Checking proxy authentication mechanism

Hello

We have Windows XP SP3 clients. Their IE is configured to use an auto.pac file which will determine if a website is internal or external. The PAC is located at http:\\server1\auto.pac.

If the server is external, there are HTTP proxies that the request will get sent to, let's name it Proxy1.

If I ran Wireshark on an XP machine, is this the result I should expect to see when attempting to browse an external site (www.google.com)

1.  DNS resolution for server1
2. Contact server1's IP
3. After reading the auto.pac and realising Google is externally hosted, a request for DNS resolution of Proxy1
3. Contact Proxy1's IP
4. Proxy1 sends authentication request
5. User returns details
6. Contact Proxy1's IP again with an HTTP GET

Also, how can I work out what authentication mechanism the Proxy1 device is using? I have used Wireshark and can see this:

"Proxy authenticate: NTML .. Proxy Authenticate: BASIC realm="proxy".."

So is it using NTLM or Basic?

I would like to know what sort of authentication mechanism these proxies use.

neil4933Asked:
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giltjrConnect With a Mentor Commented:
It uses both.  If it does not get the appropriate user-id/password using NTML it will then prompt the user using basic.
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neil4933Author Commented:
Hi

Thanks...

""Proxy authenticate: NTML .. Proxy Authenticate: BASIC realm="proxy".."

You're saying that the above means that either no username/password or an incorrect one was given by NTLM, so it's prompting for one in BASIC?
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giltjrCommented:
Yes.
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neil4933Author Commented:
Surely if an incorrect username/password was given it should just deny access rather than asking for a new one in Basic?
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giltjrCommented:
No.  Typically with web servers you are given up to 3 chances to enter the correct name/password before you are denied.
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