Symptoms
Accelerated connections appear in the Active Connections list even when there is no partner unit enabled.
Cause
The WANScaler administrative tool tracks and displays half-open TCP connections as accelerated connections on the Active Connections list until the idle connection timer is reached. This behavior generally occurs in asymmetrically routed environments.
A TCP half-open connection is established when a client computer sends a SYN packet to the remote server and no response is received. The client-side WANScaler tracks the connection and attempts to accelerate it. Due to asymmetric routers, the server-side WANScaler never receives the SYN packet and so the connection is never fully established.
The client-side WANScaler continues to track the connection because it does not receive an RST or dropped packet from the remote side on the initial TCP connection. The connection is now a half-open TCP connection and will be purged from the client-side Accelerated Connection list after the idle timeout value has been reached.
Refer to the following screen shot:
The remote-side WANScaler does not display the connection in the Accelerated (or non-accelerated) Connection list because it does not see the initial TCP-SYN in the TCP 3-way handshake process.
Refer to the following screen shot:
Resolution
This is expected behavior.
More Information
http://en.wikipedia.org/wiki/Half-open_connection
