Taking SIP Beyond Dial Tone

by Andrew Prokop | Arrow Systems Integration

Source: No Jitter

If you are like most people in the communications industry, you will tell me that SIP is used to make telephone calls. Some of you might also mention point-to-point or multiparty video, but in general, most people think of SIP as a way to make some sort of call -- SIP for physical, soft, and mobile telephones and telephone-like devices.

While these are certainly valid uses of SIP, the notion of making calls only scratches the surface of what it can do. I often wonder how different our impressions would be if the inventors of SIP had chosen to pioneer a different use case. Would we still think of it as a replacement for TDM telephony if the first SIP-enabled devices had been electrocardiogram monitors?

If you have been following my articles, you may have picked up that for many years I was a software developer working on SIP endpoints and backend services. During that time, I wrote thousands of lines of Java and C++ code that established and managed SIP calls. However, I also wrote just as many lines that had nothing to do with calling.

For instance, I once worked on a project that used SIP to create a shared whiteboard/drawing space. Think of extending the Microsoft Paint program across the Internet; two people could play with the same drawing canvas at the same time. SIP was used to send commands and graphics coordinates to draw lines, curves, points, and write text.

Around the same time, I did something similar for a network chess program. This application used SIP to convey chess moves from one PC to another across a LAN or WAN.

One of my more interesting creations was a method to pass clipboard data between different PCs. A user was able to do a copy (Ctrl+C) on one PC, and another user could paste (Ctrl+V) that data on a different PC. How did that data get from one machine to the other? With SIP, of course.

The point is that SIP can be used for things far beyond dial tone. While it's certainly true that telephony is currently the largest user of SIP, there may come a day when voice traffic has been dwarfed by other forms of media.


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