На voip-info.org англицким по-белому:
secret : If Asterisk is acting as a SIP Server, then this SIP client must login with this Password (A shared secret). If Asterisk is acting as a SIP client to a remote SIP server that requires SIP INVITE authentication, then this field is used to authenticate SIP INVITEs that Asterisk sends to the remote SIP server. Asterisk 1.6.2.x: Changed the secret parameter to remotesecret.
Asterisk-1.8 сообщает, что secret is deprecated. А вот skype с remotesecret не работает. А D-Link с secret не всегда работает. А правда где?