7 IMS Concepts IMS User Identification An IMS user is allocated one or more Public User Identities by the home operator A Public User Identity is either a SIP URI or a TEL URL – When the Public User Identity contains a SIP URI, it typically takes the form of sip:first.last@operator.com – When the Public User Identity contains a TEL URL representing a phone number in international format it typically takes the form of tel:+1-212-555-0293 – It is possible to include a telephone number in a SIP URI using the following format: sip:+1-212-555-0293@operator.com;user=phone – TEL URLs are needed for inter-working with PSTN phones In IMS, Public User Identities are used to route SIP signaling
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