Hi,
Symantec Network Access Control protects networks from unauthorized, misconfigured, and infected endpoint computing devices. For example, Symantec Network Access Control can deny network access to the client computers that do not run specific versions of software and signatures. If client computers do not comply, Symantec Network Access Control can quarantine and remediate the computers. For example, if client computers have antivirus definitions that are more than a week old, Symantec Network Access Control can quarantine the computers. Symantec Network Access Control can update the computers with the latest antivirus definitions (remediation), and then permit the computers to access the network.
Title: 'What is Symantec Network Access Control?'
Web URL: http://service1.symantec.com/support/ent-security....
Check this article as well:
What's new in SNAC 12.1
https://www-secure.symantec.com/connect/articles/whats-new-snac-121