The ICSI is defined to fulfil the requirements as stated in
TS 23.228. An ICSI may have specialisations which refine it by adding subclass identifiers separated by dots. Any specialisations of an ICSI shall have an
"is a" relationship if the subclasses are removed. For example, a check for ICSI urn:urn-7:3gpp-service.ims.icsi.mmtel will return true when evaluating ICSI urn:urn-7:3gpp-service.ims.icsi.mmtel.hd-video.
This parameter is coded as a URN. The ICSI URN may be included as:
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a tag-value within the g.3gpp.icsi-ref media feature tag as defined in subclause 7.9.2 and RFC 3840, in which case those characters of the URN that are not part of the tag-value definition in RFC 3840 shall be represented in the percent encoding as defined in RFC 3986;
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a feature cap value within the "g.3gpp.icsi-ref" feature-capability indicator, as defined in subclause 7.9A.1 and RFC 6809, in which case those characters of the URN that are not part of the feature-capability indicator value definition syntax shall be represented in the percent encoding, as defined in RFC 3986; or
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as a value of the P-Preferred-Service or P-Asserted-Service header fields as defined RFC 6050.
A list of the URNs containing ICSI values registered by 3GPP can be found at
http://www.3gpp.org/specifications-groups/34-uniform-resource-name-urn-list
An example of an ICSI for a 3GPP defined IMS communication service is:
urn:urn-7:3gpp-service.ims.icsi.mmtel
An example of a g.3gpp.icsi-ref media feature tag containing an ICSI for a 3GPP defined IMS communication service is:
g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel"
An example of a g.3gpp.icsi-ref feature-capability indicator containing an ICSI for a 3GPP defined IMS communication service is:
g.3gpp.icsi-ref="urn%3Aurn-7%3A3gpp-service.ims.icsi.mmtel"
An example of an ICSI for a 3GPP defined IMS communication service in a P-Preferred-Service header field is
P-Preferred-Service: urn:urn-7:3gpp-service.ims.icsi.mmtel
An example of an ICSI for a 3GPP defined IMS communication service in a P-Asserted-Service header field is
P-Asserted-Service: urn:urn-7:3gpp-service.ims.icsi.mmtel
An example of an ICSI for a defined IMS communication service with a specialisation is:
P-Asserted-Service: urn:urn-7:3gpp-service.ims.icsi.mmtel.game-v1
An example of an ICSI for a 3GPP defined IMS communication service with an organisation-y defined specialisation is:
P-Asserted-Service: urn:urn-7:3gpp-service.ims.icsi.mmtel.organisation-y.game-v2