I think that is why it is important to set it manually when having problems. Autodiscovery is dependant on too many variables. We have several gateways and it depends on which is queried as to which is set (even though they are all set to the same mtu).
Detecting the correct one and hard coding it ensures the best size for your equipment. The drawback is if someone changes the equipments MTU at a later date, which I don't know about where you are, but SBC has done it to some of our people's DSL networks from time to time. That's OK as long as they go up, its when they go down that performance really starts to suck. -----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Roger Seielstad Sent: Friday, May 21, 2004 8:39 AM To: Exchange Discussions Subject: RE: Latency Issue Exch03 - Outlook I missed that - although I've personally seen evidence that leads me to believe the default is 0, not 1. -------------------------------------------------------------- Roger D. Seielstad - MTS MCSE MS-MVP Sr. Systems Administrator Inovis Inc. > -----Original Message----- > From: Reasoner, Bob (PHES) [mailto:[EMAIL PROTECTED] > Sent: Friday, May 21, 2004 8:42 AM > To: Exchange Discussions > Subject: RE: Latency Issue Exch03 - Outlook > > The important part of that article is that the "Key" doesn't exist, > but it is the default setting on 2000 and higher, so it is assumed to > exist in its absence. Creating the Key and enabling it shouldn't > actually change anything as it is the default setting for all > interfaces. > > That particular article if you follow it would have you set that key > to 0 which is OK, but only if you use the other article to hard code > your MTU at the appropriate size as disabling the discovery key > creates a very low MTU for off local network transmissions. > > -----Original Message----- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] On Behalf Of > Roger Seielstad > Sent: Friday, May 21, 2004 7:05 AM > To: Exchange Discussions > Subject: RE: Latency Issue Exch03 - Outlook > > For most clients, its more effective to set the following registry > key: > HKLM\System\CCS\Services\TCP\Parameters > EnablePMTUDiscovery to 1 (doesn't exist by default) > > More info on that particular tweak (plus a few others) is available > here: > http://support.microsoft.com/default.aspx?scid=kb;en-us;q31566 > 9&sd=tech > > > -------------------------------------------------------------- > Roger D. Seielstad - MTS MCSE MS-MVP > Sr. Systems Administrator > Inovis Inc. > > > > -----Original Message----- > > From: Dave Vantine [mailto:[EMAIL PROTECTED] > > Sent: Friday, May 21, 2004 7:43 AM > > To: Exchange Discussions > > Subject: RE: Latency Issue Exch03 - Outlook > > > > Most people probably know this but I ran across this information on > > TechRepublic a few months ago on determining the ideal MTU size and > > was surprised to see the results when I followed the > instructions and > > tested some connections. Thought I would pass it on for what its > > worth. > > > > -Dave Vantine > > > > >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>> > > >>>>>>>>>> > > > > Adjusting the Maximum Transmission Unit size Of all the registry > > tweaks that I've found for TCP/IP, perhaps the most useful is the > > ability to adjust the Maximum Transmission Unit (MTU) size. > MTU size > > dictates the maximum packet size (in bytes) that the TCP/IP > transport > > will attempt to transmit over the underlying network. > > Networks that use Internet Connection Sharing (ICS) or > Point-to-Point > > Protocol over Ethernet (PPPoE) for their broadband connections must > > have an MTU size of 1,492 or lower to run efficiently. > > > > An incorrect MTU size can make your network run slowly. > Administrators > > tend to dismiss this problem as low bandwidth on the ISP's end, and > > that might be a source of the problem. But you'd be > surprised at the > > difference an MTU adjustment can make. > > > > The MTU is such a factor because, by default, Windows 2000 > and Windows > > XP set the MTU size to 1,500. It's been my experience that if a > > network is running slowly, even the 1,492 value I mentioned > earlier is > > too high. > > I usually have the best luck by setting the MTU to around 1,454. > > > > You can check the MTU size for your environment by opening > a command > > prompt on your administration workstation and typing PING -F -I > > <MTUsize> <gateway> > > > > where MTUsize is the size you want to experiment with and > gateway is > > the gateway of your network. Start out by using an MTU size > of 1,454. > > Doing so will make the command look something like this: > > PING -F -I 1454 147.100.100.50 > > > > When you enter the command, the PING will either be > successful or it > > will fail with a message stating that the data must be > fragmented. If > > you receive the error message, decrease the MTU value and > keep trying > > until you find a value that works. If the PING command > works the first > > time, try incrementing the value by five or 10 until you > see the error > > message. You can then narrow down to the appropriate value. > > > > Once you've discovered an MTU size that works, the next trick is to > > embed the value into the registry. The key's actual location within > > the registry varies depending on the version of Windows > you're using. > > If you're using Windows NT, the MTU key is located at: > > HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services > > \Parameters\Tcpip > > > > If you're using Windows 2000 or higher, the MTU key is located at: > > HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services > > \Tcpip\Parameters\Interfaces\adapter ID > > > > There's a good chance that the MTU key doesn't presently > exist in your > > system and that you'll have to create it at the specified > location. To > > do so, open the Registry Editor and create a new DWORD value called > > MTU. > > The minimum value for this key is 68, and the maximum value > is the MTU > > for the underlying network. > > > > > > >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>> > > >>>>>>>>>> > > >>>> > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of > > Horner, Josh > > Sent: Thursday, May 20, 2004 1:38 PM > > To: Exchange Discussions > > Subject: RE: Latency Issue Exch03 - Outlook > > > > The VPN is most likely using an MTU Size Outlook doesn't > like. This > > might be useful. > > > > http://support.microsoft.com/default.aspx?scid=kb;EN-US;329918 > > > > > > Josh > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of > > David, Andy > > Sent: Thursday, May 20, 2004 1:11 PM > > To: Exchange Discussions > > Subject: RE: Latency Issue Exch03 - Outlook > > > > > > MTU size is often a culprit with VPNs. > > > > > > -----Original Message----- > > From: [EMAIL PROTECTED] > > [mailto:[EMAIL PROTECTED] On Behalf Of > > Crista Murphy > > Sent: Thursday, May 20, 2004 1:12 PM > > To: Exchange Discussions > > Subject: Latency Issue Exch03 - Outlook > > > > We have a large WAN with remote offices connecting to the > > exch03 office > > via > > PIX 501 to Sonicwall VPN. We are noticing severe latency > problems in > > 90% of our remote offices when trying to use Outlook (2k > std & pro and > > XP) which has shown up in conjunction with the move from the PIX to > > PIX VPN to the current configuration. > > > > Anyone have any suggestions on which diag logging to turn up on the > > exch server that might help diagnose this problem? The people in > > charge of the vpn's are 100% blaming the exch server for dropping > > sessions. > > > > Exch works fine in the local office and via webmail, it is > only when > > connecting thru the VPN with Outlook. > > > > Thanks! > > > > _________________________________________________________________ > > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > > Web Interface: > > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&t > > ext_mode=& > > lang > > =english > > To unsubscribe send a blank email to %%email.unsub%% > > Exchange List admin: [EMAIL PROTECTED] > > To unsubscribe via postal mail, please contact us at: > > Jupitermedia Corp. > > Attn: Discussion List Management > > 475 Park Avenue South > > New York, NY 10016 > > > > Please include the email address which you have been contacted with. > > > > > > _________________________________________________________________ > > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > > Web Interface: > > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&t > > ext_mode=& > > lang > > =english > > To unsubscribe send a blank email to %%email.unsub%% > > Exchange List admin: [EMAIL PROTECTED] > > To unsubscribe via postal mail, please contact us at: > > Jupitermedia Corp. > > Attn: Discussion List Management > > 475 Park Avenue South > > New York, NY 10016 > > > > Please include the email address which you have been contacted with. > > > > > > _________________________________________________________________ > > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > > Web Interface: > > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&t > > ext_mode=& > > lang=english > > To unsubscribe send a blank email to %%email.unsub%% > > Exchange List admin: [EMAIL PROTECTED] > > To unsubscribe via postal mail, please contact us at: > > Jupitermedia Corp. > > Attn: Discussion List Management > > 475 Park Avenue South > > New York, NY 10016 > > > > Please include the email address which you have been contacted with. > > > > This email and any files transmitted with it are confidential and > > intended solely for the use of the individual or entity to > whom they > > are addressed. If you have received this email in error > please notify > > the system manager. This message contains confidential > information and > > is intended only for the individual named. If you are not the named > > addressee you should not disseminate, distribute or copy > this e-mail. > > > > _________________________________________________________________ > > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > > Web Interface: > > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&t > ext_mode=&lang=english > > To unsubscribe send a blank email to %%email.unsub%% > > Exchange List admin: [EMAIL PROTECTED] > > To unsubscribe via postal mail, please contact us at: > > Jupitermedia Corp. > > Attn: Discussion List Management > > 475 Park Avenue South > > New York, NY 10016 > > > > Please include the email address which you have been contacted with. > > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&t ext_mode=&lang > =english > To unsubscribe send a blank email to > %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: > Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > > > > _________________________________________________________________ > List posting FAQ: http://www.swinc.com/resource/exch_faq.htm > Web Interface: > http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&t ext_mode=&lang=english > To unsubscribe send a blank email to > %%email.unsub%% > Exchange List admin: [EMAIL PROTECTED] > To unsubscribe via postal mail, please contact us at: > Jupitermedia Corp. > Attn: Discussion List Management > 475 Park Avenue South > New York, NY 10016 > > Please include the email address which you have been contacted with. > _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Web Interface: http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&lang =english To unsubscribe send a blank email to %%email.unsub%% Exchange List admin: [EMAIL PROTECTED] To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. Attn: Discussion List Management 475 Park Avenue South New York, NY 10016 Please include the email address which you have been contacted with. _________________________________________________________________ List posting FAQ: http://www.swinc.com/resource/exch_faq.htm Web Interface: http://intm-dl.sparklist.com/cgi-bin/lyris.pl?enter=exchange&text_mode=&lang=english To unsubscribe send a blank email to [EMAIL PROTECTED] Exchange List admin: [EMAIL PROTECTED] To unsubscribe via postal mail, please contact us at: Jupitermedia Corp. Attn: Discussion List Management 475 Park Avenue South New York, NY 10016 Please include the email address which you have been contacted with.
