Internet Connection Sharing
Encyclopedia
Internet Connection Sharing (ICS) is the use of a device with Internet access such as 3G cellular service, broadband via Ethernet, or other Internet gateway as an access point for other devices. It was implemented by Microsoft as a feature of its Windows operating system (as of Windows 98 Second Edition and later) for sharing a single Internet
connection on one computer between other computers on the same local area network
. It makes use of DHCP
and network address translation
(NAT).
ICS offers configuration for other standard services and some configuration of NAT.
to the Internet. ICS maps individual IP address
es of local computers to unused port
numbers in the TCP/IP stack. Due to 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.
On the host computer the shared connection is made available to other computers by enabling ICS in Network Connections, and other computers that will connect to and use the shared connection. Therefore, ICS requires at least two network connections. Normally ICS is used when there are several network interface cards installed on the host. In special cases, only one network interface card is required and other connections may be logical. For example, the host may connect to Internet using a modem/router configured in the bridge mode
and share the PPPoE connection with ICS.
Starting with Windows XP, there are some improvements to ICS. Internet Connection Sharing is integrated with UPnP, allowing remote discovery and control of the ICS host. It also has a Quality of Service Packet Scheduler component. 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 calculcate 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.
Internet Connection Sharing 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. ICS is also location-aware, that is, when connected to a domain, the computer can have a Group Policy to restrict the use of ICS but when at home, ICS can be enabled.
The server will normally have the IP address 192.168.0.1 (changeable from the registry) and will provide NAT services to the whole 192.168.0.x subnet, even if the address on the client was set manually, not by the DHCP server. Windows 7 uses the subnet 192.168.137.x by default.
Besides making sure that the firewall settings are correct, for Windows XP hosts with more than one Ethernet interface card and a wireless WAN connection, bridging the Ethernet interface cards may help eliminating some ICS problems.
is required to resolve the condition. (eg.
access points, and other serial communication options have replaced widespread use of Internet Connection Sharing. These alternatives to using Internet Connection Sharing can utilize either dial-up networking (Most focus on the computer with a phone modem to act as a gateway server to the others sharing the connection) or other connection methods.
Internet
The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...
connection on one computer between other computers on the same local area network
Local area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
. It makes use of DHCP
Dynamic Host Configuration Protocol
The Dynamic Host Configuration Protocol is a network configuration protocol for hosts on Internet Protocol networks. Computers that are connected to IP networks must be configured before they can communicate with other hosts. The most essential information needed is an IP address, and a default...
and network address translation
Network address translation
In computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
(NAT).
ICS offers configuration for other standard services and some configuration of NAT.
Operation
ICS routes TCP/IP packets from a small LANLocal area network
A local area network is a computer network that interconnects computers in a limited area such as a home, school, computer laboratory, or office building...
to the Internet. ICS maps individual IP address
IP address
An Internet Protocol address is a numerical label assigned to each device participating in a computer network that uses the Internet Protocol for communication. An IP address serves two principal functions: host or network interface identification and location addressing...
es of local computers to unused port
Computer port (software)
In computer programming, port has a wide range of meanings.A software port is a virtual/logical data connection that can be used by programs to exchange data directly, instead of going through a file or other temporary storage location...
numbers in the TCP/IP stack. Due to 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.
On the host computer the shared connection is made available to other computers by enabling ICS in Network Connections, and other computers that will connect to and use the shared connection. Therefore, ICS requires at least two network connections. Normally ICS is used when there are several network interface cards installed on the host. In special cases, only one network interface card is required and other connections may be logical. For example, the host may connect to Internet using a modem/router configured in the bridge mode
Bridge mode
Bridge mode is a configuration option to enable Transparent Bridging.In 802.11a/b/g/n-type wireless networks, configuring bridge mode requires that the wireless side be configured to be a Station for a particular Access Point, so a configuration interface, often via an integrated webserver, is...
and share the PPPoE connection with ICS.
Starting with Windows XP, there are some improvements to ICS. Internet Connection Sharing is integrated with UPnP, allowing remote discovery and control of the ICS host. It also has a Quality of Service Packet Scheduler component. 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 calculcate 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.
Internet Connection Sharing 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. ICS is also location-aware, that is, when connected to a domain, the computer can have a Group Policy to restrict the use of ICS but when at home, ICS can be enabled.
