The predominant availability of phones with 12-digit keypads (10 numeri-
cal digits, plus the special characters “#” and “*”) makes this the most practi-
cal near-term option for address entry.
If there is a desire not to give out one’s home phone number, another phone
number (such as a work number) could be given as the single contact address.
Thus, by knowing just one telephone number, all the other communication
addresses can be found.
An example of a contact list for SIP is:Contact: <sip:[email protected]
;service=IP,voice mail;media=>;audio ;duplex=”full ;q=0.7”;actor=”msg-taker” ;automata ;q=0.7
Contact: phone: +1-972-555-1212; service=ISDN
<tel:+19725551212>;mobility=”fixed;“;language=”en,es,” ;q=0.568 Chapter 4
DO YOU REALLY HAVE VOIP?
Users may want to check commercial claims for what is a VoIP service. If they
get only a PSTN phone number and can call only PSTN phone numbers, that is
really a “PSTN over IP” service, since no Internet applications can be used and
no Internet user experience is provided. Using IP inside the plumbing of the
“PSTN over IP” network of that service provider does not justify the term “VoIP”
in our opinion, even though some added features are available that go beyond
what the PSTN can support (new features such as global mobility and good
quality video phones).
There are two tests to apply for any VoIP service claim:- Does the subscriber get a URI so as to be reachable from the Internet?
- Can the caller “dial” a URI to reach anyone on the Internet?
Only if the answer is “yes” to both questions is the service true VoIP.
If the service provides only phone numbers, then it would be correctly called
“PSTN over IP” instead of VoIP.
These criteria also apply, in our opinion, to the many VoIP solutions
marketed to enterprises, especially to the so-called IP PBX that that is voice-
centric, without the benefits of presence, IM, video, and the integration of
communications and applications. It all comes down to the power of the DNS
and URIs being available to consumers and to the enterprise/institution
information technology (IT) organization in an integrated fashion, and not
having the IT organization maintain a distinctive voice-centric infrastructure.