Understanding Lync client multipart SDP with MIME

Question

Could anybody give me some pure Insight how to create multipart sdp and what is the meaning of the all attribute of this given SDP.

Content-Type: multipart/alternative;boundary="----=_NextPart_000_001B_01CDC5AC.EC1E2DE0"
ms-routing-phase:from-uri-routing-done

------=_NextPart_000_001B_01CDC5AC.EC1E2DE0
Content-Type: application/sdp
Content-Transfer-Encoding: 7bit
Content-ID: <67c36ea12e87436e8fd1133d26194444@afdgs.com>
Content-Dis; handling=optional; ms-proxy-2007fallback

v=0
o=- 0 0 IN IP4 192.168.0.179
s=session
c=IN IP4 192.168.0.179
b=CT:99980
t=0 0
m=audio 19384 RTP/AVP 114 9 112 111 0 8 116 115 4 97 13 118 101
a=candidate:oKpwKDjMnfFmkSeXlIgoUEYW0BiriMilFQluFogmIQ8 1 XJoleCXuzzNJHAdN0G5MHg UDP 0.830 192.168.0.179 19384
a=candidate:oKpwKDjMnfFmkSeXlIgoUEYW0BiriMilFQluFogmIQ8 2 XJoleCXuzzNJHAdN0G5MHg UDP 0.830 192.168.0.179 19385
a=cryptoscale:1 client AES_CM_128_HMAC_SHA1_80 inline:28zhxoLlrww36J41bGxjePNf0ft/BbQkHXd2Pwf2|2^31|1:1
a=crypto:2 AES_CM_128_HMAC_SHA1_80 inline:EHIG0MBaCja1hyD1kJJvm3A8Ld8sIbCyeY26J5TI|2^31|1:1
a=crypto:3 AES_CM_128_HMAC_SHA1_80 inline:4y2YFeVNzH/rdIrbkSD+kMMFYP5OlccmnfBeELrW|2^31
a=maxptime:200

Specially the encrypted value of a=candidate: , How to decrypt and create it.

Is there any doc or rfc please indicate.

Thanks.

Answer 1

The answer is that it is an old ICE candidate and SDP ,which is supported by Lync client with new ICE candidate support.So it is multipart which enable both old and new ICE support for a single client.(If the client have both ICE support)