-----Original Message----- From: sip-implementors-bounces@lists.cs.columbia.edu [mailto:sip- implementors-bounces@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