Base de conhecimento

This article provides information about web pages loading slowly on a server running Windows Server 2012

Issue:

Web pages take an unusually long time to render in Windows Server 2012 regardless of the web browser used to browse the Internet.

Solution:

Resolve the issue by executing the following command in a Command Prompt (search cmd on system) on the server running Windows Server 2012.

netsh interface tcp set global ecncapability=disabled

Additional Information:

This information applies to Windows Server 2012.

The root cause may be attributed to the following.

1. ECN (Explicit Congestion Notification) feature is enabled by default in Windows Server 2012
2. ECN negotiation is not handled correctly by the router

ECN is the explicit congestion notification and it allows end-to-end notification of network congestion without dropping packets. Additional information is available on Wikipedia.

ECN capability is enabled by default in Windows Server 2012. If ECN is enabled it may cause delays accessing external websites because outdated routers may drop the packets with the ECN bit set instead of ignoring the bit.

Verification that ECN is enabled in Windows Server 2012 can be achieved by running the command netsh int tcp show global in the Command Prompt.

Using Fiddler2 it is evident that long delays occur while trying to retrieve a web page.

Using Wireshark it is evident the ECN bit flag is enabled in this packet going from the network interface card (NIC) to a router.

Need more help?
	Find additional PowerEdge and PowerVault articles
	Visit and ask for support in our Communities
	Create an online support Request