ptime (NOTE)

The MGCF may add the parameter with a value according to configured preferences to the SDP offer.

If a ptime parameter is included in the received SDP answer, the MGCF shall supply the parameter to the IM-MGW for the termination towards the answerer in the remote descriptor.

maxptime (NOTE)

The MGCF may add the parameter with a value according to the IM-MGW capabilities to the SDP offer.

If a maxptime parameter is included in the received SDP answer, the MGCF shall supply the parameter to the IM-MGW for the termination towards the answerer in the remote descriptor.

NOTE 2: This SDP attribute is defined in IETF RFC 4566 [56]. It applies to all codecs offered in an SDP media line.

ptime (NOTE)

If a ptime parameter is included in the received SDP offer, the MGCF shall supply the parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF may add the parameter with a value according to configured preferences to the SDP answer.

maxptime (NOTE)

If a maxptime parameter is included in the received SDP offer, the MGCF shall supply the parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF may add the parameter with a value according to the IM-MGW capabilities to the SDP answer.

NOTE: This SDP attribute is defined in IETF RFC 4566 [56]. It applies to all codecs offered in an SDP media line.

evs-mode-switch (NOTE 1)

If the MGCF expects that interworking between AMR-WB and EVS is required, it shall include the evs-mode-switch with value 1. Otherwise the MGCF shall not include the evs-mode-switch.

If an evs-mode-switch parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW for the termination towards the answerer in the remote descriptor.

hf-only (NOTE 1)

If the MGCF is configured to negotiate using only the header-full EVS RTP payload format, the MGCF shall include the hf-only parameter with a value 1.

If an hf-only parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

dtx (NOTE 1)

If the usage of DTX is not desired in the sending and receiving direction (e.g. due to DTX capabilities of expected codecs to transcode with), the MGCF shall include the dtx parameter with a value 0.

If a dtx parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

dtx-recv (NOTE 1)

If receiving DTX is not desired and the dtx parameter is not included, the MGCF shall include the dtx-recv parameter with a value 0.

If both the dtx and dtx-recv parameters are included, those parameters shall have the same value; however, inclusion of the dtx-recv parameter is not required if the dtx parameter is included.

If a dtx-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

br (NOTE 1)

If the MGCF desires the same bit rate range for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range to match IM-MGW capabilities and possible configured policies, it shall supply the br parameter in the SDP offer it sends. Otherwise the MGCF shall not include this parameter in the SDP offer.

If the MGCF also supplies the bw, bw-send or bw-recv parameter, the value of the br parameter shall be compatible with the values of those parameters.

If a br parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

br-send (NOTE 1)

If the MGCF desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the send direction to match IM-MGW capabilities and possible configured policies, it shall supply the br-send parameter in the SDP offer it sends. Otherwise the MGCF shall not include this parameter in the SDP offer.

If the MGCF also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters.

If a br-send parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

br-recv (NOTE 1)

If the MGCF desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the receive direction to match IM-MGW capabilities and possible configured policies, it shall supply the br-recv parameter in the SDP offer it sends. Otherwise the MGCF shall not include this parameter in the SDP offer.

If the MGCF also supplies the bw or bw-recv parameter, the value of the br-recv parameter shall be compatible with the values of those parameters.

If a br-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

bw (NOTE 1)

If the MGCF desires the same sampling bandwidth(s) for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths to match IM-MGW capabilities, sampling bandwidths of expected codecs EVS will be transcoded to, and possible configured policies, it shall supply the bw parameter in the SDP offer it sends. Otherwise the MGCF shall not include this parameter in the SDP offer.

If a bw parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

bw-send (NOTE 1)

If the MGCF desires different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths in the send direction to match IM-MGW capabilities, sampling bandwidths of expected codecs EVS will be transcoded to and possible configured policies, it shall supply the bw-send parameter in the SDP offer it sends. Otherwise the MGCF shall not include this parameter in the SDP offer.

If a bw-send parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

bw-recv (NOTE 1)

If the MGCF desires different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths in the receive direction to match IM-MGW capabilities, sampling bandwidths of expected codecs EVS will be transcoded to, and possible configured policies, it shall supply the bw-recv parameter in the SDP offer it sends. Otherwise the MGCF shall not include this parameter in the SDP offer.

If a bw-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

cmr (NOTE 1)

If the MGCF desires to disable codec mode requests within the RTP payload of the EVS primary mode (due to the IM-MGW capabilities or policies), it shall include the cmr parameter with value -1 in the SDP offer it sends.

