Per Cisco:

The Cisco Secure Services Client (CSSC) is a software client that enables customers to deploy a single authentication framework using the 802.1X authentication standard across multiple device types to access both wired and wireless networks. A lightweight version of the CSSC client is also a component of the Cisco Trust Agent (CTA) within the Cisco Network Admission Control (NAC) Framework solution.

It is Ciscos' xsupplicant client for 802.1x