VPN (Virtual Private Network) is a network implemented on top of another network, and private from it, providing transparent services between networks or devices and networks. VPNs often use some form of cryptographic security to provide this separation.
Relevant NENA Documents
Note: To find and download the document, copy the document number (like NENA-STA-010) from below and search the NENA Standards and Documents page.
NENA 75-001, NENA Security for Next-Generation 9-1-1 Standard (NG-SEC)