Troubleshooting Network Latency

Network latency issues can have various causes. Listed below are the most common troubleshooting steps to narrow down the specific reasons for inconsistent connectivity.

First steps:

• Restart your computer to see if that alleviates the problem.
• Spyware and antivirus software often slow down the PC; follow the steps in Article D1 to scan your PC.
• Open Outlook and check the connection status in the lower right hand corner of the window. If it says "Offline", deselect it.
• Hold CTRL key down, click on the Outlook icon in the System Tray and select "Connection Status". For each line it should read Established or Connecting, and the average response time should be below 400ms.

Ensure Outlook is running in cached mode:

For Outlook 2003:
From within Outlook go to: Tools > Email Accounts > View/Change Existing Email Accounts > Next. Highlight Microsoft Exchange Server and click Change. Check the Use Cached Exchange Mode box.

Click on More Settings >Advanced Tab. Make sure that Use Cached Exchange Mode and Download Public Folder Favorites are both checked. Click OK > Next > Finish.

For Outlook 2007
From within Outlook go to: Tools > Account Settings. Highlight the name of the user and click Change. Check the Use Cached Exchange Mode box.

XP Users:

• If you're using Windows XP make sure you have upgraded to SP2.
• The Windows Firewall can cause latency issues - try disabling the Windows XPsp2 Firewall to alleviate the issue.

Port 135 may be blocked:
Your ISP may have started blocking port 135. To test if you can connect to this port open a command prompt window and type telnet "mailXXX 135" without the quotes. Replace the X's in "mailXXX" with the name of your mail server. You can find this information by going to Control Panel > Users > Outlook Setup. The name of your mail server is listed in the Exchange Server field. Press the Enter key.

A blank page with a blinking cursor in the left hand corner should open. If the command prompt window displays "connecting…", the port is blocked.

Your host file has been changed:
Open a command prompt window and at the prompt type "telnet 69.25.74.34 135" without the quotes. Press the Enter key.

Was the port still blocked? If not, then your hosts file has been changed or you have not run OLSetup.exe – please run it now: OLSetup.exe.

Problem with the internet infrastructure:
To determine if a backbone between your location and the Exchange server is having issues:

• Open a command prompt window and type "ping mx1.MyOutlookOnline.com –t" without the quotes; press Enter. This is a continuous ping - keep an eye out for times that exceed 200ms.
• If you are not able to ping mx1.MyOutlookOnline.com you may have DNS issues. Type "ping 69.25.74.34 –t" without the quotes; press Enter. Let the ping run 5-10 minutes and look for erratic time behavior with times jumping into the hundreds. You may be experiencing latency from your ISP.
• Also in the command prompt "tracert 69.25.74.34" or "tracert mailXXX" without the quotes and press Enter. Replace the X's in "mailXXX" with the name of your mail server. You can find this information by going to Control Panel > Users > Outlook Setup. The name of your mail server is listed in the Exchange Server field.

Repeat this action 3 or 4 times. Look for "*" which means that the router is dropping packets. Also look for extremely high times over 200 ms. If one router is having intermittent issues, then it will affect all routers following it.

Installation of new systems or infrastructure:
Have you recently installed VoIP phones or other systems in your network that use large amounts of bandwidth? Have you recently changed your network connections--router, hub or switch? Or, have you recently updated them? Try reconfiguring the connections to alleviate the network congestion.