TMS zl Management and Configuration Guide ST.1.0.090213

4-5
Firewall
Overview
Advantages of an Integrated Firewall
Although firewall software can protect individual PCs, a firewall integrated
into a switch has several advantages:
■ Software firewalls often use mainstream operating systems. Attackers
study such systems for vulnerabilities. These operating systems are more
vulnerable to targeted attacks and sporadic lock-ups, which can take
down your firewall and leave your network unprotected.
■ A switch firewall protects your network entry points, stopping threats
before they get through the switch.
■ A firewall integrated with a switch allows your organization to enforce a
standard security policy for all hosts.
Stateful Firewall
The TMS zl Module has a stateful firewall, which examines packet content at
several OSI layers. It combines aspects of:
■ A packet-filtering firewall
■ A circuit-level gateway
■ An application-level gateway
Packet-Filtering Firewall
A packet-filtering firewall is a router, switch, or computer that runs firewall
software that has been configured to screen incoming and outgoing packets.
Operating at the Network Layer (Layer 3) of the OSI model, a packet-filtering
firewall accepts or denies packets based on information contained in the
packet’s TCP and IP headers.
You must establish the access policies against which a packet-filtering firewall
compares the full association of the packets. Policies consist of the following:
■ Source zone
■ Destination zone
■ Source address
■ Destination address
■ Protocol
■ Source port number
■ Destination port number
See “Firewall Access Policies” on page 4-19.