Hello,

I have some trouble with sdp negotiation after received re-invites.
In my application (running with sofia 1.12.8) I start a call to an ISP.
The call to nua_invite() contains SOATAG_USER_SDP_STR and NUTAG_AUTOANSWER(0) to
handle re-invites in my application later.
The call is established correctly. Then the ISP wants to switch to T.38. It
sends a re-invite with changed sdp. My application gets the nua_i_invite and
later the nua_i_state which I use to handle remote sdp.
>From nua_i_state callback my application calls nua_respond with 
>SOATAG_USER_SDP_STR
containing my modified sdp.

The Problem now is, that sofia-sip increases the sdp version in o-line by two 
and
not by one as stated in RFC 3264 section 8:

"When issuing an offer that modifies the session,
 the "o=" line of the new SDP MUST be identical to that in the
 previous SDP, except that the version in the origin field MUST
 increment by one from the previous SDP. "

Version in my INVITE:              4138572302028389133
Version in my Answer to Re-INVITE: 4138572302028389135

What happens now is, that the ISP ignores my sdp. Seems that they have
a very strict implementation there...

Can anyone please give me a hint on how to fix this problem?

Timo

**************************************************************************************************

SEND Request-Line: INVITE sip:[EMAIL PROTECTED];transport=udp SIP/2.0
     Message body
         Session Description Protocol
             Session Description Protocol Version (v): 0
             Owner/Creator, Session Id (o): - 8396384725478307013 
4138572302028389133 IN IP4 192.168.172.42
             Session Name (s): -
             Connection Information (c): IN IP4 192.168.172.42
             Time Description, active time (t): 0 0
             Media Description, name and address (m): audio 49156 RTP/AVP 8 0 
13 111
             Media Attribute (a): rtpmap:8 PCMA/8000
             Media Attribute (a): rtpmap:0 PCMU/8000
             Media Attribute (a): rtpmap:13 CN/8000
             Media Attribute (a): rtpmap:111 telephone-event/8000
             Media Attribute (a): fmtp:111 0-15

RECV Status-Line: SIP/2.0 183 Session Progress
     Message body
         Session Description Protocol
             Session Description Protocol Version (v): 0
             Owner/Creator, Session Id (o): - 295984490200000252 1 IN IP4 
222.222.222.222
             Session Name (s): session
             Connection Information (c): IN IP4 222.222.222.222
             Time Description, active time (t): 0 0
             Media Description, name and address (m): audio 11090 RTP/AVP 8 111
             Media Attribute (a): rtpmap:8 PCMA/8000
             Media Attribute (a): ptime:20
             Media Attribute (a): sendrecv
             Media Attribute (a): rtpmap:111 telephone-event/8000

RECV Status-Line: SIP/2.0 200 Ok

SEND Request-Line: ACK sip:213.218.28.164:5060 SIP/2.0

***SIP-Provider sends Re-Invite to switch to T.38:
RECV Request-Line: INVITE sip:[EMAIL PROTECTED]:5071 SIP/2.0
     Message body
         Session Description Protocol
             Session Description Protocol Version (v): 0
             Owner/Creator, Session Id (o): - 295984490200000252 2 IN IP4 
222.222.222.222
             Session Name (s): session
             Connection Information (c): IN IP4 222.222.222.222
             Time Description, active time (t): 0 0
             Media Description, name and address (m): image 11090 udptl t38

***I send 200ok with modified SDP using nua_respond
SEND Status-Line: SIP/2.0 200 OK
     Message body
         Session Description Protocol
             Session Description Protocol Version (v): 0
             Owner/Creator, Session Id (o): - 8396384725478307013 
4138572302028389135 IN IP4 192.168.172.42
             Session Name (s): -
             Connection Information (c): IN IP4 192.168.172.42
             Time Description, active time (t): 0 0
             Media Description, name and address (m): image 49156 UDPTL t38

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