If a cmr parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

ch-aw-recv (NOTE 1)

The MGCF shall include the ch-aw-recv parameter in the SDP offer if it desires to control the channel-aware-mode of EVS in the receive direction, e.g. to disable it with value -1. The MGCF shall consider the capabilities of the IM-MGW when it chooses an appropriate value.

If a ch-aw-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

number of channels (NOTE 2)

The MGCF shall only include the "number of channels" parameter in the SDP offer if it desires to send or receive multiple channels. If the desired number of channels in the send and receive direction differs, the MGCF shall include the higher value. The MGCF should consider the number of channels of expected codecs EVS will be transcoded to.

If a "number of channels" parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

ch-send (NOTE 1)

The MGCF shall only include the ch-send parameter in the SDP offer if it desires to send multiple channels, with different numbers of channels in the send and receive direction. The MGCF should consider the number of channels of expected codecs EVS will be interworked with.

If a ch-send parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

ch-recv (NOTE 1)

The MGCF shall only include the ch-recv parameter in the SDP offer if it desires to receive multiple channels, with different numbers of channels in the send and receive direction. The MGCF should consider the number of channels of expected codecs EVS will be interworked with..

If a ch-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

mode-set (NOTE 4)

The MGCF shall only include the mode-set parameter in the SDP offer if it desires to restrict the mode-set of AMR-WB IO mode. The MGCF should only restrict the mode-set if the expected codec EVS will be interworked with is AMR-WB and has a restricted mode set.

If a mode-set parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

mode-change-period (NOTE 3)

The MGCF shall only include the mode-change-period parameter with value 2 in the SDP offer if it desires to restrict the mode change period of received packets in AMR-WB IO mode. The MGCF should only restrict the mode-change-period if the expected codec EVS will be interworked with is AMR-WB and has such a restriction.

If a mode-change-period parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

mode-change-capability (NOTE 3)

The MGCF shall include the mode-change-capability parameter with value 2 or omit it in the SDP offer.

If a mode-change-capability parameter is contained in the SDP answer, the MGCF may forward this parameter to the IM-MGW in the remote descriptor.

mode-change-neighbor (NOTE 3)

The MGCF shall only include the mode-change-neighbor parameter in the SDP offer if it desires to restrict the mode change within received packets of AMR-WB IO mode to neighboring modes. The MGCF should consider the mode-change-neighbor parameter of the expected codec EVS will be interworked with if this is AMR-WB.

If a mode-change-neighbor parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

max-red (NOTE 5)

The MGCF shall only include the max-red parameter in the SDP offer if it desires to restrict the maximum redundancy of received packets. MGCF shall consider the capabilities of the IM-MGW, and should consider a max-red parameter of the expected codec EVS will be interworked with if this is AMR-WB.

If a max-red parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

3gpp_mtsi_app_adapt (NOTE 4)

If the IM-MGW supports RTCP APP based adaptation messages defined in TS 26.114 [104], and the MGCF has a policy to negotiate the usage of those messages, the MGCF shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the supported APP messages in the SDP offer.

If a 3gpp_mtsi_app_adapt attribute is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445 [147]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 2: This number of channels are encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in IETF RFC 4566 [56].

NOTE 3: This MIME parameter of the EVS RTP payload type relates to AMR-WB IO mode and is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 4: This SDP attribute is defined in TS 26.114 [104]. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS.

NOTE 5: This MIME parameter of the EVS RTP payload type is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

evs-mode-switch (NOTE 1)

If an evs-mode-switch parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If an evs-mode-switch parameter is contained in the SDP offer, the MGCF shall include the evs-mode-switch parameter with unmodified value in the SDP answer.

Otherwise, if the MGCF decides to interwork between AMR-WB and EVS, it shall include the evs-mode-switch with value 1.

Otherwise the MGCF shall not include the evs-mode-switch.

If the MGCF supplies the evs-mode-switch in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

hf-only (NOTE 1)

If an hf-only parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If an hf-only parameter is contained in the SDP offer, the MGCF shall include the hf-only parameter with unmodified value in the SDP answer.

Otherwise, if the MGCF is configured to negotiate using only the header-full EVS RTP payload format, the MGCF shall include the hf-only parameter with a value 1.

If the MGCF supplies the hf-only parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

dtx (NOTE 1)

If a dtx parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a dtx parameter is contained in the SDP offer, the MGCF shall include the dtx parameter with unmodified value in the SDP answer.

