I have the following problem:

swf file is located at www.server_source.com/source.swf

html file which embeds swf file is located on www.server_target.com/index.html

xml file which is used by the swf file is located on
www.server_source.com/source.xml

Should I:

a: place crossdomain.xml on www.server_source.com, allowing access to
server_target.com?
b: place crossdomain.xml on www.server_target.com, allowing access to
server_source.com?
c: do both?
d: do something else?

My crossdomain.xml file looks like this:

<?xml version="1.0">
<cross-domain-policy>
<allow-access-from domain="*.server_x.com"/>
</cross-domain-policy>

From Flash Help:
"Policy files must be named crossdomain.xml, and can reside either at the root
directory or in another directory on the server that is serving the data with
some additional ActionScript"