From: "Dan Wing" <[EMAIL PROTECTED]>
> Sorry, I don't understand. You said "sending a SIP request towards
> the E.164", by which I understand an Enum lookup. Did you mean
> "sending a SIP request towards a SIP URI which purposts to represent
> an E.164"?
draft-wing-sip-e164-rrc-01.txt says to turn the SIP URI into a TEL URI,
and then generate a Return Routability Check (RRC) towards that TEL URI:
"1. Strip the domain name of the From: of the incoming INVITE. This
results in a TEL URI. For example,
"sip:[EMAIL PROTECTED];user=phone" is rewritten to
"tel:+14085551212".
2. Rewrite the TEL URI to a SIP URI, following the Verifier's
default routing rules. For example, if outgoing calls are sent
to the service provider example.net, then "tel:+14085551212" is
rewritten to "sip:[EMAIL PROTECTED];user=phone".
3. Generate a random nonce.
4. Using the SIP URI constructed in step (2), construct a SIP
SUBSCRIBE message with Request-URI and To headers that use that
SIP URI, and an "Expires" header of 0. The SUBSCRIBE contains
the random nonce in its body as Content-Type application/
return-routability-nonce.
5. Send the SUBSCRIBE message. This will cause the calling party to
send a NOTIFY."
Interesting... Because the verification generated by this algorithm
is not quite what I expected from how it was described, and it is both
narrower and probably more useful than what I expected. The
verification is that "Within the Verifier's context, the routing rules
that are in effect send tel:+1234 to the given domain." This actually
doesn't say anything about ownership of E.164 numbers (other than that
E.164 numbers are the space of URIs), but it says a tremendous amount
about how requests are routed from the Verifier's context: "If I call
the given number, will I reach the given domain?" That's not useful
for validating an incoming caller based on an asserted E.164 origin
number (unless one's local E.164 routing is known to be trustable),
but it's really useful for knowing if I can call the caller back using
the asserted E.164 number.
Dale
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