Fibre Channel

Fibre Channel
Layer 4. Protocol mapping
LUN masking
Layer 3. Common services
Layer 2. Network
Fibre Channel fabric
Fibre Channel zoning
Registered State Change Notification
Layer 1. Data link
Fibre Channel 8B/10B encoding
Layer 0. Physical

Fibre Channel, or FC, is a high-speed network technology (commonly running at 2-, 4-, 8- and 16-gigabit per second rates) primarily used to connect computer data storage.[1][2] Fibre Channel is standardized in the T11 Technical Committee of the International Committee for Information Technology Standards (INCITS), an American National Standards Institute (ANSI)-accredited standards committee. Fibre Channel was primarily used in supercomputers, but has become a common connection type for storage area networks (SAN) in enterprise storage. Despite its name, Fibre Channel signaling can run on an electrical interface in addition to fiber-optic cables.[1][2]

Fibre Channel Protocol (FCP) is a transport protocol (similar to TCP used in IP networks) that predominantly transports SCSI commands over Fibre Channel networks.[1][2]

Etymology

When the technology was developed, it supported only optical cabling (fiber); support for copper cables was added later. Despite this the development committee decided to keep the same name but switch to the British English spelling fibre for the standard. In American English spelling fiber refers only to optical cabling.[3] Thus, a network using fibre channel can be implemented either with copper or optical fiber.

History

Fibre Channel was developed in a committee through industry cooperation, while SCSI was developed by a single vendor and later submitted for standardization.[3]

Fibre Channel started in 1988, with ANSI standard approval in 1994, as a way to simplify the HIPPI system then in use for similar roles. HIPPI used a massive 50-pair cable with bulky connectors, and had limited cable lengths. When fibre channel started to compete for the mass storage market its primary competitor was IBM's proprietary Serial Storage Architecture (SSA) interface. Eventually the market chose fibre channel over SSA, depriving IBM of control over the next generation of mid- to high-end storage technology. Fibre Channel was primarily concerned with simplifying the connections and increasing distances, as opposed to increasing speeds. Later, designers added the goals of connecting SCSI disk storage, providing higher speeds and far greater numbers of connected devices.

It also added support for any number of "upper layer" protocols, including ATM, IP and FICON, with SCSI being the predominant usage.

Initially, the standard also ratified lower speed Fibre Channel versions with 132.8125 Mbit/s ("12,5 MB/s"), 265.625 Mbit/s ("25 MB/s"), and 531.25 Mbit/s ("50 MB/s") that were already growing out of use at the time.[4]

Fibre channel has seen active development since its inception, with numerous speed improvements on a variety of underlying transport media.

For example, the following table shows native fibre channel speed variants:[5]

Fibre Channel Variants
NAME Line-rate (gigabaud) Line coding Nominal throughput
full duplex; MB/s
 Net throughput
per direction; MB/s[v 1][v 2]		 Efficiency[v 3][v 2] Availability
1GFC 1.0625 8b10b 200 98.44 77.7% 1997
2GFC 2.125 8b10b 400 196.9 77.7% 2001
4GFC 4.25 8b10b 800 393.8 77.7% 2004
8GFC 8.5 8b10b 1,600 787.6 77.7% 2005
10GFC 10.51875 64b66b 2,400 1,181 94.2% 2008
16GFC 14.025 64b66b 3,200 1,575 94.2% 2011
32GFC 28.05 6,400 2016 (projected)
128GFC 4x28.05 25,600 2016 (projected)
  1. ↑ 1 MB = 10242 Byte (MiB)
  2. 1 2 taking into account line coding (L1), interframe gap, and frame header (L2) overhead
  3. ↑ based on nominal bitrate

Fibre Channel topologies

There are three major fibre channel topologies, describing how a number of ports are connected together. A port in fibre channel terminology is any entity that actively communicates over the network, not necessarily a hardware port. This port is usually implemented in a device such as disk storage, an HBA on a server or a fibre channel switch.[1]

Attribute Point-to-Point Arbitrated loop Switched fabric
Max ports 2 127 ~16777216 (224)
Address size N/A 8-bit ALPA 24-bit port ID
Side effect of port failure Link fails Loop fails (until port bypassed) N/A
Mixing different link rates No No Yes
Frame delivery In order In order Not guaranteed
Access to medium Dedicated Arbitrated Dedicated

Layers

Fibre Channel does not follow the OSI model layering, but is split similarly into five layers:

Layers FC0 through FC2 are also known as FC-PH, the physical layers of fibre channel.

Fibre Channel routers operate up to FC4 level (i.e. they may operate as SCSI routers), switches up to FC2 and hubs on FC0 only.

