WARNING[21426]: chan_sip.c:4864 check_auth: Stale nonce received from ‘sip:user@serverip’
i am running an asterisk server, i keep getting these messages frequently.
what i know so far is when a phone tries to register, the server passes a nonce to the phone on which all sip related activity is performed.
and with the network delay the nonce gets expired, thus resulting in stale nonce
but can anyone define this whole message in details, like what really happening, cause this message seems to be getting more frequent than before… 
