It is certainly not included with Windows, nor is it required for Windows to work properly. It will have been installed when some third-party software was installed or updated, Flash Player being one possibility.
This page explains what it is & what it does: http://www.akamai.com/html/solutions/client_faq.html
Take note of where it says it can use some of your upload bandwidth "to allow other users of the NetSession interface to download pieces of the publisher's content from your computer"
(like P2P software).
That alone would be enough for me to uninstall it asap.
Uninstall instructions are halfway down the page whose link I have provided above.