If the dtx parameter is not contained in the SDP offer and if a dtx-recv parameter is contained in the SDP offer, the MGCF may include the dtx parameter in the SDP answer , and the value of the dtx parameter shall then be identical to that of the dtx-recv parameter in the SDP offer (e.g, if that value matches DTX capabilities of expected codecs to transcode with).

If the dtx parameter is not contained in the SDP offer and if the dtx-recv parameter is not contained in the SDP offer, and if the usage of DTX is not desired (e.g. due to DTX capabilities of expected codecs to transcode with), the MGCF shall include in the SDP answer the dtx parameter with a value 0.

If the MGCF supplies the dtx parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

dtx-recv (NOTE 1)

If a dtx-recv parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If no dtx parameter is included in the SDP answer and if the reception of DTX is not desired, the MGCF shall include in the SDP answer the dtx-recv parameter with a value 0.

If both the dtx and dtx-recv parameters are included, those parameters shall have the same value; however, inclusion of the dtx-recv parameter is not required if the dtx parameter is included.

If the MGCF supplies the dtx-recv parameter in the SDP answer, it should also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

br (NOTE 1)

If a br parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated bit rates, or a subset of them, in EVS primary mode in the send and receive direction. If the indicated bit rates, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a br parameter is contained in the SDP offer, the MGCF shall select a bit rate value, which is either the received br value or a subset of it, based on IM-MGW capabilities and possible configured policies, and shall include the br parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise, if the MGCF desires the same bit rate range for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range to match IM-MGW capabilities and possible configured policies, the MGCF shall supply the br parameter in the SDP answer it sends.

Otherwise the MGCF shall not include this parameter in the SDP answer.

If the MGCF also supplies the bw, bw-send or bw-recv parameter, the value of the br parameter shall be compatible with the values of those parameters.

If the MGCF supplies the br parameter in the SDP answer, it shall also supply to the IM-MGW the br parameter in the local descriptor for the termination towards the offerer with the same value.

br-send (NOTE 1)

If a br-send parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated bit rates, or a subset of them, in EVS primary mode in the receive direction. If the indicated bit rates, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a br-recv parameter is contained in the SDP offer, the MGCF shall select a bit rate value, which is either the received br-recv value or a subset of it, based on IM-MGW capabilities and possible configured policies, and the MGCF shall include the br-send parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise, if the MGCF desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the send direction to match IM-MGW capabilities and possible configured policies, it shall supply the br-send parameter in the SDP answer it sends.

Otherwise the MGCF shall not include the br-send parameter in the SDP answer.

If the MGCF also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters.

If the MGCF supplies the br-send parameter in the SDP answer, it shall also supply to the IM-MGW the br-send parameter in the local descriptor for the termination towards the offerer with the same value.

br-recv (NOTE 1)

If a br-recv parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated bit rates, or a subset of them, in EVS primary mode in the send direction. If the indicated bit rates, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a br-send parameter is contained in the SDP offer, the MGCF shall select a bit rate value, which is either the received br-send value or a subset of it, based on IM-MGW capabilities and possible configured policies, and the MGCF shall include the br-recv parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise, if the MGCF desires a different bit rate (range) for the send and receive direction in EVS primary mode, and wants to restrict the bit rate range for the receive direction to match IM-MGW capabilities and possible configured policies, it shall supply the br-recv parameter in the SDP answer it sends.

Otherwise the MGCF shall not include the br-recv parameter in the answer.

If the MGCF also supplies the bw or bw-recv parameter, the value of the br-recv parameter shall be compatible with the values of those parameters.

If the MGCF supplies the br-recv parameter in the SDP answer, it shall also supply to the IM-MGW the br-recv parameter in the local descriptor for the termination towards the offerer with the same value.

bw (NOTE 1)

If a bw parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated sampling bandwidth(s), or a subset of them, in EVS primary mode in the send and receive direction. If the indicated sampling bandwidth(s), and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a bw parameter is contained in the SDP offer, the MGCF shall select a sampling bandwidth value, which is either the received bw value or a subset of it, based on IM-MGW capabilities, possible configured policies, and the bw range of other codecs to transcode with, and the MGCF shall include the bw parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise, if the MGCF desires the same sampling bandwidth(s) for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidth(s) to match IM-MGW capabilities, possible configured policies, and the bw range of other codecs to transcode with, the MGCF shall supply the bw parameter in the SDP answer it sends.

Otherwise the MGCF shall not include this parameter in the answer.

If the MGCF also supplies the br, br-send or br-recv parameter, the value of the bw parameter shall be compatible with the values of those parameters.

