[Serusers] problem with ser and mediaproxy when multiple media descriptions exist and client is natted

[Gerd Feiner]

hi there

we got a weird problem on our ser when dealing with multiple media  
descriptions in SDP packets:

the INVITE comes from a SIP-enabled TDM-switch and looks like that  
(notice 3(!) different media descriptions, but pointing to the same  
port):

(just media-descriptions shown for brevity):

             Media Description, name and address (m): audio 17728 RTP/ 
AVP 0 8 4 18 2 101
             Media Attribute (a): fmtp:101 0-15
             Media Attribute (a): rtpmap:101 telephone-event/8000
             Media Description, name and address (m): audio 17728 RTP/ 
AVP 97
             Media Attribute (a): rtpmap:97 /8000
             Media Attribute (a): sendonly
             Media Description, name and address (m): audio 17728 RTP/ 
AVP 97
             Media Attribute (a): rtpmap:97 /8000
             Media Attribute (a): recvonly

when the SER receives this packet it looks up the client (b-number)  
and recognizes it is behind a NAT - so mediaproxy stuff is done  
(notice SER/mediaproxy generating 3(!) different(!) ports for the  
media-descriptions):

(same brevity here):

             Media Description, name and address (m): audio 16014 RTP/ 
AVP 0 8 4 18 2 101
             Media Attribute (a): fmtp:101 0-15
             Media Attribute (a): rtpmap:101 telephone-event/8000
             Media Description, name and address (m): audio 16016 RTP/ 
AVP 97
             Media Attribute (a): rtpmap:97 /8000
             Media Attribute (a): sendonly
             Media Description, name and address (m): audio 16018 RTP/ 
AVP 97
             Media Attribute (a): rtpmap:97 /8000
             Media Attribute (a): recvonly

the client (a sipura 2100/1001) now sends media to the last specified  
port (16018 in our case) while the audio from the switch goes to  
16014 - resulting in mediaproxy not being able to connect the two of  
them ... and we sit there with neither in- nor outbound audio ...

how do i get mediaproxy/SER to send only one port to the client, just  
like the switch initially did?

any clues?


mit freundlichen Grüßen / with best regards

Gerd Feiner
Leitung IP-Dienste

Kabelfernsehen München ServiCenter GmbH & Co. KG
Abt. Mediaport
Medienallee 24
85774 Unterföhring

T: +49 89 95083 243
F: +49 89 95083 132
E: g.feiner at cablesurf.de
W: www.cablesurf.de

-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 3098 bytes
Desc: not available
URL: <http://lists.sip-router.org/pipermail/sr-users/attachments/20060518/e9b5f704/attachment.bin>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: PGP.sig
Type: application/pgp-signature
Size: 186 bytes
Desc: Signierter Teil der Nachricht
URL: <http://lists.sip-router.org/pipermail/sr-users/attachments/20060518/e9b5f704/attachment.pgp>