Ethernet based networks primarily use the protocol of the Internet
(TCP/IP), they allow an easy and seamless connection from in-home
applications and subsystems to the Internet. More and more home automation
systems, A/V equipment, and even appliances rely on a broadband, always-on
connection to the Internet for everything from remote monitoring to
Home networks have traditionally
been driven by homeowners who have high-speed Internet connections,
such as cable modems or DSL modems. Typically, these connections
cost at least $30 a month or more. Rather than having to pay a separate
connection fee for each computer, a properly installed home network
will allow two or more computers to share the same high-speed connection.
Having a good working
knowledge of home network technology, components, and installation
techniques will continue to be a necessity for automating and interconnecting
subsystems in the home.
This section will overview
the basics of Ethernet based high-speed data networks, the components,
and the basics of how to configure the networks for the most common
applications. You can read through this section in the order it
is presented (recommended for those new to this subsystem), or jump
directly to the section that interests you.
The network–referred to as the home LAN–connects several
computers and peripheral devices (printers, storage devices) together
through a hub device and through a router and gateway to the Internet.
The network allows any networked device to communicate with any
other device on the network, sending text, pictures, music, control
information, and data files as well as providing any device access
to the Internet.
The hub connects all
the networked devices together at a central location, thus forming
the "hub" of the network. The hub receives network packets
transmitted from any attached device and relays them to all other
attached devices including the router.
The router does the work
of interfacing the network to the Internet. It examines the destination
address of each packet on the network. If the address is on the
home LAN, it ignores the packet. If the destination address is not
on the LAN, it assumes the packet destination lies outside the LAN
and sends the packet to the Internet via the gateway. Likewise,
if the router receives a packet from the internet via the gateway,
it examines the destination address. If the address is one assigned
to a device on the home LAN, it forwards the packet to the hub.
If it is not a home LAN address, the packet is discarded.
The gateway is an interface
between two dissimilar networks. It performs protocol translation
as well as the physical interface between the service providers
network and the home network (typically a TP based Ethernet network).
Typical gateways include cable and DSL modems that convert the WAN
analog signals to a local network protocol. Figure 4.9.2 shows a
representation of the network in a more schematic form.
Schematic representation of a typical Ethernet
home network. This shows five networked deviced connected to a hub
or switch via CAT5 TP cable. The hub connects to a router to provice
shared internet access for all devices. The router is in turn connected
to some type of Internet gateway such as a cable or DSL modem. The
router and hub/switch are typically enclosed in the same box
networks rely on unshielded twisted pair cable, either installed
in new construction or retrofit as part of a structured cabling system.
Wired networks use either 10 Mbps or 100 Mbps (10Base-T or 100Base-T)
Ethernet technology over CAT5 TP cable with 8-pin modular connectors
as described in Section 2. Structured cabling systems, wired per the
TIA-570A specification, using CAT5 TP cable or better will support
data rates of 100 Mbps (100Base-T Ethernet). Wired networks are the
most reliable since they are dedicated to carrying the network data
and use digital baseband signaling.
LAN Network Types
There are basically three types of physical networks that can be
installed in the home: wired networks, no-new-wires networks, and
wireless networks. These network types can be combined in a typical
home network installation
No-new-wires technology is intended to be used in homes with little or no high
quality TP cable by utilizing the existing older phone wiring or
the power line wiring to carry the data. These networks use a modified
Ethernet physical layer technology to "piggy-back" analog
signals on the existing phone wiring or power line wiring in the
home. The most popular technologies are currently HomePNA and HomePlug.
HomePNA is a
technology that uses the existing phone wiring to send analog signals
modulated by digital data up to about 10 Mbps. It places a high-frequency,
broadband signal on the same wires used for phone service in the
home. This lets the phone lines be used for regular voice service
and data transmission service at the same time. HomePNA devices
simply plug into existing phone jacks using regular phone cords.