If the MGCF supplies the bw parameter in the SDP answer, it shall also supply to the IM-MGW the bw parameter in the local descriptor for the termination towards the offerer with the same value.

bw-send (NOTE 1)

If a bw-send parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the receive direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a bw-recv parameter is contained in the SDP offer, the MGCF shall select a sampling bandwidths value, which is either the received bw-recv value or a subset of it, based on IM-MGW capabilities, possible configured policies, and the bw range of other codecs to transcode with, and the MGCF shall include the bw-send parameter with the selected value in the SDP answer.

Otherwise, if the MGCF desires a different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths for the send direction to match IM-MGW capabilities, possible configured policies, and the bw range of other codecs to transcode with, the MGCF shall supply the bw-send parameter in the SDP answer it sends.

Otherwise the MGCF shall not include the br-send parameter in the SDP answer.

If the MGCF also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters.

If the MGCF supplies the bw-send parameter in the SDP answer, it shall also supply to the IM-MGW the bw-send parameter in the local descriptor for the termination towards the offerer with the same value.

bw-recv (NOTE 1)

If a br-recv parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the send direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward the bw-recv parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a bw-send parameter is contained in the SDP offer, the MGCF shall select a sampling bandwidths value, which is either the received bw-send value or a subset of it, based on IM-MGW capabilities, possible configured policies, and the bw range of other codecs to transcode with, and the MGCF shall include the bw-recv parameter with the selected value in the SDP answer.

Otherwise, if the MGCF desires a different sampling bandwidths for the send and receive direction in EVS primary mode, and wants to restrict the sampling bandwidths for the receive direction to match IM-MGW capabilities, possible configured policies, and the bw range of other codecs to transcode with, the MGCF shall supply the bw-recv parameter in the SDP answer it sends.

Otherwise the MGCF shall not include the bw-recv parameter in the SDP answer.

If the MGCF also supplies the br or br-recv parameter, the value of the bw-recv parameter shall be compatible with the values of those parameters.

If the MGCF supplies the bw-send parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

cmr (NOTE 1)

If a cmr parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a cmr parameter is contained in the SDP offer, the MGCF shall include the cmr parameter with unmodified value in the SDP answer.

Otherwise, if the IM-MGW desires to disable codec mode requests within the RTP payload of the EVS primary mode (due to the IM-MGW capabilities and possible configured policies), it shall include the cmr parameter with value -1 in the SDP answer it sends

If the MGCF supplies the cmr parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

ch-aw-recv (NOTE 1)

If a ch-aw-recv parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated mode in the send direction. If the indicated mode is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If the MGCF it desires to control the channel-aware mode of EVS in the receive direction, e.g. to disable it with value -1, it shall include the ch-aw-recv parameter in the SDP offer and shall also supply the ch-aw-recv parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value. The MGCF shall consider the capabilities of the IM-MGW when it chooses an appropriate value.

number of channels (NOTE 2)

If a "number of channels" parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated number of channels. If the indicated number of channels is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a "number of channels" parameter is contained in the SDP offer, the MGCF shall include the "number of channels" parameter with unmodified value in the SDP answer and shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

ch-send (NOTE 1)

If a ch-send parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated number of channels in the receive direction. If the indicated number of channels is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, the MGCF shall forward the ch-send parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a ch-recv parameter is contained in the SDP offer, the MGCF shall include the ch-send parameter with unmodified value in the SDP answer and shall also supply the ch-send parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

ch-recv (NOTE 1)

If a ch-recv parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated number of channels in the send direction. If the indicated number of channels is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type for transcoding, the MGCF shall forward the ch-recv parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a ch-send parameter is contained in the SDP offer, the MGCF shall include the ch-recv parameter with unmodified value in the SDP answer and shall also supply the ch-recv parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

mode-set (NOTE 3)

If a mode-set parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a mode-set parameter is contained in the SDP offer, the MGCF shall include the mode-set parameter with unmodified value in the SDP answer.

Otherwise, if AMR-WB is used to interwork with, the MGCF should include the mode-set parameter with a value indicating the mode that was negotiated for AMR-WB (or omit it if no restrictions applied before).

If the MGCF supplies the mode-set parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

mode-change-period (NOTE 3)

If a mode-change-period parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If AMR-WB is used to interwork with, the MGCF should include the mode-change-period parameter with a value indicating the mode that was negotiated for AMR-WB (or omit it if no restrictions applied before) in the SDP answer.

If the MGCF supplies the mode-change-period parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

mode-change-capability (NOTE 3)

If a mode-change-capability (Note 4) parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF may forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If the MGCF selects the EVS payload type, the MGCF shall include the mode-change-capability parameter with value 2 or omit it in the SDP answer.

