Fiber channel

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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 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.

Contents

[edit] 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 (my HIPPI drives use a 50-pin DD50 connector), 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.

[edit] Fibre Channel topologies

There are three major Fibre Channel topologies,

  • 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. Often an arbitrated loop between two ports will negotiate to become a P2P connection, but this is not required by the standard.
  • 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. Very limited security is available in today's fibre channel switches.
Attribute Point-to-Point Arbitrated loop Switched fabric
Max ports 2 127 ~16777216 (224)
Max bandwidth 2× link rate 2× link rate (Number of ports) × link rate
Address size N/A 8-bit ALPA 24-bit port ID
Address assignment N_port login Loop init. and fabric login Fabric login
Concurrent connections 1 1 Switch ports/2
Effect of port failure Link fails Loop fails unless bypassed Switch and port link fails
Concurrent maintenance Link down May disrupt entire loop Switch and port link down
Expansion Additional P2P links Attach loop to fabric Expand fabric
Redundancy Add redundant P2P link Use dual loops Use redundant switches
Link rates supported All All (all devices must be same) All (mixed rates available)
Media types supported All All All
Classes of service supported All 1, 2, & 3 All
Frame delivery In order In order Not guaranteed
Access to medium Dedicated Arbitrated Dedicated
Cost per port Port cost Port cost + loop function Port cost + fabric port

[edit] 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 products are available at 1 Gbit/s, 2 Gbit/s and 4 Gbit/s. An 8 Gbit/s standard is being developed. A 10 Gbit/s standard has been ratified, but is currently only used to interconnect switches. No 10 Gbit/s initiator or target products are available yet based on that standard. Products based on the 1, 2, 4 and 8 Gbit/s standards should be interoperable, and backward compatible; the 10 Gbit/s standard, however, will not be backward compatible with any of the slower speed devices.

[edit] Ports

The following types of ports are defined by Fibre Channel:

  • 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 InterSwitch Link or 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.
  • F_port is a fabric connection in a switched fabric topology. Also known as Fabric port. An F_port is not loop capable.
  • FL_port is the fabric connection in a public loop for an arbitrated loop topology. 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.
  • 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.
  • N_port is the node connection pertaining to hosts or storage devices in a Point-to-Point or switched fabric topology. Also known as Node port.
  • NL_port is the node connection pertaining to hosts or storage devices in an arbitrated loop topology. Also known as Node Loop 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.

[edit] Optical Carrier Medium Variants

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

[edit] Fibre Channel Infrastructure

Fibre Channel switches are divided into two classes of switches. These classes are not part of the standard, and the classification of every switch is left up to the manufacturer.

  • Director switches are characterized by offering a high port-count in a modular (slot-based) chassis with no single point of failure (high availability).
  • Fabric switches are typically fixed-configuration (sometimes semi-modular) non-redundant switches.

Brocade, Cisco, McData and QLogic provide both Director and fabric switches. If multiple switch vendors are used in the same fabric, the fabric will default to "interoperability mode" where some proprietary advanced features may be disabled.

[edit] 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 (16 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 Logic, QLogic and ATTO Technology. ATTO was the first to market with 4Gb and Quad Channel Host Adapters.

[edit] Fibre Channel References

RFCs
  • RFC 4369 - Definitions of Managed Objects for Internet Fibre Channel Protocol iFCP
  • RFC 4044 - Fibre Channel Management MIB
  • RFC 3723 - Securing Block Storage Protocols over IP
  • RFC 2837 - Definitions of Managed Objects for the Fabric Element in Fibre Channel Standard
  • RFC 2625 - IP and ARP over Fibre Channel (Obsoleted by: RFC 4338)
  • RFC 3831 - Transmission of IPv6 Packets over Fibre Channel (Obsoleted by: RFC 4338)
  • RFC 4338 - Transmission of IPv6, IPv4, and Address Resolution Protocol (ARP) Packets over Fibre Channel
Drafts
Other References

[edit] See also

[edit] External links

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