AIX Version 4.3 Differences Guide

Following are some examples of using delayack:
# no -o delayack=3
sets delay the ACK for both SYN and FIN.
# no -d delayack
sets delayack to the default value 0.
delayackports
The delayackports option allows a user to specify a list of up to ten ports for
which the ACKs for SYNs and/or FINs defined by the delayack port option will be
performed.
This allows a system administrator to configure this operation for specific
applications that use a specific port. Although this will improve the performance
for Web servers, this may not be good for other applications.
The delayackports option takes a list of ports numbers separated by commas and
enclosed in curly braces.
For example: no -o delayackports={80,1080,1180}
An empty list, no -o delayackports={}, will clear the ports.
# no -d delayackports, sets delayackports to the default. "{}" means no ports.
The send_file() system call with the SF_CLOSE flag will send the FIN packet with
the last data.
7.9.3 Reducing the Contention of INIFADDR and Route Lock
There are some changes in kernel to the route lock and inifaddr lock in order to
improve performance. These changes decrease the processing time for each
incoming and outgoing packet. These changes are internal and do not affect
external user interfaces.
The route lock and inifaddr are used by the TCP/IP protocol packets:
INIFADDR lock examined by every incoming packet
Route lock examined by every outgoing packet
7.9.3.1 Reducing the Contention of INIFADDR Lock
Currently, for every incoming packet, the inifaddr list must be searched with the
lock held. This causes a great deal of lock contention.
The INIFADDR lock contention is serious for SMP machines. This lock is used for
all input packets, causing unacceptable lock contention on machines with
multiple adapters. Therefore, it is a critical lock on 12-way RS/6000 S70 machine
with multiple adapters.
Since this inifaddr list is changed very rarely, but searched so often, the lock
contention is reduced by:
• Allowing concurrent searches
Networking Enhancements 175