We have discovered that IP Phones with recent firmwares send an TCP SYNC to try to reopen a connection on the same IP port than a correctly closed TCP connection. This arrive from time to time once every 50 http request. The issue is that with Windows IIS applications, IP port get unavailable (status TIME_WAIT) for at least 30s. It is not clear if it is an additional TCP connection sent unattendedly by the phone or due to an http request from the phone. Anyway, after 30s another connection with a different port is made and succeed.
Do someone have noticed this issue ? Do you know any workaround to avoid ip ports been locked in TIME_WAIT for 30s ?
Have a good day,