The Semaphore Timeout Period Has Expired — Fix

What Does This Error Mean?

For network drives: reset the network stack with netsh winsock reset in an elevated Command Prompt, then restart. For USB drives: unplug and replug the device, or try a different USB port. Disabling Large Send Offload (LSO) on the network adapter fixes this error for many users with network storage.

Affected Models

Windows 11
Windows 10
Windows 8.1
Windows Server

Common Causes

Network adapter Large Send Offload (LSO) feature causing packet timing issues
Slow or unstable network connection timing out during large file transfers
USB device or hub not responding within the Windows timeout window
SMB network share latency exceeding Windows' transfer timeout
Outdated network adapter or USB controller driver

How to Fix It

Reset the network stack

Open Command Prompt as Administrator. Run: netsh winsock reset → netsh int ip reset → ipconfig /flushdns. Restart the PC. This resolves the error when it appears during network file transfers.
Disable Large Send Offload (LSO)

Device Manager → Network Adapters → right-click your adapter → Properties → Advanced tab → find 'Large Send Offload V2 (IPv4)' and 'Large Send Offload V2 (IPv6)' → set both to Disabled. Click OK and restart.
Update the network adapter driver

Device Manager → Network Adapters → right-click adapter → Update Driver. Or download the latest driver from the motherboard or laptop manufacturer's support page. Outdated NIC drivers are a leading cause of this error.
For USB drives: try a different port and cable

Unplug the USB device and reconnect it to a different USB port directly on the PC (not through a hub). USB hubs can introduce latency that triggers the timeout. Also test with a shorter, higher-quality cable.
Increase the SMB timeout (network shares)

Open Command Prompt as Administrator → run: net config server /autodisconnect:-1 — this disables the automatic SMB session timeout. Also try: reg add HKLM\SYSTEM\CurrentControlSet\Services\LanmanWorkstation\Parameters /v SessTimeout /t REG_DWORD /d 60 /f

When to Call a Professional

The semaphore timeout error is always software or driver related. No hardware service is needed — disabling LSO and updating drivers resolves it in most cases.

Frequently Asked Questions

Semaphore timeout copying to NAS or network drive — how to fix?

Large Send Offload (LSO) is the most common cause for NAS transfers. Disable LSO on your network adapter: Device Manager → network adapter → Properties → Advanced → Large Send Offload V2 → Disabled.

0x80070079 in Windows Backup — how to fix?

Windows Backup uses the same network stack. Reset Winsock (netsh winsock reset), disable LSO, and ensure the backup destination drive has enough space and is not disconnecting during the backup.

Semaphore timeout only on large files — why?

Large file transfers stress the network connection longer and are more likely to hit a timeout. This confirms the issue is network latency or LSO — disabling LSO almost always fixes large-file transfer timeouts specifically.