Patent ID: 7571269

Claim:
A communication apparatus for conveying supplemental messages via a link between a host and a point within a system of storage devices, the communication apparatus comprising: a link interface configured to communicatively couple the communication apparatus to the link for accessing a data stream passing through the link in accordance with a standardized protocol; and a supplemental message interface configured to exchange a supplemental message with the data stream to establish a covert communication channel in the link, the supplemental message interface including a supplemental message observer configured to identify a supplemental downlink message in the data stream, the supplemental message observer including: a downlink receiver configured to: identify a portion of the supplemental downlink message, and acquire the portion of the supplemental downlink message, the downlink receiver being responsive to a first protocol-compliant message, and a supplemental message composition buffer configured to compose the supplemental downlink message from a number of portions of the supplemental downlink message; wherein the supplemental message supplements the standardized protocol.