TCP Retransmission Lab

Adjust a lossy network and watch packets fly from sender to receiver. Lost packets flash red and trigger visible retransmissions driven by the actual RFC 6298 RTO calculation. Built for DevOps and SRE interview prep — the exact question interviewers ask.

Network Conditions

Packet Loss 15%

Base One-Way Delay 80ms

Initial CWND 4 MSS

Simulation

Zero-Window Deadlock

Social Card

Live Simulation

Reduced-motion mode: particle flight disabled. Use the timeline strip and session log below to observe send, loss, retransmit, and ACK events in order.

SRTT—

RTTVAR—

RTO1000ms

Sent0

ACKed0

Retrans0

Timeline (Seq #)

Sent Lost Retransmit ACKed

Session Log

RFC 6298: SRTT = (1−⅛)·SRTT + ⅛·R · RTTVAR = (1−¼)·RTTVAR + ¼·|SRTT−R| · RTO = SRTT + max(G, 4·RTTVAR) with G=100ms, floor=1s, ceiling=60s. Karn's algorithm: retransmitted segments skip RTT sampling.