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In storage networking, Fibre Channel zoning is the partitioning of a Fibre Channel fabric into smaller subsets to restrict interference, add security, and to simplify management. While a SAN makes available several virtual disks (LUNs), each system connected to the SAN should only be allowed access to a controlled subset of the LUNs. Zoning applies only to the switched fabric topology (FC-SW), it does not exist in simpler Fibre Channel topologies.

Zoning is sometimes confused with LUN masking, because it serves the same goals. LUN masking, however, works on Fibre Channel level 4 (i.e. on SCSI level), while zoning works on level 2. This allows zoning to be implemented on switches, whereas LUN masking is performed on endpoint devices - host adapters or disk array controllers.

Zoning is also different from VSANs, in that each port can be a member of multiple zones, but only one VSAN. VSAN (similarly to VLAN) is in fact a separate network (separate sub-fabric), with its own fabric services^{[clarification needed]} (including its own separate zoning).

Zoning types[link]

There are two main methods of zoning, the two methods being hard and soft, that combine with two sets of attributes, name and port.

Soft and Hard zoning[link]

The fabric name service allows each device to query the addresses of all other devices. Soft zoning restricts only the fabric name service, to show only an allowed subset of devices. Therefore, when a server looks at the content of the fabric, it will only see the devices it is allowed to see. However, any server can still attempt to contact any device on the network by address. In this way, soft zoning is similar to the computing concept of security through obscurity.

In contrast, hard zoning restricts actual communication across a fabric. This requires efficient hardware implementation (frame filtering) in the fabric switches, but is much more secure.

Port and WWN zoning[link]

Zoning can also be applied to either switch ports or end-station names. Port zoning restricts specific switch ports from seeing unauthorized ports. WWN zoning (also called name zoning) restricts access by a device's World Wide Name (WWN). With port zoning, even when a device is unplugged from a switch port and a different one is plugged in, the new device has access to the zone instead of the old one - i.e. the fact that a device's WWN changed is ignored. With WWN zoning, when a device is unplugged from a switch port and plugged into a different port (perhaps on a different switch) it still has access to the zone, because the switches check only a device's WWN - i.e. the specific port that a device connects to is ignored. This is more flexible, but WWNs can be easily spoofed, reducing security. http://en.wikipedia.org/wiki/Template:Confusing

Use[link]

Currently, the combination of hard and WWN zoning is the most popular. Because port zoning is non-standard, it usually requires a homogeneous SAN (all switches from one vendor).

In order to bring the created zones together for ease of deployment and management a zoneset is employed (also called zoning config). A zoneset is merely a logical container for the individual zones, that are designed to work at the same time. A zoneset can contain WWN zones, port zones, or a combination of both (hybrid zones). The zoneset must be activated within the fabric (i.e. distributed through all the switches and then simultaneously enforced). Switches may contain more than one zoneset, but only one zoneset can be active in the entire fabric.

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Fibre Channel, or FC, is a gigabit-speed network technology primarily used for storage networking.^[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 the supercomputer field, but now, has become the standard connection type for storage area networks (SAN) in enterprise storage. Despite its name, Fibre Channel signaling can run on both twisted pair copper wire and fiber-optic cables.^[1][2]

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

History[link]

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, rather than give IBM 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 and IP, with SCSI being the predominant usage.

The following table shows Fibre Channel speed variants:^[3]

* – Throughput for duplex connections

Fibre Channel topologies[link]

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]

• Point-to-point (FC-P2P). Two devices are connected directly to each other. This is the simplest topology, with limited connectivity.^[1]

• 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.
  • Only one pair of ports can communicate concurrently on a loop.
  • Maximum speed of 8GFC.

• Switched fabric (FC-SW). All devices or loops of devices are connected to Fibre Channel switches, similar conceptually to modern Ethernet implementations. Advantages of this topology over FC-P2P or FC-AL include:
  • The switches manage the state of the fabric, providing optimized interconnections.
  • The traffic between two ports flows through the switches only, it is not transmitted to any other port.
  • Failure of a port is isolated and should not affect operation of other ports.
  • Multiple pairs of ports may communicate simultaneously in a fabric.

