3.6.2. Link Layer Retry (LLR)

Fig. 3.27 Architectural Position of LLR in UE Link Layer

Link Layer Retry (LLR) is a link-local reliability mechanism that improves Ethernet performance by enabling fast retransmission of lost or corrupted frames directly at the link layer.

LLR operates between adjacent nodes, where frames are tagged with sequence numbers and checked for integrity upon reception. When an error, loss, or sequence gap is detected, the receiver signals the sender to retransmit starting from the first missing frame. The sender maintains a buffer of transmitted frames and performs retransmission using a Go-Back-N approach, replaying the missing frame and all subsequent frames in the transmission window.

By handling loss locally and quickly, LLR significantly reduces the performance impact of packet loss, making Ethernet better suited for latency-sensitive and large-scale HPC/AI workloads.

LLR CLI Commands

• LLR Configuration
• LLR Statistics
• LLR Error Injection