✓ Move, Share and Control Calls
✓ High-Def Call Recording
✓ HTTP Live Streaming
✓ Speech Recognition
✓ Personal Conferencing
✓ Community integration with most cloud services
✓ Node.js API
✓ Real-Time Service Provisioning
✓ PaaS Technology (w/ Cloud Foundry)
✓ Communications ‘Add-On Store’
Tropo for IMS
✓ The IMS enables a diverse set of endpoints to participate in telco communications by leveraging
Internet protocols to unify the core network and by deﬁning a standard architecture for adding
new network services through specialized Applications Servers (AS)
✓ The Tropo AS is one such Application Server. When eligible subscribers make and receive calls,
their signaling ﬂows through Tropo, allowing 3rd party apps to enhance conversations in real-
time. This level of control is accomplished through the standardized IMS Service Control
✓ When subscribers purchase their ﬁrst Tropo-based app, a special entry is created in the
subscriber’s HSS record which instructs the IMS to route future calls and text messages through
the Tropo AS. This special entry is called an Initial Filter Criteria (IFC). This provisioning step can
be done manually by the operators or through an automated system provided by the operators.
✓ Tropo does not require direct access to the HSS
Basic IMS Signaling Model
• In the basic model, each user is assigned to a Call
Session Control Function (CSCF)
• Conversations ﬂow from one CSCF to the other by
interrogating the HSS for routing information
• SIP is used as the standard signaling protocol
between the terminals, and the network and also
between network elements
IMS w/ Application Server
• In addition to basic routing information, the HSS contains
information about enhanced services enabled on the user’s
• Historically, these services were implemented through
complicated a deeply specialized technologies such as
CAMEL with no standard model for on-boarding and
provisioning new services.
• IMS opted for a simpler model by providing a standard
model for provisioning and allowing new services to
participate directly in the underlying network signaling. The
nodes providing these new services as referred to as IMS
Application Servers (AS)
• The HSS maintains and list of Application Servers on behalf
of each user with instructions on how to route calls and other
network events through them.
• A SIP-based protocol is used between the CSCF and the
Applications Servers called ISC. The ISC speciﬁes certain
special SIP headers that must be maintained between call
legs to preserve core subscriber functions such as billing.
Apps in your Calls
• While the AS model is quite ﬂexible, operators are still faced
with the risk and operational overhead of adding network
elements for each new service; resulting in missed market
• Tropo builds on the IMS/AS model by providing a secure
multi-tenant execution environment for network-based
• Tropo Provisioning Server maintains a list of apps for each
subscriber. Each app contains a set of permissions, allowing
the subscriber to control access to their calls and sensitive
• Apps are provisioned into and execute in an elastic
environment powered by the Cloud Foundry suite of PaaS
• Only a single IFC entry is required per subscriber as the Tropo
AS distributes events to all interested applications.
• New services are deployed and provisioned in real-time
without adding servers or making any changes to the core
4 5a 5b
‣ Alice is a sales representative for a local car dealership. She is calling Bob
to let him know that his car is ready for pickup.
Prior to making this call, Alice signed up for a cool new service from her
mobile carrier that automatically logs her work calls to Salesforce.com
‣ Alice’s mobile network routes her outgoing call to the CSCF, which in turn
performs and standard HSS lookup to ﬁnd Alice’s dialing preferences,
roaming status and detailed proﬁle information.
‣ The CSCF ﬁnds an IFC entry in Alice’s proﬁle instructing it to route any
incoming (INVITE/ORIG) or outgoing (INVITE/TERM) calls through Tropo.
The CSCF proxies Alice’s outgoing call to the Tropo AS via the ISC protocol.
‣ Tropo AS uses the P-Served-User header to lookup Alice’s list of
applications in the Provisioning Server. At this time, Alice has two two apps
‣ Tropo AS dispatches an ‘outgoing call’ event to both apps via a secure call
+media control protocol called Rayo.
‣ In this example, the SFDC app (orange in color) makes a request to the Web
to log a call record in Alice’s CRM.
‣ Using the Route header provided in step 3, the Tropo AS sends the call back
to the CSCF allowing normal call processing to continue as normal.
SIP / ISC
Apps in your Calls