Mark Stuart Day is Chief Scientist at Netskope. From time to time he is a Visiting Lecturer at the Massachusetts Institute of Technology (MIT). He was formerly Chief Scientist at Riverbed Technology for 10 years as the company grew from about 40 people to more than 2500 people, and from less than a million dollars to more than a billion dollars in revenue.

Before Riverbed, he was technical leader for product management in the content networking business unit of Cisco Systems. He joined Cisco with the acquisition of SightPath, a Boston-area startup, in 2000. Previously, he was at Lotus, where his work contributed to the creation of Lotus Sametime.

In the IETF, he was founding chair of the working group on Content Internetworking (CDI) and was closing co-chair of the working group on Instant Messaging and Presence Protocol (IMPP). He is an author of RFCs 2778 and 2779, which define the terms and requirements for interoperable presence and instant messaging and have been widely cited in both IETF and non-IETF work.

His first job after college was at BBN. There he was responsible for the first testing of the NU network management system for the Arpanet, predecessor to the Internet.

He has 38 issued patents relating to presence, streaming media, content networking, mobile communications, security, and telephony. His most commercially significant invention is split termination for secure communication protocols, which is the basis for the SSL optimization features offered in the Riverbed Steelhead product line since 2007. His other notable technical work includes contributions to the programming languages Argus and Theta and to the distributed object database Thor.

In 2013 he was a Visiting Fellow at the Hariri Institute of Boston University. During fall term 2002, he held an adjunct appointment at Harvard University, co-teaching the graduate database class.

He is a member of the Municipal Broadband Committee of the Town of Milton, Massachusetts. He served for several years on the Governing Board of Harvard Yard Child Care Center, including three years as chair of Governing Board. He has also served as Moderator for the Parent Association of Boston University Academy, and served on the Building Committee that oversaw historic restoration work at All Saints Parish, Ashmont.

During the early 1990’s, he was lead singer for the Boston-area power-pop bands Anunga Runga, Condom Nation, LawnBoy 2000, and Hop on Pop.

He received his Ph.D. from MIT in 1995.