Limitations
However, while ICS makes use of DHCP, there is no way to review DHCP leases using ICS. The service is also not customizable in terms of which addresses are used for the internal subnet, and contains no provisions for bandwidth limiting or other features. ICS also was designed to connect only to Windows OS computers: computers on other operating systems will require different steps to be able to utilize ICS.The server will normally have the IP address 192.168.0.1 (changeable from the registry) and will provide NAT services to the whole 192.168.0.x subnet, even if the address on the client was set manually, not by the DHCP server. Windows 7 uses the subnet 192.168.137.x by default.
Besides making sure that the firewall settings are correct, for Windows XP hosts with more than one Ethernet interface card and a wireless WAN connection, bridging the Ethernet interface cards may help eliminating some ICS problems.
Windows XP SP3 bug
Windows XP Service Pack 3 (SP3) introduces a problem that causes loss of ICS connectivity after certain activities (like disconnecting the network cable). Restart of the ICS Windows serviceWindows Service
On Microsoft Windows operating systems, a Windows service is a long-running executable that performs specific functions and which is designed not to require user intervention. Windows services can be configured to start when the operating system is booted and run in the background as long as...
is required to resolve the condition. (eg.
net stop SharedAccess & net start SharedAccess)
- In Microsoft support article KB951446, the process of restarting the ICS service is explained, but there is no mention of a plan to fix this bug in the future.
- In a later Microsoft support article KB951830, more details and a hotfixHotfixA hotfix was originally the term applied to software patches that were applied to live i.e. still running systems. Similar use of the terms can be seen in hot swappable disk drives...
(Update for Windows XP (KB951830)) are given. This hotfix is not currently being distributed via Windows UpdateWindows UpdateWindows Update is a service provided by Microsoft that provides updates for the Microsoft Windows operating system and its installed components, including Internet Explorer...
, and so it must be manually installed.
Other methods
With the advent of home- and personal networking in the mid-to-late 2000s, routers, Wi-FiWi-Fi
Wi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
access points, and other serial communication options have replaced widespread use of Internet Connection Sharing. These alternatives to using Internet Connection Sharing can utilize either dial-up networking (Most focus on the computer with a phone modem to act as a gateway server to the others sharing the connection) or other connection methods.
See also
- Dial-up accessDial-up accessDial-up Internet access is a form of Internet access that uses the facilities of the public switched telephone network to establish a dialled connection to an Internet service provider via telephone lines...
- Firewall (computing)Firewall (computing)A firewall is a device or set of devices designed to permit or deny network transmissions based upon a set of rules and is frequently used to protect networks from unauthorized access while permitting legitimate communications to pass....
- ModemModemA modem is a device that modulates an analog carrier signal to encode digital information, and also demodulates such a carrier signal to decode the transmitted information. The goal is to produce a signal that can be transmitted easily and decoded to reproduce the original digital data...
- Network address translationNetwork address translationIn computer networking, network address translation is the process of modifying IP address information in IP packet headers while in transit across a traffic routing device....
- Proxy ServerProxy serverIn computer networks, a proxy server is a server that acts as an intermediary for requests from clients seeking resources from other servers. A client connects to the proxy server, requesting some service, such as a file, connection, web page, or other resource available from a different server...
- Router
- Wi-FiWi-FiWi-Fi or Wifi, is a mechanism for wirelessly connecting electronic devices. A device enabled with Wi-Fi, such as a personal computer, video game console, smartphone, or digital audio player, can connect to the Internet via a wireless network access point. An access point has a range of about 20...
and Wireless LANWireless LANA wireless local area network links two or more devices using some wireless distribution method , and usually providing a connection through an access point to the wider internet. This gives users the mobility to move around within a local coverage area and still be connected to the network...
External links
- Configuring ICS to use a different IP Range other than 192.168.0.*, on XP (ex: 192.168.2.*, 192.168.3.*, etc)
- Annoyances.org - Setting up Internet Connection Sharing
- Microsoft.com - Description of Internet Connection Sharing
- Microsoft.com - Setting Up Internet Connection Sharing With XP
- Microsoft.com - Setting Up Internet Connection Sharing With Vista
- Sniperxpx.com - How to use Internet Connection Sharing between two computers
- Setup Internet Connection Sharing between two or more computers tutorial
- Internet Connection Sharing Setup Tutorial (XP and Vista)