Layers[link]

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

• FC4 – Protocol-mapping layer, in which application protocols, such as SCSI or IP, are encapsulated into a PDU for delivery to FC2.
• FC3 – Common services layer, a thin layer that could eventually implement functions like encryption or RAID redundancy algorithms;
• FC2 – Network layer, defined by the FC-PI-2 standard, consists of the core of Fibre Channel, and defines the main protocols;
• FC1 – Data link layer, which implements line coding of signals;
• FC0 – PHY, includes cabling, connectors etc.;

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 are expected to become 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 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[link]

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.
  • 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.
  • 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).
  • D_port is a diagnostic port, used solely for the purpose of running link-level diagnostics between two switches and to isolate link level fault on the port, in the SFP, or in the cable.
  • 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 * a Cisco addition to Fibre Channel, now adopted as a standard. It is an extended ISL or EISL. The TE_port provides not only standard E_port functions but allows for routing of multiple VSANs (Virtual SANs). This is accomplished by modifying the standard Fibre Channel frame (vsan tagging) upon ingress/egress of the VSAN environment. Also known as Trunking E_port.
  • VE_Port an INCITS T11 addition, FCIP interconnected E-Port/ISL, i.e. fabrics will merge.
  • VEX_Port a INCITS T11 addition, is a FCIP interconnected EX-Port, routing needed via lsan zoning to connect initiator to a target.

• general (catch-all) types
  • Auto or auto-sensing port found in Cisco switches, can automatically become an E_, TE_, F_, or FL_port as needed.
  • Fx_port a generic port that can become a F_port (when connected to a N_port) or a FL_port (when connected to a NL_port). Found only on Cisco devices where oversubscription is a factor.
  • GL_port on a switch can operate as an E_port, FL_port, or F_port. Found on QLogic switches.
  • G_port or generic port on a switch can operate as an E_port or F_port. Found on Brocade, McData, and QLogic switches.
  • L_port is the loose term used for any arbitrated loop port, NL_port or FL_port. Also known as Loop port.
  • U_port is the loose term used for any arbitrated port. Also known as Universal port. Found only on Brocade switches.....

(*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[link]

Typical Fibre Channel connectors – modern LC on the left and older SC (typical for 1Gbit/s speeds) on the right

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

Fibre Channel infrastructure[link]

SAN switch with optical FC connectors installed.

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:

• 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.

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[link]

Fibre Channel HBAs 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[link]

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[link]

References[link]

INCITS Fibre Channel standards[link]

Sources[link]

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

Further reading[link]

• RFC 2625 – IP and ARP over Fibre Channel
• RFC 2837 – Definitions of Managed Objects for the Fabric Element in Fibre Channel Standard
• RFC 3723 – Securing Block Storage Protocols over IP
• RFC 4044 – Fibre Channel Management MIB
• RFC 4625 – Fibre Channel Routing Information MIB
• RFC 4626 – MIB for Fibre Channel's Fabric Shortest Path First (FSPF) Protocol

External links[link]

• Fibre Channel Industry Association (FCIA)
• INCITS technical committee responsible for FC standards(T11)
• IBM SAN Survival Guide
• Introduction to Storage Area Networks
• Fibre Channel overview
• Fibre Channel tutorial (UNH-IOL)
• Storage Networking Industry Association (SNIA)

v t e Computer bus official and de facto standards (wired) General System bus Front-side bus Back-side bus Daisy chain Control bus Address bus Bus contention Plug and play List of bus bandwidths Standards S-100 bus Unibus VAXBI MBus STD Bus SMBus Q-Bus ISA Zorro II Zorro III CAMAC FASTBUS LPC HP Precision Bus EISA VME VXI VXS NuBus TURBOchannel MCA SBus VLB PCI PXI HP GSC bus CoreConnect InfiniBand UPA PCI-X AGP PCI Express Intel QuickPath Interconnect HyperTransport Portable PC Card ExpressCard Embedded Multidrop bus AMBA Wishbone Storage ST-506 ESDI SMD Parallel ATA (PATA) DMA SSA HIPPI USB MSC FireWire (1394) Serial ATA (SATA) eSATA eSATAp SCSI Parallel SCSI Serial Attached SCSI (SAS) Fibre Channel (FC) iSCSI ATAoE Peripheral Apple Desktop Bus HIL MIDI Multibus RS-232 (serial port) DMX512-A IEEE-488 (GPIB) EIA/RS-422 IEEE-1284 (parallel port) UNI/O ACCESS.bus 1-Wire I²C SPI EIA/RS-485 Parallel SCSI Profibus USB FireWire (1394) Fibre Channel Camera Link External PCI Express x16 Thunderbolt Note: interfaces are listed in speed ascending order (roughly), the interface at the end of each section should be the fastest Category

v t e Solid-state drives Key terminology Encryption ECC Flash file system Flash memory - SLC/MLC Flash memory controller Garbage collection IOPS MB/s Over-provisioning Secure erase TRIM command Wear leveling Write amplification Flash manufacturers Hynix Intel Micron Samsung Toshiba Controllers Independent Indilinx JMicron Marvell Phison SandForce Captive Fusion-io Intel Samsung STEC SSD manufacturers List of solid-state drive manufacturers Interfaces SATA SAS FC USB PCIe NVM Express Related organizations INCITS JEDEC/JC-64.8 ONFI NVMHCI SATA-IO SFF Committee SNIA SSSI T10/SCSI T11/FC T13/ATA Category