RDP connections might fail due to a problem with KB2621440 – MS12-020

I was helping a colleague who was dealing with a Remote desktop connection problem where Windows 8 client was failing to access a certain Windows 2008 R2 SP1 Terminal server. We first collected some logs while reproducing the problem to better understand why the RDP connection was failing:   1) Please start TCPIP/Winsock ETL tracing…


Desktop sharing fails between federated contacts running Lync 2010 clients

I would like to talk about another Lync 2010 problem where desktop sharing was failing between two federated contacts. Network traces and Lync ETL traces were collected while reproducing the problem. Here’s the troubleshooting steps that I followed:   ANALYSIS: ======== Note: Please note that usernames, IP addresses, server names etc are all replaced for…


External users cannot sign in to Lync 2010

Today I’ll be talking about a problem where the external Lync 2010 clients fail to sign in through Lync 2010 Edge server intermittently and rebooting the Edge server helps resolve the issue for sometime until the problem reappears. There could be multiple problems that might prevent an external user from signing in successfully like authentication…


SCCM client push installation may fail due to firewall problems

I was collaborating with a colleague of mine on a problem where SCCM client push installation was failing. They suspected network connectivity problems and collected simultaneous network traces from SCCM server and from a problem client machine and involved me in for further analysis.   When I check the SCCM server and client side traces,…


TMG Safe search feature may not work as expected sometimes

In this post, I would like to talk about a TMG safe search problem which I dealt with recently. The problem was that the TMG safesearch feature wasn’t working properly even though the all the requirements were met. We decided to collect dynamic logs while reproducing the problem (TMG data packager + client side logs)….


Slow performance when accessing a Sharepoint 2010 portal through an ISA 2006 array

I was involved in a slow Sharepoint portal access through an ISA 2006 array problem and I wanted to talk about how I dealt with that issue and found the root cause of the slowness issue. The problem was that the portal home page was loaded very slowly and sometimes it wasn’ loaded at all…


Direct access client fails to connect to UAG DA server through IPHTTPS with various errors (0x800b0109 and 0x274c)

In this post, I want to talk about how I troubleshooted a direct access connectivity problem hoping that it might also help you in troubleshooting similar problems. The issue was that the IPHTTPS client cannot connect to UAG DA server. We first checked static logs collected from a problem client (GPO output, firewall outputs, etc)…


TCP delayed ACK combined with Nagle algorithm can badly impact communication performance

Recently I was involved in a network connectivity performance issue and wanted to share the root cause we found. You can find below an example communication of how the slow performance occurs: A Windows application server A UNIX application server   No.     Time                       Delta       Source                Destination           Protocol Length Info    3562 2012-12-12 18:19:53.258784 0.000000   …