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Posted on 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 …
Posted on 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 …
Posted on in voice
Trying to debug an <acronym title="Asterisk Gateway Interface">AGI</acronym> in Asterisk can be a frustrating experience. The main problem is that STDERR only outputs to the terminal Asterisk was started from. In most cases, this means the terminal is the server console. If your Asterisk server is sitting …
Posted on 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 …
Posted on 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 …
Posted on in Software
XHTML Character Entity Reference
Digital Media Minute's Jim Rutherford has developed an invaluable reference in his XHTML Character Entity Reference. With this reference in hand, I can finally ditch all my little notes about copyrights, trademarks, and cedillas. Here's an explanation of how the page works in Jim's own …
Posted on in Networking
Deciding whether to use <acronym title="Remote Authentication Dial-In User Service">RADIUS</acronym> or <acronym title="Terminal Access Controller Access Control System Plus">TACACS+</acronym> for <acronym title="Authentication, Authorization, Accounting">AAA</acronym> functionality on a Cisco-based network seems straight-forward. After all, if the network uses Cisco, shouldn't the AAA …
Posted on in Graphics Design
Important commands: sips
A few folks have asked me where I got the nice looking Software Update icon for my post regarding Apple's Security Update 2007-004. First, let me say, "Thanks for noticing!" Second, let me point out that Steve Jobs will probably be knocking on the door of the …
Posted on in System Administration
Posted on in System Administration
Posted on in Software
One of the features of Firefox 2 is Session Restore. By default, if Firefox needs to restart for an update (or crashes), it will restore your session to the state it was in at the time of restart. That means your tabs and windows will be just like you left …
Posted on in System Administration
Every machine needs a name. As soon as the second server is ready to go, the name
SERVER no longer seems like a great idea. When deciding how to name servers,
there are two primary conventions: functional names and unique names.
Functional names take the job assigned to …
Posted on in Networking
<acronym title="UniDirectional Link Detection">UDLD</acronym> is a Cisco protocol designed to detect and disable unidirectional links in Ethernet (fiber or twisted-pair). In the case of a radio-based Metro Ethernet ring, UDLD goes the extra mile in preventing Spanning-Tree loops and user service interruption.
In this simple network of …
Posted on in voice
When using Asterisk and a remote bank of <acronym title="Primary Rate Interface">PRI</acronym>s (or any other form of <acronym title="Public Switched Telephone Network">PSTN</acronym> connectivity for that matter), you may encounter an issue known as hairpinning. Hairpinning describes what happens when a call coming from …
Posted on in System Administration
A concise legacy mail-server troubleshooting note showing how trailing whitespace in a Courier credential can cause a misleading MySQL authentication failure.
You've probably been using 