[Kamailio-Users] [Sip-implementors] Secure VoIP

[Hadriel Kaplan]

> -----Original Message-----
> From: sip-implementors-bounces at lists.cs.columbia.edu [mailto:sip-
> implementors-bounces at lists.cs.columbia.edu] On Behalf Of Iñaki Baz
> Castillo
> Sent: Friday, February 27, 2009 4:59 AM
>
> >> We have at least two cases now where an update to the RFC added
> >> important MUSTs:
> >>
> >> - Tel uri - phone-context is now required, which affects all SIP
> >> devices using SIP uri with user=phone
> >>    regardless if they use a Tel: URI.
>
> Sincerelly I can't understand the usage/requeriment of "user"
> parameter. How would detect a phone if the dialed number is a PSTN
> number or an extension? For example:
> - 1004 is a short number in Spain (Telefonica)
> - 2002 could be a domain user
> How

The short answer is you don't.  Hardly anyone uses/encodes/looks-for the phone-context param in practice (and not many folks use the Tel: URI scheme either, btw - they just encode it in a sip scheme).

As for the user=phone, it's been a major source of confusion for folks since many devices don't encode it (because as you note they have no idea if it's a telephone number or just a username string of digits).  In practice what happens is the "proxies" often treat the username portion as a phone number if it's comprised of digits or looks like an E.164, regardless of the user=phone param.  So far that's worked ok, but it may lead to problems someday.

-hadriel