HomePNA is limited by the fact that typical older homes were only
wired with a few telephone outlets.
a technology that uses the existing electrical power line wiring
in the home for data transmission up to 10 Mbps. The technology
is similar to DSL in that it uses many different analog channels
in the 2 - 30 MHz spectrum to send the data over the power line
wiring. Actual data rates will depend on the noise and attenuation
on a individual home's power line but data rates of 5 Mbps are typical.
and HomePlug send normal Ethernet data using an analog broadband
technology. While some computers and network components have HomePNA
and HomePlug interfaces built-in, most devices will need to use
attached bridge products that convert 10Base-T Ethernet into phone
line or power line signals.
Ethernet to HomePlug adapter on left and
USB to HomePNA adapter on right.
networks for the home almost exclusively use the IEEE 802.11b
wireless Ethernet standard. IEEE802.11b devices transmits digital
data in the 2.4 GHz (2.4 - 2.483 MHz) unlicensed radio band at up
to 11 Mbps at ranges up to 150 feet.
devices can typically expect a range of 100 feet from an access
point (a bridge or router) to the portable device but the range
varies greatly depending on the construction and layout of the home.
some home computer and networking devices such as web tablets and
routers have 802.11b interfaces built-in, most devices such as laptops
can be made wireless by the installation of an 802.11b interface
card such as a PCMCIA card.
wireless to wired networks is done with a wireless to wire bridge
or connection point. An 802.11b bridge will typically have a 10Base-T
jack on one side and a wireless antenna on the other side (see section
4.9.3). Wireless bridges can be plugged in anywhere there is a 10Base-T
jack and more than one can be used to achieve complete coverage
of a home.
All of the network
types can and typically are combined in a home. HomePNA or HomePlug
can be used to reach areas of a home where new network wiring is
not installed and wireless technology can be used with either wired
or no-new-wires networks for remote and portable devices such as
laptop computers and web tablets
Integrating a wireless network with a wired
network. The figure shows four wireless devices "connected"
to the network by a wireless bridge or by a wireless access point
built into the router (a popular combination).
Ethernet networks are quickly becoming a central data "backbone"
in the home not only for sending files, music, and surfing the internet,
but for home automation and control applications by interfacing
to other subsystem. Several companies such as Lantronix produce
Ethernet "bridges" that provide an IP addressable interface
to a control network of some type such as RS232, RS485, IR, or even
X-10 (in development?).
Ethernet bridges to other control networks
and technologies are available to allow control
information to be sent to and from subsystems in the home such as
HVAC, A/V, and security systems.
home networks requires the use of several types of network devices.
These devices form the "glue" that connects the network
together, allows different types of networks to operate together,
and make non-networked device networkable.
Interface Cards (NIC)
are used to allow a PC to connect directly to a network. The most
popular NIC's are the 10Base-T and 100Base-T Ethernet cards with
the 8-pin modular jack. These cards are typically used to upgrade
older computers since almost all new computers come equipped with
built-in Ethernet ports. Cards are also available for HomePNA and
PC NIC card for 10/100Base-T (left) and 802.11
PCMCIA NIC Cards
NIC plug-in "cards" are typically used on laptop computers
and serve the same function as regular NIC's. However, many non-computer
devices are being equipped to accept PCMCIA cards (especially 802.11b
cards) such as cameras, appliances, even speakers!
Typical NIC PCMCIA card (this one wireless)
A "hub" is a device that connects physical wired
branch cable runs of a network together. A hub gets its name from
the analogy to the hub of a spoked wheel that connects the spokes
together. Hubs typically have from 4 to 8 "ports" (RJ-45
jacks to allow connection of network cable runs) and are intended
for relatively small networks such as a home LAN. A packet that
arrives on any port is retransmitted on all other ports. Most hubs
also have one port assigned as a "link" or "uplink"
port to allow connection of additional hubs when more ports are
Typical 6-port hub. One of the ports (on
right) can be set to link to another hub to increase the number
A switch is similar to a hub but is selective in which
port an arriving packet is retransmitted to. A switch looks at
the destination local Ethernet address of an arriving packet and
only retransmits the packet to the port that has the device with
the destination address. This greatly reduces the packet traffic
on the network and isolates the packet traffic between two devices
at a time.
are typically used in larger commercial networks and have from
8 to 24 ports. However, since the cost of switches has fallen
to only slightly more than the cost of a hub (with the same number
of ports), switches are becoming more popular in home networks.