Fibre Channel products are available at 1, 2, 4, 8, 10, 16 and 20 Gbit/s; these protocol flavors are called accordingly 1GFC, 2GFC, 4GFC, 8GFC, 10GFC, 16GFC or 20GFC. The 16GFC standard was approved by the INCITS T11 committee in 2010, and those products became available in 2011. Products based on the 1GFC, 2GFC, 4GFC, 8GFC and 16GFC standards should be interoperable and backward compatible. The 1GFC, 2GFC, 4GFC, 8GFC designs all use 8b/10b encoding, while the 10G and 16GFC standard uses 64b/66b encoding. Unlike the 10GFC and 20GFC standards, 16GFC provides backward compatibility with 4GFC and 8GFC.

The 10 Gbit/s standard and its 20 Gbit/s derivative, however, are not backward-compatible with any of the slower-speed devices, as they differ considerably on FC1 level in using 64b/66b encoding instead of 8b/10b encoding and are primarily used as inter-switch links.

Ports

FC topologies and port types

The following types of ports are defined by Fibre Channel:

(*Note: The term "trunking" is not a standard Fibre Channel term and is used by vendors interchangeably. For example: A trunk (an aggregation of ISLs) in a Brocade device is referred to as a Port Channel by Cisco. Whereas Cisco refers to trunking as an EISL.)

Optical carrier medium variants

Typical Fibre connectors – modern LC (Lucent Connector) on the left and older SC (Subscriber Connector, typical for 1 Gbit/s speeds) on the right
Fiber modality Speed (MB/s) Transmitter[6] Medium variant Distance
Single-mode fiber 1,600 1,310 nm longwave light[ITS 1] 1600-SM-LC-L[ITS 2] 0.5 m – 10 km
1,490 nm longwave light[ITS 1] 1600-SM-LZ-I[ITS 2] 0.5 m – 2 km
800 1,310 nm longwave light[ITS 3] 800-SM-LC-L[ITS 4] 2 m – 10 km
800-SM-LC-I[ITS 4] 2 m – 1.4 km
400 1,310 nm longwave light[ITS 3][ITS 5] 400-SM-LC-L[ITS 6] 2 m – 10 km
400-SM-LC-M[ITS 4] 2 m – 4 km
400-SM-LL-I[ITS 7] 2 m – 2 km
200 1,550 nm longwave light[ITS 8] 200-SM-LL-V[ITS 8] 2 m – 50 km
1,310 nm longwave light[ITS 5][ITS 3] 200-SM-LC-L[ITS 6] 2 m – 10 km
200-SM-LL-I[ITS 7] 2 m – 2 km
100 1,550 nm longwave light[ITS 8] 100-SM-LL-V[ITS 8] 2 m – 50 km
1,310 nm longwave light[ITS 9][ITS 3] 100-SM-LL-L[ITS 10]
100-SM-LC-L[ITS 6] 		2 m – 10 km
100-SM-LL-I[ITS 10] 2 m – 2 km
Multimode Fiber 1,600 850 nm shortwave light[ITS 11][ITS 12][ITS 13] 1600-M5F-SN-I[ITS 14] 0.5 m – 125 m
1600-M5E-SN-I[ITS 14] 0.5–100 m
1600-M5-SN-S[ITS 14] 0.5–35 m
1600-M6-SN-S[ITS 15] 0.5–15 m
800 800-M5F-SN-I[ITS 14] 0.5–190 m
800-M5E-SN-I[ITS 16] 0.5–150 m
800-M5-SN-S[ITS 16] 0.5–50 m
800-M6-SN-S[ITS 16] 0.5–21 m
400 400-M5F-SN-I[ITS 14] 0.5–400 m
400-M5E-SN-I[ITS 16] 0.5–380 m
400-M5-SN-I[ITS 17] 0.5–150 m
400-M6-SN-I[ITS 17] 0.5–70 m
200 200-M5E-SN-I[ITS 16] 0.5–500 m
200-M5-SN-I[ITS 17] 0.5–300 m
200-M6-SN-I[ITS 17] 0.5–150 m
100 100-M5E-SN-I[ITS 18] 0.5–860 m
100-M5-SN-I[ITS 19] 0.5–500 m
100-M6-SN-I[ITS 20] 0.5–300 m
100-M5-SL-I[ITS 20] 2–500 m
100-M6-SL-I[ITS 21] 2–175 m
Multimode fiber Fiber diameter FC media designation
OM1 62.5 µm M6
OM2 50 µm M5
OM3 50 µm M5E
OM4 50 µm M5F

Modern Fibre Channel devices support SFP transceiver, mainly with LC (Lucent Connector) fiber connector. Older 1GFC devices used GBIC transceiver, mainly with SC (Subscriber Connector) fiber connector.

