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E.164, sip URIs, and tel URIs

A global number is written in a tel URI or in a sip URI user part, and E.164 is the numbering plan those digits follow.

Learn in 5 minutes

  1. Read a global tel URI and a sip URI with user=phone
  2. Say what E.164 is without inventing an ITU clause
  3. Keep the Request-URI and the To URI as different fields

Visual

user=phone, then a redirect · study drawing · cyphermonkeylabs.com UARedirectPeer INVITE 100 302 ACK

SVG HTML PNG

The digits are the numbering plan. The scheme decides who can route the identifier.

Worked example

Dissect the phone URI Find the URI parameter that marks the user part as a phone number.

  1. Dissect the INVITE.
  2. Read the Request-URI parameters.
  3. Compare the Request-URI with the To URI.

Fault

A proxy answers 416 Unsupported URI Scheme to a request whose Request-URI is a tel URI.

A tel URI has no host. An element that cannot use it returns 416 or maps it to a sip URI.

Quiz

Which document defines the tel URI?


E.164 is


user=phone on a sip URI means


A tel URI differs from a sip URI because


On the first INVITE, To and the Request-URI


The ACK for the 302 uses


Ecosystem

Glossary, sister systems, and the integration seam for this room.

E911 / emergency calling Location has to ride with the call. RFC 6881 is the BCP, RFC 6442 carries location in SIP, and the FCC MLTS page states Kari’s Law and RAY BAUM’s Act obligations for multi-line systems.

Glossary · Ecosystem map · Ports · Troubleshooting

Sources and go deeper