Internet Connection Sharing (ICS) is a
Windows service that enables one
Internet
The Internet (or internet) is the global system of interconnected computer networks that uses the Internet protocol suite (TCP/IP) to communicate between networks and devices. It is a ''internetworking, network of networks'' that consists ...
-connected computer to share its Internet connection with other computers on a
local area network
A local area network (LAN) is a computer network that interconnects computers within a limited area such as a residence, school, laboratory, university campus or office building. By contrast, a wide area network (WAN) not only covers a larger ...
(LAN). The computer that shares its Internet connection serves as a
gateway device, meaning that all traffic between other computers and the Internet go through this computer. ICS provides
Dynamic Host Configuration Protocol (DHCP) and
network address translation (NAT) services for the LAN computers.
ICS was a feature of
Windows 98 SE and all versions of
Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
released for personal computers thereafter.
Operation
ICS routes
TCP/IP packets from a small LAN to the Internet. ICS provides NAT services, mapping individual
IP address
An Internet Protocol address (IP address) is a numerical label such as that is connected to a computer network that uses the Internet Protocol for communication.. Updated by . An IP address serves two main functions: network interface ident ...
es of local computers to unused
port
A port is a maritime facility comprising one or more wharves or loading areas, where ships load and discharge cargo and passengers. Although usually situated on a sea coast or estuary, ports can also be found far inland, such as ...
numbers in the sharing computer. Because of the nature of the NAT, IP addresses on the local computer are not visible on the Internet. All packets leaving or entering the LAN are sent from or to the IP address of the external adapter on the ICS host computer.
Typically, ICS can be used when there are several
network interface cards installed on the host computer. In this case, ICS makes an Internet connection available on one network interface to be accessible to one other interface that is explicitly designated as the private network. ICS can also share
dial-up (including
PSTN
The public switched telephone network (PSTN) provides infrastructure and services for public telecommunication
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other el ...
,
ISDN
Integrated Services Digital Network (ISDN) is a set of communication standards for simultaneous digital transmission of voice, video, data, and other network services over the digitalised circuits of the public switched telephone network. Wor ...
and
ADSL
Asymmetric digital subscriber line (ADSL) is a type of digital subscriber line (DSL) technology, a data communications technology that enables faster data transmission over copper telephone lines than a conventional voiceband modem can provide. ...
connections),
PPPoE
The Point-to-Point Protocol over Ethernet (PPPoE) is a network protocol for encapsulating Point-to-Point Protocol (PPP) frames inside Ethernet frames. It appeared in 1999, in the context of the boom of DSL as the solution for tunneling packets ...
and
VPN connections.
Starting with Windows XP, ICS is integrated with
UPnP
Universal Plug and Play (UPnP) is a set of networking protocols that permits networked devices, such as personal computers, printers, Internet gateways, Wi-Fi access points and mobile devices to seamlessly discover each other's presence on the n ...
, allowing remote discovery and control of the ICS host. It also has a Quality of Service Packet Scheduler component.
[Windows XP Quality of Service (QoS) enhancements and behavior](_blank)
/ref> When an ICS client is on a relatively fast network and the ICS host is connected to the Internet through a slow link, Windows may incorrectly calculate the optimal TCP receive window size based on the speed of the link between the client and the ICS host, potentially affecting traffic from the sender adversely. The ICS QoS component sets the TCP receive window size to the same as it would be if the receiver were directly connected to the slow link. ICS also includes a local DNS resolver in Windows XP to provide name resolution for all network clients on the home network, including non-Windows-based network devices.
When connected to a Windows domain, the computer can have a Group Policy
Group Policy is a feature of the Microsoft Windows NT family of operating systems (including Windows 7, Windows 8.1, Windows 10, Windows 11, and Windows Server 2003+) that controls the working environment of user accounts and computer accounts. ...
to restrict the use of ICS, but when at home, ICS can be enabled.
Limitations
The service is not customizable in terms of which addresses are used for the internal subnet, and contains no provisions for bandwidth limiting or other features. ICS was initially designed to connect only to Windows computers: computers on other operating systems required different steps to utilize ICS.Windows Registry
The Windows Registry is a hierarchical database that stores low-level settings for the Microsoft Windows operating system and for applications that opt to use the registry. The kernel, device drivers, services, Security Accounts Manager, and u ...
.) It provides NAT services to the entire 192.168.0.x subnet, even if the address on the client was set manually, not by the DHCP server. Since Windows 7
Windows 7 is a major release of the Windows NT operating system developed by Microsoft. It was released to manufacturing on July 22, 2009, and became generally available on October 22, 2009. It is the successor to Windows Vista, released nearl ...
, the 192.168.137.x subnet has been used by default.
Alternatives
Alternatives to ICS include hardware home routers and Wireless access points with integrated Internet access hardware, such as broadband over power lines
Broadband over power lines (BPL) is a method of power-line communication (PLC) that allows relatively high-speed digital data transmission over the public electric power distribution wiring. BPL uses higher frequencies, a wider frequency range a ...
, WiMAX
Worldwide Interoperability for Microwave Access (WiMAX) is a family of wireless broadband communication standards based on the IEEE 802.16 set of standards, which provide physical layer (PHY) and media access control (MAC) options.
The WiMA ...
or DSL modems
A digital subscriber line (DSL) modem is a device used to connect a computer or router to a telephone line which provides the digital subscriber line (DSL) service for connection to the Internet, which is often called ''DSL broadband''. The m ...
.
See also
* Proxy server
In computer networking, a proxy server is a server application that acts as an intermediary between a client requesting a resource and the server providing that resource.
Instead of connecting directly to a server that can fulfill a requ ...
* SOCKS
A sock is a piece of clothing worn on the feet and often covering the ankle or some part of the calf. Some types of shoes or boots are typically worn over socks. In ancient times, socks were made from leather or matted animal hair. In the lat ...
References
External links
Microsoft.com - Description of Internet Connection SharingMicrosoft.com - Setting Up Internet Connection Sharing With XPMicrosoft.com - Setting Up Internet Connection Sharing With VistaMicrosoft.com - Using ICS (Internet Connection Sharing) ''with Windows 7''
{{Windows Components
Windows communication and services
Routing software