[Sip] Some question about draft:A Framework for Session Initiation Protocol (SIP) Session Policies

[马骥 <[e-mail]>]

    I have some questions about the frame work proposed in the draft which defines a framework for SIP policy. See bellow:          1. What the advantage is in the proposed framework in which UA require its policy (which means it contacts policy server after contacts proxy) by itself? An alternative is, the proxy contacts the proxy server on behalf of the UA, and return or not return determined policies, which means UA need not involved in the procedure of contacting policy server. So why the one proposed in the draft is better?
   
      2. If it retrieves policies according to call flow this draft, how a proxy knows that the policies in the resending request for the UA is genuine, especially for the specific ongoing request?(which means there should be security mechanism to avoid replay attacks).Can anyone give me some ideas or solutions?
   
  Thanks.
  _______
  mjhorse



       
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