List of Figures

• Conceptual View of Services and Layers in TCP/IP.
• TELNET Port, IP Interaction.
• Router and Application Gateway Firewall Example.
• Use of Advanced Authentication on a Firewall to Preauthenticate TELNET, FTP Traffic.
• Representation of Packet Filtering on TELNET and SMTP.
• Virtual Connection Implemented by an Application Gateway and Proxy Services.
• Packet Filtering Firewall.
• Dual-homed Gateway Firewall with Router.
• Screened Host Firewall.
• Screened Subnet Firewall with Additional Systems.
• Modem Pool Placement with Screened Host Firewall.
• Modem Pool Placement with Screened Subnet and Dual-Homed Firewalls.