Mark Townsley

Cisco Fellow

Cisco Development Organization

Mark Townsley is a Cisco Fellow currently focused on the challenges of IPv4 address exhaustion and IPv6 deployment. Mark has over 20 years experience as a software engineer, joining Cisco from IBM in 1997. Mark’s first task at Cisco was the implementation of L2TP in Cisco’s IOS, as well as the scaling of virtual interfaces in IOS to support the new challenges of large-scale dialup and broadband deployment. Mark has authored a number of IETF RFCs including the L2TP specification itself (RFC 2661), served as co-chair of the IETF L2TP Extensions Working Group, Technical Advisor to the IETF PWE3 Working Group, and two terms as IETF Internet Area Director and member of the IESG as well as IESG liaison to the Internet Architecture Board (IAB).

As Internet Area Director, Mark was responsible for the standardization of a number of Internet protocols, including IPv6, DNS, MPLS VPNs, Pseudowires, DHCP, PPP, L2TP, and Mobile IP, among others. Mark earned his BS in Electrical Engineering from Auburn University and MS in Computer Science from Johns Hopkins University. He also teaches part-time at École Polytechnique. When not traveling, Mark lives with his wife and family in Paris, France.


Happy First Birthday, World IPv6 Launch!

2 min read

No more tests, no more trials, IPv6 has left the laboratory -- for good. Happy First Birthday, World IPv6 Launch! May you have many, many, more.

November 19, 2012


Worldwide IPv6 Usage Reaches Key Threshold

4 min read

The aim of the World IPv6 Launch was to spark a steady, sustained, growth of IPv6 usage leading up to and continuing after June 6, 2012. The continued growth since June 6 and the milestone reached this weekend is an indicator that this commitment had its intended affect thus far. Cisco now has its own AS (#109) on the network operator list, making it the first in the world that is participating in all three categories of the World IPv6 Launch. User activity as measured by Google hit 0.25% for the first time in March 2011. A year later, on March 10, 2012, it doubled to 0.5% for the first time. It's taken about 8 months to double that again to reach 1.0% today. If this trend continues, it will double again by mid next year and could break past 10% by the end of 2014. The trend is increasingly clear: If you are a network operator, network-enabled application developer, or anyone else that works with IP and are not running IPv6 now or don't have a plan in place to make it happen soon, now is the time to get started.