If the MGCF supplies the mode-change-capability parameter in the SDP answer, it may also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

mode-change-neighbor (NOTE 3)

If a mode-change-neighbor parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If AMR-WB is used to interwork with, the MGCF should include the mode-change-neighbor parameter with a value indicating the mode that was negotiated for AMR-WB (or omit it if no restrictions applied before) in the SDP answer.

If the MGCF supplies the mode-change-neighbor parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

max-red (NOTE 5)

If a max-red parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF shall only include the max-red parameter in the SDP answer if it desires to restrict the maximum redundancy of received packets. When selecting the value of the max-red parameter, the MGCF shall consider the capabilities of the IM-MGW.

If the MGCF supplies the max-red parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

3gpp_mtsi_app_adapt (NOTE 4)

If a 3gpp_mtsi_app_adapt SDP attribute is contained in the SDP answer, and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

If the IM-MGW supports RTCP APP based adaptation messages defined in TS 26.114 [104], and the MGCF has a policy to negotiate the usage of those messages, the MGCF shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the allowed APP messages in the SDP answer.

NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445 [147]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 2: This number of channels are encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in IETF RFC 4566 [56].

NOTE 3 This MIME parameter of the EVS RTP payload type relates to AMR-WB IO mode and is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 4: This SDP attribute is defined in TS 26.114 [104]. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS.

NOTE 5: This MIME parameter of the EVS RTP payload type is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

evs-mode-switch (NOTE 1)

The MGCF shall not include the evs-mode-switch parameter in the SDP offer.

If an evs-mode-switch parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW for the termination towards the answerer in the remote descriptor.

hf-only (NOTE 1)

If the MGCF is configured to negotiate using only the header-full EVS RTP payload format, the MGCF shall include the hf-only parameter with a value of 1 in the SDP offer.

Using only the header-full EVS RTP payload format is recommended.

If an hf-only parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

dtx (NOTE 1)

The MGCF shall include the dtx parameter in the SDP offer and shall set it to 1 i.e. DTX enabled.

If a dtx parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

dtx-recv (NOTE 1)

The MGCF shall include the dtx-recv parameter in the SDP offer and shall set it to 1 i.e. DTX enabled.

If a dtx-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

br (NOTE 1)

The MGCF shall include the br parameter in the SDP offer and shall set it to a range corresponding to the CS configuration received in the Single Codec IE (see subclause B.2.5.5).

If a br parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

br-send (NOTE 1)

The MGCF shall not include the br-send parameter in the SDP Offer.

If a br-send parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

br-recv (NOTE 1)

The MGCF shall not include the br-recv parameter in the SDP Offer.

If a br-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

bw (NOTE 1)

The MGCF shall include the bw parameter in the SDP offer and shall set it to a range corresponding to the CS configuration received in the Single Codec IE (see subclause B.2.5.5).

If a bw parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

bw-send (NOTE 1)

The MGCF shall not include the bw-send parameter in the SDP Offer.

If a bw-send parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

bw-recv (NOTE 1)

The MGCF shall not include the bw-recv parameter in the SDP Offer.

If a bw-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

cmr (NOTE 1)

If the MGCF desires to disable codec mode requests on Mb within the RTP payload of the EVS primary mode (due to the IM-MGW capabilities or policies) and desires to use RTCP-APP instead for codec mode request, then it shall include the cmr parameter with a value of -1 in the SDP offer.

Otherwise, the MGCF shall include the cmr parameter with a value of 1 in the SDP offer in order to request EVS-CMR in every RTP packet.

The use of code mode requests on Mb within the RTP payload of the EVS primary mode is recommended.

If a cmr parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

ch-aw-recv (NOTE 1)

The MGCF shall include the ch-aw-recv parameter in the SDP offer and shall set it to an allowed value for the CS configuration received in the Single Codec IE (see subclause B.2.5.5).

If a ch-aw-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

number of channels (NOTE 2)

The MGCF shall include the number of channels parameter with a value of 1 in the SDP offer.

If a "number of channels" parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

ch-send (NOTE 1)

The MGCF shall not include the ch-send parameter in the SDP offer.

If a ch-send parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

ch-recv (NOTE 1)

The MGC shall not include the ch-recv parameter in the SDP offer.

If a ch-recv parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

mode-set (NOTE 4)

The MGCF shall include the mode-set parameter in the SDP offer and shall set it as per the received Single Codec IE (see subclause B.2.5.5).

