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Annotation of src/share/pf/ackpri, Revision 1.2

1.2     ! henning     1: # $OpenBSD: ackpri,v 1.1 2003/03/02 12:19:58 dhartmei Exp $
1.1       dhartmei    2:
1.2     ! henning     3: # Use a simple priority queue to prioritize empty (no payload) TCP ACKs,
1.1       dhartmei    4: # which dramatically improves throughput on (asymmetric) links when the
                      5: # reverse direction is saturated. The empty ACKs use an insignificant
                      6: # part of the bandwidth, but if they get delayed, downloads suffer
1.2     ! henning     7: # badly, so prioritize them.
1.1       dhartmei    8:
                      9: # Example: 512/128 kbps ADSL. Download is 50 kB/s. When a concurrent
                     10: # upload saturates the uplink, download drops to 7 kB/s. With the
                     11: # priority queue below, download drops only to 48 kB/s.
                     12:
                     13: # Replace lo0 with your real external interface
                     14:
                     15: ext_if="lo0"
                     16:
                     17: # For a 512/128 kbps ADSL with PPPoE link, using "bandwidth 100Kb"
                     18: # is optimal. Some experimentation might be needed to find the best
                     19: # value. If it's set too high, the priority queue is not effective, and
                     20: # if it's set too low, the available bandwidth is not fully used.
                     21: # A good starting point would be real_uplink_bandwidth * 90 / 100.
                     22:
                     23: altq on $ext_if priq bandwidth 100Kb queue { q_pri, q_def }
                     24: queue q_pri priority 7
                     25: queue q_def priority 1 priq(default)
                     26:
                     27: pass out on $ext_if proto tcp from $ext_if to any flags S/SA \
                     28:        keep state queue (q_def, q_pri)
                     29:
                     30: pass in  on $ext_if proto tcp from any to $ext_if flags S/SA \
                     31:        keep state queue (q_def, q_pri)
                     32: