Method and apparatus for high speed satellite communication

Claim 2

An improved satellite communications system of the type including first and second means for transmitting and receiving sequentially numbered frames of information, means for communicating said information between the first and second means, said first and second means each including means for evaluating the information received from the other and for transmitting status information to the other to indicate whether said information was successfully received, and each first and second transmitting and receiving means further including means responsive to the status information received from the other for controlling subsequent transmission of frames of information to the other, the improvement comprising selective reject means coupled to the evaluating means for controlling the transmitting and receiving means to send a selective reject command to the other transmitting and receiving means which command identifies each frame which has not been successfully received from said other; and response means responsive to the selective reject commands from the other transmitting and receiving means for controlling the transmitting and receiving means to retransmit the identified selectively rejected frames to said other, wherein a multiplicity of rejected frames can be identified for retransmission at any point in time.

Claim 3

The apparatus of claim 1 wherein at least one of said first and second transmitting and receiving means further comprise means for detecting the absence of ones of the frames in the sequence of sequentially numbered frames being received and including means for controlling the transmitting and receiving means to send a selective reject range command to the other transmitting and receiving means which selective reject range command specifies a range that defines the sequence numbers of the missing frames.

Claim 4

The apparatus of claim 1 wherein at least one of said first and second transmitting and receiving means further include means for monitoring the receipt of a response frame from the other transmitting and receiving means which frame was transmitted in response to a selective reject command to the other; and means for initiating a retransmission of the selective reject command to the other whenever the response frame is not received within a predetermined time period after the issuance of the selective reject command to the other.

Claim 5

The apparatus of Claim 1, wherein each frame of information transmitted by either the first or second transmitting and receiving means includes a send sequence number which identifies the frame of information being transmitted and a receive sequence number which acknowledges receipt of a frame of information from the other and identifies the sequence number of that received frame.

Claim 6

The apparatus of Claim 1, wherein at least one of said first and second transmitting and receiving means are supplied by a data source with frames of information for transmission and supply received frames of information to a data sink and further include first means coupled to one of the transmitting and receiving means for monitoring the status information received from the other transmitting and receiving means and the sequence numbers of the frames of information which are to be transmitted by the one transmitting and receiving means, and for inhibiting the further transmission of the frames by the one transmitting and receiving means whenever the difference in sequence numbers between the next frame to be transmitted by the one transmitting and receiving means and the last frame acknowledged as received by the other transmitting and receiving means exceeds a send sliding window quantity; and second means for monitoring sequence numbers of the frames being received from the other transmitting and receiving means and the selectively rejected frames identified by the other transmitting and receiving means, and for inhibiting the receipt of further frames whenever the difference in sequence number between the next frame expected to be received from the other transmitting and receiving means and the earliest, unreceived selectively reject frame exceeds a receive sliding window quantity.

Claim 7

The apparatus of Claim 4 further including means for restricting the received sequence number which can be transmitted to the other transmitting and receiving means to be less than the sequence number of the earliest selectively rejected frame which has yet to be received by the rejecting transmitting and receiving means which sent the selective reject command for that frame.

Claim 8

The apparatus of Claim 5, wherein said each first and second monitoring and inhibiting means include memory means for storing all frames which have been transmitted or are awaiting transmission and which lie between and including the lowest frame for which receipt has yet to be acknowledged by the other transmitting and receiving means and the last frame received from the host for transmission; memory means for storing all frames between and including the last frame which is to be passed to the host and the last frame which has been received from the other transmitting and receiving means; and means for determining an upper limit of the sequence number of a next frame which can be received from the host and the sequence number of a next frame expected from the other transmitting and receiving means which sequence numbers define the send sliding window quantity and the receive sliding window quantity respectively, so that each of said memory means maintains a sliding window over the sequentially numbered frames of information being exchanged between the first and second transmitting and receiving means.

Claim 9

The apparatus of Claim 2 further including means for controlling the transmitting and receiving means to send a "Go_back_n" reject command to the other transmitting and receiving means whenever the size of the hole exceeds a predetermined number.

Claim 10

The apparatus of Claim 2 wherein the range defined in the selective reject range command is specified by a first sequence number designating the low end of the range and a second sequence number designating the high end of the range.

Claim 11

The apparatus of Claim 1 further including heartbeat means responsive to the frames being transmitted by one of the transmitting and receiving means for causing the transmission of a heartbeat frame when there is an absence of transmission of other frames by the one transmitting and receiving means.

Claim 12

The apparatus of Claim 10 wherein the heartbeat means include means for forming a frame which indicates that the one transmitting and receiving means is still active and provides current received and transmitted sequence number information.

Claim 13

The apparatus of Claim 11 wherein the frame forming means further forms frames which include information about frames sent and received by the one transmitting and receiving means.

Claim 14

The apparatus of Claim 2 wherein the controlling means include means for issuing a reject command for transmission to the other transmitting and receiving means whenever the absence of a sequence of frames is detected and the number of frames in the absent sequence exceeds as predetermined reject threshold.

Claim 15

The apparatus of Claim 7 wherein each host provides a perferred set of link parameters to its associated transmitting and receiving means which sets are a function of system resources available to the particular host, and further including initialization means coupled to each transmitting and receiving means for controlling the initialization of communication between the first and second transmitting and receiving means, the initialization means comprising means for requesting communication with the other transmitting and receiving means; means for exchanging the perferred sets of link parameters between the first and second transmitting and receiving means; and means for generating a modified set of link parameters which represent a compromise between the preferred sets of link parameters and the system resources available to each host, wherein one of the parameters specified is the transmitting and receiving window size.

