Shibboleth AA timed out

[XiaoXia Dong]

Shibboleth experts,

I have an intermittent question about AA timeout. Here is an example of errors:
2012-02-21 13:05:50 DEBUG XMLTooling.SOAPTransport.CURL [9]: getting connection handle to https://fed.it.northwestern.edu:8443/shibboleth-idp/AA
...
2012-02-21 13:06:10 ERROR Shibboleth.AttributeResolver.Query [9]: exception during SAML query to https://fed.it.northwestern.edu:8443/shibboleth-idp/AA: CURLSOAPTransport failed while contacting SOAP endpoint (https://fed.it.northwestern.edu:8443/shibboleth-idp/AA): Operation timed out after 20000 milliseconds with 0 bytes received
2012-02-21 13:06:10 ERROR Shibboleth.AttributeResolver.Query [9]: unable to obtain a SAML response from attribute authority

I have no clue where the 20 seconds timeout comes from.  Would you be able to help to see where the problem comes from or point me to the right direction?

Thanks in advance for any help that you could provide.
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