UDP GSO Burst Dynamics and Burst Loss in Transpacific Routes

With QUIC and HTTP/3 adoption, UDP is now carrying substantial production traffic across our backbone. Because standard UDP has historically bypassed kernel segmentation, user-space implementations relied on sendmmsg(), which still incurs significant per-packet overhead. UDP Generic Segmentation Offload (UDP GSO) allows passing up to 64KB payloads in a single syscall via UDP_SEGMENT.

In our tests between Silicon Valley and Hong Kong, sending large GSO bursts without traffic shaping caused sudden 12–15% packet drop bursts at specific transit hops. Many intermediate transit routers enforce token-bucket rate limiters calibrated for smaller MTU frames. Pacing individual GSO bursts using SO_TXTIME eliminated these drops entirely.