Reinventing the
Dialplan
Astricon Oct 14, 2009
Copyright 2009 Twilio

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Voice Applications
Asterisk

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Voice Applications
The Cloud
Asterisk

Voice Applications
Voice Guru

Maintained by your Voice Guru
Asterisk
Native scripting language
Dialplan written by your Voice Guru
Application
Asterisk Dialplan
Language: Native Scripting Where: Local on call router

IP
Asterisk AGI/AMI
Java/C/Ruby...
Application
Asterisk AGI/AMI
Language: AGI/AMI API + Where: Remote via IP
Java/C/Ruby/Python/Etc

Maintained by your Voice Guru
IP
Asterisk AGI/AMI
Java/C/Ruby...
Application
Asterisk AGI/AMI
Language: AGI/AMI API + Where: Remote via IP
Java/C/Ruby/Python/Etc

Maintained by your Programmer
IP
Asterisk AGI/AMI
Java/C/Ruby...
Application
Asterisk AGI/AMI
Language: AGI/AMI API + Where: Remote via IP
Java/C/Ruby/Python/Etc

Enter the Programmer
• Commodity skillset
• Easy to hire
• Cheap
Programmer

Better but...
IP
Asterisk
Large API with "lite" documentation. AGI/AMI
The distinction between AGI/AMI can
be confusing.
Tight integration between call router
and voice app: direct socket Java/C/Ruby...
connections Application
SCALING=HARD
Asterisk AGI/AMI
Language: AGI/AMI API + Where: Remote via IP
Java/C/Ruby/Python/Etc

IP
Asterisk AGI/AMI
Lets mull this over...

IP
Asterisk AGI/AMI
Why do I need a
Voice Guru?

IP
Asterisk AGI/AMI
Expert
What if I outsourced
my voice guru?

IP
AGI/AMI
Asterisk in
the Cloud

IP
?????
Asterisk in
the Cloud
What is the ideal voice app API?

Web developers are (one of)
the largest engineering workforces
on the planet
• HTTP
• Request/Response
• XML/JSON
• WAV/MP3

Magic
Ruby
Java
Asterisk in
PHP
the Cloud
Python
.
.
.
Create new messaging protocol
and new API for each language?

HTTP/XML
Ruby
REST
Java
Asterisk in
PHP
the Cloud
Python
.
.
.
Normal Web Server
HTTP/XML/REST

HTTP/XML
Ruby
REST
Java
PHP
Python
Twilio .
.
.
Normal Web Server
HTTP/XML/REST

HTTP/XML
REST Google App Engine
Microsoft Azure
Twilio Heroku
Leverage existing cloud hosting
Scale: 1-10,000’s of simultaneous calls

Request/Response
1 Procedural programming
digits = GetKeypadPresses();
switch(digits) {
case 1:
blah();
break;
}

Request/Response
1 Procedural programming
digits = GetKeypadPresses();
switch(digits) {
case 1:
blah();
break;
}
Not how HTML works!

Request/Response
2 Web programming
<form action=”digits.php”>
<input type=”text” name=”digits” />
<input type="submit" value="Go"/>
</form>

Request/Response
2 Web programming
<form action=”digits.php”>
<input type=”text” name=”digits” />
<input type="submit" value="Go"/>
</form>
Submit back to digits.php
on input

Request/Response
3 Web-like voice programming
<Gather numDigits=”5”
action=”digits.php”/>
Apply the same model for
voice applications

Request/Response
3 Web-like voice programming
<Gather numDigits=”5”
action=”digits.php”/>
Submit back to digits.php
on input

Request/Response
4 Language-specific libraries
$r = new Response();
$r->append(new Say("Hello World"); PHP
$r->Respond();
r = twilio.Response()
r.append(twilio.Say("Hello World")) Python
print r
@r = Twilio::Response.new
@r.append(Twilio::Say.new "Hello World") Ruby
puts @r.respond
TwiMLResponse response = new TwiMLResponse();
Say say = new Say("Hello World"); Java
System.out.println(response.toXML());

⤸
⤸
⤸
HTTP 307 HTTP 307
u.com b.com c.com
PBX Application Authorization CRM
Service Integration
Response Chaining

Stateless ‘Twimlet’ URLs + REST

curl -fSs -u "$ACCOUNTSID:
$AUTHTOKEN" -d "Caller=$CALLERID" -d
"Called=$PHONE" -d "Url=http://
twimlets.com/message?Message=$MSG"
"https://api.twilio.com/2008-08-01/
Accounts/$ACCOUNTSID/Calls
Stateless ‘Twimlet’ URLs + REST

Put the Voice Guru in the Cloud
1 Asterisk in the cloud
Adopt a standards-based web API
2 HTTP/XML/REST
Leverage existing web infrastructure
3 Apache/Tomcat/AWS/AppEngine/Azure/Heroku
Let the cloud handling scaling
4 1-10,000’s simultaneous calls
Don’t break request/response model
5 Build libraries for PHP/Python/Java/C#/Ruby etc.

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Voice Applications
The Cloud
Asterisk

Simplifying Telecom
Simple • Powerful • Pay-As-You-Go
Evan Cooke
Co-Founder & CTO
twitter: @twilio
phy@twilio.com
http://www.twilio.com