如题，VoLTE信令中的媒体feature-tag汇总全集。在volte信令中，有很多媒体相关的media feature-tag。比如：g.3gpp.cs-voice、g.3gpp.cs-video、g.3gpp.smsip、g.3gpp.icsi-ref、g.3gpp.iari-ref、g.3gpp.ics、g.3gpp.accesstype、g.3gpp.pne-id、g.3gpp.cs2ps-srvcc-alerting、g.3gpp.path、g.3gpp.cs2ps-srvcc、g.3gpp.ti、g.3gpp.drvcc-alerting等等20多个，都是什么意思呢？

都在这里了哈。

Feature Tag Description Reference
g.3gpp.cs-voice This feature-tag indicates that the device supports circuit switched
voice when combining circuit switched calls and IM sessions.		 [ETSI TS 124 279]
g.3gpp.cs-video This feature-tag indicates that the device supports circuit switched
video when combining circuit switched video calls and IM sessions.		 [ETSI TS 124 279]
g.3gpp.smsip This feature-tag indicates that the device is capable of accepting
SMS messages via SIP as specified by ETSI TS 124 341.		 [ETSI TS 124 341]
g.3gpp.icsi-ref Each value of the Service Reference media feature-tag indicates the software applicationssupported by the agent. The values for this tag equal the IMS communication Service Identifier (ICSI) values supported by the agent. The Service Reference media feature tag is defined to fulfil the requirements for forking to an appropriate UE when multiple UEs are
registered and dispatch to an appropriate application within the UE
based upon the IMS communication Service Identifier (ICSI) values as
 stated in 3GPP TS 23.228.		 [3GPP TS 24.229]
g.3gpp.iari-ref Each value of the Application Reference media feature-tag indicates the software applications supported by the agent. The values for this tag equal IMS Application Reference Identifier (IARI) values supported by the agent The Application Reference media feature tag is defined to fulfil the
requirements for forking to an appropriate UE when multiple UEs are
 registered and dispatch to an appropriate application within the UE
based upon and IMS Application Reference Identifier (IARI) values as
stated in 3GPP TS 23.228.		 [3GPP TS 24.229]
g.3gpp.ics This feature-tag when used in a SIP REGISTER request indicates that the function is ICS capability and may operate in ICS mode. This feature-tag when used is a none SIP REGISTER method indicates that the function wants to invoke ICS functionality. [3GPP TS 24.292]
g.3gpp.accesstype This feature-tag when used in a SIP REGISTER request indicates access network technology used by the device and the particular registration flow that the device is using to register over. [3GPP TS 24.292]
g.3gpp.pne-id This media feature-tag when used in a SIP request or a SIP response indicates the identifier of a PNE other than a UE. [3GPP TS 24.259]
g.3gpp.iut-controller This media feature-tag when used in a SIP request or a SIP response indicates that the function sending the SIP message supports the IUT Controller functionality.This media feature tag does not imply that the controller UE capabilities are handled in the same protocol manner. [3GPP TS 24.337]
g.3gpp.iut-focus This media feature-tag when used in a Contact header field or a Accept-Contact  header field of a SIP request or a SIP response indicates that the function sending the SIP message supports anchoring a IUT session and/or the SIP message is an inter-UE transfer operation. [3GPP TS 24.337]
g.3gpp.current-iut-controller This media feature-tag when used in a Contact header field of SIP request or SIP response indicates that the UA is the currently active IUT controller for the collaborative session or is a controllee in the collaborative. The values of the feature tag are "active" and "passive". [3GPP TS 24.337]
g.3gpp.mid-call This feature-tag when used in a SIP request or a SIP response indicates that the function sending the SIP message supports the MSC server assisted mid-call feature. [3GPP TS 24.237]
g.3gpp.srvcc-alerting This media feature-tag when used in a Contact header field of a SIP request or a SIP response indicates that the functional entity sending the SIP message supports SRVCC access transfer for calls in alerting phase, i.e. for calls whith early dialog. [3GPP TS 24.237]
g.3gpp.cs2ps-srvcc-alerting This media feature-tag when used in a Contact header field of a SIP request or a SIP response indicates that the functional entity sending the SIP message supports CS to PS SRVCC access transfer for calls in alerting phase. [3GPP TS 24.237 11.10.0]
g.3gpp.path This media feature tag when used in a Contact header field in SIP REGISTER request or SIP response to the SIP REGISTER request indicates capability of identifying the registration path and binding SRVCC related information to it. [3GPP TS 24.237 11.10.0]
g.3gpp.cs2ps-srvcc This media feature tag when included in Contact header field indicates support of the CS to PS single radio voice call continuity as specified in 3GPP TS 24.237. [3GPP TS 24.237 11.10.0]
g.3gpp.pstops-sti This media feature-tag when used in a Contact header field of a SIP request or a SIP response indicates that the functional entity sending the SIP message supports the use of the PS to PS STI URI. [3GPP TS 24.237 11.10.0
g.3gpp.ti This media feature tag when used in a Contact header field as specified in IETF RFC 3840 in SIP INVITE request or SIP response to the SIP INVITE request indicates the capability of associating a CS call with dialog created by the SIP INVITE request. [3GPP TS 24.237 11.10.0]
g.3gpp.drvcc-alerting This media feature-tag when used in a Contact header field of a SIP request or a SIP response indicates that the functional entity sending the SIP message supports the PS to CS dual radio access transfer for calls in alerting phase. [3GPP TS 24.237 12.8.0]
g.3gpp.dynamic-stn This media feature-tag when used in a Contact header field of
a SIP request or a SIP response indicates that the functional entity
 sending the SIP message supports the use of dynamic STN.		 [3GPP TS 24.237 12.8.0]
g.3gpp.ps2cs-drvcc-orig-pre-alerting This media feature-tag when used in a Contact header field of
a SIP request or a SIP response indicates that the functional entity
 sending the SIP message supports the PS to CS dual radio access transfer for originating calls in pre-alerting phase.		 [3GPP TS 24.237 12.8.0]
g.3gpp.ps2cs-srvcc-orig-pre-alerting This media feature tag when used in a Contact header field ofa SIP request or a SIP response indicates that the functional entity
 sending the SIP message supports the PS to CS SRVCC for originating calls in pre-alerting phase.		 [3GPP TS 24.237 12.8.0]

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