TCP Provider: The semaphore timeout period has expired error from SQL Server agent and other applications at times.

1. Disable TCP Chimney.Refer KB:942861

2. If you are in windows 2003 Change the value of the processor affinity to match the number of processors in the system.Follow KB:892100

{
1.Click Start, click Run, type regedit, and then click OK.
2.Expand the following registry subkey:
HKEY_LOCAL_MACHINE\System\CurrentControlSet\Services\NDIS\Parameters
3.Right-click ProcessorAffinityMask, and then click Modify.
4.In the Value data box, type one of the following values, and then click OK:
◦If you have two processors, use the binary value 0b11, or hex value 0x3.
◦If you have three processors, use the binary value 0b111, or hex value 0x7.
◦If you have four processors, use the binary value 0b1111, or hex value 0xF.
5.Quit Registry Editor.
Note The 0x0 or 0xFFFFFFFF values are used to disable the ProcessorAffinityMask entry.
}

3. Check if priority boost is enabled for SQL Server. If yes disable it.

4. Make sure there is no working set trim and system wide memory pressure. You can use second query in significant part of sql server process memory has been paged out to identify and follow the same blog to fix it)

5. Check if paged pool and non-paged is empty. (Event ID:  2019  in event log)

6. If you see this problem in cluster make sure you have set the network priority of “private heart beat” network higher than the “public” network.Refer KB:258750