RFC 4282:The Network Access Identifier
RFC-Ref

tunnel


Click on the red underlined text to get to the source

... Layer 2 Tunneling Protocol (L2TP) [RFC2661], and the IPsec tunnel mode [RFC2401]. ...
... PPTP, L2F, L2TP, and IPsec tunnel mode. One example of a tunneling service is secure access ...
... NASes will use the NAI as part of the process of opening a new tunnel, in order to determine the tunnel endpoint. ...
... NAI as part of the process of opening a new tunnel, in order to determine the tunnel endpoint. ...



Google
Web
RFC-Ref