Claim 16

The apparatus of Claim 14 wherein the exchanging means include means for selecting one of the transmitting and receiving means to transmit its set of perferred link parameters to the other transmitting and receiving means, and further wherein the means for generating modified link parameters include means responsive to the received set of perferred link parameters from the other transmitting and receiving means for resolving the received set of perferred link parameters with that of its associated host; and means for transmitting a resolved set of link parameters to the other transmitting and receiving means.

Claim 17

The apparatus of Claim 1 wherein the first transmitting and receiving means has a high level of information traffic and the second transmitting and receiving means has a low level of information traffic and futher wherein the communication means include a high speed link for communicating the sequentially numbered frames from the first transmitting and receiving means to the second transmitting and receiving means and a low speed link for communicating the sequentially numbered frames from the second transmitting and receiving means to the first transmitting and receiving means.

Claim 20

The method of Claim 17 futher include the steps of detecting the absence of ones of the frames in the sequence of sequentially numbered frames being received by one of the transmitting and receiving means; controlling the one transmitting and receiving means to send a selective reject range command to the other transmitting and receiving means which selective reject range command specifies a range that defines the sequence numbers of the missing frames.

Claim 21

The method of claim 17 further including the steps of monitoring in one of the transmitting and receiving means the receipt of a response frame from the other transmitting and receiving means which frame was transmitted in response to a selective reject command to the other; and initiating a retransmission of the selective reject command to the other whenever the response frame is not received within a predetermined time period after the issuance of the selective reject command to the other.

Claim 22

The method of Claim 17 wherein each frame of information transmitted by either the first or second transmitting and receiving means includes a send sequence number which identifies the frame of information being transmitted and a receive sequence number which acknowledges receipt of a frame of information from-the other and identifies the sequence number of that received frame.

Claim 23

The method of Claim 17 wherein at least one of said first and second transmitting and receiving means are supplied by a host with frames of information for transmission and supply received frames of information to the host and further including the steps of monitoring the status information received from the other transmitting and receiving means and the sequence numbers of the frames of information which are to be transmitted by the one transmitting and receiving means; inhibiting the further transmission of the frames by the one transmitting and receiving means whenever the difference in sequence numbers between the next frame to be transmitted by the one transmitting and receiving means and the last frame acknowledged as received by the other transmitting and receiving means exceeds a send sliding window quantity; monitoring sequence numbers of the frames being received from the other transmitting and receiving means and the selectively rejected frames identified by the other transmitting and receiving means; and inhibiting the receipt of further frames whenever the difference in sequence number between the next frame expected to be received from the other transmitting and receiving means and the earliest, unreceived selectively reject frame exceeds a receive sliding window quantity.

Claim 24

The method of Claim 20-further including the step of restricting the received sequence number which can be transmitted to the other transmitting and receiving means to be less than the sequence number of the earliest selectively rejected frame which has yet to be received by the rejecting transmitting and receiving means which sent the selective reject command for that frame.

Claim 25

The method of Claim 21 further including the steps of storing in a memory means all frames which have been transmitted or are awaiting transmission and which lie between and including the lowest frame, for which receipt has yet to be acknowledged by the other transmitting and receiving means, and the last frame received from the host for transmission; storing in the memory means all frames between and including the last frame which is to be passed to the host and the last frame which has been received from the other transmitting and receiving means; and determining an upper limit of the sequence number of a next frame which can be received from the host and the sequence number of a next frame expected from the other transmitting and receiving means which sequence numbers define the send sliding window quantity and the receive sliding window quantity respectively, so that said memory means maintains a sliding window over the sequentially numbered frames of information being exchanged between the first and second transmitting and receiving means.

Claim 26

The method of Claim 18 further including the step of controlling the transmitting and receiving means to send a "Go_back_n" reject command to the other transmitting and receiving means whenever the size of the hole exceeds a predetermined number.

Claim 27

The apparatus of Claim 18 wherein the range defined in the selective reject range command is specified by the steps of designating a first sequence number for the low end of the range; and designating a second sequence number for the high end of the range.

Claim 28

The method of Claim 17 further including the step of causing the transmission of a heartbeat frame when there is an absence of transmission of other frames by the one transmitting and receiving means.

Claim 29

The methodof Claim 26 wherein the heartbeat transmitting step includes the step of forming a frame which indicates that the one transmitting and receiving means is ready to receive frames.

Claim 30

The method of Claim 27 wherein the frame forming step includes the step of forming frames which include information about frames sent and received by the one transmitting and receiving means.

Claim 31

The method of Claim 18 wherein the controlling step includes the step of issuing a reject command for transmission to the other transmitting and receiving means whenever the absence of a sequence of frames is detected and the number of frames in the absent sequence exceeds as predetermined reject threshold.

Claim 32

The method of Claim 23 wherein each host provides a perferred set of link parameters to its associated transmitting and receiving means which sets are a function of system resources available to the particular-host, and further including the steps of controlling the initialization of communication between the first and second transmitting and receiving means by requesting communication with the other transmitting and receiving means; exchanging the perferred sets of link parameters between the first and second transmitting and receiving means; and generating a modified set of link parameters which represent a compromise between the preferred sets of link parameters and the system resources available to each host.

Claim 33

The apparatus of claim 14 wherein further parameter values specified include timing values by which retransmission of selective reject commands can be automatically initiated.