The advantages of Fibre Channel technology are mainly reflected
(1) High bandwidth, the data transfer rate of 200MB/s has been achieved at present, and the 400MB/s has passed the test;
(2) High-capacity addressing capability and capacity expansion capability, which can access 16 million nodes;
(3) Highly centralized data and global sharing of storage capabilities;
(4) The long connection distance between each pair of nodes, the multi-mode optical cable can reach 500 meters, and the single-mode optical cable can reach 10 kilometers;
(5) Modular expansion and connection;
(6) High availability or fault-tolerant service system can be established by using optical fiber switches and related software;
(7) It can facilitate the establishment of load balancing and server cluster systems.
Fibre Channel technology is a new technology developed by combining the advantages of "channel technology" and "network technology": channel technology is a hardware-intensive technology, because it is designed to quickly transmit a large amount of data in the buffer area, which can Connect devices directly without using too much logic; network technology is software-intensive because packets need to be routed across the network to one node among many devices, and network technology has the ability to operate a large number of nodes. Fibre Channel technology has been designed from the outset to combine the above-mentioned advantages of channel technology and network technology. Five independent layers are defined in the Fibre Channel protocol, from the physical medium to the high-level protocol transmitted in the Fibre Channel, which contains the overall picture of the Fibre Channel technology. The following are the functional modules of these five layers: ① FC-0, physical layer, defines the physical port characteristics of the connection, including the physical characteristics, electrical characteristics and optical characteristics of the medium and connectors (drivers, receivers, transmitters, etc.), transmission speed and some other port characteristics. Physical media are fiber optic, twisted pair, and coaxial cable. This layer defines how light travels on optical fibers and how the transmitter and receiver work over various physical media.
②FC-1, transmission protocol, FC-1 stipulates the encoding method and transmission protocol of 8B/10B according to the ANSI X3 T11 standard, including serial encoding, decoding rules, special characters and error control. The transfer encoding must be DC balanced to meet the electrical requirements of the receiving unit. Special characters ensure that what appears in the serial bit stream is a short character length and a certain transition signal for clock recovery. This layer is responsible for taking a sequence of signals and encoding them into usable character data.
③ FC-2, frame protocol, defines the transmission mechanism, including frame positioning, frame header content, usage rules, and flow control. Fibre Channel data frames are of variable length and addressable. The length of the Fibre Channel data frame used to transmit data is up to 2K, so it is very suitable for the transmission of large-capacity data. The content of the frame header includes control information, source address, destination address, transmission sequence identification and switching equipment. The 64-byte optional header is used for protocol mapping when other types of networks are transmitted over Fibre Channel. Fibre Channel relies on the contents of the data frame header to initiate operations.
④ FC-3, public service, provides public services with advanced features, that is, structural protocol and flow control between ports, it defines three services: striping (Striping), search group (Hunt Group) and multicast (Multicast) ). The purpose of striping is to use multiple ports to transmit in parallel on multiple connections, so that the I/O transmission bandwidth can be extended to a corresponding multiple; the search group is used for multiple ports to respond to an address with the same name. Improve efficiency by reducing the probability of reaching a "busy" port; multicast is used to deliver a message to multiple destinations.
⑤ FC-4, the protocol mapping layer, defines the mapping relationship between the bottom layer of Fibre Channel and the upper layer protocol (Upper Layer Protocol) and the application interface with the current standard. The current standard here includes all existing channel standards and network protocols. , such as SCSI interface and IP, ATM, HIPPI, etc.
It can be seen that the Fibre Channel protocol stack is the transmission carrier of various high-level data protocols, especially the transmission of SCSI and IP data. The process of transmitting the high-level data protocol as a carrier is actually a process of mapping the high-level data protocol to the physical layer transmission service of the protocol stack. Among them, the most commonly used Fibre Channel Protocol is the mapping of SCSI data, commands and status information to the FC physical layer transmission service. FCP has the independence to work on all Fibre Path topologies and all types of services.
