Fibre Channel Technology

Development of Fibre Channel architecture began in 1988-making it the newest technology for true channel-based data transfer. Fibre Channel combines the best of the channel and network environments in an attempt to meet the needs of both worlds. Today, Fibre Channel provides bandwidth at one and two Gigabit speeds - with promises to go to ten.

At the physical layer, Fibre Channel is frame based. Each frame has a 2KB payload and is protected with a 32-bit CRC. Flow control is credit based. There is never a fear of collision-a packet simply waits until it receives permission to transmit. This flow mechanism maintains maximum throughput even during peak loads.

Different levels of reliability are available depending on the class of service requested by the application. Class 1 service provides classic, dedicated, connection based service. It guarantees reliable delivery. More common is Class 2 service, which is connectionless and provides guaranteed delivery with an acknowledgement of receipt. Class 3 service is connectionless without delivery acknowledgement. Classes are available for fractional bandwidth, unidirectional or multicast services.

The specifications for Fibre Channel define a variety of physical topologies: point-to-point, loop and switched.

Point-to-point offers dedicated bandwidth between the connected systems. Data may flow directly between two connected endpoints, or multiple devices may share a switch that is dynamically configured for several point-to-point configurations.

A loop topology shares bandwidth with devices attached in a loop configuration. Up to 128 nodes may reside on a loop.

The switched topology resembles telephone service-the node provides the desired address and the switch is responsible for making the connection. One switch, or a "fabric" of switches, appears to the node as a single entity. As switches are added or removed, the fabric is responsible for its own reconfiguration.

Fibre channel nodes perform a login process to establish a connection with the appropriate class of service. Login also determines what is attached to the other end of the point-to-point link-whether it is another node, a loop or a switch-and communicates with it appropriately.

Fibre channel provides a transport layer above which any of a variety of protocols may exists. The transport layer provides for common services, which are available to all nodes. These services include a name server (address database), an alias server (for multicasting), a timeserver and others.

Protocols traditionally thought of as either channel or network may co-exist on a single Fibre Channel physical layer. The lower Fibre Channel transport layers are not cognizant of the "ULP" (Upper Layer Protocol). Many ULPs have been specified or are in the process of specification. These include SCSI, IP, HiPPI and ESCON.

Fibre Channel combines high performance with flexibility in class of service, physical topology and protocol layering.

Crossroads Products

To learn more about Crossroads products that provide support for this industry standard and enable you to connect business with information regardless of technology or location, see our industry leading Fibre Channel to SCSI storage routers:

Crossroads 6240 Storage Router
Crossroads 6000 Storage Router
Crossroads SA20

To learn more about how to purchase our products, see:

How To Buy