<p>Section 3.1.1. in RFC 6665 is the correct reference here. But it does point to RFC 3261.<br>
"200-class responses to SUBSCRIBE requests also MUST contain an<br>
"Expires" header field. The period of time in the response MAY be<br>
shorter but MUST NOT be longer than specified in the request."</p>
<p style="font-size:small;-webkit-text-size-adjust:none;color:#666;">—<br>Reply to this email directly or <a href="https://github.com/kamailio/kamailio/pull/78#issuecomment-73863674">view it on GitHub</a>.<img alt="" height="1" src="https://github.com/notifications/beacon/AF36ZT03hU-ewpYYw74z9z4hZEFr8_CYks5nqyzSgaJpZM4DewSe.gif" width="1" /></p>
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