Over a p2p vpls connection service between 2 ACXs while performing e2e BER test, frame loss events are observed on the 64bytes frame size.

This is a limitation of ASIC which will drop packets having frame size less than 300 byte.

Hence it is advised to send bigger than 300 bytes frame size for better performance.

Findings:

1. It is identified that RED-dropped packets are observed in the egress queue during the issue state.

2. No CRC errors or physical interface errors were seen.

3. Issue seems to be related to small (64B) packets rapidly consuming output queue, causing congestion and RED drops when traffic is high.

4. As indicated earlier, the ACX5448 platform has known ASIC limitations when processing small packets(<300 bytes), leading to up to ~40% throughput drop at high-rate traffic conditions due to PPS processing constraints.

  Also, stable line-rate performance (~99.95%) is achieved with packet sizes <300 bytes, without any traffic drops.

5. Even if 64 byte packets don't drop at lesser line rates, the results are not consistent or reliable indicators for testing high-speed performance on this platform.

6. In the reported scenario, the performance improvement for 64B frames between Junos 22.1R1.10 and 22.3R3.8 is due to below key fixes introduced in 22.3R3.

7. PR:1635292, which makes the MAC wait until 9 internal buffer units (64B each) are filled before transmission. This helps prevent TX MAC starvation and improves throughput for small packets.

8. PR:1635845, which Fixes a QoS classification issue when both family inet and family mpls are configured on the same interface. It applies a unified QoS map to classify both IP and MPLS traffic properly, avoiding RED drops during congestion.

These two fixes contribute to an improvement in small-packet performance at high line rates in Junos 22.3R3.