Routers

When you have several locations within your house where you’d like to have a computer, you have probably noticed that not all locations are equal. You’d like for each to have access to the same files and internet services. However, you only have one internet connection for a modem or cable, and you can’t splice it or run an additional cable because you have computers all over the house and don’t want to run messy, aesthetically unpleasing wires all through the house. You can find many aids on the internet or in the library to assist you in building a wireless home network setup.

A wireless home network setup is probably the solution to your problems. You’ll only need one wired workstation to begin configuring your setup, and you’ll be able to access the same information at all locations within the home. You’ll need some hardware, including network interface cards in all the wireless computers and other devices you plan to have on your network. With the help of additional resources, as well as following directions on all devices that are being installed, you’ll be able to determine exactly what you need and where it should be installed. Be sure that you also have information on the operating systems for all computers to be added to the network, as setup may be different for each one.

You’ll first need to find a location to mount the network access point. Look for tips, tricks, and other suggestions regarding locations that minimize obstructions and distance, as well as those that maximize reception capability. Note that the access point should be in the same place as the router, modem, or other internet capability connection for ease of setup. This will allow you to access the World Wide Web from all satellite locations once the system is configured. Both antennas of the access point should be perpendicular to the ground, though even with proper installation some obstacles may still interfere with reception. However, if installed in an area where distance to other devices within the network is minimized, your access point should be able to locate all wireless home network setup devices within your own home. Try to have the access point in a centralized area of the house for best results. Once you have the device set up, you can begin configuration. Follow manufacturer’s instructions for connecting to the hub and setting all options.

To test the wireless home network setup, turn on all the other devices you have put on the network for purpose of configuration. Instructions are available for all operating systems, and resources like http://netsupportcenter.com can assist you in the start up process. Make sure the wireless cards in these devices are set for Infrastructure or Access Point, rather than Ad Hoc mode. All channel, SSID, and WEP settings should also match the access point.

For the pure Internet Protocol (IP) forwarding function, router design tries to minimize the state information kept on individual packets. Once a packet is forwarded, the router should retain no more than statistical information about it. It is the sending and receiving endpoint that keeps information on such things as errored or missing packets.

Forwarding decisions can involve decisions at layers other than the IP internetwork layer or OSI layer 3. Again, the marketing term switch can be applied to devices that have these capabilities. A function that forwards based on data link layer, or OSI layer 2, information, is properly called a bridge. Marketing literature may call it a layer 2 switch, but a switch has no precise definition.

Among the most important forwarding decisions is deciding what to do when congestion occurs, i.e., packets arrive at the router at a rate higher than the router can process. Three policies commonly used in the Internet are Tail drop, Random early detection, and Weighted random early detection. Tail drop is the simplest and most easily implemented; the router simply drops packets once the length of the queue exceeds the size of the buffers in the router. Random early detection (RED) probabilistically drops datagrams early when the queue exceeds a configured size. Weighted random early detection requires a weighted average queue size to exceed the configured size, so that short bursts will not trigger random drops.

Control Plane processing leads to the construction of what is variously called a routing table or routing information base (RIB). The RIB may be used by the Forwarding Plane to look up the outbound interface for a given packet, or, depending on the router implementation, the Control Plane may populate a separate Forwarding Information Base (FIB) with destination information. RIBs are optimized for efficient updating with control mechanisms such as routing protocols, while FIBs are optimized for the fastest possible lookup of the information needed to select the outbound interface.

The Control Plane constructs the routing table from knowledge of the up/down status of its local interfaces, from hard-coded static routes, and from exchanging routing protocol information with other routers. It is not compulsory for a router to use routing protocols to function, if for example it was configured solely with static routes. The routing table stores the best routes to certain network destinations, the “routing metrics” associated with those routes, and the path to the next hop router.

Routers do maintain state on the routes in the RIB/routing table, but this is quite distinct from not maintaining state on individual packets that have been forwarded.