I believe it is a Download Manager (DLM) used by Adobe, Autodesk and many other major software companies to deliver downloads of big files. It is explained at http://www.akamai.com/client/ (see the FAQ section on the right side which has instructions on how to uninstall it. FYI: it will be installed again next time you download software that uses this download manager from one of those sites).
Download managers have several benefits like for example allowing people with older browsers to download files larger than 4GB.
I have installed NetSession on my PC as well and I do not see it affecting my system's performance. It has an icon in the control panel (system preferences in MAC) called "Akamai NetSession Interface" that allows you to find out which company you used that made you install that DLM