As many folks probably know, Group Policy slow link detection prior to Windows Vista relied on a series of ICMP pings to determine link speed between the client and domain controller. This process was fairly inprecise and was fraught with issues because many folks have turned off ICMP on their internal networks to prevent malware that leverages this protocol from exploiting this. The end result was that you either had to disable slow link detection, or watch GP processing fail completely.
When Windows Vista and Server 2008 shipped, they introduced a completely new way of detecting slow links for Group Policy processing that no longer leverages ICMP. The process uses the Network Location Awareness (NLA) service to determine the link speed between client and DC, but the explanation of HOW that works has been relatively undocumented…until now. Mike Stephens at Microsoft has written a great blog that describes this process in great detail. Check it out!
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About the Author:
Darren Mar-Elia is CTO & Founder of SDM Software, Inc. Darren has over 25 years of IT and Software experience in the Microsoft technology area, including serving as a Director in Infrastructure at Charles Schwab, CTO of Windows Management Solutions at Quest Software, and Sr. Director of Product Engineering at DesktopStandard. He has been a Microsoft MVP in Group Policy technology for the last 6 years and has written and spoken on Active Directory, Group Policy and PowerShell topics frequently over the years. He maintains the popular Group Policy resource web site at www.gpoguy.com and has been a contributing editor for Windows IT Pro Magazine since 1997. He has written and contributed to twelve books on Windows. Darren also speaks frequently at conferences on Windows infrastructure topics.