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I ran into a fun problem today. The HTTP session cookie for one of my websites was not being retained in the Safari web browser. Packet sniffing clearly showed the server was sending a ‘Set-Cookie’ in the HTTP header. Safari accepted the cookie just fine with other virtual hosts having identical code base and similar configurations for Apache webserver and Tomcat. FireFox 3 accepted the cookie from all the virtual hosts. It was quite a perplexing issue.

It turns out that Safari, Version 3.1.1 at least, does not retain cookies from hosts with an underscore (_) in its name and my troubled website host did indeed have one in its name. I changed the underscore to a dash (-) and Safari was happy.

Who woulda thunk?


Discussion of the issue from the Ruby Forum
Internet Explorer probably would have given me the same behaviour, but I didn’t test it.
Host name specifications are documented in RFC 952 and RFC 1035. The underscore is not among valid characters.


The Tiger and Leopard releases of MacOS X include an implementation of BSD’s dummynet. Dummynet is “a system facility that permits the control of traffic going through the various network interfaces“.

There are many uses for this feature. I use it as part of my website development to simulate a slow network connection. Many of the users of our websites are in developing countries with slow, dialup-speed, network connections. By using a couple of quick commands I can throttle my connection to the webserver down to similar speeds. As such, I can feel their pain even though I’m on a snazzy gigabit connection, two hops away from the webserver.

The following series of commands will slow my communications to and from the webserver down to 56K modem speeds. It only affects http connections (to any web server, not just mine). My other network connections – ssh, for example – operate with native network performance.

$ sudo ipfw add pipe 1 src-port http
$ sudo ipfw add pipe 1 dst-port http
$ sudo ipfw pipe 1 config bw 56kbit/s

Adam Knight’s Traffic Shaping in Mac OS X is a good starter tutorial.

Additional articles and documentation.


January 2019
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