Wi-Fi Structures
Types of Wi-Fi Network Products
• Access Point
– Radio transceiver
(transmitter/receiver) unit
that plugs into a router,
switch, or hub on a home
network to let wireless
clients– your computers –
access your wired
network (and Internet
connection).
Types of Wi-Fi Network Products
• router (gateway)
– Shares broadband
Internet connection
among all the client PCs
on the network.
– Only difference between
wired and wireless router
is the latter has the
access point built in.
Types of Wi-Fi Network Products
• router (gateway), continued...
– Built in Ethernet switch allows for
communication between clients, as well.
Expect enough Ethernet ports to connect from
2 to 8 computers using Cat 5 cable.
Types of Wi-Fi Network Products
• Wireless Network Interface Cards
(NICs)
– The adapter that allows a PC to
connect to the access point, and
thus talk to the wireless network.
– All shapes and sizes:
1. Internal – PC Card (Sometimes called
CardBus) for laptops
2. Internal --PCI Card for desktops
3. External – USB or Ethernet-to3
Wireless Adapter
4. Embedded (non-removable) –
miniPCI, comes with laptop.
1
2
4
Other Equipment
• Repeaters – used to extend the signal range
of a WLAN component.
• Bridge – connects two separate wired or
wireless LANs
Basic Home Wi-Fi Network
Cable/DSL
Modem
The Internet
AKA the WAN
Router
Access Point
Home PC
connected
by Ethernet
Second
Home PC
connected
by Wi-Fi
Second Laptop
First Laptop
Basic Home Wi-Fi Network
(alternate)
Cable/DSL
Hub or Switch
Modem
The Internet
Wireless Router
Home PCs
connected
by Ethernet
Home PC
via Wi-Fi
PDA
Laptop
Game Console
Get the LAN Talking
• DHCP
– A Dynamic Host Configuration Protocol (DHCP)
server will provide IP addresses to all the computers
on the network.
Most
routers
include a
DHCP
server to
serve a
range of
addresses.
Get the LAN Talking
• DHCP
– Each computer should
be set to be a DHCP
client.
– In Windows, set the
network card’s settings
to “Obtain IP address
automatically.”
Get the LAN Talking
• DHCP
– The router will typically be your “default
gateway” to the Internet and will provide the
IP address indicating that to all clients.
– If your router’s IP address is 192.168.0.1, all
computers using 192.168.0.2 to
192.168.0.254 will use that router to access
the Internet.
Home Network- IP Addresses
Cable/DSL Modem –
gets IP from your ISP,
64.185.133.92
The Internet
Router
Gateway for
LAN: 192.168.0.1;
To Internet
appears as
64.185.133.91
Access Point:
192.168.0.102
192.168.0.103
192.168.0.105
192.168.0.104
192.168.0.100
Home Networking Tip
• “ipconfig”
– If you need to quickly find out the IP address of your
computer and the router/gateway, go to a command
window and type ipconfig. (winipcfg in Windows 9x)
Get the WLAN Talking
• Set up the SSID:
– To connect to an access point, each client
must know the Service Set Identifier (SSID)
– the name of the wireless network -- of the
access point and set that in its configuration
utility.
– CHANGE the SSID -- Vendors typically set the
SSID of products to a simple, generic name,
like the company name or “default”
– Good Security: Pick a hard-to-guess SSID,
such as a mix of letters and numbers with no
obvious identifying logic.
Get the WLAN Talking
• Set the channel
– Most access points run on a single channel
– Set the access point channel and all the
clients that associate to it will use the same
channel:
– NOTE: 802.11b has 14 channels worldwide
and 11 in the United States, but no more than
three – 1, 6, and 11 -- that don’t overlap and
thus don’t cause interference. This is only a
problem if you’re near other WLANs.
Home Networking Tip
• “ping”
– Want to find out if your computer is talking to other
computers, or the Internet? Send a ping. At a DOS
window, type “ping” and the IP address for a
computer or a Web site.
Home LAN Issues
WAN settings
• The Wide Area Network (WAN), at least when it
concerns your home network, is the network
connection from your Internet Service Provider
or broadband Cable/DSL company.
• Some ISPs require you to enter information in
your router such as:
– Static IP address
– Domain Name Server (DNS)
– Point to Point Protocol over Ethernet (PPPoE) for
DSL providers, with username and password
Network Address Translation
(NAT)
• NAT lets you share the one “real” IP
address provided by the ISP among
multiple computers on the home LAN.
• The router/gateway gets that IP address
from the ISP and translates it for the other
computers, working hand-in-hand with
DHCP.
Firewall
• Uses rules to filter traffic from the outside
Internet to your LAN, and sometimes vice
versa.
– Built into many routers; also available via
software installed on each computer.
IP Ports
• Not the physical jacks on the back of the PC...
• Each port number Identifies the type of data
being sent to/from a computer.
– Port 80: HTTP (Hypertext Transfer Protocol, web
browser traffic)
– Port 25 & 110: SMTP & POP (Simple Mail Transfer
Protocol & Point Of Presence, e-mail)
– Port 21: FTP (File Transfer Protocol)
– Port 53: DNS (Domain Name Resolution)
Port Forwarding
• Port Forwarding associates traffic meant
for a specific port on the computer and
allows it through.
• Setting a computer as a Web server
means you forward traffic to port 80
(reserved for Web traffic) on one specific
computer, based on its IP address.
– Also called port mapping, pass-through,
punch-through
– Could require use of a “Dynamic DNS”
service
DMZ
• The Demilitarized Zone (DMZ) is the term used
for a single computer on the network that is
given completely unfettered access to the
Internet.
• Traffic can be incoming or outgoing.
• Reserve for PCs that are
– Web servers
– Gaming systems
– Use video conferencing
• That computer is wide open to the Internet and
hackers– keep isolated from others.
Universal Plug and Play (UPnP)
• UPnP (www.upnp.org) developed by Microsoft,
is meant to automate connection, installation,
and configuration of network products
• Performs “NAT Traversal” to automatically open
the ports on a PC needed to work with a routers
firewall
• Both router and PC must support UPnP to get
the benefit
– Mainly works under Windows XP for now
VPN Pass-Through
• Virtual Private Networks (VPNs) allow
people to create a direct “tunnel”
connection to their corporate network.
Many routers will allow you to have the
tunnel “pass-through” to the Internet and
on to the corporate network.
• Watch for how many simultaneous tunnels
are supported
Firmware Upgrades
• Firmware is the built-in software inside of a
device that defines functions and features
• Updating most access points/routers
requires a firmware upgrade.
• Download a software file and generally
install via a utility or through the Web
browser interface.