Subject: [SIP] what is the detail meaning for Require, Support, Unsupport header

From: "Roland" <[email-masked]>
Date: Fri, 20 Apr 2001 10:50:12 -0700

Hello all,
   The Require header is described like this:
      Require = "Require" ":" 1#option-tag
  same as Support and unsupport header.

  I don't know what is the meaning of option-tag here. 
  does it represcent a header? 

  the example in 2543 shows     Require: org.ietf.sip.encrypt-response
  so what is  detail meaning of org.ietf.sip.encrypt-response, 
  how do I process this in the UAS .
 
Thanks very much
 
roland