If a mode-set parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

mode-change-period (NOTE 3)

The MGCF shall include the mode-change-period parameter in the SDP offer and shall set it to 2.

If a mode-change-period parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

mode-change-capability (NOTE 3)

The MGCF shall either include the mode-change-capability parameter with a value of 2 or omit it in the SDP offer.

If a mode-change-capability parameter is contained in the SDP answer, the MGCF may forward this parameter to the IM-MGW in the remote descriptor.

mode-change-neighbor (NOTE 3)

The MGCF shall include the mode-change-neighbor parameter in the SDP offer and shall set it to 1.

If a mode-change-neighbor parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

max-red (NOTE 5)

The MGCF shall not include the max-red parameter in the SDP offer.

If a max-red parameter is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor. (NOTE 6)

3gpp_mtsi_app_adapt (NOTE 4)

If the IM-MGW supports RTCP APP based adaptation messages defined in TS 26.114 [104], and the MGCF has a policy to negotiate the usage of those messages, the MGCF shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the supported APP messages in the SDP offer.

If a 3gpp_mtsi_app_adapt attribute is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445 [147]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 2: This number of channels is encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in IETF RFC 4566 [56].

NOTE 3: This MIME parameter of the EVS RTP payload type relates to the EVS AMR-WB IO major operation mode and is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 4: This SDP attribute is defined in TS 26.114 [104]. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS.

NOTE 5: This MIME parameter of the EVS RTP payload type is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 6: RTP redundancy is only applicable on the Mb interface. In such a case, the IM-MGW performs repacking. Transcoding is not required.

evs-mode-switch (NOTE 1)

If an evs-mode-switch parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.
(NOTE 6)

If an evs-mode-switch parameter is contained in the SDP offer, the MGCF shall include the evs-mode-switch parameter with unmodified value in the SDP answer.

Otherwise the MGCF shall not include the evs-mode-switch parameter.

hf-only (NOTE 1)

If an hf-only parameter is contained in the SDP offer, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If an hf-only parameter is contained in the SDP offer, the MGCF shall include the hf-only parameter with unmodified value in the SDP answer.

Otherwise, if the hf-only parameter is not contained in the SDP offer and if the MGCF is configured to negotiate using only the header-full EVS RTP payload format, then the MGCF shall include the hf-only parameter with a value of 1.

If the MGCF supplies the hf-only parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer.

dtx (NOTE 1)

If a dtx parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a dtx parameter is not contained in the SDP offer and a dtx-recv parameter is not contained in the SDP offer, the MGCF shall include the dtx parameter with a value of 1 in the SDP answer.

If a dtx parameter is not contained in the SDP offer and a dtx-recv parameter is contained in the SDP offer with a value of 1, the MGCF shall include the dtx parameter in the SDP answer with a value identical to that of the dtx-recv parameter in the SDP offer.

If a dtx parameter is contained in the SDP offer, the MGCF shall include the dtx parameter with unmodified value in the SDP answer.

The MGCF shall also supply the dtx parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

dtx-recv (NOTE 1)

If a dtx-recv parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If no dtx parameter is included in the SDP answer, the MGCF may include the dtx-recv parameter with a value of 1 in the SDP answer.

The MGCF should also supply the dtx-recv parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

br (NOTE 1)

If a br parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated bit rates, or a subset of them, in EVS primary mode in the send and receive direction. If the indicated bit rates, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a br parameter is contained in the SDP offer, the MGCF shall select a bit rate value, which is either the received br value or a subset of it, based on IM-MGW capabilities, possible configured policies and the CS configuration received Single Codec IE (see subclause B.2.5.5), and shall include the br parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise, the MGCF shall include the br parameter in the SDP answer and shall set it to a range corresponding to the CS configuration received in the Single Codec IE (see subclause B.2.5.5).

If the MGCF also supplies the bw, bw-send or bw-recv parameter, the value of the br parameter shall be compatible with the values of those parameters.

The MGCF shall also supply the br parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

br-send (NOTE 1)

If a br-send parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated bit rates, or a subset of them, in EVS primary mode in the receive direction. If the indicated bit rates, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a br-recv parameter is contained in the SDP offer, the MGCF shall select a bit rate value, which is either the received br-recv value or a subset of it, based on IM-MGW capabilities, possible configured policies and the br parameter value included in the SDP answer, and the MGCF shall include the br-send parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise the MGCF shall not include the br-send parameter in the SDP answer.

