Group-based low-overhead retransmission system for lossy rdma network

A group-based low-overhead retransmission system for a lossy remote direct memory access (RDMA) network, wherein the system uses an RDMA network interface card (RNIC) as an execution unit and comprises:

• a transmitter and a receiver;
• the transmitter comprises:
• an adaptive grouping module, a group header construction module, a retransmission module, and a bitmap module;
• and the receiver comprises:
• an initialization and determination module, a packet loss processing module, and a bitmap module;
• in the transmitter, the adaptive grouping module dynamically adjusts a logical group size based on a feedback packet sent by the packet loss processing module;
• the bitmap module updates a local bitmap based on the feedback packet sent by the packet loss processing module, and stores transmission status bitmaps organized by logical groups;
• and the group header construction module inserts an extended protocol header into each data packet based on the logical group size and the local bitmap;
• and
• in the receiver, the initialization and determination module parses the extended protocol header;
• when a logical group to which a received data packet belongs is a logical group arriving for a first time, the bitmap module initializes a logical group tracking structure for the logical group arriving for the first time, to track data packets within the logical group;
• alternatively when a logical group to which a received data packet belongs is not a logical group arriving for the first time, a logical group tracking structure of the logical group to which the received data packet belongs detects continuity of data packets based on intra-group sequence numbers;
• when the intra-group sequence numbers are discontinuous, the packet loss processing module generates the feedback packet and sends the feedback packet back to the transmitter via the RNIC;
• the retransmission module retransmits a lost data packet based on the feedback packet;
• and the bitmap module is updated when all the data packets in the logical group tracking structure arrive;
• wherein the adaptive grouping module dynamically adjusts the logical group size based on the feedback packet sent by the packet loss processing module, expressed as:
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• initializing δ2 to 0, and executing a following loop when x ranges from 1 to γk+1:
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• ending the loop;
• updating δ2 to δ2=Gk+1×delta2_term, and determining a value of Gk+1 that minimizes δ1+δ2, wherein
• δ1 represents a number of redundant retransmitted packets, δ2 represents an expected retransmission data volume due to bitmap overflow, Gk+1 represents a logical group size for a (k+1)th round, Lk+1 represents a predicted packet loss rate for the (k+1)th round, obtained based on a prediction coefficient Ak, L′k represents an actual packet loss rate under a group size Gk in a kth round, Sk+1 represents a number of logical groups in the (k+1)th round, Ak represents a prediction coefficient for the kth round, Nk represents a number of lost logical groups in a first transmission using Gk as the logical group size, Pk represents a number of data packets in the first transmission using Gk as the logical group size, Gk represents a logical group size in the kth round, Lnew represents a predicted packet loss rate for the (k+1)th round, obtained based on a prediction coefficient Ak+1, Ak+1 represents a prediction coefficient for the (k+1)th round, Nk+1 represents a number of lost logical groups in a second transmission using Gk as the logical group size, Pk+1 represents a number of data packets in the second transmission using Gk as the logical group size, Rk+1 represents a network transmission rate during the second transmission using Gk as the logical group size, RTTk+1 represents a round-trip time (RTT) during the second transmission using Gk as the logical group size, MTU represents a maximum transmission unit, γk+1 represents a maximum number of logical groups supported by a bitmap in the (k+1)th round, α represents a smoothing factor, prob_success represents a probability that first x−1 logical groups are successfully transmitted, prob_loss_at_x represents a probability that an xth logical group is lost, remaining represents a number of additional logical groups requiring retransmission when the xth logical group causes bitmap overflow, and delta2_term represents an intermediate variable.