NETGEAR DG824M - Manual (Page 121)

Reference Manual for the Model DG824M Wireless ADSL Modem Gateway
Network and Routing Basics B-13
Stateful Packet Inspection
Unlike simple Internet sharing routers, a firewall uses a process called stateful packet inspection to
ensure secure firewall filtering to protect your network from attacks and intrusions. Since
user-level applications such as FTP and Web browsers can create complex patterns of network
traffic, it is necessary for the firewall to analyze groups of network connection "states." Using
Stateful Packet Inspection, an incoming packet is intercepted at the network layer and then
analyzed for state-related information associated with all network connections. A central cache
within the firewall keeps track of the state information associated with all network connections.
All traffic passing through the firewall is analyzed against the state of these connections in order to
determine whether or not it will be allowed to pass through or rejected.
Denial of Service Attack
A hacker may be able to prevent your network from operating or communicating by launching a
Denial of Service (DoS) attack. The method used for such an attack can be as simple as merely
flooding your site with more requests than it can handle. A more sophisticated attack may attempt
to exploit some weakness in the operating system used by your router or gateway. Some operating
systems can be disrupted by simply sending a packet with incorrect length information.
Wireless Networking
The DG824M gateway conforms to the Institute of Electrical and Electronics Engineers (IEEE)
802.11b standard for wireless LANs (WLANs). On an 802.11b wireless link, data is encoded using
direct-sequence spread-spectrum (DSSS) technology and is transmitted in the unlicensed radio
spectrum at 2.5GHz. The maximum data rate for the wireless link is 11 Mbps, but it will
automatically back down from 11 Mbps to 5.5, 2, and 1 Mbps when the radio signal is weak or
when interference is detected.
The 802.11b standard is also called Wireless Ethernet or Wi-Fi by the Wireless Ethernet
Compatibility Alliance (WECA, see http://www.wi-fi.net), an industry standard group promoting
interoperability among 802.11b devices.
Wireless Network Configuration
The 802.11b standard offers two methods for configuring a wireless network - ad hoc and
infrastructure.