| 主权项 |
1. A Universal Serial Bus (USB) extension designed for a lossy channel, comprising:
a state machine comprising first, second and third states for the USB extension; a packet loss inference mechanism configured to identify loss of at least one of a USB IN token, and a reply to the USB IN token; wherein the lossy channel is characterized by a packet loss ratio higher than zero, and the packet loss inference mechanism is capable of indicating the state machine to switch to the first state; when the state machine is in its first state, the USB extension is configured to receive a USB IN token from a standard USB host coupled to the USB extension, return Negative-Acknowledgment (NAK) to the standard USB host, transmit the USB IN token over the lossy channel to another USB extension, and switch the state machine to its second state; the state machine is configured to stay in its second state until at least one of the following occurs: (a) the packet loss inference mechanism identifies loss of the USB IN token or the reply, and as a result indicates the state machine to switch back to its first state, or (b) the USB extension receives, from the another USB extension, data packet without error, in reply to the USB IN token, and as a result switches the state machine to its third state; while the state machine is in its second state, the USB extension is further configured to return NAK to additional USB IN tokens received from the standard USB host, and not transmit the additional USB IN tokens over the lossy channel to the another USB extension; and while the state machine is in its third state, the USB extension is configured to receive a new USB IN token from the standard USB host, return the data packet to the standard USB host as reply to the new USB IN token, and switch the state machine back to its first state. |