Fibre Channel infrastructure

SAN switch with LC optical connectors installed and multimode fiber (orange).

Fibre Channel switches can be divided into two classes. These classes are not part of the standard, and the classification of every switch is a marketing decision of the manufacturer:

A fabric consisting entirely of one vendor is considered to be homogeneous. This is often referred to as operating in its "native mode" and allows the vendor to add proprietary features which may not be compliant with the Fibre Channel standard.

If multiple switch vendors are used within the same fabric it is heterogeneous, the switches may only achieve adjacency if all switches are placed into their interoperability modes. This is called the "open fabric" mode as each vendor's switch may have to disable its proprietary features to comply with the Fibre Channel standard.

Some switch manufacturers offer a variety of interoperability modes above and beyond the "native" and "open fabric" states. These "native interoperability" modes allow switches to operate in the native mode of another vendor and still maintain some of the proprietary behaviors of both. However, running in native interoperability mode may still disable some proprietary features and can produce fabrics of questionable stability.

Fibre Channel host bus adapters

Fibre Channel HBAs, as well as CNAs, are available for all major open systems, computer architectures, and buses, including PCI and SBus. Some are OS dependent. Each HBA has a unique World Wide Name (WWN), which is similar to an Ethernet MAC address in that it uses an Organizationally Unique Identifier (OUI) assigned by the IEEE. However, WWNs are longer (8 bytes). There are two types of WWNs on a HBA; a node WWN (WWNN), which can be shared by some or all ports of a device, and a port WWN (WWPN), which is necessarily unique to each port.

Development tools

When developing and/or troubleshooting the Fibre Channel bus, examination of hardware signals can be very important to find problems. Logic analyzers and bus analyzers are tools which collect, analyze, decode, store signals so people can view the high-speed waveforms at their leisure.

See also

References

  1. 1 2 3 4 5 Preston, W. Curtis (2002). "Fibre Channel Architecture". Using SANs and NAS. Sebastopol, CA: O'Reilly Media. pp. 19–39. ISBN 978-0-596-00153-7. OCLC 472853124.
  2. 1 2 3 Riabov, Vladmir V. (2004). "Storage Area Networks (SANs)". In Bidgoli, Hossein. The Internet Encyclopedia. Volume 3, P-Z. Hoboken, NJ: John Wiley & Sons. pp. 329–338. ISBN 978-0-471-68997-3. OCLC 55610291.
  3. 1 2 page 31 of http://www.redbooks.ibm.com/redbooks/pdfs/sg245470.pdf
  4. ↑ Fibre Channel Physical and Signaling Interface (FC-PH) Rev 4.3, June 1, 1994
  5. ↑ "Roadmaps". Fibre Channel Industry Association. Retrieved 2013-01-06.
  6. ↑ Transmitter values listed are the currently specified values for the variant listed. Some older versions of the FC standards listed slightly different values (however, the values listed here fall within the +/- variance allowed). Individual variations for each specification are listed in the references associated with those entries in this table. FC-PH = X3T11 Project 755D; FC-PH-2 = X3T11 Project 901D; FC-PI-4 = INCITS Project 1647-D; FC-PI-5 = INCITS Project 2118D. Copies are available from INCITS.

INCITS Fibre Channel standards

  1. 1 2 FC-PI-5 Clause 6.3
  2. 1 2 FC-PI-5 Clause 8.1
  3. 1 2 3 4 FC-PI-4 Clause 6.3
  4. 1 2 3 FC-PI-4 Clause 8.1
  5. 1 2 FC-PH-2 lists 1300nm (see clause 6.1 and 8.1)
  6. 1 2 3 FC-PI clause 8.1
  7. 1 2 FC-PH-2 clause 8.1
  8. 1 2 3 4 FC-PI-4 Clause 11
  9. ↑ FC-PH lists 1300nm (see clause 6.1 and 8.1)
  10. 1 2 FC-PH Clause 8.1
  11. ↑ FC-PI-5 Clause 6.4
  12. ↑ FC-PI-4 Clause 6.4
  13. ↑ The older FC-PH and FC-PH-2 list 850nm (for 62.5µm cables) and 780nm (for 50µm cables)(see clause 6.2, 8.2, and 8.3)
  14. 1 2 3 4 5 FC-PI-5 Clause 8.2
  15. ↑ FC-PI-5 Annex A
  16. 1 2 3 4 5 FC-PI-4 Clause 8.2
  17. 1 2 3 4 FC-PI Clause 8.2
  18. ↑ PC-PI-4 Clause 8.2
  19. ↑ PC-PI Clause 8.2
  20. 1 2 PC-PI Clause 8.2
  21. ↑ FC-PH Annex C and Annex E

Sources

Further reading

External links

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