Why the messae-integrity attrtube is differ from lync packet with my computation?

Question

when I test  lync 2013  client with our sip client , after we make call with each other, then our client receive stun request, then I response with stun  response message.
but it like it is  wrong, after 10 second, lync 2013 bye the call,
so I mind that the stun message is wrong, then I test two lync client in same way and I get the packet for stun process.
Lync A  send offer:
m=video 23208 RTP/SAVP 121 34
a=ice-ufrag:JarR
a=ice-pwd:ajHTvaDF2fOSFgsHQcWRDbD4
Lync B send answer:
m=video 9920 RTP/SAVP 121 34
a=ice-ufrag:w7bO
a=ice-pwd:3m7jMp31613moND5lYL6o2jf
Lync A send stun request to Lync  B
srcip:200.55.25.7
srcport:19420
dstip:200.56.0.136
srcport:8280
stun request:
00 01 00 54 21 12 a4 42 19 e2 18 f8 42 50 52 f9
6b 95 8a 80 00 06 00 0c 4a 61 72 52 3a 77 37 62
4f 00 00 00 00 24 00 04 6e ff fc ff 80 29 00 08
00 00 00 00 00 08 9a f7 80 54 00 04 32 00 00 00
80 70 00 04 00 00 00 02 00 08 00 14 17 54 2a 7d
de 07 e6 d8 6a f0 08 9d da a7 37 10 a4 98 ad bb
80 28 00 04 1f 0c 2f 33
stun response:
01 01 00 44 21 12 a4 42 19 e2 18 f8 42 50 52 f9
6b 95 8a 80 00 20 00 08 00 01 6a ce e9 25 bd 45
00 06 00 0c 4a 61 72 52 3a 77 37 62 4f 00 00 00
80 70 00 04 00 00 00 02 00 08 00 14 c2 68 98 3f
26 b4 44 50 5d 74 12 a1 61 44 ab 5a 99 d1 83 e2
80 28 00 04 70 ce 16 de
but when I compute the message-integrity attribue using the same stun request message, the result is differ from content that I get from packet.
my process is following:
1、 compute all the attribute before message-integrity attribue, the value is following:
01 01 00 3c 21 12 a4 42 19 e2 18 f8 42 50 52 f9
6b 95 8a 80 00 20 00 08 00 01 6a ce e9 25 bd 45
00 06 00 0c 4a 61 72 52 3a 77 37 62 4f 00 00 00
80 70 00 04 00 00 00 02 
2、 then I get password from sdp message
3m7jMp31613moND5lYL6o2jf
3、then compute hmac-sha1
input string is from the head of stun resopne
input string length is 56byte,(accord to Simple Traversal of UDP Through Network Address Translators (NAT) (STUN)   draft-ietf-behave-rfc3489bis-02, it may be 64 byte, but the result is same))
input key is 3m7jMp31613moND5lYL6o2jf
input key length is 24
when input string length is 56, the hash is: 34 7E E7 7B 97 E1 2A BC B3 B9 5B 5D E5 47 09 68 E3 88 75 3D
when input string length is 64, the hash is :FA 1A 62 21 50 95 3D 7D CC 83 6E F9 37 6F 14 17 1F 56 09 39
but the same input , the packet hash is:  c2 68 98 3f 26 b4 44 50 5d 74 12 a1 61 44 ab 5a 99 d1 83 e2
so I winder which step is wrong in my compute, hope some one can help me, thank you very much.

Answer 1

I am not sure whether your computation is correct. I did see Message-Integrity attribute are different between request and response.
 It seems you have problem with Lync Edge Server.
Where is the call from and to?
Please try to enable logging in Lync client and use Lync logging tool to collect trace file on Lync Edge Server for further troubleshooting.
Please check the port 443 and 3478 are opened inbound to A/V conferencing service.
Lisa Zheng
TechNet Community Support