If the MGCF also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters.

br-recv (NOTE 1)

If a br-recv parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated bit rates, or a subset of them, in EVS primary mode in the send direction. If the indicated bit rates, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a br-send parameter is contained in the SDP offer, the MGCF shall select a bit rate value, which is either the received br-send value or a subset of it, based on IM-MGW capabilities, possible configured policies and the br parameter value included in the SDP answer, and the MGCF shall include the br-recv parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise the MGCF shall not include the br-recv parameter in the answer.

If the MGCF also supplies the bw or bw-recv parameter, the value of the br-recv parameter shall be compatible with the values of those parameters.

If the MGCF supplies the br-recv parameter in the SDP answer, it shall also supply to the IM-MGW the br-recv parameter in the local descriptor for the termination towards the offerer with the same value.

bw (NOTE 1)

If a bw parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated sampling bandwidth(s), or a subset of them, in EVS primary mode in the send and receive direction. If the indicated sampling bandwidth(s), and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a bw parameter is contained in the SDP offer, the MGCF shall select a sampling bandwidth value, which is either the received bw value or a subset of it, based on IM-MGW capabilities, possible configured policies and the CS configuration received in the Single Codec IE (see subclause B.2.5.5), and the MGCF shall include the bw parameter with the selected value that is also supplied towards the IM-MGW in the SDP answer.

Otherwise the MGCF shall include the bw parameter in the SDP answer and shall set it to a range corresponding to the CS configuration received in the Single Codec IE (see subclause B.2.5.5).

If the MGCF also supplies the br, br-send or br-recv parameter, the value of the bw parameter shall be compatible with the values of those parameters.

The MGCF shall also supply the bw parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

bw-send (NOTE 1)

If a bw-send parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the receive direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a bw-recv parameter is contained in the SDP offer, the MGCF shall select a sampling bandwidths value, which is either the received bw-recv value or a subset of it, based on IM-MGW capabilities, possible configured policies and the bw parameter value included in the SDP answer, and the MGCF shall include the bw-send parameter with the selected value in the SDP answer.

Otherwise the MGCF shall not include the br-send parameter in the SDP answer.

If the MGCF also supplies the bw or bw-send parameter, the value of the br-send parameter shall be compatible with the values of those parameters.

If the MGCF supplies the bw-send parameter in the SDP answer, it shall also supply to the IM-MGW the bw-send parameter in the local descriptor for the termination towards the offerer with the same value.

bw-recv (NOTE 1)

If a br-recv parameter is contained in the SDP offer, the MGCF shall check if the IM-MGW supports the indicated sampling bandwidths, or a subset of them, in EVS primary mode in the send direction. If the indicated sampling bandwidths, and even each subset of them, are not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, it shall forward the bw-recv parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a bw-send parameter is contained in the SDP offer, the MGCF shall select a sampling bandwidths value, which is either the received bw-send value or a subset of it, based on IM-MGW capabilities, possible configured policies and the bw parameter value included in the SDP answer, and the MGCF shall include the bw-recv parameter with the selected value in the SDP answer.

Otherwise the MGCF shall not include the bw-recv parameter in the SDP answer.

If the MGCF also supplies the br or br-recv parameter, the value of the bw-recv parameter shall be compatible with the values of those parameters.

If the MGCF supplies the bw-send parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

cmr (NOTE 1)

If a cmr parameter is contained in the SDP offer, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a cmr parameter is contained in the SDP offer, the MGCF shall include the cmr parameter with unmodified value in the SDP answer.

Otherwise, if the IM-MGW desires to disable codec mode requests within the RTP payload of the EVS primary mode (due to the IM-MGW capabilities and possible configured policies), it shall include the cmr parameter with value -1 in the SDP answer.

Otherwise the MGCF shall include the cmr parameter with a value of 1 in the SDP answer.

The MGCF shall also supply the cmr parameter to the IM-MGW in the local descriptor for the termination towards the offerer.

ch-aw-recv (NOTE 1)

If a ch-aw-recv parameter is contained in the SDP offer the MGCF shall check if the CS side supports the indicated mode. If the indicated mode is not supported, the MGCF shall set this parameter to -1 and forward it to the IM-MGW for the termination towards the offerer in the remote descriptor.

