Articles in the system_administration category

1. Mac OS X TCP Performance Tuning

   Posted on May 05, 2007 in system_administration

   Because Darwin is BSD-based, it's no surprise that Mac OS X TCP Performance Tuning is very similar to FreeBSD TCP Performance Tuning. It is no longer necessary to enable RFC 1323 TCP Extensions (in fact, the option to do so is gone). Also, we'll set the TCP send and receive …

2. Linux TCP Performance Tuning

   Posted on May 04, 2007 in system_administration

   If you have been following our TCP Performance Tuning series, you'll know that we want to enable RFC 1323 Window Scaling and increase the TCP window size 1 MB. To do this, we'll add the following lines to /etc/sysctl.conf and issue sudo sysctl -p to apply the changes …

3. TCP Performance Tuning and Broken Routers

   Posted on May 03, 2007 in System Administration

   In TCP window scaling and broken routers posted in July of 2004, LWN.net's corbet points out that certain routers are setting the RFC 1323 window scale to 0. This effectively sets the TCP window size for the transmission to the minimum value and greatly inhibits performance. As corbet notes …

4. FreeBSD TCP Performance Tuning

   Posted on May 02, 2007 in system_administration

   To enable RFC 1323 Window Scaling and increase the TCP window size to 1 MB on FreeBSD, add the following lines to /etc/sysctl.conf and reboot.

   net.inet.tcp.rfc1323=1  
   kern.ipc.maxsockbuf=16777216  
   net.inet.tcp.sendspace=1048576  
   net.inet.tcp.recvspace=1048576
   

   You can make these …

5. What is TCP Window Scaling?

   Posted on May 01, 2007 in System Administration

   The original TCP specification included a window size no larger than 64 KB. This limitation was introduced by the 16 bit header that specified window size. To achieve the recommended 1 MB window size, RFC 1323 TCP extensions must be enabled. The rest of this post is a somewhat detailed …

6. 14 Algorithms For TCP Congestion Control

   Posted on April 29, 2007 in system_administration

   Note: Although this is a continuation of the TCP Performance Tuning article series, it's also valuable as a standalone reference.

   This is a list of 14 congestion control algorithms available in TCP. I'm presenting it in alphabetical order.

   1. BIC TCP - Binary Increase Congestion Control, this is the default congestion control …

7. TCP Performance Tuning

   Posted on April 28, 2007 in system_administration

   Note: Stanislav Shalunov wrote an excellent article on TCP over WAN Performance Tuning and Troubleshooting. In this series of articles, I want to summarize his findings and provide tuning suggestions for popular operating systems.

   Most operating systems today ship with TCP stacks optimized for either LAN (high speed, low latency …

8. Redirecting User Email To Google With Postfix

   Posted on April 26, 2007 in System Administration

   Note: Now that Google is hosting email domains for free, it has become an interesting alternative for both new and old domains. As always, I've changed the names to protect those affected.

   Transitioning a domain to Google can be an arduous task. Once you have set up the domain with …

9. Courier Announces Updates

   Posted on April 22, 2007 in System Administration

   Sam Varshavchik with the Courier Mail Server project announced updates for all their major software packages including courier-imap, courier-authlib, and maildrop, in addition to the Courier MTA. The major fix common to most packages appears to be the plugging of a memory leak which only came into play once a …

10. Postfix 2.3 and clamav-milter

    Posted on April 22, 2007 in System Administration

    You've probably been using Postfix and ClamAV for a long time. Prior to Postfix 2.3, you had to have an AMaViS daemon running to act as the glue between Postfix and ClamAV.

    As of version 2.3, Postfix now supports Sendmail 8 Milter protocol. Now you can cut AMaViS …