Residential gateway

From DSL router

This article is about the types of network routers and modems found in many homes, known colloquially as "residential gateways".

There are multiple devices that have been described as "residential
gateways," each with a quite different function. Each type of device
allows the connection of a LAN (used in the home) to a WAN (wide area network).
The WAN can be the "Internet" or can merely be a larger LAN of which
the home is a part (such as a municipal WAN that provides connectivity
to the residences within the municipality).

The term "residential gateway" was originally used to distinguish
the inexpensive networking devices designated for use in the home from
similar devices used in corporate LAN environments (which generally
offered a greater array of capabilities). In recent years, however, the
less expensive "residential gateways" have gained many of the
capabilities of corporate gateways and the distinctions are fewer. Many
home LANs now are able to provide most of the functions of small
corporate LANs.
Therefore the term "residential gateway" is becoming obsolete and
merely implies a less expensive, lower capability networking device.
Multiple devices have been described as "residential gateways":

• Cable Modems
• DSL modems
• Routers or wireless routers
• Switch
• VoIP ATA
• Wireless access points
• Or, Any combination of the above

Types
A router provides:

• IP address routing
• network address translation (NAT)
• DHCP functions
• firewall functions
• LAN connectivity like a network switch

Most routers are self-contained components, using internally-stored
firmware. They are generally OS-independent (i.e. can be used with any operating system).

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• Wireless routers
  perform the same functions as a router, but also allows connectivity
  for wireless devices with the LAN, or between the wireless router and
  another wireless router. (The wireless router-wireless router
  connection can be within the LAN or can be between the LAN and a WAN).
• A modem (or ADSL modem)
  provides none of the functions of a router. It merely allows digital
  Ethernet data traffic to be modulated into analogue information
  suitable for transmission across telephone lines, cable wires, optical
  fibers, or wireless radio frequencies. On the receiving end is another
  modem that re-converts the transmission format back into digital data
  packets.
• This allows network bridging using telephone, cable, optical, and
  radio connection methods. The modem also provides handshake protocols,
  so that the devices on each end of the connection are able to recognize
  each other. However, a modem generally provides few other network
  functions.

• A USB
  modem plugs into a single PC and allow connection of that single PC to
  a WAN. If properly configured, the PC can also function as the router
  for a home LAN.
• An internal modem can be installed on a single PC (e.g. on a PCI card), also allowing that single PC to connect to a WAN. Again, the PC can be configured to function as a router for a home LAN.

• A wireless access point
  can function in a similar fashion to a modem. It can allow a direct
  connection from a home LAN to a WAN, if a wireless router or access
  point is present on the WAN as well.