Fibre Channel

Information about Fibre Channel

Fibre Channel 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 (INCITS), an American National Standards Institute (ANSI)–accredited standards committee. It started for use primarily in the supercomputer field, but has become the standard connection type for storage area networks (SAN) in enterprise storage. Despite common connotations of its name, Fibre Channel signaling can run on both twisted pair copper wire and fiber-optic cables.

Fibre Channel Protocol (FCP) is the interface protocol of SCSI on the Fibre Channel.

History

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. 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 SCSI, ATM, and IP, with SCSI being the predominant usage.

Fibre Channel Variants
NAME	Line-Rate (Gbit/s)	'''Throughput ( Mbyte/s)
1GFC	1.0625	100
2GFC	2.125	200
4GFC	4.25	400
8GFC	8.5	800
10GFC Serial	10.51875	1000
20GFC	10.52	2000
10GFC Parallel	12.75

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. Port is usually implemented in a device such as disk storage, an HBA on server or a Fibre Channel switch.

Point-to-Point (FC-P2P). Two devices are connected back to back. This is the simplest topology, with limited connectivity.
Arbitrated loop (FC-AL). In this design, all devices are in a loop or ring, similar to token ring networking. Adding or removing a device from the loop causes all activity on the loop to be interrupted. The failure of one device causes a break in the ring. Fibre Channel hubs exist to connect multiple devices together and may bypass failed ports. A loop may also be made by cabling each port to the next in a ring.
A minimal loop containing only two ports, while appearing to be similar to FC-P2P, differs considerably in terms of the protocol.
Switched fabric (FC-SW). All devices or loops of devices are connected to Fibre Channel switches, similar conceptually to modern Ethernet implementations. The switches manage the state of the fabric, providing optimized interconnections.

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	N/A	Loop fails (until port bypassed)	N/A
Mixing different link rates	N/A	No	Yes
Frame delivery	In order	In order	Not guaranteed
Access to medium	Dedicated	Arbitrated	Dedicated

Fibre Channel layers

Fibre Channel is a layered protocol. It consists of 5 layers, namely:

FC0 The physical layer, which includes cables, fiber optics, connectors, pinouts etc.
FC1 The data link layer, which implements the 8b/10b encoding and decoding of signals.
FC2 The network layer, defined by the FC-PI-2 standard, consists of the core of Fibre Channel, and defines the main protocols.
FC3 The common services layer, a thin layer that could eventually implement functions like encryption or RAID.
FC4 The Protocol Mapping layer. Layer in which other protocols, such as SCSI, are encapsulated into an information unit for delivery to FC2.

FC0, FC1, and FC2 are also known as FC-PH, the physical layers of fibre channel.

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

Fibre Channel products are available at 1 Gbit/s, 2 Gbit/s, 4 Gbit/s, 8 Gbit/s and 10 Gbit/s. 10 Gbit market is currently still developing. Products based on the 1, 2, 4 and 8 Gbit/s standards should be interoperable, and backward compatible. The 10 Gbit/s standard, however, is not backward compatible with any of the slower speed devices, as it differs considerably on FC1 level (64b/66b encoding instead of 8b/10b encoding).

Ports

FC topologies and port types

The following types of ports are defined by Fibre Channel:

node ports
N_port is a port on the node (e.g. host or storage device) used with both FC-P2P or FC-SW topologies. Also known as Node port.
NL_port is a port on the node used with an FC-AL topology. Also known as Node Loop port.
switch/router ports (used with FC-SW topology only)
F_port is a port on the switch that connects to a node point-to-point (i.e. connects to an N_port). Also known as Fabric port. An F_port is not loop capable.
FL_port is a port on the switch that connects to a FC-AL loop (i.e. to NL_ports). Also known as Fabric Loop port. Note that a switch port may automatically become either an F_port or an FL_port depending on what is connected.
E_port is the connection between two fibre channel switches. Also known as an Expansion port. When E_ports between two switches form a link, that link is referred to as an inter-switch link (ISL).
EX_port is the connection between a fibre channel router and a fibre channel switch. On the side of the switch it looks like a normal E_port, but on the side of the router it is a EX_port.
TE_port is a term used for multiple E_ports trunked together to create high bandwidth between switches. Also known as Trunking Expansion port.
general (catch-all) types
G_port or generic port on a switch can operate as an E_port or F_port.
L_port is the loose term used for any arbitrated loop port, NL_port or FL_port. Also known as Loop port.

Optical Carrier Medium Variants

Typical Fibre Channel connectors - modern LC on the left and older SC (typical for 100 MB/s speeds) on the right

Media Type	Speed (MB/s)	Transmitter	Variant	Distance
Single-Mode Fiber	400	1300 nm Longwave Laser	400-SM-LL-I	2 m - 2 km
	200	1550 nm Longwave Laser	200-SM-LL-V	2 m - >50 km
	200	1300 nm Longwave Laser	200-SM-LL-I	2 m - 2 km
	100	1550 nm Longwave Laser	100-SM-LL-V	2 m - >50 km
		1300 nm Longwave Laser	100-SM-LL-L	2 m - 10 km
		1300 nm Longwave Laser	100-SM-LL-I	2 m - 2 km
Multimode Fiber (50µm)	400	850 nm Shortwave Laser	400-M5-SN-I	0.5 m - 150m
	200		200-M5-SN-I	0.5 m - 300m
	100		100-M6-SN-I	0.5 m - 300m
	100		100-M6-SL-I	2 m - 175m

Fibre Channel Infrastructure

Fibre Channel switches are 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.

Directors offer a high port-count in a modular (slot-based) chassis with no single point of failure (high availability).
Switches are typically smaller, fixed-configuration (sometimes semi-modular), less redundant devices.

