FICON
Encyclopedia
FICON is the IBM
proprietary name for the ANSI
FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol for Fibre Channel
(FC) protocol. It is a FC layer 4 protocol used to map both IBM’s antecedent (either ESCON
or parallel) channel
-to-control-unit cabling infrastructure and protocol onto standard FC services and infrastructure. The topology is fabric
utilizing FC switches or directors
. Valid rates include 1, 2, 4, and 8 Gigabit data rates at distances up to 100 km. FICON has replaced ESCON in current deployments because of FICON's technical superiority (especially its higher performance) and lower cost.
FICON channels use five classes of IUs 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.
As with prior Z channel protocols, there is a concept of a channel to control unit "connection." In its most primitive form, a connection is associated with a single channel program. In practice, a single channel program may result in the establishment of several sequential connections. This normally occurs during periods where data transfers become dormant while waiting for some type of independent device activity to complete (such as the physical positioning of tape or a disk access arm). In such cases, the connection may be closed by action of the device's control unit with the signaling of appropriate status. When the control unit is ready to resume such an interrupted connection, it signals the channel to reconnect and resume the interrupted channel program. By closing temporarily dormant connections, channel and control unit facilities may be better utilized to serve other active channel programs and certain protocol timeouts that might otherwise occur may be avoided.
FICON uses two Fibre Channel exchanges for a channel - control unit connection—one for each direction. So while a Fibre Channel exchange is capable of carrying a command and response on a single exchange, and all other FC-4 protocols work that way, the response to a FICON IU is always on a different exchange from the IU to which it is a response. The two exchanges that implement a connection are called an exchange pair (Note that the concept of the two exchanges being related exists only at the FC-4 layer). While other FC-4s have a single "data structure type" code that characterizes their IUs in Fibre Channel frame headers, FICON has two. One is for IUs from channel to control unit; the other for control unit to channel.
Except for some initialization dialogue that requires stronger synchronization, FICON uses Fibre Channel class of service 3 (Datagram). Thus, at the Fibre Channel physical (FC-2 and below) level, the communication is connectionless, frames and sequences may arrive out of order, and there is no acknowledgement of arrival. But all of that exists at the FC-4 level.
(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.
(current descendant of System/360
, System/370
, etc.), commonly called mainframe
s. FICON and its predecessors are the only protocols sufficient to communicate with traditional mainframe peripheral devices, especially for z/OS
. However, most mainframe operating systems also support FCP (SCSI
command set over Fibre Channel).
FICON is technically quite similar to more popular storage protocols, such as FCP. Both FICON and FCP share levels 1-3 of Fibre Channel specifications. Some administrators argue that FICON offers somewhat easier troubleshooting in mainframe environments, but the inherent technical advantages and disadvantages between FICON and FCP are much alike. Some mainframe-specific setups, such as GDPS, require FICON (or its predecessor ESCON). Mainframe-attached storage, such as IBM's System Storage DS8000, often supports both protocols. The storage is divided into fixed block storage volumes and mainframe-specific CKD/ECKD storage volumes. To access the fixed block volumes, one uses FCP. To access the CKD/ECKD volumes, one uses the FICON and/or ESCON.
Tape storage facilities include:
Switches/directors that support FICON include:
Other older FICON switching platforms are still in use. These include the McDATA 6064, CNT UMD, and CNT (Inrange) FC/9000. Inrange was acquired by CNT in 2003, CNT was acquired by McDATA in 2005, and in 2007 McDATA was in turn acquired by Brocade Communications Systems
. Approximately 80% of FICON directors and switches installed globally in mainframe environments are Brocade products. McDATA (now a part of Brocade) was particularly well established in the mainframe directors space, manufacturing the 9032-3 and 9032-5 ESCON directors for IBM, as well as the FICON Bridge Card. Brocade has many co-patents with IBM for FICON and ESCON technology. Cisco was a relative newcomer to this space, with their first FICON director coming out in 2003.
Other manufacturers producing FICON-compatible equipment include Optica Technologies, and InfoPrint Solutions Company, which offers high-volume printers that can attach via FICON.
IBM
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
proprietary name for the ANSI
Ansi
Ansi is a village in Kaarma Parish, Saare County, on the island of Saaremaa, Estonia....
FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol for Fibre Channel
Fibre Channel
Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking. Fibre Channel is standardized in the T11 Technical Committee of the InterNational Committee for Information Technology Standards , an American National Standards Institute –accredited standards...
(FC) protocol. It is a FC layer 4 protocol used to map both IBM’s antecedent (either ESCON
ESCON
ESCON is a data connection created by IBM, and is commonly used to connect their mainframe computers to peripheral devices such as disk storage and tape drives. ESCON is an optical fiber, half-duplex, serial interface. It originally operated at a rate of 10 Mbyte/s, which was later increased to...
or parallel) channel
Channel I/O
In computer science, channel I/O is a generic term that refers to a high-performance input/output architecture that is implemented in various forms on a number of computer architectures, especially on mainframe computers...
-to-control-unit cabling infrastructure and protocol onto standard FC services and infrastructure. The topology is fabric
Switched fabric
Switched fabric, switching fabric, or just fabric, is a network topology where network nodes connect with each other via one or more network switches . The term is popular in telecommunication, Fibre Channel storage area networks and other high-speed networks, including InfiniBand...
utilizing FC switches or directors
Fibre Channel switch
In the computer storage field, a Fibre Channel switch is a network switch compatible with the Fibre Channel protocol. It allows the creation of a Fibre Channel fabric, that is currently the core component of most storage area networks . The fabric is a network of Fibre Channel devices which...
. Valid rates include 1, 2, 4, and 8 Gigabit data rates at distances up to 100 km. FICON has replaced ESCON in current deployments because of FICON's technical superiority (especially its higher performance) and lower cost.
Protocol internals
Each FICON channel port is capable of 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 use five classes of IUs 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.
As with prior Z channel protocols, there is a concept of a channel to control unit "connection." In its most primitive form, a connection is associated with a single channel program. In practice, a single channel program may result in the establishment of several sequential connections. This normally occurs during periods where data transfers become dormant while waiting for some type of independent device activity to complete (such as the physical positioning of tape or a disk access arm). In such cases, the connection may be closed by action of the device's control unit with the signaling of appropriate status. When the control unit is ready to resume such an interrupted connection, it signals the channel to reconnect and resume the interrupted channel program. By closing temporarily dormant connections, channel and control unit facilities may be better utilized to serve other active channel programs and certain protocol timeouts that might otherwise occur may be avoided.
FICON uses two Fibre Channel exchanges for a channel - control unit connection—one for each direction. So while a Fibre Channel exchange is capable of carrying a command and response on a single exchange, and all other FC-4 protocols work that way, the response to a FICON IU is always on a different exchange from the IU to which it is a response. The two exchanges that implement a connection are called an exchange pair (Note that the concept of the two exchanges being related exists only at the FC-4 layer). While other FC-4s have a single "data structure type" code that characterizes their IUs in Fibre Channel frame headers, FICON has two. One is for IUs from channel to control unit; the other for control unit to channel.
Except for some initialization dialogue that requires stronger synchronization, FICON uses Fibre Channel class of service 3 (Datagram). Thus, at the Fibre Channel physical (FC-2 and below) level, the communication is connectionless, frames and sequences may arrive out of order, and there is no acknowledgement of arrival. But all of that exists at the FC-4 level.
Additional CRC
The integrity of customer data carried within one or more IUs is protected by a running 32-bit cyclic redundancy checkCyclic redundancy check
A cyclic redundancy check is an error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data...
(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.
Cables
FICON may employ Fibre Channel fiber 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. FICON cannot use Copper Fibre Channel cables.Usage
FICON is used exclusively with computers based on the IBM z/ArchitectureZ/Architecture
z/Architecture, initially and briefly called ESA Modal Extensions , refers to IBM's 64-bit computing architecture for IBM mainframe computers. IBM introduced its first z/Architecture-based system, the zSeries Model 900, in late 2000. Later z/Architecture systems include the IBM z800, z990, z890,...
(current descendant of System/360
System/360
The IBM System/360 was a mainframe computer system family first announced by IBM on April 7, 1964, and sold between 1964 and 1978. It was the first family of computers designed to cover the complete range of applications, from small to large, both commercial and scientific...
, System/370
System/370
The IBM System/370 was a model range of IBM mainframes announced on June 30, 1970 as the successors to the System/360 family. The series maintained backward compatibility with the S/360, allowing an easy migration path for customers; this, plus improved performance, were the dominant themes of the...
