Windows Firewall
Internet Connection Sharing
Windows Internet Connection Firewall and Windows Internet Connection Sharing are components of Windows XP for small business networks or home networks to connect and manage connections to the Internet. Windows Firewall is a software firewall for Windows XP which protects the computer from intruders on the Internet. Internet Connection Sharing (ICS) allows a small business or home network to share a connection to the Internet from one Windows XP computer which then allows other computers to pass through this computer's connection to also allow access to the Internet.
Windows XP Firewall
The Windows XP Firewall protects the computer and network by limiting or preventing access to the computer and the private business network from the Internet. The Windows XP Firewall uses port mapping to determine if inbound connections should be allowed into the private network and also provides stateful firewall protection, monitoring additional aspects of the network traffic and providing a deeper inspection of network packets than Network Address Translation (NAT) provides.
Windows Internet Connection Firewall
To enable the Windows Internet Connection Firewall protection, from the Start Menu, click on Network Connections, and then double click on the network adapter for the Internet connection. Click on the Properties button and select the Advanced tab from the properties dialog box. Under Internet Connection Firewall, check the box: Protect my computer and network by limiting or preventing access to this computer from the Internet.
Windows Firewall Security Logging
A security audit logging feature is provided with the Windows XP Firewall. The control panel for Windows Firewall Security Logging is accessed from the Internet connection properties dialog box by selecting the Settings button from the Advanced tab. The option to log dropped packets will record all connection attempts that have been denied by the Window Firewall. The option to log successful connections will record all successful connections that pass through the windows firewall. Internet Control Message Protocol (ICMP), is part of the TCP network protocol suite and is an error detection and correction protocol that reports errors and network packet delivery information such as outgoing time exceeded or if the destination host is unreachable. ICMP allows computers on a network to share error and status information. Windows Firewall allows the user to select requests for information from the Internet that the host computer will respond to such as whether the host computer will respond to incoming echo requests issued from the ping command. Data sent from the host computer can then be acknowledged with a confirmation message that indicates the time the data was received.
Windows Internet Connection Sharing
To enable and configure the sharing of an Internet connection in a small business network, one computer will be configured with a connection to the Internet. This computer will also have another connection to its private business network. The connection to the Internet can be a dial-up modem or network adapter with a high-speed connection such as a network interface card (NIC), cable modem, Digital Subscriber Line (DSL) or T1 Internet connection. The computer that maintains the connection to the Internet acts as the computer network ICS host. Other computers on the business network that connect through the host are client ICS computers.
Internet Connection Sharing Host
Once the Internet Connection Sharing host computer has been configured with a connection to the Internet, ICS is enabled on the network device that is connected to the Internet, so that the Internet connection can be shared with other computers on the business network. After ICS has been enabled host computer, the TCP-IP address of the ICS host will be configured with a static IP address of 192.168.0.1 with a default subnet mask of 255.255.255.0. This statically assigned network address defines the private business network: the 192.168.0.nnn (nnn=2-254) network. The ICS host computer will act as a DHCP server to dynamically assign network addresses in the 192.168.0 range to ICS client computers.
Internet Connection Sharing Client
In order for Internet Connection Sharing client computers to pass through the ICS host to get out to the Internet, each client will need to have an IP address on the 192.168.0.nnn network. A total of 252 client computer can be assigned from the network address range of 192.168.0.2 thru 192.168.0.254. To allow the client computers to obtain an IP address from this range, each client computer is configured to obtain its IP address automatically from a DHCP server. Once ICS has been enabled on the host computer and the client computers have an IP address from this range of private IP addresses, the client computers are able to find the Internet Connection Sharing host because the ICS host will advertise its shared Internet connection to the client computers with a network broadcast message on the private business network.
