Internet Connection Sharing
As an Internet Connection Sharing (English: Internet Connection Sharing, ICS short ) refers to a functionality of the Microsoft Windows operating system that allows it without major technical effort to establish an Internet connection with one or more Windows computers.
In this case, the computer, the ICS makes available the services of Network Address Translation ( NAT), DHCP ( Dynamic Host Configuration Protocol ) and DNS ( Domain Name Service ) and thus makes it possible that computer ( clients) that are connected via LAN, the Internet connection can be used without any additional services or servers must be available.
On Windows, the function is since Windows 98 SE available. However there all clients on the subnet 192.168.0.0/24 need to be. For Windows 2000/XP/Vista, this is the network segment 192.168.0.x/24, the ICS server gets the 192.168.0.1. This can be changed. If you want to use with Windows 98 SE or ME Internet Connection Sharing of Windows NT from the series, so you have to, as described in the help, use a special client. In practice, the establishment of an Internet Connection Sharing on Windows 98SE and ME, however, is often more tedious and was prone to error - Windows 2000 Professional ICS is easily possible. Provided, however, that no other device provides the DHCP Server service on the same network is available, because this may only be available once per network because the access to it is not taxable. Modern DSL router or wireless router often offer a DHCP Server service. With the use of ICS DHCP on the router must be switched off, otherwise it may cause duplicate IP addresses.
With the advent of low-cost hardware router ( often available as a Wi-Fi version ), which are mostly offered at reduced prices with online contracts, the use of Windows' own "Internet Connection Sharing " has declined. Reasons for this are fairly simple installation and largely error-free operation of the router. These two points were 98 SE and Windows ME often a bigger issue on the Windows operating system versions.
Also under Windows XP is setting up an Internet Connection Sharing to be very error-prone, because the service is not activated often as desired or disabled. When assigning IP addresses ICS does not screen for conflicts with static addresses that are already used by computers on the network. By default, gets the computer, the ICS is enabled, the IP address 192.168.0.1. However, this can be changed, so problems can be eliminated by manually change the IP address.
On 30 October 2006 specialists discovered the ability to perform a DoS attack on the service. The vulnerability is caused by a null pointer reference in the Windows NAT Helper Components ( ipnathlp.dll ). Attackers can bring about a spoofed DNS query the service to crash. Currently no patch available. Through the Internet Sharing with PC can also cost a UMTS routers are built, since most UMTS router cost much more than a Windows XP license. Thus, the release of permanent work under Windows XP at UMTS devices, the UMTS Internet connection must be permanently displayed a dial-up connection. The software of Deutsche Telekom, this is not the case.