (SAS) as the most recent evolution of SCSI required redefining the related standard for enclosure management, called SCSI Enclosure Services. SES-2, or SCSI Enclosure Management 2 first revision, was introduced in 2002 and is now at revision 20. SES-2 SCSI Enclosure Services (SES) permit the management and sense the state of power supplies, cooling devices, LED displays, indicators, individual drives, and other non-SCSI elements installed in an enclosure. SES2 alerts users about drive, temperature and fan failures with an audible alarm and a fan failure LED.
In computing, a hang or freeze occurs when either a process or system ceases to respond to inputs. A typical example is when computer's graphical user interface no longer responds to the user typing on the keyboard or moving the mouse. The term covers a wide range of behaviors in both clients and servers, and is not limited to graphical user interface issues.
iSCSI conformance testing is testing to determine whether an iSCSI Initiator/Target meets the iSCSI standard.
