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Discussion

The switch mechanisms described in this section illustrate several key points about the Anypoint architecture. Most importantly, transport equivalence says that Anypoint does not affect the transport connection semantics perceived by the end nodes. This architectural choice yields several benefits:

Although the switch maintains per-flow control state, it is bounded by the flow window w. Because acknowledgments and buffering remain end-to-end in Anypoint, a failed switch does not lose user data. However connections maintained by the failed switch must be re-initiated for the service to recover a failed session. Support for session recovery is common in new service protocols including iSCSI and DAFS [16].

Note also that no mutable state is shared across connections within an Anypoint switch. Thus an Anypoint switch design could spread frame processing load across processors at each external switch port. An ensemble may also partition communication traffic from different peers across multiple switches to further improve scalability.


next up previous
Next: Anypoint Prototype Up: Inside the Anypoint Switch Previous: Rate Control
Kenneth G. Yocum
2003-01-20