Fc Technology Overview

Fibre Channel Technology Definition: Fibre Channel is a technology for transmitting data between computer devices at data rates of up to 4 Gbps (and 10 Gbps in the near future). Fibre Channel is especially suited for connecting computer servers to shared storage devices and for interconnecting storage controllers and drives. Since Fibre Channel is three times as fast, it has begun to replace the Small Computer System Interface (SCSI) as the transmission interface between servers and clustered storage devices. Fibre channel is more flexible; devices can be as far as ten kilometers (about six miles) apart if optical fiber is used as the physical medium. Optical fiber is not required for shorter distances, however, because Fibre Channel also works using coaxial cable and ordinary telephone twisted pair. Fibre Channel offers point-to-point, switched, and loop interfaces. It is designed to interoperate with SCSI, the Internet Protocol (IP) and other protocols, but has been criticized for its lack of compatibility primarily because (like in the early days of SCSI technology) manufacturers sometimes interpret specifications differently and vary their implementations. Standards for Fibre Channel are specified by the Fibre Channel Physical and Signaling standard, and the ANSI X3.230-1994, which is also ISO 14165-1

Fibre Channel Overview For demanding applications, Fibre Channel (FC) technology has entrenched itself as the quintessential storage area network (SAN) interconnect, providing high speed, high reliability, and inherent security for storage network users. Fibre Channel technology is a block-based networking approach based on ANSI standard X3.230-1994 (ISO 14165-1). It specifies the interconnections and signaling needed to establish a network "fabric" between servers, switches and storage subsystems such as disk arrays or tape libraries. FC can carry virtually any kind of traffic. Fibre Channel uses optical fiber, coaxial copper or twisted pair copper cabling to carry SAN data at speeds of 1 Gbps, 2 Gbps, 4 Gbps and (more recently) 10 Gbps. At the same time, latency is kept very low, minimizing the delay between data requests and deliveries. For example, the latency across a typical FC switch is only a few microseconds. It is this combination of high speed and low latency that makes FC an ideal choice for time-sensitive or transactional processing environments. These attributes also support high scalability, allowing more storage systems and servers to be interconnected. Fibre Channel is also supports a variety of topologies, and is able to operate between two devices in a simple point-to-point mode, in an economical arbitrated loop to connect up to 126 devices, or (most commonly) in a powerful switched fabric providing simultaneous full-speed connections for many thousands of devices. Topologies and cable types can easily be mixed in the same SAN. Fibre Channel technology denotes four main service "classes" to meet a variety of enterprise needs. FC Class-1 involves a dedicated connection running at full bandwidth using delivery confirmations. FC Class2 still provides confirmed delivery, but does not use a dedicated connection. FC Class-3 does not confirm delivery, though this reduction in overhead can improve apparent performance slightly. FC Class-4 provides confirmed delivery along with advanced features such as virtual connections and fractional bandwidth. Fibre Channel is regarded as a very reliable SAN technology. The host bus adapters (HBAs) and switches are generally quite robust, minimizing the rate of device failures. The FC SAN fabric allows for multiple connection paths and redundant connections, so if a hardware fault or cabling issue arises, a new path can

be found and communication can failover to an alternate connection -- keeping storage and applications connected (even at reduced performance) until corrective action can be taken. Alternatively, multiple connections can be aggregated (or trunked) for even better bandwidth. For example, two 2 Gbps connections can be aggregated so that they effectively behave as one 4 Gbps connection. The availability of multiple or redundant connections enables load balancing where SAN traffic is analyzed and can be dynamically rerouted from busy paths (bottlenecks) through less-used paths. Security is another important attribute of Fibre Channel technology. A "network" lets multiple devices communicate together. But for a SAN, it's generally not desirable to allow every server to recognize or access every LUN on the SAN. In actual practice, LUNs must be configured so that they are visible to only certain applications -- configuring security is a core part of the storage provisioning process. Zoning makes it possible for devices within a Fibre Channel network to see each other. By limiting the visibility of end devices, servers (hosts) can only see and access storage devices that are placed into the same zone. Once the SAN is zoned, LUNs are masked so that each host server can only see specific LUNs. However, there are some recognized disadvantages to FC. Fibre Channel has been widely criticized for its expense and complexity. A specialized HBA card is needed for each server. Each HBA must then connect to corresponding port on a Fibre Channel switch -- creating the SAN "fabric." Every combination of HBA and switch port can cost thousands of dollars for the storage organization. This is the primary reason why many organizations connect only large, high-end storage systems to their SAN. Once LUNs are created in storage, they must be zoned and masked to ensure that they are only accessible to the proper servers or applications; often an onerous and error-prone procedure. These processes add complexity and costly management overhead to Fibre Channel SANs.

