Termos e Definições - F


This article is about Fiber Connectivity in computing. For the USAF Fighter Conveyor project with B-36 and F-84,see FICON project.
FICON (Fiber Connectivity) is the IBM proprietary name for the ANSI FC-SB-3 (Single-Byte Command Code Sets-3 Mapping Protocol) for Fibre Channel protocol. It is a Fibre Channel layer 4 protocol used to map both IBM’s antecedent (either ESCON or parallel) channel-to-control-unit cabling infrastructure and protocol onto standard lower layer FibreChannel services and infrastructure. The supported topology is fabric utilizing Fibre Channel switches or directors. Supported rates include 1, 2, and 4 Gigabit data rates at distances up to 100 km.
Protocol internals:
Each FICON channel port provides support for multiple concurrent data exchanges (currently a maximum of 32) in full duplex mode. Information for active exchanges is transferred in Fibre Channel sequences mapped as FICON Information Units (IUs) which consist of one to four Fibre Channel frames, only the first of which carries 32 bytes of FICON (FC-SB-3) mapping protocol. Each FICON exchange may transfer one or many such IUs.
FICON channels support five classes of IUs which are used to conduct information transfers between a channel and a control unit. They are: Data, Command, Status, Control, Command and Data, and lastly Link Control. Only a channel port may send Command or Command and Data IUs, while only a control unit port may send Status IUs.
FICON uses two independent Fibre Channel class-3 (connectionless) services for normal information transfers between a channel port and a control unit port; one Fibre Channel exchange is used for all inbound IUs while another exchange is used for all outbound IUs. A “connected” state is said to exist between a FICON channel and its control unit when one or more such exchange-pairs is established between a channel and a control unit. Exchange pairs are only bound together by FICON (layer 4) services.
Additional CRC:
The integrity of customer data carried within one or more IUs is protected by a running 32-bit cyclic redundancy check (CRC) contained in the last frame of an IU classified as an ending IU within each data transfer. This is in addition to the standard Fibre Channel CRC used to verify the integrity of each individual FC frame. As such, the FICON CRC has the capability of detecting missing or out of sequence frames/IUs.
FICON may employ Fibre Channel optic cables with either short wavelength (multi-mode; 62.5 or 50 micrometer core) or long wavelength (single mode; 9 micrometer core). Long wavelength is used in the majority of applications owing to its superior optical power budget and bandwidth. Copper Fibre Channel cables are not supported.
FICON technology is normally used to connect high-performance/high-capacity storage devices such as Direct Access Storage Devices (DASD, sometimes referred to as ECKD disk) as well as tape devices to their host attached data channels.
FICON distance limitations have been overcome through the use of channel extenders. These extenders have been utilized to span continents as well as oceans for specific applications without subjecting FICON information transfers to performance sags imposed by FICON protocol delays normally associated with such distances.

FEPI (Front-End Programming Interface)
A programming-interface component of IBM's Customer Information Control System (CICS). See CICS.

Fibre Channel
A high-speed serial communication technology developed by IBM and other vendors, and now being standardized by the American National Standards Institute (ANSI) within ANSI Technical Committee X3T11. It is usually used for storage network data transmission over fiber-optic or copper cabling. Fibre Channel is a higher-speed alternative to Small Computer System Interface (see SCSI), a technology with which it is compatible.

FICON (Fibre Channel Connectivity)
An IBM channel architecture introduced in 1998.

FP (function point)
Function points measure the size of an application system based on the functional view of the system. The size is determined by counting the number of inputs, outputs, queries, internal files and external files in the system and adjusting that total for the functional complexity of the system. Function point analysis, originally developed at IBM, has as an advantage its focus on measuring software produced in terms of functionality delivered to the end user, rather than in terms of development deliverables, which have no direct bearing on the end user.

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