This is the starting retransmission timeout SCTP uses for the very first chunks sent on a new association, before any real round-trip-time measurements exist to adapt from, with 3000ms as the RFC-recommended default. It matters most during association setup, since a value set too aggressively low on a high-latency path can cause the initial INIT/COOKIE-ECHO handshake to retransmit prematurely and slow down connection establishment rather than speed it up. Lowering this toward 1000ms on a low-latency data center interconnect can shave meaningful time off association setup for short-lived SCTP sessions.