authentication --Process during which any unrecognized command causes the Cisco IOS Firewall to drop the packet and close the connection.
CBAC --Context-Based Access Control. A Cisco IOS Firewall set feature that scrutinizes source and destination addresses to enhance security for TCP and UDP applications that use well-known ports, such as FTP and e-mail traffic.
ESMTP --Extended Simple Mail Transfer Protocol. An extended version of the Simple Mail Transfer Protocol (SMTP), which includes additional functionality, such as delivery notification and session delivery.
IMAP --Internet Message Access Protocol. A method of accessing e-mail or bulletin board messages kept on a mail server that can be shared. IMAP permits client e-mail applications to access remote message stores as if they were local without actually transferring the message.
POP --Post Office Protocol. A protocol that client e-mail applications use to retrieve mail from a mail server.
SMTP --Simple Mail Transfer Protocol. An Internet protocol providing e-mail services.
SSL --Secure Socket Layer Protocol. This protocol is used to deliver secure information over the Internet.
state router --A router that tracks the client/server commands until the client is authenticated.
TCP --Transmission Control Protocol. A connection-oriented transport layer protocol that provides reliable full-duplex data transmission. TCP is part of the TCP/IP protocol stack.
UDP --User Datagram Protocol. A connectionless transport-layer protocol for exchanging datagrams without acknowledgments or guaranteed delivery.
VPN --Virtual Private Network. A network that enables IP traffic to travel securely over a public TCP/IP network by encrypting all traffic from one network to another. A VPN network uses "tunneling" to encrypt all information at the IP level.