K.4 Handling T.38 SDP attributes at the O-MGCF

29.1633GPPInterworking between the IP Multimedia (IM) Core Network (CN) subsystem and Circuit Switched (CS) networksTS

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Table K.4.1: T.38 SDP attributes values supplied by the O-MGCF and actions at O-MGCF depending on SDP attribute values in SDP answer

	Value provided in sent SDP offer	Handling of received SDP answer
T38FaxVersion	Supply highest version supported at MGCF and IM-MGW, maximum 3 (NOTE 1).	Accept any value. Provide to the IM-MGW the received value or the maximum supported value at the IM-MGW (whatever is lower).
T38MaxBitRate	Supply value according to IM-MGW capabilities.	Accept any value and provide it to the IM-MGW.
T38FaxFillBitRemoval	Do not include parameter (NOTE 2).	Accept offer with value "FALSE" or parameter omitted. (NOTE 3)
T38FaxTranscodingMMR	Do not include parameter (NOTE 2).	Accept offer with value "FALSE" or parameter omitted. (NOTE 3)
T38FaxTranscodingJBIG	Do not include parameter (NOTE 2).	Accept offer with value "FALSE" or parameter omitted. (NOTE 3)
T38FaxRateManagement	Supply "transferredTCF" value.	Only accept calls with "transferredTCF" in the answer for T38FaxVersion 2 or higher. (NOTE 3)
T38FaxMaxBuffer	Supply value according to IM-MGW capabilities.	Accept any value and provide it to the IM-MGW.
T38FaxMaxDatagram	Supply value according to IM-MGW capabilities	Accept any value and provide it to the IM-MGW.
T38FaxMaxIFP	If T.38 version 4 is indicated in the offer, supply value according to IM-MGW capabilities. Otherwise omit the parameter.	Accept any value. If T.38 version 4 is supported by the IM-MGW, provide it to the IM-MGW.
T38FaxUdpEC	Supply value according to IM-MGW capabilities.	Accept value according to MGW capabilities and provide it to the IM-MGW. (NOTE 3)
T38FaxUdpECDepth	If T.38 version 4 is indicated in the offer, supply value according to IM-MGW capabilities. Otherwise omit the parameter.	Accept any value. If T.38 version 4 is supported by the IM-MGW, provide it to the IM-MGW.
T38FaxUdpFECMaxSpan	If T.38 version 4 is indicated in the offer, supply value according to IM-MGW capabilities. Otherwise omit the parameter.	Accept any value. If T.38 version 4 is supported by the IM-MGW, provide it to the IM-MGW.
T38ModemType	Do not include parameter (NOTE 2).	Accept any value. If T.38 version 4 is supported by the IM-MGW, provide it to the IM-MGW.
T38VendorInfo	Do not include parameter.	Accept any value.
NOTE 1: With Version 4, default values for the SDP attributes apply if the attributes are omitted. NOTE 2: In the Mn H.248 profile the IM-MGW does not modify the T.30 bit stream encapsulated within T.38 when passing it to or from the CS network. NOTE 3: Due to SDP offer-answer procedures for this attribute, an unacceptable value in the SDP answer is due to a protocol error. The error handling at the O-MGCF is left unspecified. NOTE 4: "Any value" means any valid value that conforms to ITU-T Recommendation T.38 [72].