Fast Recovery

• Four things can happen in Fast Recovery

• • Receive an ACK for the lost data (a “new ACK”)
  • • cwnd = ssthresh
    • Go to Congestion Avoidance
  • Receive an ACK for some, but not all of the lost data (“partial ACK”)
  • • Don’t change state variables
  • Receive another duplicate ACK
  • • cwnd = cwnd + MSS
    • Send more data if allowed to
  • Timeout
  • • Same as timeout in Slow Start

• Goal: slow down the sender to a self-clocked rate.