Load balancing virtual server or VPN VServers does not work fine with protocol HTTP/HTTPS.

Sporadically, some contents (images, javascripts, etc.) on the VPN Gateway login page do not load properly or page stuck at loading with progress spinning circle.

Upon detailed review of a network trace capture the are Reset codes coming from ADC with RESET code 9826 under "Window Size Value" in TCP parameter.

Example of content: jquery-3.3.1.min.js
HTTP GET :: /logon/LogonPoint/receiver/js/external/jquery-3.3.1.min.js

ADC responds with TCP RESET : Windows Size Value: 9826

Transmission Control Protocol, Src Port: 443, Dst Port: 50937, Seq: 57901, Ack: 1653, Len: 0
    Source Port: 443
    Destination Port: 50937
    [Stream index: 7]
    [TCP Segment Len: 0]
    Sequence number: 57901    (relative sequence number)
    Sequence number (raw): 2250568975
    [Next sequence number: 57901    (relative sequence number)]
    Acknowledgment number: 1653    (relative ack number)
    Acknowledgment number (raw): 1242823613
    0101 .... = Header Length: 20 bytes (5)
    Flags: 0x014 (RST, ACK)
    Window size value: 9826

Reset code 9826: Means there is not enough memory for NET buffers.

Check the Integrated Caching Feature is enabled by License and by Settings on ADC. If the Integrated caching is enabled :

Verify the output by executing the below command. In this example IC is enabled and allocated properly.

> sh cache parameter
        Integrated cache global configuration:
        Memory usage limit: 1024 MBytes
        Memory usage limit (active value): 1024 MBytes
        Maximum value for Memory usage limit: 1720 MBytes

If the Memory Usage Limit is not assigned with any value or it shows "0" Mbytes, assign the memory by executing the following command.

You can allocate up to 50% of the available memory to the Integrated Caching feature.

> set cache parameter –memLimit 1024
> savec
> reboot

After reboot, execute the command "show cache parameter", if the value of "Memory usage limit" is increased to 500 Mbytes.

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Problem Cause

Integrated Caching memory either exhausted / not configured with memory.

https://support.citrix.com/article/CTX124553