The T11 standards bodies have been working diligently over the past two years to codify the Fibre Channel Backbone 6 (FC-BB-6) standard.
One of the principal developments in its predecessor, FC-BB-5, was the concept of the “Fibre Channel Forwarder,” or FCF. In a nutshell, the FCF is the heart of a traditional FCoE infrastructure, as it is a “DomainID” of the fabric, encapsulating and decapsulating Fibre Channel from Ethernet frames. While this works well in replicating Fibre Channel topologies and creating hybrid FCoE/FC architectures, new initiatives in the industry were making it clear that even more flexible options were required.
So, the next iteration, FC-BB-6, set out to improve upon these capabilities. The key objectives were:
• Support point-to-point and multipoint storage network designs
• Eliminate unnecessary bottlenecks in the storage network design and provide high performance solutions
• Reduce the administrative burden by reducing the number of Domain IDs used in a SAN design, thereby addressing domain ID scalability issues with traditional Fibre Channel SANs
One key concept that is defined in FC-BB-6 is the “Distributed FCF” or, in layman terms, a distributed-switch architecture. Essentially, the control and data plane in a switching fabric are separated out in this new switch architecture. Let me explain what these separate planes are defined to do:
Control plane –Fibre Channel Forwarders (FCF)
• Controlling FCFs and FCoE Data Forwarders (FDFs) share one or more single virtual domains. A virtual domain is simply providing similar functionality to a traditional FC domain (physical switch), albeit with functionality distributed in multiple physical switches
• Controlling FCFs have a principle domain, wherein the FC-BB-6 FCF acts just like a FC-BB-5 FCF connected to traditional FC fabrics
• FCFs provide Fibre Channel Services
• BB-5 FCF could be upgraded to BB-6 with a firmware update (providing investment protection)
Data plane – Fibre Channel Data Forwarders (FDF)
• FDFs obtain routing and zoning information from their controlling FCFs.
• No Changes at the end nodes (ENodes) are required. ENodes operate the same as FC-BB-5 ensuring investment protection at the end nodes unless you want to deploy point to point and multipoint storage network designs (VN2VN, see below for more detail).
• Routing at the FC Layer rather than the MAC layer
• Single FC Domain shared by Controlling FCF and FDFs
The FC-BB-6 standard has been ratified by the T11.3 and now it has been forwarded to INCITS for approval. It has achieved the goals and objectives that were set by the committee. Let me list a few:
• VN2VN Node support
• Establish virtual links between FCF’s and FDF’s to allow separation of Control and Data plane in a switching fabric
• Domain ID Scalability Issue
FC-BB-6 based converged storage area networks will result in more efficient network designs for converged Fibre Channel and Ethernet networks thereby resulting in higher performance and lower cost networks.
For more information on Fibre Channel and how it supports evolving storage requirements, please visit the interactive FCIA Knowledge Vault full of entertaining and insightful stories such as a video from Rackspace on the importance of availability and scalability, that will help you deliver greater business value though your IT infrastructure.