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MikeJ-UK
Asked: 2009-09-18 08:08:53 +0800 CST

Slow IE8 Start-up due to LDAP DNS queries

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Recently (in the last few days), my installation of IE8 has been taking 15 to 20 seconds to load my home page. Specifically, the sequence of events (as reported by WireShark) is:-

  • Browser issues a DNS A query to resolve the home page server's IP address.
  • Browser then spends the next 15-20 seconds broadcasting DNS SRV _LDAP._TCP queries, (roughly on a 2 second tick) to which it receives no answer (we have no LDAP servers).
  • Browser re-issues the DNS A query and resolves the server's IP address again.
  • Finally, the browser issues an HTTP GET for the home page.

Does anyone know why this is happening?

EDIT:
@Massimo, LDAP query is :-

Domain Name System (query)
  Transaction ID: 0x11c5
  Flags: 0x0100 (Standard query)
  Questions: 1
  Answer RRS: 0
  Authority RRS: 0
  Additional RRS: 0
  Queries
    _LDAP._TCP: type SRV, class IN
      Name: _LDAP._TCP
      Type: SRV (Service location)
      Class: IN (0x0001)
ldap

6 Answers

  1. You could perform the same testing with Firefox. Install the Firebug addon and see if the same result with regards to DNS is occuring. The NET tab will be able to display DNS query times for all elements. Be sure to flushdns (ipconfig /flushdns) between tests. Perhaps it's not IE8 and if not this might help you.

    Good luck

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  2. Is your computer a domain member, or was it ever?

    Those LDAP queries looks a lot like what happens when a domain member is trying desperately to find a domain controller.

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  3. If I remember correctly, Wireshark doesn't show the process information involved in the packets captured. Can you install Microsoft Network Monitor 3.3 (which does show the processes) to see if it's actually IE8 or if it's another process issuing the DNS LDAP queries?

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  4. Why does it receive no answer? It's a DNS Query, the lack of LDAP servers shouldn't stop your firewall/router/dns server/coffee maker from negatively responding to an SRV _LDAP lookup. I bet if your DNS server properly responded to this query, IE8 (Or whatever process is actually making these requests) wouldn't have to retry for 15 seconds.

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  5. On the PC involved, can you switch the DNS server configuration from the local router to OpenDNS servers 208.67.222.222 and 208.67.220.220, and see if the problem is resolved.

    It sounds like the broadband router isn't handling the DNS requests correctly, though I'd think IE8 shouldn't be waiting that long for responses either.

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  6. I'm seeing the same behaviour on a recent install. Mines a Win2K3 server with Terminal Services and Citrix Xenapp5.

    I dont have AD or a Windows domain.The machine is configured as a "Workgroup" server

    When I startup IE8 in a TS session it takes 20 seconds + to load the home page ( a local intranet server). My Wireshark confirms exact same DNS lookup, maybe 8 queries in 20 seconds or so. As above the DNS query does NOT have the local domain appended. A normal query should have the form "_ldap._tcp.domain.com". Bit of a stinker because without the domain you cant even blackhole the query via DNS or local hosts file.

    What in the world is an Internet browser doing looking for an Active Directory service on startup ???? Neil.

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