Device and method for selective retransmission of lost packets

A second network device, comprising:

• processing circuitry configured to:
• receive a sequence of data packets from a first network device;
• transmit, to the first network device, at least one notification message indicative of the largest sequence number L of a data packet among sequence numbers of data packets that have been received at the second network device and one or more missing data packets of the sequence of data packets up to the largest sequence number L that are missing at the second network device;
• and
• receive one or more missing data packets after transmitting the at least one notification message, wherein each of the one or more missing data packets is indicated as a missing data packet by the at least one notification message, and a sequence number X of the each respective missing data packet of the one or more missing data packets is less than L−K, wherein K is a parameter that is a non-negative integer,
• wherein the first network device is configured to:
• maintain a first data structure indicative of the one or more missing data packets that are indicated by the at least one notification message,
• update the first data structure in response to the at least one notification message,
• maintain a second data structure that is indicative of to-be-retransmitted data packets,
• add the one or more missing data packets that are indicated by the at least one notification message into the second data structure, and
• remove a to-be-retransmitted data packet from the second data structure after retransmitting the to-be-retransmitted data packet,
• wherein the first network device is configured to operate in a first state and a second state,
• wherein, in the first state, the first network device is configured to:
• transmit new data packets, and
• enter the second state based on the second data structure being not empty and/or stay in the first state based on the second data structure being empty, and
• wherein in the second state, the first network device is configured to retransmit to-be-retransmitted data packets according to the second data structure.

A method, performed by a first network device, the method comprising:

• transmitting a sequence of data packets to a second network device;
• receiving, from the second network device, at least one notification message indicative of:
• a largest sequence number L of a data packet among sequence numbers of data packets that have been received at the second network device, and
• one or more missing data packets that are missing from the sequence of data packets at the second network device up to the largest sequence number L;
• and
• retransmitting one or more missing data packets as the next step after receiving the at least one notification message, wherein each of the one or more missing data packets is indicated as a missing data packet after its first transmission by the at least one notification message, and a sequence number X of the each respective missing data packet of the one or more missing data packets is less than L−K, wherein K is a parameter that is a non-negative integer,
• maintaining a first data structure indicative of the one or more missing data packets that are indicated by the at least one notification message;
• updating the first data structure in response to the at least one notification message;
• maintaining a second data structure that is indicative of to-be-retransmitted data packets;
• adding the one or more missing data packets that are indicated by the at least one notification message into the second data structure;
• and
• removing a to-be-retransmitted data packet from the second data structure after retransmitting the to-be-retransmitted data packet,
• wherein the method further comprises operating in a first state and a second state,
• wherein, in the first state, the method further comprises:
• transmitting new data packets, and
• entering the second state based on the second data structure being not empty and/or staying in the first state based on the second data structure being empty, and
• wherein in the second state, the method further comprises retransmitting the to-be-retransmitted data packets according to the second data structure.

A method, performed by a second network device, the method comprising:

• receiving a sequence of data packets from a first network device;
• and
• transmitting, to the first network device, at least one notification message indicative of the largest sequence number L of a data packet among sequence numbers of data packets that have been received at the second network device and one or more missing data packets of the sequence of data packets up to the largest sequence number L that are missing at the second network device;
• and
• receiving one or more missing data packets after transmitting the at least one notification message, wherein each of the one or more missing data packets is indicated as a missing data packet by the at least one notification message, and a sequence number X of the each respective missing data packet of the one or more missing data packets is less than L−K, wherein K is a parameter that is a non-negative integer,
• wherein the first network device is configured to:
• maintain a first data structure indicative of the one or more missing data packets that are indicated by the at least one notification message,
• update the first data structure in response to the at least one notification message,
• maintain a second data structure that is indicative of to-be-retransmitted data packets,
• add the one or more missing data packets that are indicated by the at least one notification message into the second data structure, and
• remove a to-be-retransmitted data packet from the second data structure after retransmitting the to-be-retransmitted data packet,
• wherein the first network device is configured to operate in a first state and a second state,
• wherein, in the first state, the first network device is configured to:
• transmit new data packets, and
• enter the second state based on the second data structure being not empty and/or stay in the first state based on the second data structure being empty, and
• wherein in the second state, the first network device is configured to retransmit to-be-retransmitted data packets according to the second data structure.