Hi Everyone,
environment: CUCM 8.0.3.22900-5
I would like to know if CUCM supports, in a SIP/SDP offer, multiple "ptime" fields for each "m" line
Example:
1. A SIP device answers a SIP invite from the CUCM with a SIP 100, then SIP 180, then SIP "200 Ok"
The SIP "200 Ok" packet sent from the device to the CUCM contains SDP information, as follows:
=======================
Session Description Protocol
<...lines removed...>
Media Description, name and address (m): audio 5004 RTP/AVP 96 97 9 8 0
Media Type: audio
Media Port: 5004
Media Protocol: RTP/AVP
Media Format: DynamicRTP-Type-96
Media Format: DynamicRTP-Type-97
Media Format: ITU-T G.722
Media Format: ITU-T G.711 PCMA
Media Format: ITU-T G.711 PCMU
Media Attribute (a): rtpmap:96 L16/48000/1
Media Attribute (a): ptime:4
Media Attribute (a): rtpmap:97 MPA/90000
Media Attribute (a): fmtp:97 layer=2;samplerate=48000;bitrate=160000;mode=single_channel
Media Attribute (a): rtpmap:9 G722/8000/1
Media Attribute (a): ptime:20
Media Attribute (a): rtpmap:8 PCMA/8000/1
Media Attribute (a): ptime:20
Media Attribute (a): rtpmap:0 PCMU/8000/1
Media Attribute (a): ptime:20
Media Attribute (a): sendrecv
=======================
Note the many "ptime" values, depending on the media offered.
2. The CUCM answers with a SIP ACK packet with SDP information, choosing the "PCMU/8000/1" protocol, but accepting the *wrong* ptime value - it chooses the first ptime value presented, not the one related to the "PCMU/8000/1" protocol after "rtpmap:0 PCMU/8000/1"
================================
Session Description Protocol
Session Description Protocol Version (v): 0
Owner/Creator, Session Id (o): CiscoSystemsCCM-SIP 2000 1 IN IP4 10.0.205.10
Session Name (s): SIP Call
Connection Information (c): IN IP4 10.70.0.142
Time Description, active time (t): 0 0
Media Description, name and address (m): audio 20242 RTP/AVP 0
Media Type: audio
Media Port: 20242
Media Protocol: RTP/AVP
Media Format: ITU-T G.711 PCMU
Media Attribute (a): rtpmap:0 PCMU/8000
Media Attribute (a): ptime:4
================================
I have found a Cisco document, which is not about CUCM but rather about IOS SIP support (http://www.cisco.com/en/US/docs/ios/12_2/voice/configuration/guide/vvfsip.html), stating
"Cisco SIP gateways present or respond to the a=ptime parameter in the SDP body of a SIP message. However, only one a=ptimeattribute is allowed per m-line block."
Therefore I would like to know if the said behavior is as expected and if it is documented anywhere.
Thanks
Regards
Gabriele
