FICON protocol. Short educational program
In this article I will briefly talk about the basics of FICON - the protocol is inextricably linked with the world of mainframes. This is a small introduction article describing the FICON concept and therefore I will refrain from deep technical details. If necessary, this will be done in the following articles.
FICON (FIber CONnection) is a proprietary protocol and industry I / O standard used to connect mainframes to storage systems and peripherals. It appeared in 1998 as a replacement for the outdated ESCON protocol (Enterprise Server CONnection) and greatly surpasses it in all basic characteristics. As you have already guessed, this standard was invented within the walls of the company, which is the main mainframe manufacturer on our planet - IBM.
At the moment, IBM-compatible mainframes are also produced by Fujitsu, NEC, Hitachi, although they practically do not compete with IBM and are sold mainly in the Japanese market. FICON is also used in their products. And the data storage systems and tape libraries with FICON support are produced by all the major players in the data storage market (EMC, Hewlett-Packard, IBM, Hitachi). In fact, the FICON protocol's storage system support is hardly any indication that this is a Hi-End system.
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The FICON switch market is not replete with so many manufacturers. In fact, this market is divided by two manufacturers: most of it is occupied by Brocade (according to various estimates, about 70-80%), and the rest is controlled by the well-known Cisco Systems.
The need to develop this protocol was due to the fact that mainframes were always built on a closed architecture and, in particular, were not supported by everyone’s favorite SCSI. And in our century, the SCSI protocol is used on almost every first server: SAS disks on servers (Serial Attached SCSI), virtual volumes from external storage systems using the FCP protocol (SCSI over FC), virtual volumes from external storage systems using the iSCSI protocol. In a historic race of speeds of interfaces, one day there was such a situation that ESCON speeds were not convenient for anyone, and replacements from open systems (in particular, SCSI) could not be used for mainframes, since this migration led to the need to make a large number of architectural changes to the mainframe software. Therefore, clever minds from IBM decided to develop a protocol similar to the ESCON format but on an open and dynamically developing infrastructure. This infrastructure was Fiber Channel. Developed by IBM in 1998, FICON - is nothing more than an adaptation and some modification of ESCON to use it as a top-level protocol on the Fiber Channel stack.
Existing FICON devices currently support speeds of 2, 4, 8, 16 Gbit / s. The truth is worth noting that at the moment the speed is 16 Gbit / s. can be obtained exclusively on the Brocade hardware, since Cisco does not yet have such solutions. The maximum distance depends on the speed of the interfaces, the equipment used and other factors, but usually does not exceed 100 kilometers (without using FCIP routers). At distances of more than 500 meters, it will be necessary to use special optical modules (long-wave SFP) and single-mode optical fiber (dark fiber).
There are three main ways to connect mainframes to peripheral equipment through FICON:
FICON uses Fiber Channel hardware infrastructure. That is, the same switches are used, the same fiber optic cables with an LC-LC connector, the same transceivers that are used to connect open systems servers (not mainframes) to storage systems. FICON is just one of the upper level protocols that is encapsulated into the Fiber Channel stack at the top level (FC-4). It is encapsulated on the FC stack as well as SCSI in the most popular FCP. FICON and FCP can be used simultaneously on the same hardware infrastructure (share the same switches and director of the storage area network). The administration of FICON factories is very similar to the administration of ordinary factories for open systems, but it has its own very funny features, primarily related to device addressing in mainframes.
That's all! Thank you for reading to the end! If suddenly someone will be interested in technical continuation, then it will not take long.
A bit of history
FICON (FIber CONnection) is a proprietary protocol and industry I / O standard used to connect mainframes to storage systems and peripherals. It appeared in 1998 as a replacement for the outdated ESCON protocol (Enterprise Server CONnection) and greatly surpasses it in all basic characteristics. As you have already guessed, this standard was invented within the walls of the company, which is the main mainframe manufacturer on our planet - IBM.
At the moment, IBM-compatible mainframes are also produced by Fujitsu, NEC, Hitachi, although they practically do not compete with IBM and are sold mainly in the Japanese market. FICON is also used in their products. And the data storage systems and tape libraries with FICON support are produced by all the major players in the data storage market (EMC, Hewlett-Packard, IBM, Hitachi). In fact, the FICON protocol's storage system support is hardly any indication that this is a Hi-End system.
')
The FICON switch market is not replete with so many manufacturers. In fact, this market is divided by two manufacturers: most of it is occupied by Brocade (according to various estimates, about 70-80%), and the rest is controlled by the well-known Cisco Systems.
The need to develop this protocol was due to the fact that mainframes were always built on a closed architecture and, in particular, were not supported by everyone’s favorite SCSI. And in our century, the SCSI protocol is used on almost every first server: SAS disks on servers (Serial Attached SCSI), virtual volumes from external storage systems using the FCP protocol (SCSI over FC), virtual volumes from external storage systems using the iSCSI protocol. In a historic race of speeds of interfaces, one day there was such a situation that ESCON speeds were not convenient for anyone, and replacements from open systems (in particular, SCSI) could not be used for mainframes, since this migration led to the need to make a large number of architectural changes to the mainframe software. Therefore, clever minds from IBM decided to develop a protocol similar to the ESCON format but on an open and dynamically developing infrastructure. This infrastructure was Fiber Channel. Developed by IBM in 1998, FICON - is nothing more than an adaptation and some modification of ESCON to use it as a top-level protocol on the Fiber Channel stack.
Specifications
Existing FICON devices currently support speeds of 2, 4, 8, 16 Gbit / s. The truth is worth noting that at the moment the speed is 16 Gbit / s. can be obtained exclusively on the Brocade hardware, since Cisco does not yet have such solutions. The maximum distance depends on the speed of the interfaces, the equipment used and other factors, but usually does not exceed 100 kilometers (without using FCIP routers). At distances of more than 500 meters, it will be necessary to use special optical modules (long-wave SFP) and single-mode optical fiber (dark fiber).
Topologies
There are three main ways to connect mainframes to peripheral equipment through FICON:
- The use of direct connections (point-to-point). This is the easiest way. In this case, the FICON mainframe port connects directly to the peripheral device port.
- Switched point-to-point. In this case, the mainframe port and the peripheral port are connected to the same FC switch.
- Cascade Ficon. In this case, the mainframe port is connected to one switch, and the peripheral device port is connected to another switch that is connected to the first one through an inter-switch link (ISL, Inter-Switch Link).
These three methods differ not only in the physical aspect of connectivity, but also directly affect the way you configure FICON switches and mainframe. They even use different types of addressing. In particular, when using direct connections, point-to-point address consists of only one byte, which is used to address the device. When using the topology cascade FICON address consists of two bytes. The first byte is used to identify the FC of the switch to which the peripheral device (domain ID of the switch) is connected, the second to identify the physical port address of the device on the switch.
Similarities and Differences with Fiber Channel Protocol (FCP)
FICON uses Fiber Channel hardware infrastructure. That is, the same switches are used, the same fiber optic cables with an LC-LC connector, the same transceivers that are used to connect open systems servers (not mainframes) to storage systems. FICON is just one of the upper level protocols that is encapsulated into the Fiber Channel stack at the top level (FC-4). It is encapsulated on the FC stack as well as SCSI in the most popular FCP. FICON and FCP can be used simultaneously on the same hardware infrastructure (share the same switches and director of the storage area network). The administration of FICON factories is very similar to the administration of ordinary factories for open systems, but it has its own very funny features, primarily related to device addressing in mainframes.
That's all! Thank you for reading to the end! If suddenly someone will be interested in technical continuation, then it will not take long.
Source: https://habr.com/ru/post/167931/
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