One of the NetScaler service which uses HTTP monitor fluctuates between up and down state frequently.

From newnslog, it is observed that the TCP connection is successfully, but application timed out.

4807  5243 (PART-46337) PPE-0 MonServiceBinding_192.168.2.107:443_(https)(B2C_WBC02_C02A_SSL): DOWN; Last response: Failure - TCP connection successful, but application timed out Fri Sep 11 07:34:36 2015
4808     0 (PART-698) PPE-0 'server_svc_cfg_NSSVC_SSL_192.168.2.107:443(B2C_WBC02_C02A_SSL)' DOWN Fri Sep 11 07:34:36 2015
4530     0 (PART-17174) PPE-1 'server_svc_cfg_NSSVC_SSL_192.168.2.107:443(B2C_WBC02_C02A_SSL)' DOWN Fri Sep 11 07:34:36 2015
4399     0 (PART-33460) PPE-2 'server_svc_cfg_NSSVC_SSL_192.168.2.107:443(B2C_WBC02_C02A_SSL)' DOWN Fri Sep 11 07:34:36 2015

To resolve this issue increase the time-out value, if your network has high latency.

Problem Cause

By default, HTTPS monitor response time-out is 2 seconds and NetScaler did not receive response within 2 seconds.