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IMG 1010 - SIP Profile - 10.5.3
Diagram:
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Examples:
Below are examples of how IMG would react to SIP offers with different types of Media Descriptors. (Ex: Audio, Video, Fax). See Additional Information below explaining how the IMG selects which Media Descriptor.
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The IMG will NOT select the best matching media stream, it will match on the first media stream (m-line) from a valid Offer which has multiple media streams. Matching the first Media Stream assumes the media streams are sorted by preference and the first being the highest preference. |
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In both examples below, the Codec Priority setting will have no effect on the IMG behavior to accept the first matching media stream in the offer. Codec Priority setting will only affect the IMG method used to select media formats for answer after having selected a media stream. |
Audio:
A SIP INVITE comes into IMG with an Offer indicating that there are two audio streams. The IMG parses the message and sends back an answer with both the accepted and rejected audio stream. In this example, the m-line with payload type of 0 is accepted and m-line with the payload type 8 is rejected. Note that the rejected m-line has a port value of 0. The rejected m-line is sent back in a response to the Offer even though it was rejected.
VoIP Configuration in IMG | Offer to IMG | Answer from IMG |
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Profile 5 Default Codec = G.711 ulaw Codec Priority = Local | m=audio 38400 RTP/AVP 0 a=rtpmap:0 PCMU/8000 m=audio 49500 RTP/AVP 8 a=rtpmap:8 PCMA/8000 | m=audio 6000 RTP/AVP 0 a=..(a-line present as applicable) m=audio 0 RTP/AVP 8 |
A SIP INVITE comes into IMG with an Offer indicating that there are three audio streams. The IMG parses the message and rejects the first m-line because of the Codec. It accepts the second m-line even though the second and third m-line are acceptable. The IMG accepts the FIRST ACCEPTABLE m-line.
VoIP Configuration in IMG | Offer to IMG | Answer from IMG |
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Profile 5 Default Codec = G.711 ulaw Codec Priority = Local | m=audio 10000 RTP/AVP 98 a=rtpmap:98 ilbc/8000 m=audio 18000 RTP/AVP 18 m=audio 38400 RTP/AVP 0 8 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMU/8000 | m=audio 0 RTP/AVP 98 m=audio 0 RTP/AVP 18 m=audio 6000 RTP/AVP 0 a=..(a-line present as applicable) |
The IMG will select the CODEC depending on the Codec Priority field (Local/Remote) setting in the SIP SGP Profile.
VoIP Configuration in IMG | Offer to IMG | Answer from IMG |
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Profile 5 Default Codec = G.711 alaw (default), G.711 ulaw Codec Priority = Local | m=audio 10000 RTP/AVP 98 a=rtpmap:98 ilbc/8000 m=audio 38400 RTP/AVP 0 8 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 m=audio 18000 RTP/AVP 18 | m=audio 0 RTP/AVP 98 m=audio 6000 RTP/AVP 8 a=..(a-line present as applicable) m=audio 0 RTP/AVP 18 |
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The IMG selected the first matching media stream and the media format selected is based on codec priority setting (local) |
The IMG will select the CODEC depending on the Codec Priority field (Local/Remote) setting in the SIP SGP Profile.
VoIP Configuration in IMG | Offer to IMG | Answer from IMG |
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Profile 5 Codec = G.711 alaw (default)G.711 ulaw Codec Priority = Remote | m=audio 10000 RTP/AVP 98 a=rtpmap:98 ilbc/8000 m=audio 38400 RTP/AVP 0 8 a=rtpmap:0 PCMU/8000 a=rtpmap:8 PCMA/8000 m=audio 18000 RTP/AVP 18 | m=audio 0 RTP/AVP 98 m=audio 6000 RTP/AVP 0 a=..(a-line present as applicable) m=audio 0 RTP/AVP 18 |
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The IMG selected the first matching media stream and the media format selected is based in codec priority setting (Remote) as the preference. |
The IMG will always accept fax (m=image line) if one of the Media streams offered in Re-INVITE is for fax.
VoIP Configuration in IMG | Offer to IMG | Answer from IMG |
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Profile 5 Default Codec = G.711 Ulaw Codec Priority = Local Fax T38 Enabled | m=image 7228 udptl t38 a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxRateManagement:transferredTCF a=T38FaxUdpEC:t38UDPRedundancy m=audio 7228 RTP/AVP 8 0 a=rtpmap:8 PCMA/8000 a=rtpmap:0 PCMU/8000 a=ptime:20 a=silenceSupp:off - - - - a=ecan:fb on - a=X-fax | m=image 8001 udptl t38 m=audio 0 RTP/AVP 8 0 |
Profile 5 Default Codec = G.711 Ulaw Codec Priority = Local Fax T38 Enabled | m=audio 7228 RTP/AVP 8 0 a=rtpmap:8 PCMA/8000 a=rtpmap:0 PCMU/8000 a=ptime:20 a=silenceSupp:off - - - - a=ecan:fb on - a=X-fax m=image 7228 udptl t38 a=T38FaxVersion:0 a=T38MaxBitRate:14400 a=T38FaxRateManagement:transferredTCF a=T38FaxUdpEC:t38UDPRedundancy | m=audio 0 RTP/AVP 8 0 m=image 8001 udptl t38 |
Additional Information:
The IMG by default will accept all offers with multiple valid m-lines.
IMG supports a minimum of 1 m-line and a Maximum of 4 m-lines. A 488 Not Acceptable Here will be sent if less than 1 or more than 4 m-lines are sent. The only exception to this is in a PRACK scenario.
The answer will contain the same number of m-lines as was in the Offer.
The IMG will accept the first matching media stream from an offer with multiple m-lines except when offer has a media stream of fax.
IMG supports fax only in RE-INVITE scenarios. If Offer contains m=image, it will be rejected.
When IMG rejects a Media stream, it will set the port number to 0 in the answer and will include the media formats.
The IMG cannot generate an offer with multiple m-line.
IMG will reject the session with a 488 Not Acceptable Here if none of the media streams is accepted.
IMG Shall log all codec information and media types across all m-lines in the Radius VSA. Support for m=video is added but not supported as of Software release 10.5.2. The remote m-line parameters will be logged as follows:
dialogic-voip-remote-vocoders ="PCMU,PCMA,Video"
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