Brocade, Cisco and QLogic provide both directors and switches.

If multiple switch vendors are used in the same fabric (i.e. fabric is heterogeneous), the fabric will default to "interoperability mode", that is to a pure standarized Fibre Channel protocol. Some proprietary, advanced features may be disabled.

Fibre Channel Host Bus Adapters

Fibre Channel HBAs are available for all major open systems, computer architectures, and buses, including PCI and SBus (obsolete today). 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 is shared by all ports on a host bus adapter, and a port WWN (WWPN), which is unique to each port. Some Fibre Channel HBA manufacturers are Emulex, LSI, QLogic and ATTO Technology.

References

Clark, T. Designing Storage Area Networks, Addison-Wesley, 1999. ISBN 0-201-61584-3

External links

In computing, a storage area network (SAN) is an architecture to attach remote computer storage devices (such as disk arrays, tape libraries and optical jukeboxes) to servers in such a way that, to the operating system, the devices appear as locally attached.
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The International Committee for Information Technology Standards, or INCITS (pronounced "insights" ^[1]), is an ANSI-accredited forum of IT developers. It was formerly known as the X3 and NCITS.
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American National Standards Institute or ANSI (IPA pronunciation: [ænsiː]) is a private nonprofit organization that oversees the development of voluntary consensus standards for products, services, processes,
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For other uses, see Supercomputer (disambiguation).

A supercomputer is a computer that led the world (or was close to doing so) in terms of processing capacity, particularly speed of calculation, at the time of its introduction.
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Enterprise storage is the field of information technology focused on the storage, protection, and retrieval of data in large-scale environments (as is common in the field, the term 'enterprise' is used exclusively to mean large enterprises).
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Twisted pair cabling is a form of wiring in which two conductors are wound together for the purposes of canceling out electromagnetic interference (EMI) from external sources, electromagnetic radiation from the UTP cable, and crosstalk between neighboring pairs.
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2, 1
(mildly basic oxide)
Electronegativity 1.90 (Pauling scale)
Ionization energies
(more) 1st: 745.5 kJmol⁻¹
2nd: 1957.9 kJmol⁻¹
3rd: 3666 kJmol⁻¹

Atomic radius 135 pm
Atomic radius (calc.
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A wire is a single, usually cylindrical, elongated strand of drawn metal. Wires are used to bear mechanical loads and to carry electricity and telecommunications signals . Standard sizes are determined by various wire gauges.
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Fiber-optic communication is a method of transmitting information from one place to another by sending light through an optical fiber. The light forms an electromagnetic carrier wave that is modulated to carry information.
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cable is one or more wires or optical fibers bound together, typically in a common protective jacket or sheath. The individual wires or fibers inside the jacket may be covered or insulated. Combination cables may contain both electrical wires and optical fibers.
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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.
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HIPPI (HIgh Performance Parallel Interface) is a computer bus for the attachment of high speed storage devices to supercomputers. It was popular in the late 1980s and into the mid-to-late 1990s, but has since been replaced by ever-faster standard interfaces like SCSI and
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Asynchronous Transfer Mode (ATM) is a cell relay, packet switching network and data link layer protocol which encodes data traffic into small (53 bytes; 48 bytes of data and 5 bytes of header information) fixed-sized cells.
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Internet protocol may refer to:

The Internet Protocol, a data-oriented protocol used for communicating data across a packet-switched internetwork
The Internet protocol suite, a set of communications protocols that implement the protocol stack on which the Internet runs

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software port (usually just called a 'port') is a virtual data connection that can be used by programs to exchange data directly, instead of going through a file or other temporary storage location.
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In computer hardware, a 'port' serves as an interface between the computer and other computers or devices. Physically, a port is a specialized outlet on a piece of equipment to which a plug or cable connects.
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host controller, host adapter, or host bus adapter (HBA) connects a host system (the computer) to other network and storage devices. The terms are primarily used to refer to devices for connecting SCSI, Fibre Channel and eSATA devices, but devices for
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In a computer storage field, a Fibre Channel switch is a network switch compatible with Fibre Channel (FC) protocol. It allows the creation of a Fibre Channel fabric, that is currently the core component of most storage area networks.
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Fibre Channel point-to-point (FC-P2P) is a Fibre Channel topology where exactly two ports (devices) are directly connected to each other.

It is the simplest topology, no network addressing is needed, because each message has only one possible receiver.

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Arbitrated loop, also known as FC-AL, is a Fibre Channel topology in which devices are connected in a one-way loop fashion in a ring topology. Historically it was a lower-cost alternative to a fabric topology.
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Token ring local area network (LAN) technology was conceived in the late 1960s by Olof Söderblom, then working for IBM [1] ). US Patents were awarded in 1981 and Token-Ring was developed and promoted by IBM in the early 1980s and standardized as IEEE 802.
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A Fibre Channel fabric (or Fibre Channel switched fabric, FC-SW) is a switched fabric of Fibre Channel devices enabled by a Fibre Channel switch. Fabrics are normally subdivided by Fibre Channel zoning. Each fabric has a name server and provides other services.
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Ethernet is a family of frame-based computer networking technologies for local area networks (LANs). The name comes from the physical concept of the ether. It defines a number of wiring and signaling standards for the physical layer, through means of network access at the Media
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The Fibre Channel electrical interface is one of two related standards that can be used to physically interconnect computer devices. The other standard is a Fibre Channel optical interface, which is not covered by this article.
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In telecommunications, 8b/10b is a line code that maps 8-bit symbols to 10-bit symbols to achieve DC-balance (see DC coefficient) and bounded disparity, and yet provide enough state changes to allow reasonable clock recovery.
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