RapidIO Connections - September 2003
Technical Working Group Update
Knowing where one is going is crucial to reaching a destination. Roadmaps in our industry should demonstrate how products can remain relevant in the future. In the past quarter, the TWG has reached significant milestones on our RapidIO roadmap.
For example, final approval was given to the Flow Control Extensions Specification. As originally conceived, RapidIO was targeted at control-plane applications. As attention grew and a serial physical layer was added, interest grew in leveraging RapidIO as a data plane interconnect.
In moving beyond its initial role of connecting chips in the control plane into a system-level interconnect, RapidIO faced a new technical challenge. When systems use cascaded or staged switches, end-to-end flow control is needed to relieve fabric congestion that occurs from high-order head-of-line blocking among other factors.
With this issue as their charter, a task group began work early in 2002 to define how flow control should be done. After nearly eighteen months of work, this effort has borne fruit in the Flow Control Extensions Specification.
While specification writing is never an easy process, this effort had special challenges in that detailed simulation was required to demonstrate the effectiveness of the solution. By the time the specification was complete, two independent simulation efforts demonstrated that the proposed solution significantly increased fabric throughput and reduced average latency when congestion otherwise threatened performance collapse.
This work will be built upon when addressing future technical challenges. As part of our roadmap, work has already begun to define extensions that move RapidIO even further into the data plane to address carrier-grade data plane applications. These demanding systems require efficient support for thousands of traffic flows, QoS, protocol encapsulation and multicasting.
Fortunately, the road we've already paved presents us with an elegant and clean foundation upon which to address these and other technical requirements as we look to address future applications.
Greg Shippen
Chair, Technical Working Group
RapidIO Trade Association
