RFC4395: Guidelines and Registration Procedures for New URI Schemes
Topic: Registration requests for URIs containing telephone numbers
The IETF has found that there are many special cases when dealing
with telephone numbers as identifiers or locators. Duplicating the
special case logic in many different URIs is going to be error-
prone as well as costly.
The IESG feels that since the Tel URI is quite extensible,
extending it is the preferred approach over defining new URIs
containing telephone numbers.
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