142a227f8SMax Laier# $OpenBSD: ackpri,v 1.3 2006/10/07 04:48:01 mcbride Exp $ 29d7ccc0fSMax Laier 39d7ccc0fSMax Laier# Use a simple priority queue to prioritize empty (no payload) TCP ACKs, 49d7ccc0fSMax Laier# which dramatically improves throughput on (asymmetric) links when the 59d7ccc0fSMax Laier# reverse direction is saturated. The empty ACKs use an insignificant 69d7ccc0fSMax Laier# part of the bandwidth, but if they get delayed, downloads suffer 79d7ccc0fSMax Laier# badly, so prioritize them. 89d7ccc0fSMax Laier 99d7ccc0fSMax Laier# Example: 512/128 kbps ADSL. Download is 50 kB/s. When a concurrent 109d7ccc0fSMax Laier# upload saturates the uplink, download drops to 7 kB/s. With the 119d7ccc0fSMax Laier# priority queue below, download drops only to 48 kB/s. 129d7ccc0fSMax Laier 139d7ccc0fSMax Laier# Replace lo0 with your real external interface 149d7ccc0fSMax Laier 159d7ccc0fSMax Laierext_if="lo0" 169d7ccc0fSMax Laier 179d7ccc0fSMax Laier# For a 512/128 kbps ADSL with PPPoE link, using "bandwidth 100Kb" 189d7ccc0fSMax Laier# is optimal. Some experimentation might be needed to find the best 199d7ccc0fSMax Laier# value. If it's set too high, the priority queue is not effective, and 209d7ccc0fSMax Laier# if it's set too low, the available bandwidth is not fully used. 219d7ccc0fSMax Laier# A good starting point would be real_uplink_bandwidth * 90 / 100. 229d7ccc0fSMax Laier 239d7ccc0fSMax Laieraltq on $ext_if priq bandwidth 100Kb queue { q_pri, q_def } 249d7ccc0fSMax Laierqueue q_pri priority 7 259d7ccc0fSMax Laierqueue q_def priority 1 priq(default) 269d7ccc0fSMax Laier 2742a227f8SMax Laierpass out on $ext_if proto tcp from $ext_if to any queue (q_def, q_pri) 289d7ccc0fSMax Laier 2942a227f8SMax Laierpass in on $ext_if proto tcp from any to $ext_if queue (q_def, q_pri) 309d7ccc0fSMax Laier 31