The SIP Geolocation specification [RFC 6442
] describes the "Geolocation" SIP header field, which is used to indicate that the SIP message is conveying location information. [RFC 6442
] specifies that SIP intermediaries should not add locationValues to a SIP request that already contains a locationValue. [RFC 6442
] also states that if a SIP intermediary adds location, it is fully responsible for addressing the concerns of any 424 (Bad Location Information) SIP response it receives. However, some communications architectures, such as 3GPP [TS23-167
] and ETSI [M493
], prefer to use information provided by edge proxies or acquired through the use of core-network nodes before using information provided solely by user equipment (UE). These solutions don't preclude the use of UE-provided location but require a means of being able to distinguish the identity of the node adding the locationValue to the SIP message from that provided by the UE.
] stipulates that the order of locationValues in the Geolocation header field is the same as the order in which they were added to the header field. Whilst this order provides guidance to the recipient as to which values were added to the message earlier in the communication chain, it does not identify which node added the locationValue. Knowing the identity of the entity that added the location to the message allows the recipient to choose which location to consider first rather than relying solely on the order of the locationValues in the Geolocation header field.
This document extends the Geolocation header field of [RFC 6442
] by allowing an entity adding the locationValue to identify itself using a hostname. This is done by defining a new geoloc-param header field parameter, "loc-src". How the entity adding the locationValue to the header field obtains the location information is out of scope of this document. Please note that the "loc-src" parameter field does not alter the subject of the locationValue.