RE: [squid-users] WPAD and Internet Explorer 6

On Tue, 19 Apr 2005, Damien Nguyen wrote:

> I can see name resolution activities from Windows 2000 and XP PCs but not
> from NT4 workstations.
>
> Like I mentioned in my previous post, if I specify the automatic
> configuration script (the URL to the wpad.dat file) I can see the NT4
> workstation issue the "GET /WPAD.DAT" command from Ethereal.
>
> Again, if I set it back to "automatically detect settings" (even did a
> reboot after the change), does not work, nothing DNS related in Ethereal...

If you use DHCP then you could try specifying the PAC path in the DHCP
responses.

    SUMMARY OF WPAD DISCOVERY MECHANISMS

       +-------------------------+--------+----------+
       | Discovery | | Document |
       | Mechanism | Status | Section |
       +-------------------------+--------+----------+
       | DHCP | MUST | 5.4.1 |
       | SLP | SHOULD | 5.4.2 |
       | "Well Known Alias" | MUST | 5.4.3 |
       | DNS SRV Records | SHOULD | 5.4.4 |
       | DNS TXT "service: URLs" | SHOULD | 5.4.5 |
       +-------------------------+--------+----------+

5.4.1 DHCP

    Client implementations MUST support DHCP. DHCP has widespread
    [...]

    The DHCP option code for WPAD is 252 by agreement of the DHC working
    group chair. This option is of type STRING. This string contains a
    URL which points to an appropriate config file. The STRING is of
    arbitrary size.

    -> URL as specified in DHCP

5.4.2 Service Location Protocol /SLP

    [RFC2608]

    -> URL as specified by SLP

5.4.3 DNS A/CNAME "Well Known Aliases"

    Client implementations MUST support this mechanism. This should be
    [...]

    The client performs the following DNS lookup:
    QNAME=wpad.TGTDOM., QCLASS=IN, QTYPE=A

    -> http://wpad.TGTCOM/wpad.dat

5.4.4 DNS SRV Records

    [RFC2052]

    Client implementations SHOULD support the DNS SRV mechanism. Details
    [...]

    The client issues the following DNS lookup:
    QNAME=wpad.tcp.TGTDOM., QCLASS=IN, QTYPE=SRV

    -> http://server:port/wpad.dat

5.4.5 DNS TXT service: Entries

    Client implementations SHOULD support this mechanism. If the
    [...]

    The client should attempt to retrieve TXT RRs from the DNS to obtain
    "service: URLs" contained therein. The "service: URL" will be of the
    following format, specifying a complete candidate CURL for each
    record located:

        service: wpad:http://<HOST>:<PORT><PATH>

    The client should first issue the following DNS query:
    QNAME=wpad.TGTDOM., QCLASS=IN, QTYPE=TXT

    -> URL as specified by the DNS TXT service: record

Regards
Henrik
Received on Tue Apr 19 2005 - 18:22:14 MDT