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Archives for December 2010

Roundcube performance

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There are many configuration options with inpact on performance in Roundcube and behind it (Database and Webserver). As Roundcube installation administrator you can set them to some defaults and prevent users to change them by using the ‘dont_override‘ option.

I tested some options and created my tiny boost list.
Here’s the list of options with impact on performance

Messages listing is a main task of a mail client. Sorting is expensive. First of all you should use an IMAP server with SORT capability. If message list displaying is still too slow you should set ‘message_sort_col’ to an empty string.
‘message_sort_col’
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Trainig for CCNA 640-802

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Q: What are three examples of TCP/IP application layer protocols? (Choose three.)
A: a terminal emulation protocol that supports remote console connections with various network devices
A: a protocol responsible for transporting electronic mail on TCP/IP networks and the Internet
A: a protocol that exchanges network management information between a network device and a management console

Q: Refer to the exhibit. The exhibit shows simplified protocol data units from different OSI model layers. Which three statements are true
about the PDUs and the encapsulation process?


A: PDU #1 is a frame.
A: PDU #3 is a segment.
A: The order in which these PDUs are created during the encapsulation process is 3, 4, 1, 2.
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Test spam rejection

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Sometimes it’s interesting to test some MTA’s and their spam behavior, every mail system has his own spam behavior like SPAM_MARK_LEVEL or SPAM_REJECT_LEVEL.
If you send a mail with GTUBE string your mail should be rejected.

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rejected after DATA: This message scored 1000.0 spam points

The GTUBE String to test spam rejection of mail servers:

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XJS*C4JDBQADN1.NSBN3*2IDNEN*GTUBE-STANDARD-ANTI-UBE-TEST-EMAIL*C.34X

Say no to GIF

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I visit very often GNU/OpenSource websites like debian.org, and I’ve never seen there pictures in GIF format.
Why there are no GIFs on GNU Web Pages?

And of course, I found an answer on gnu.org:
There are no GIFs on the GNU web site because of the existing GIF patents Unisys and IBM covering the LZW compression algorithm which is used in making GIF files. These patents make it impossible to have free software to generate proper GIFs. They also apply to the compress program, which is why GNU does not use it or its format.

Unisys and IBM both applied for patents in 1983.

The Unisys patent expired on 20 June 2003 in the USA, in Europe it expired on 18 June 2004, in Japan the patent expired on 20 June 2004 and in Canada it expired on 7 July 2004. The U.S. IBM patent expired 11 August 2006, The Software Freedom Law Center says that after 1 October 2006, there will be no significant patent claims interfering with employment of the GIF format.

Webserver Benchmark

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ab (Apache Benchmark) is a tool for benchmarking your HTTP server. It provides a quick an easy way to evaluate your http serving capabilities. ab overloads the server with http requests and measures the time it takes to serve all those requests.

How to install ab and where to get it? The real thing is that ab comes preconfigured with your apache installation. Apache by himself is just an extension command for the Apache Web Server. So if you have already installed Apache, then you should be able to run ab.

What we need in order to get ab to work is type the command and append the URL address we want to test. The command is issued as follows.

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server ~ # ab -n10000 -c8 http://piper/
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# Number of connections to send to the server
-n
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# Number concurrent requests to be made
-c
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# Option activates the KeepAlive feature
-k
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# Is the timelimit (in seconds)
-t

ab testing mechanism actually is a good example of a Denial of Service (DoS) attack.