, etc.), commonly called mainframe
Mainframe computer
Mainframes are powerful computers used primarily by corporate and governmental organizations for critical applications, bulk data processing such as census, industry and consumer statistics, enterprise resource planning, and financial transaction processing.The term originally referred to the...
s. FICON and its predecessors are the only protocols sufficient to communicate with traditional mainframe peripheral devices, especially for z/OS
Z/OS
z/OS is a 64-bit operating system for mainframe computers, produced by IBM. It derives from and is the successor to OS/390, which in turn followed a string of MVS versions.Starting with earliest:*OS/VS2 Release 2 through Release 3.8...
. However, most mainframe operating systems also support FCP (SCSI
SCSI
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, and electrical and optical interfaces. SCSI is most commonly used for hard disks and tape drives, but it...
command set over Fibre Channel).
FICON is technically quite similar to more popular storage protocols, such as FCP. Both FICON and FCP share levels 1-3 of Fibre Channel specifications. Some administrators argue that FICON offers somewhat easier troubleshooting in mainframe environments, but the inherent technical advantages and disadvantages between FICON and FCP are much alike. Some mainframe-specific setups, such as GDPS, require FICON (or its predecessor ESCON). Mainframe-attached storage, such as IBM's System Storage DS8000, often supports both protocols. The storage is divided into fixed block storage volumes and mainframe-specific CKD/ECKD storage volumes. To access the fixed block volumes, one uses FCP. To access the CKD/ECKD volumes, one uses the FICON and/or ESCON.
Devices That Use FICON
Disk storage facilities that can be attached via FICON include:- EMC V-MAX
- EMC DMX
- EMC Symmetrix
- Hewlett Packard XP24000/XP20000 Disk Array
- Hitachi Data Systems Lightning
- Hitachi Data Systems Universal Storage Platform
- IBM System StorageIBM System StorageIBM System Storage is the brand name for IBM's computer storage products, covering both Disk and Tape products.-DS3000 Series:The DS3000 products are made for IBM by LSI* DS3200...
ESSIBM Enterprise Storage ServerThe IBM Enterprise Storage Server or the Shark is an enterprise storage array from IBM.-History:Originally, in 1998 IBM released the IBM 2105 Versatile Storage Server...
(Shark) - IBM System Storage DS6000
- IBM System Storage DS8000
- Sun StorageTek V2X4f
Tape storage facilities include:
- IBM Virtual Tape Server (VTS)
- IBM UltraScalable Tape Library
- Sun StorageTek Virtual Storage Manager (VSM)
- Bus-Tech MAS and MDL Virtual Tape Library
- LuminexLuminex Software, Inc.Luminex Software, Inc. is a developer and provider of disk-based mainframe virtual tape products and technologies for backup, archive and disaster recovery.- History :Luminex was founded in 1994 by Brian Hawley, Michael Saunders and Arthur Tolsma....
Channel Gateway Mainframe Virtual Tape Solutions
Switches/directors that support FICON include:
- Brocade DCX and DCX-4S
- Brocade 48000
- Brocade MI10k (formerly McDATA 10000)
- Brocade M6140 (formerly McDATA 6140)
- Brocade 5300
- Cisco MDS 9000 Series
Other older FICON switching platforms are still in use. These include the McDATA 6064, CNT UMD, and CNT (Inrange) FC/9000. Inrange was acquired by CNT in 2003, CNT was acquired by McDATA in 2005, and in 2007 McDATA was in turn acquired by Brocade Communications Systems
Brocade Communications Systems
Brocade Communications Systems, Inc. , based in Silicon Valley , is a vendor of storage area network hardware and software. The company also designs, manufactures, and sells networking products and management applications for local, metro, and wide area networks...
. Approximately 80% of FICON directors and switches installed globally in mainframe environments are Brocade products. McDATA (now a part of Brocade) was particularly well established in the mainframe directors space, manufacturing the 9032-3 and 9032-5 ESCON directors for IBM, as well as the FICON Bridge Card. Brocade has many co-patents with IBM for FICON and ESCON technology. Cisco was a relative newcomer to this space, with their first FICON director coming out in 2003.
Other manufacturers producing FICON-compatible equipment include Optica Technologies, and InfoPrint Solutions Company, which offers high-volume printers that can attach via FICON.