Port Details Assigned Value

Type

Meaning

Reference

1

unknown

for use when the type is not known, or is [RFC4044] "unidentified" as specified in section 5.1.2.10 of "Fibre Channel - Generic Services - 3 (FC-GS-3)", ANSI INCITS 348-2001, 2001.

2

other

used for types without assigned values

[RFC4044]

3

--

an obsolete value, not to be re-assigned

[RFC4044]

4

N_Port

see "Fibre Channel - Framing and Signaling (FCFS)", ANSI INCITS 373-2003, April 2003.

[RFC4044]

5

NL_Port

see "Fibre Channel - Framing and Signaling (FCFS)", ANSI INCITS 373-2003, April 2003.

[RFC4044]

6

F_Port

see "Fibre Channel - Framing and Signaling (FCFS)", ANSI INCITS 373-2003, April 2003.

[RFC4044]

7

FL_Port

see "Fibre Channel - Framing and Signaling (FCFS)", ANSI INCITS 373-2003, April 2003.

[RFC4044]

8

E_Port

see "Fibre Channel - Framing and Signaling (FCFS)", ANSI INCITS 373-2003, April 2003.

[RFC4044]

9

B_Port

see "Fibre Channel - Framing and Signaling (FCFS)", ANSI INCITS 373-2003, April 2003.

[RFC4044]

10

G_Port

see "Fibre Channel - Switch Fabric - 3 (FC-SW-3)", [RFC4044] ANSI INCITS 384-2004, June 2004. December 2003.

11

GL_Port

see "Fibre Channel - Switch Fabric - 3 (FC-SW-3)", [RFC4044] ANSI INCITS 384-2004, June 2004. December 2003.

12

F/NL_Port

see "Fibre Channel - Arbitrated Loop (FC-AL-2)", ANSI INCITS 332-1999, 1999.

13-9999

Unassigned

1000099999

Private Use

[RFC4044]

[RFC2434]

100000 and Reserved higher

References ---------[FC-AL-2] "Fibre Channel - Arbitrated Loop (FC-AL-2)", ANSI INCITS 332-1999, 1999. [FC-FS] "Fibre Channel - Framing and Signaling (FC-FS)", ANSI INCITS 373-2003, April 2003. [FC-GS-3] "Fibre Channel - Generic Services - 3 (FC-GS-3)", ANSI INCITS 348-2001, 2001.

[FC-SW-3] "Fibre Channel - Switch Fabric - 3 (FC-SW-3)", ANSI INCITS 384-2004, June 2004. December 2003. [RFC4044] 2005.

K. McCloghrie, "Fibre Channel Management MIB", RFC 4044, May

FC Communications Fiber optic communications is an established technology in the telecommunications industry. In the computer industry it is an emerging technology due to its high bandwidth and its ability to communicate at high speeds over distances that far exceed what is possible using wire cable. In the last six years, fiber optic technology for Fibre Channel (FC) applications has advanced from 266 Mb/sec to 1063 Mb/sec. This paper will describe the testing of FC cards and the manufacture of low cost plastic optical subassemblies (OSAs). Future trends in fiber optic communications cards will also be discussed. Fiber channel is a new interface being developed for data system communications. This paper discusses the aspects of the physical interface including the technology options and interoperability considerations. Emphasis is given to the flexibility inherent in the structure of the standard that allows it to adapt to many communications technologies and allows for future extensions.

Communication between devices in a fibre channel network uses different elements of the Fibre Channel standards. The following sections introduce the main concepts and show how a combination of primitives and frames is required.

The following Fibre Channel communication standards are supported on Xserve RAID:      

Fibre Channel Physical Interfaces (FC-PI) Fibre Channel Physical and Signaling Interface (FC-PH) Fibre Channel Arbitrated Loop (FC-AL-2) Fibre Channel Private Loop Direct Attach (FC-PLDA) Fibre Channel Fabric Loop Attachment (FC-FLA) Fibre Channel Protocol for SCSI (FCP)