FICON
| Company type | Trademark / Protocol |
|---|---|
| Industry | Computer networking / Mainframe technology |
| Founded | 1998 |
| Founder | IBM |
| Products | Fibre Channel protocol for mainframe connectivity |
| Parent | IBM |
FICON (short for Fibre Connection) is IBM’s trademarked designation for the ANSI standard FC-SB-3 Single-Byte Command Code Sets-3 Mapping Protocol utilized in Fibre Channel (FC) technology. Functioning at the FC layer 4 level, it translates IBM’s traditional channel-to-control-unit communication methods (such as ESCON or parallel Bus and Tag) onto conventional Fibre Channel networks. The architecture employs fabric configurations with FC switches or directors, delivering data rates of 1, 2, 4, 8, 16, and 32 Gigabits per second across distances reaching up to 100 kilometers.
Debuting in 1998 alongside the System/390 G5 mainframe, FICON superseded ESCON starting with the IBM Z series models zEnterprise BC12 and EC12 in 2013, driven by its enhanced throughput and cost efficiency.
Protocol internals
A single FICON channel port can handle as many as 32 simultaneous full-duplex data exchanges. Data movement is accomplished through Fibre Channel sequences that are interpreted as FICON Information Units (IUs), each comprising between one and four Fibre Channel frames; only the initial frame contains the 32-byte FICON protocol information. Multiple IUs may be transmitted within a single exchange.
FICON categorizes IUs into five types: Data, Command, Status, Control, and Link Control. Command or combined Command and Data IUs originate exclusively from channel ports, whereas Status IUs are sent solely by control unit ports.
A "connection" linking a channel to a control unit represents a single channel program execution but may be fragmented into several sequential connections during periods of device inactivity (for example, while positioning tape). Temporarily closing inactive connections helps conserve resources and prevents protocol timeouts.
Unlike other FC-4 protocols that merge commands and responses within one exchange, FICON employs two separate Fibre Channel exchanges per connection—one dedicated to each direction. These paired exchanges exist solely at the FC-4 layer. Additionally, FICON differentiates IU types by using distinct data structure codes depending on whether communication is from channel to control unit or vice versa.
With the exception of initialization phases that require enhanced synchronization, FICON operates over Fibre Channel class of service 3 (Datagram), implying that communication at the physical layer is connectionless, allowing frames to arrive out of order without acknowledgment; reliability is instead ensured at the FC-4 protocol level.
Additional CRC
To safeguard customer data integrity across one or multiple IUs, FICON implements a continuous 32-bit cyclic redundancy check (CRC) appended in the final frame of each concluding IU during data transfers. This mechanism supplements the standard Fibre Channel CRC—which validates individual frames—enabling detection of missing or misordered frames or IUs.
Cables
FICON utilizes Fibre Channel fiber optic cabling with either short wavelength (multi-mode fibers with 62.5 or 50 micrometer core diameters) or long wavelength (single mode fibers with a 9 micrometer core). The long wavelength option predominates due to its superior optical power budget and bandwidth capabilities. Copper-based Fibre Channel cables are not compatible with FICON.
Usage
Exclusively deployed on IBM z/Architecture mainframes, FICON plays a vital role in interfacing with traditional mainframe peripherals, particularly when operating under z/OS. Although most mainframe operating systems also support FCP (which encapsulates SCSI over Fibre Channel), FICON remains indispensable for specific environments such as GDPS, which mandates either FICON or ESCON connectivity. Many mainframe storage solutions—including IBM’s System Storage DS8000—offer dual protocol support: FCP for fixed block storage and FICON/ESCON for mainframe-oriented CKD/ECKD volumes.
Devices
Among the disk storage systems compatible with FICON are:
- EMC Symmetrix, DMX, VMAX, and PowerMax series
- Hewlett Packard Enterprise's HP XP Storage
- Hitachi Vantara's Universal Storage Platform and Virtual Storage Platform
- IBM's Enterprise Storage Server (Shark), DS6000, and DS8000 models
- INFINIDAT InfiniBox
- StorageTek FlexLine V2Xf/V2X4f SVA
FICON-supporting tape storage offerings include:
- Advanced TS Migrations' zAppliance Solutions featuring VTL and zPDT
- Bus-Tech (EMC) MAS and MDL Virtual Tape Libraries
- EMC Disk Library tailored for mainframe environments (DLm)
- IBM 3584 UltraScalable Tape Library (TS3500)
- IBM TS7680G ProtecTIER Deduplication Gateway designed for System z
- IBM Virtual Tape Server (VTS)
- Luminex Mainframe Virtual Tape (MVT) and CGX Solutions
- Oracle StorageTek SL3000 and SL8500 Tape Libraries
- Oracle StorageTek Virtual Storage Manager
- Tributary Systems Storage Director
The Hardware Security Module (HSM) that supports FICON is:
- Thales payShield 9000
Switches and directors compatible with FICON include:
- NOKIA (previously Alcatel-Lucent) 1830 PSS
- Brocade DCX series
- Brocade M-Series (formerly McDATA)
- Cisco MDS 9000 Series
- EMC Connectrix family, provided by Brocade or Cisco
Managed File Transfer solutions supporting FICON are:
- Alebra Technologies Parallel Data Mover
- Luminex Mainframe Data Integration (MDI) Platform
Legacy FICON switching platforms still operational encompass McDATA 6064, CNT UMD, and CNT (Inrange) FC/9000. The corporate history involves Inrange's acquisition by CNT in 2003, CNT's subsequent purchase by McDATA in 2005, followed by Brocade Communications Systems acquiring McDATA in 2007. Approximately 80% of installed FICON directors and switches originate from Brocade. McDATA began as a manufacturer of mainframe directors producing IBM ESCON directors and the FICON Bridge Card. Brocade maintains several joint patents with IBM related to FICON and ESCON technologies. Cisco Systems entered the FICON director market in 2003 with its initial offering.
Additional vendors producing FICON-compatible hardware include Optica Technologies and InfoPrint Solutions Company, which offers high-volume printers equipped with FICON connectivity.