If the MGCF desires to control the channel-aware mode of EVS in the receive direction, e.g. to disable it with value -1, it shall include the ch-aw-recv parameter in the SDP offer and shall also supply the ch-aw-recv parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value. The MGCF shall consider the capabilities of the IM-MGW when it chooses an appropriate value.

number of channels (NOTE 2)

If a "number of channels" parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated number of channels. If the indicated number of channels is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF shall include the "number of channels" parameter with a value of 1 in the SDP answer and shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

ch-send (NOTE 1)

If a ch-send parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated number of channels in the receive direction. If the indicated number of channels is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, the MGCF shall forward the ch-send parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a ch-recv parameter is contained in the SDP offer, the MGCF shall include the ch-send parameter with a value of 1 in the SDP answer and shall also supply the ch-send parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

ch-recv (NOTE 1)

If a ch-recv parameter is contained in the SDP offer the MGCF shall check if the IM-MGW supports the indicated number of channels in the send direction. If the indicated number of channels is not supported, the MGCF shall not select the EVS payload type. If the MGCF selects the EVS payload type, the MGCF shall forward the ch-recv parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a ch-send parameter is contained in the SDP offer, the MGCF shall include the ch-recv parameter with a value of 1 value in the SDP answer and shall also supply the ch-recv parameter to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

mode-set (NOTE 3)

If a mode-set parameter is contained in the SDP offer and the mode-set parameter does not include mode set 0, the MGCF shall not select the EVS payload type.

Otherwise, if a mode-set parameter is contained in the SDP offer, the mode-set parameter includes mode set 0 and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

If a mode-set parameter is contained in the SDP offer, the MGCF shall include the mode-set parameter with a value which is either the received mode-set parameter value or a subset of it, based on the CS configuration received in the Single Codec IE (see subclause B.2.5.5), in the SDP answer.

Otherwise, the MGCF shall include the mode-set parameter in the SDP answer and shall set it to the range corresponding to the CS configuration received in the Single Codec IE (see subclause B.2.5.5).

The MGCF shall also supply the mode-set parameter to the IM-MGW in the local descriptor for the termination towards the offerer.

mode-change-period (NOTE 3)

If a mode-change-period parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF shall include the mode-change-period parameter in the SDP answer and shall set it as per the received Single Codec IE (see subclause B.2.5.5).

The MGCF shall also supply the mode-change-period parameter to the IM-MGW in the local descriptor for the termination towards the offerer.

mode-change-capability (NOTE 3)

If a mode-change-capability (NOTE 4) parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF may forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF shall either include the mode-change-capability parameter with a value of 2 or omit it in the SDP answer.

The MGCF may also supply the mode-change-capability parameter to the IM-MGW in the local descriptor for the termination towards the offerer.

mode-change-neighbor (NOTE 3)

If a mode-change-neighbor parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF shall include the mode-change-neighbor parameter in the SDP answer and shall set it as per the received Single Codec IE (see subclause B.2.5.5).

The MGCF shall also supply the mode-change-neighbor to the IM-MGW in the local descriptor for the termination towards the offerer.

max-red (NOTE 5)

If a max-red parameter is contained in the SDP offer and the MGCF select the EVS payload type, the MGCF shall forward this parameter to the IM-MGW for the termination towards the offerer in the remote descriptor.

The MGCF shall only include the max-red parameter in the SDP answer if it desires to restrict the maximum redundancy of received packets. When selecting the value of the max-red parameter, the MGCF shall consider the capabilities of the IM-MGW.

If the MGCF supplies the max-red parameter in the SDP answer, it shall also supply it to the IM-MGW in the local descriptor for the termination towards the offerer with the same value.

3gpp_mtsi_app_adapt (NOTE 4)

If a 3gpp_mtsi_app_adapt SDP attribute is contained in the SDP answer, the MGCF shall forward this parameter to the IM-MGW in the remote descriptor.

If the IM-MGW supports RTCP APP based adaptation messages defined in TS 26.114 [104], and the MGCF has a policy to negotiate the usage of those messages, the MGCF shall include the 3gpp_mtsi_app_adapt SDP attribute indicating the allowed APP messages in the SDP answer.

NOTE 1: This MIME parameter of the EVS RTP payload type is defined in TS 26.445 [147]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 2: This number of channels are encoded as "encoding parameters" of the SDP "a=rtpmap" attribute defined in IETF RFC 4566 [56].

NOTE 3 This MIME parameter of the EVS RTP payload type relates to EVS AMR-WB IO major operation mode and is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 4: This SDP attribute is defined in TS 26.114 [104]. It applies to all codecs offered in an SDP media line. However, some values are specific to EVS.

NOTE 5: This MIME parameter of the EVS RTP payload type is defined in IETF RFC 4867 [23]. It is encapsulated within the SDP "a=fmtp" attribute defined IETF RFC 4566 [56].

NOTE 6: The received evs-mode-switch parameter has no influence on the Config-EVS-Code.