Method and apparatus are described for improving information transfer over
USB. In one approach, hub-based extension is realized wherein power is
distributed using auxiliary wiring distinct from signal and power wiring
present in conventional USB cabling. Additional signals allow
optimization of power distribution for powering attached devices, and for
detecting and handling illegal connection configurations.In another
approach, improvements are realized through use of alternative signaling
techniques which eschew reflective and high-speed common-mode signaling.
Described are various configuration, media and signal-protocol
combinations, including implementations containing embedded hubs. Methods
ensuring reliable system behavior are also described, including
determination of extension path delay and use of topology-enforcement
hubs.In other approaches, further improvements are realized by allowing
information exchanges to take longer than the nominal timeout period, or
by allowing host requests to be delayed for transmission until the
extended bus is available for use.