Typical 24-port switch. Status lights show
port activity, collission status, speed of attached device.
router connects two networks together. The name router comes from
the fact that the routers job is to "route" data between
the two networks in an intelligent way. In the case of home networks,
It joins the home network and the Internet, passing information
from one to the other. It also protects the networks from one another,
preventing the traffic on one from unnecessarily spilling over to
the other. Regardless of how many networks are attached, the basic
operation and function of the router remains the same. Since the
Internet is one huge network made up of tens of thousands of smaller
networks, routers are an absolute necessity.
two or more physical ports. One port is typically assigned to the
home LAN and the other port to the WAN (Internet). When the LAN
port receives a packet, a software routine called a routing process
looks inside the TCP/IP address fields for the destination address.
It then compares this address against an internal database called
a routing table to determine if the address is in the home (the
LAN), or outside the home (the Internet). The routing table has
detailed information about the ports to which packets with various
IP addresses should be sent. Based on what if finds in the routing
table, the router either forwards the packet to the WAN or discards
it. It does the inverse when it receives a packet from the Internet
Typical router with built-in wireless access
point and built-in 5-port hub. Most consumer routers have a
built-in hub or switch. Routers will always have a WAN port connection
to attach to the Internet.
device on a TCP/IP network need to have an IP address (it's source
address). IP addresses are dynamic and are assigned to a product
when it is attached to the network (unlike Ethernet physical addresses
which are hard-wired into a product when it is manufactured).
When a PC is
turned on and connected to the network, it needs to have an IP address
to connect to the Internet. Normally, when a PC is connected directly
to a cable modem or DSL modem (i.e. no network), the IP address
is given to the computer by the ISP that operates the cable modem
or DSL service.
In a home network,
each device needs an IP address. The addresses are assigned by the
router. The router uses the single IP address assigned by the ISP
(it takes the place of the attached PC in the above example).
The router and
each attached device uses an address assignment protocol called
DHCP (Dynamic Host Control Protocol). The router assigns addresses–such
as 192.168.1.100 —from its internal IP address table that
is used only inside the home network. When a second networked device
in the home is turned on, it does the same thing the first PC does:
It contacts the router using DHCP and gets an internal IP address.
This internal IP address will be different from the first —
for example, it might be 192.168.1.148. Other devices on the home
network can get internal IP addresses and access to the Internet
in the same way using the home router.
One of the most
valuable feature that the router implements is Internet access sharing.
The router uses a procedure known as Network Address Translation
(NAT) to translate all in-home IP address to the common IP address
assigned to the home account by the ISP. To the outside world every
device in the home appears to use the same IP address or the same
following steps assume a typical home network consisting of several
PC's, a shared printer, a few networked client devices (cameras,
internet radios, etc.), connected to a router, and a gateway modem.
a configured PC web browser to configure any non-computer networked
It will be helpful
to have a known working laptop PC available that you can take to
the customer site to help configure the network and test whether
the customers PC's are working properly.
In general, each computer attached to the network will
need to be configured for connection to the network. Two categories
of software will need to be configured: the OS components that deal
with network protocol, and client software such as email programs
that connect to the Internet via the network.
There are too
many versions of operating systems for PC's and Macintosh computers
to cover in this Guide. The particular OS documentation must be
consulted. In general, the OS must be configured for:
> The network
protocol being used
> The port
used for network attachment
security and naming parameters
IP addresses used by the ISP
> Use of networked
peripherals such as printers
The WAN side and LAN "side" of the router will
need to be configured. Most routers are configured by the use of
a web server in the router accessible by any configured PC web browser
attached to the network. Routers typically use a default IP address
of 192.168.1.1. This address is typed directly into the web browser.
The WAN side will need you to configure the IP address assigned
to the customer account and any other addresses assigned by the
On the LAN side
you will need to configure various firewall settings, address types
to assign, and a host of optional parameters such as whether any
of the attached devices should be "visible" from the Internet
(no filtering or firewall protection from the router). This is useful
when the customer would like to access an in-home security camera
Client Device Configuration
Once the PC's and the router are configured, the remaining
devices on the network can be configured by attaching them to the
network (the router will provide them with an IP address), and using
a web browser. The web server in most networked devices is fairly
self-explanatory and many have help pages (even the manual) built-in.