Amodem (e.g.DSL modem,cable modem) by itself provides none of the functions of a router.[3] It merely allowsATM orPPP orPPPoE traffic to be transmitted across telephone lines, cable wires, optical fibers, wireless radio frequencies, or other physical layers.[4] On the receiving end is another modem that re-converts the transmission format back into digital data packets.[5]This allows network bridging using telephone, cable, optical, and radio connection methods. The modem also provideshandshake protocols, so that the devices on each end of the connection are able to recognize each other.[6] However, a modem generally provides few other network functions.
AUSB modem plugs into a single PC and allows a connection of that single PC to a WAN. If properly configured, the PC can also function as the router for a home LAN.
Aninternal modem can be installed on a single PC (e.g. on aPCI card), also allowing that single PC to connect to a WAN.[7] Again, the PC can be configured to function as a router for a home LAN.
A cellularwireless access point can function in a similar fashion to a modem. It can allow a direct connection from a home LAN to aWWAN, if a wireless router or access point is present on the WAN as well andtethering is allowed.
Many modems now incorporate the features mentioned below and thus are appropriately described as residential gateways, such as some Internet providers which offer a cable modem router combo.[8]
Most gateways are self-contained components, using internally stored firmware. They are generally platform-independent, i.e., they can serve anyoperating system.
Wireless routers perform the same functions as a wired router and base station, but allow connectivity for wireless devices with the LAN, or as abridge between the wireless router and another wireless router for ameshnet (the wireless router-wireless router connection can be within the LAN or can be between the LAN and WWAN).[14]
Low-cost production and requirement for user friendliness make gateways vulnerable to network attacks, which resulted in large clusters of such devices being taken over and used to launch DDoS attacks.[15] A majority of the vulnerabilities were present in the web administration frontends of the routers, allowing unauthorized control either viadefault passwords, vendorbackdoors, orweb vulnerabilities.[16]
^Penttinen, Jyrki T. J. (2015).The Telecommunications Handbook: Engineering Guidelines for Fixed, Mobile and Satellite Systems. John Wiley & Sons. p. 91.ISBN9781118678886.
