Q&A: SIP pioneer/Cisco Fellow jumps ship to Skype

Jonathan Rosenberg, co-author of the Session Initiation Protocol, joined Skype in November 2009 as chief technology strategist to apply what he's learned about disruptive IP technologies. He's learned a lot. He began working on IP communications in 1996 at Bell Laboratories, and left there in 1999 to join start-up Dynamicsoft as CTO working on service provider VoIP. Cisco acquired that company in 2004 and Rosenberg stayed there for five years working on both service provider and enterprise VoIP, ultimately becoming a Cisco Fellow. Besides SIP, Rosenberg was inventor of SIMPLE - SIP for presence and IM, and is the principal author of multiple VoIP firewall and NAT transversal technologies. Network World Editor in Chief John Dix caught up with Rosenberg over a Skype voice connection to see what the Skype lure was for him.

What do you do at Skype?

My role is to direct our high-level system-level architectures across our products and work on our technology strategies and figure out what areas of investment we make, which technologies we bet on. That is a pretty broad mandate, especially for one guy, so I tend to focus on particular areas in projects. Much of my work has been focused in two areas, the Web and Skype For Business.

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Jonathan Rosenberg, co-author of the Session Initiation Protocol, joined Skype in November 2009 as chief technology strategist to apply what he's learned about disruptive IP technologies. He's learned a lot. He began working on IP communications in 1996 at Bell Laboratories, and left there in 1999 to join start-up Dynamicsoft as CTO working on service provider VoIP. Cisco acquired that company in 2004 and Rosenberg stayed there for five years working on both service provider and enterprise VoIP, ultimately becoming a Cisco Fellow. Besides SIP, Rosenberg was inventor of SIMPLE - SIP for presence and IM, and is the principal author of multiple VoIP firewall and NAT transversal technologies. Network World Editor in Chief John Dix caught up with Rosenberg over a Skype voice connection to see what the Skype lure was for him.

What do you do at Skype?

My role is to direct our high-level system-level architectures across our products and work on our technology strategies and figure out what areas of investment we make, which technologies we bet on. That is a pretty broad mandate, especially for one guy, so I tend to focus on particular areas in projects. Much of my work has been focused in two areas, the Web and Skype For Business.

Speaking of architecture, can you give us a thumbnail of the Skype architecture at this point? Has it evolved much?

Wow, that is a big question. As with any technology that has added new products, Skype has seen a lot of change over the years. We've added mobile, we've invested in business via the Skype for SIP product and we've invested in video calling features, all of which have had an impact on our architecture. But we remain a peer-to-peer service for many of our core features and functionality and that works in concert with back-end services and infrastructure that support many of our paid products. So we are a hybrid technology today.

Still no Skype backbone to speak of, right?

We don't have a dedicated IP network.

Every time I log onto Skype I see there are X million number of people online, but what does the Skype customer universe look like?

We have approximately 560 million registered users and we have online simultaneously around 23 million users at a time, which is something we're proud of. In terms of minutes, we've done about 250 billion worth of minutes of Skype-to-Skype calls since we started and now account for 12% of all international calls -- not voice over IP international calls, all international calls worldwide -- a growth of 50% year-over-year compared to 2009. So that is huge. We are preloaded on eight out of 10 PC's. And in terms of financials we exited 2009 with about $716 million in revenues, which is 30% annualized growth.

Of that international traffic, is that mostly voice calling or a combination of voice and video?

Glad you asked. Very much a combination of voice and video. Approximately 36% of all our Skype-to-Skype calls include video and that is a number that peaks at over 50% on holidays like Mother's Day. In fact, if you multiply those numbers together -- we represent 12% of international traffic and 36% of that is video -- it means 4% of the world's international long distance traffic is now video based and that is an astounding number given it was effectively nonexistent just a couple years ago.