System information

Unified Messaging
This is a term that has been hyped by the telecom industry for years, but adoption has
been far slower than predicted.
Unified messaging refers to the concept of tying voice and text-messaging systems into
one. With Asterisk, the two don’t need to be artificially combined, as Asterisk already
treats them the same way.
Just by examining the terms, unified and messaging, we can see that the integration of
email and voicemail must be merely the beginning—unified messaging needs to do a
lot more than just that if it is to deserve its name.
Perhaps we need to define “messaging” as communication that does not occur in real
time. In other words, when you send a message, you expect that the reply may take
moments, minutes, hours, or even days to arrive. You compose what you wish to say,
and your audience is expected to compose a reply.
Contrast this with conversing, which happens in real time. When you talk to someone
on a telephone connection, you expect no more than a few seconds’ delay before the
response arrives.
Several years ago, Tim O’Reilly delivered a speech entitled “Watching the Alpha Geeks:
OS X and the Next Big Thing” (http://www.macdevcenter.com/pub/a/mac/2002/05/14/
oreilly_wwdc_keynote.html), in which he talked about someone piping IRC through a
text-to-speech engine. One could imagine doing the reverse as well, allowing us to join
an IRC or instant messaging chat over a WiFi phone, with our Asterisk PBX providing
the speech-to-text-to-speech translations.
Peering
As monopoly networks such as the PSTN give way to community-based networks like
the Internet, there will be a period of time where it is necessary to interconnect the two.
While the traditional providers would prefer that the existing model be carried into the
new paradigm, it is increasingly likely that telephone calls will become little more than
another application the Internet happily carries.
But a challenge remains: how to manage the telephone numbering plan with which we
are all familiar and comfortable?
E.164
The ITU defined a numbering plan in its E.164 specification. If you’ve used a telephone
to make a call across the PSTN, you can confidently state that you are familiar with the
concept of E.164 numbering. Prior to the advent of publicly available VoIP, nobody
cared about E.164 except the telephone companies—nobody needed to.
590 | Chapter 27: Asterisk: A Future for Telephony