Re: What's happened to Microsoft Support?

AlanTerrill <AlanTerrill@xxxxxxxxxxxxxxxxxxxxxxxxx> wrote:

I tried clearing the browser cache but no luck. I then phoned the firm that
supports our servers and they suggested it could be the router that controls
our internet access. I've had the MTU setting changed from 1400 to 1500 at
their suggestion,(I've no idea what this means), and it worked! I can now see
all the tech support pages on microsoft I couldn't see before. I wonder why
I could see them until recently, but then they suddenly became unavailable?

It doesn't take very much for some intermediate router to add just a
single byte of control bits to packets. If that causes the packet size
to exceed the negotiated MTU size the packets may be fragmented, and
that's hardly ever a "good thing". This happens a lot when using VPN
or when a DSL provider adds 'stuff" to packets, and it's never easy to
diagnose.

A simple test is to use "ping <address> -f -l 1472" If that works, the
MTU size of 1500 should be okay, but if it fails reduce the 1472 to,
say, 1400 and try again. Eventually you'll find an appropriate size
that passes through all the routers without fragmenting. Drop another
100 bytes off that size (to be safe) and make it your MTU size.

--
Rich Matheisen
MCSE+I, Exchange MVP
MS Exchange FAQ at http://www.swinc.com/resource/exch_faq.htm
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Relevant Pages

  • Re: TCPIP performance for VMS
    ... encapsulation is reducing the available MTU ... its packets through intact while the DSL modem is forced to fragment ... Thewww.speedguide.net:8080looks at the TCP options. ... If you're still using Cisco router gear, there is a tweak you can try. ...
    (comp.os.vms)
  • Re: How to see frag/defrag utilization of the router.
    ... > defragmentin/fragmenting of packets about wrong settings of MTU. ... > I have IPsec traffic going through the router and when it is present ... > 400-500 kbytes per second while the IPsec traffic only 30/40 kBytes ...
    (comp.dcom.sys.cisco)
  • Re: TCPIP performance for VMS
    ... links bonded into one), the headers are larger. ... its packets through intact while the DSL modem is forced to fragment ... VMS doesn't have MTU discovery enabled. ... If you're still using Cisco router gear, there is a tweak you can try. ...
    (comp.os.vms)
  • Understanding path MTU discovery
    ... As far as I can tell from my reading, if a computer on the internet accesses our web server, but the reply from the server is too big (for example, the client computer is using a PPPoE link with an MTU of 1492), the client's ISP's gateway router will send an ICMP package back to our router. ... I understand that I could mark incoming packets from clients so that replies are sent out through the same interface they came in, but I would prefer to balance the output packets. ...
    (comp.os.linux.networking)
  • Re: SBS 2003 Setup recommendation
    ... Your suggestion about MTU looks very interesting. ... We want something lige the following setup: http://pings.dk/sbssetup.gif ... agaist SBS2003 server. ... IPSec adds a small overhead the size of a packet which would make packets ...
    (microsoft.public.windows.server.sbs)