What is SIP and why do I care?

Tropo sits in Voxeo’s live communications cloud; an environment specifically designed for real-time voice, instant messaging and SMS applications. On the voice side, a key feature of the Tropo platform is its extensive support for SIP. The Session Initiation Protocol is a Voice over IP (VoIP) technology enabling two ends of a conversation (or session) to negotiate media formats much like the Accepts/Content-Type header does for HTTP.

As a voice provider, SIP is the best way to guarantee seamless interoperability between existing phone systems, carriers and call centers. Not having SIP is like playing Call of Duty on a 15” with no HDMI. Sure it technically works…. but why?!?

Read on for real world example.

In this example, Acme Flowers has an Asterisk based phone system that rings two sales people (Bob and Alice) when a call comes in on 555-1212. Before integrating with Tropo, the phone system would simply drop the caller into voicemail if no one was available.

Tropo FTW! With a couple tweaks, callers are now automatically transferred to a voice-driven menu in the Tropo cloud, providing them with driving directions, order status and store hours all over the Internet, all with industry leading speech synthesis and speech recognition. No extra phone line. No additional telco charges. On top of that, customers get all the same services via SMS and IM using the same exact code!

SIP allows Tropo applications to seamlessly integrate with existing phone systems and call centers over the Internet; cutting the telco out entirely!

Enabled on every app!

Tropo assigns a personal SIP address for every application. This special address is accessible from any modern phone system or SIP-enabled device. You can also use  a soft phone like SJPhone for Mac/PC or iSIP / fring for the iPhone.

Give it a try now by calling my demo app at sip:9991429776@sip.tropo.com

SIP Headers

Ever been asked for your account information 20 times only to be transferred to a live person who has no idea who you are or why you’re calling? The problem lies in that most phone systems are a black box, blindly sending calls from one department to another. SIP solves this problem by allowing phone systems to exchange information in between hops. 

SIP borrows many concepts from HTTP; one of which is the concept of a header. When SIP endpoints communicate, they send key/value pairs that help route the call. Wouldn’t it be nice if you could leverage this pipeline to communicate non-telephony data? With Tropo, you certainly can. 

Tropo exposes SIP headers to your application on every incoming call allowing your application to easily integrate with other systems.

Further reading

To learn more about SIP and related technologies check out these sites:

• SIP Overview @ Wikipedia – http://en.wikipedia.org/wiki/Session_Initiation_Protocol
• VoIP Info – http://www.voip-info.org/wiki/view/SIP
• IETF SIP Specification (not for the faint of heart) – http://www.ietf.org/rfc/rfc3261.txt

That’s it for now. I hope to follow up this post with more examples of using Tropo and SIP to unlock you calls.

Until then,

Good Hunting

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