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Counter

TCP Window Probe is a counter of all TCP Window Probe events over a period of 
time per segment. A count of all TCP Window Probe events displays in the 

 counters of Expert View. A threshold for this counter can be set in Expert 

Alarms. 

Expert Symptom

TCP Window Probe events are automatically logged as expert symptoms. The 

 field provides information about the well-known ports (WKP) 

involved, including the port number and the IP address. For example:

Between [206.250.228.69]/[TCP/IP WKP:1988] and

[206.250.228.11]/[SMTP]

The TCP window size is examined for every packet to check for one-byte data 
packets. If a TCP/IP packet with one byte of data is encountered, the event is 
logged. One-byte data packets are sent periodically by the sender to see if the 
receiver’s window has reopened to allow the sender to resume transmitting.

Diagnostic Details

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A TCP/IP packet with one byte of data has been sent to check whether the receiver’s 
window has been reopened.

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1. The receiver is overloaded. 
2. The receiver has run out of buffer space. 
3. The non-responsive receiver intends the sender to close the connection. 
4. There may be a problem with the receiver’s TCP/IP stack. 
5. There are too many connections to the receiver resulting in reduced buffer space.

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1. Upgrade the receiver’s CPU and/or Memory.
2. Reduce the number of connections to the receiver.
3. Increase the network bandwidth.