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Fibre Channel



Definition

Fibre Channel

Fibre Channel or FC is a high-speed network technology (usually in terms of 1, 2, 4, 8, 16, 32 and 128 thousand Mbit/s rate operation), using NMb encoding method, synchronous serial transmission. Mainly used to connect computer data storage to the server.

Fibre Channel is mainly used for storage area networks (SAN) in commercial data centers. Fibre Channel networks form a switching structure because they work together as a large switch. Fibre Channel usually runs on fiber optic cables inside and between data centers.

Transmission medium

Its transmission medium can be optical fiber or copper cable. Generally, optical fiber is used. If optical fiber is used, GBIC equipment must be added at the receiving end to convert it into electricity. Signal.

Fibre Channel Protocol

Most block storage runs through the Fibre Channel structure and supports many upper layer protocols. From the perspective of the layered protocol stack, FC only includes specifications from the physical layer to the transport layer. Its upper layer defines interfaces that encapsulate other protocols as application layer protocols, such as SCSI or IP protocols. After encapsulating SCSI3, the entire protocol is FCP (FCProtocol).

Fibre Channel Protocol (FCP) is a transmission protocol that mainly transmits SCSI commands through a Fibre Channel network. The host computer runs FICON commands set via Fibre Channel due to its high reliability and throughput. Fibre Channel can be used for flash memory transferred through the NVMe interface protocol.

Development history

Fibre Channel is standardized in the T11 Technical Committee of the International Information Technology Standards Committee (INCITS), which is a standards committee recognized by the American National Standards Institute (ANSI). Fibre Channel started in 1988 and obtained ANSI standard certification in 1994 to combine multiple physical layers to achieve advantages, including SCSI, HIPPI and ESCON.

Fibre Channel is designed as a serial interface to overcome the limitations of SCSI and HIPPI interfaces. FC adopts leading multi-mode optical fiber technology development, which overcomes the speed limitation of ESCON protocol. By attracting a large number of SCSI disk drives and the use of mainframe technology, the development of advanced Fibre Channel technologies and deployment economies of scale has become economical and widespread.

Initially, the standard also approved 132.8125Mbit/s ("12.5MB/s"), 265.625Mbit/s ("25MB/s") and 531.25Mbit/s ("50MB/s") "), is no longer in use. Since 1996, the speed of Fibre Channel has doubled every few years.

Since its establishment, Fibre Channel has seen positive developments in various underlying transmission media. There have been countless speed improvements. The figure "Speed ​​Development" shows the speed development of native Fibre Channel.

Topology

There are three main Fibre Channel topologies, describing multiple How the 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 in the disk storage, HBA on the server or Fibre Channel switch Implemented in the device.

Point-to-point

Two devices are directly connected to each other. This is the simplest topology, but has limited connections.

Arbitration loop

In this structure, all devices are in a loop or loop, similar to a token ring network. Adding or removing devices from the loop will cause all activities on the loop to be interrupted. Failure will cause the loop to be interrupted. There is a Fibre Channel hub to connect multiple devices together and can bypass the failed port. The loop can also be achieved by wiring each port to the next in the ring.

The smallest loop containing only two ports is similar to point-to-point, and is significantly different in terms of protocol. Only one pair of ports can communicate on the loop at the same time. The maximum speed is 8GFC.

But the arbitrated loop is It is rarely used after 2010.

Switch structure

In this structure, all devices are connected to a Fibre Channel switch, which is conceptually similar to modern Ethernet implementations. The topology is relatively The advantages of point-to-point or arbitrated loop include:

1. The structure can be extended to tens of thousands of ports.

2. Switch management status, providing optimization through shortest path first (FSPF) Path.

3. The traffic between the two ports passes through the switch, not through any other ports.

4. Port failure and link isolation should not affect others Port operation.

5. Multiple pairs of ports can communicate simultaneously in the structure.

Layered

Fibre Channel does not follow the OSI model layering and needs to be divided There are five layers:

FC-4-protocol mapping layer, where high-level protocols such as SCSI, IP or FICON are encapsulated in the information unit (IU) and transmitted to FC-2. FC-4 includes FCP- 4. FC-SB-5 and FC-NVMe.

FC-3-public service layer, a layer that can implement functions such as encryption or RAID redundancy algorithms; Multi-port connection;

FC-2-The signaling protocol defined by the Fibre Channel Frame and Signaling 4 (FC-FS-4) standard is composed of low-level Fibre Channel protocols; port-to-port connection;

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FC-1-transmission protocol, realize signal line coding;

FC-0-PHY, including cables, connectors, etc.;

ports

There are various logical configurations for Fibre Channel ports. The most common port types are:

N_Port (node ​​port) N_Port is usually connected to the F_Port of the switch or another N_Port HBA port. Nx_Port communicates through PN_Port that does not operate the loop port state machine

F_Port (Fabric port) F_Port is the switch port connected to N_Port.

E_Port (expansion port) is a switch port that connects to another E_Port to create an inter-switch link

The following types of ports are also used for Fibre Channel:

A_Port (adjacent port) combines PA_Port and VA_Port to work together.

B_Port (Bridge Port) is used to connect the port between structural elements of bridge devices with E_Port on the switch

D_Port (Diagnostic Port) is used to link with another D_Port The configured port for performing diagnostic tests.

EX_Port is used to connect to the E_Port type of the FC router structure

G_Port (general Fabric port) can be used as a switch port for E_Port, A_Port or F_Port

GL_Port (Universal structure loop port) can work as E_Port, A_Port or Fx_Port switch port

PE_Port is connected to another PE_Port in Fabric or LCF through a link to a B_Port

PF_Port is connected to the LCF in the Fabric of PN_Port through a link

TE_Port (TrunkingE_Port) relay expansion port, extending the function of E port to support VSAN relay, transmission quality of service (QoS) parameters and fiber channel tracking (Fctrace) function.

U_Port (universal port) is waiting to become another port type port

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