Transcript Home Networking

Home Networking
Objectives
 Understand the basics Network Addressing
 Learn the basic hardware needed to form a
home network
 Learn basic Firewall functionality
 Learn how to share files among hosts on a
network
Internet Addresses
 Every host connected to the Internet is identified by an IP
address
 Acts as your computer’s Phone Number
 Multiple programs can run on any one host



FTP
Internet Explorer
IM
 Every program (i.e. client or server) on a host is identified by a
number, called a “port”
 IP Address Format
 <address>:<port>
 Examples:


136.142.185.31:22 (SSH on unixs.cis.pitt.edu)
216.109.118.66 (www.yahoo.com)
DNS
 Humans prefer to work with text
 unixs.cis.pitt.edu
 www.yahoo.com
 [email protected]
 DNS (Domain Name System) translates a text
address to an IP address
unixs.cis.pitt.edu
136.142.185.31
pitt.edu
136.142.11.143
www.yahoo.com
216.109.117.106
 Notice: similarity between pitt.edu IP addresses
 Indicates that these hosts exist on same network
Address assignment
 Two ways a host’s IP address can be assigned
 Manually assigned by the user of the host
 May not be consistent with network
 May already be used by another host
 DHCP (Dynamic Host Configuration Protocol)
 Another host assigns IP addresses to every host on a
network
 Ensures every host gets a unique IP address
 (among other tasks)
 Which to use is up to the network administrator (you)
Finding IP address in Windows
 Click Start Menu ->
Control Panels
 Double Click “Network
Connections” Icon
 Displays all network
connections
 Most common for us
is “Local Area
Connection”
 Double Click “Local
Area Connection”
 Click “Support” Tab
Setting IP address in Windows
 Right click “Local Area Connection” in Network Connections
Control Panel
 Go to Properties
 Click Internet
Protocol
 Click Properties
Button
Setting IP address in Windows
 Obtain an IP address
automatically
 Uses DHCP
 This is the default setting
 Use the following IP address
 Allows user to enter a
specific IP address
 Subnet mask specifies
how many of the fields in
the IP address uniquely
identify the PC
 Default gateway is the
address of the computer to
where data can be sent to
get to “the outside world”
Basic Network Hardware
 Network Interface Card (NIC)
Inside PC
 Transfers data between PC and network
 Provides the Plug on the back of your PC
 Hub
 Simple interconnection between computers
 Collisions occur if more than one PC sends data at the same
time
 Switch
 Also simple interconnection
 Prevents collisions by time multiplexing
 Router
 Actively transfers data on correct path to reach its destination

Simple Network
 Assume we have a PC, a laptop, a PDA, a Media
Center, and an Xbox
 Simplest network involves connecting each to a
single hub or switch
 Provides the interconnection shown below
PC
PDA
Xbox
Laptop
Media
Center
Simple Network
 Can specify IP address manually for each device
 PC (or laptop) can act as a DHCP server to assign IP
addresses
PC
PDA
Xbox
Laptop
Media
Center
Connecting to the Outside
 Must add routing functionality

a device that has two NICs


One connected to our simple network
One connected to the outside
 Two means of doing this:


The PC (or Laptop) can be set up to do this
Can add a separate device
Internet
PC
Router
Xbox
PDA
Laptop
Media
Center
Configuring your PC
 Assume the PC has:
 Dialup connection to the Internet (a modem)


Already setup to properly dial
LAN connection to our simple network
 Configure “Local Area Connection” in
Network Connections Control Panel to use
DHCP as described earlier

It will be it’s own DHCP server
 Similarly, each device on the network can be
configured to use DHCP
Configuring your PC
 Right click dialup connection icon, go to “Properties”
 Click “Advanced” tab
 Check “Allow other
network users to
connect through
this computer’s
Internet
connection”
 Select “Local Area
Connection” from
the drop down
menu
Configuring your PC
 Other network devices can now send and receive information to and
from the Internet



First, through the switch to the PC
PC transfers the data to the modem
PC decides to which device to send incoming data

“routes” incoming data
 Note: Instead of a dialup connection, the PC could have a second
Local Area Connection
Internet
PC
PDA
Xbox
Laptop
Media
Center
Alternative
 Use a separate router for the network
Usually for broadband connections (Cable, DSL)
 Faster and more configurable than PC
 Most act as a DHCP server too
 For simple networks, comes preconfigured
 Plug it in and Go

Internet
PC
Router
Xbox
PDA
Laptop
Media
Center
Adding Wireless
 Wireless Network Access is becoming more popular
 Access provided by another device
Wireless Access Point (WAP)
 Transfers data received over wireless through wired network to
Internet and back
 Default configuration works on most networks
 Best to enable security features


Varies from manufacturer to manufacturer
Internet
PC
Router
Xbox
WAP
PDA
Laptop
Media
Center
Simple Network Summary
 Started with PC, laptop, PDA, Xbox, and Media
Center
 For networking, added switch, router, WAP, and an
implied DHCP server

Vendors collect these devices into a single box
Internet
PC
Router
Xbox
WAP
PDA
Laptop
Media
Center
Using the All-in-one
 Now have a single
networking device
 If the network grows



Another switch can be
added
Another WAP can be
added
 Geographical
distance will
increase coverage
Only a single router is
needed for the entire
network
Internet
WiFi
Router
PDA
PC
Laptop
Media
Center
Xbox
How data travels
 Data sent over Internet is organized into “packets”
 Contain chunks of a sequence of data
 A single unit of transmission
 Similar to an envelope sent through US Mail
 Packaged with:
 Address (destination IP address)
 Return address (Source IP address)
 Name of recipient (Port Number of Application)
 Name of sender (Port Number of Sender Program)
Basic Routing
 Router receives packet on either NIC
 Forwards it on the other
Uses IP address and Port to decide where packet should go
 If specified destination is unknown, router forwards it to
another router that does know the destination
 Similar to Post Office
 Picks up mail at your home
 Transfers it to large Distribution Centers
 Forwarded to office of correct zip code
 Delivered to destination

NIC
NIC
Router
Problem
 Internet Service Providers
(ISP) provide a single IP
address per account
 Other hosts only see one
destination
 Our network has several
different hosts
 A packet received from
Internet has the ISP
assigned IP address as the
destination
 Which host on our network
should get the packet?
Internet
24.133.65.78
WiFi
Router
PC
Laptop
Media
Center
192.168.1.100 192.168.1.101 192.168.1.102
Xbox
192.168.1.103
Network Address Translation
 For packets crossing the router (in either direction)
 Router replaces local network IP address with ISP
address
 Remembers the Internet destination (or source)
 Pairs that with the local network host for future
packets
Router
NIC
NIC
Internet
Introduction to Firewalls
 NAT requires local hosts to initiate connections to outside world
first
 Router needs to know where to send return packets
 All traffic coming from outside world is blocked from accessing
local network
 By default
 Administrator can let specific traffic into network
 This is the basic idea of a Firewall
 Note: NAT and Firewalls are mutually exclusive functions
NIC
NIC
Router
Firewall
 Examines each packet it receives
 Decides to allow or deny the packet to pass through
the device

Decision based on a list of rules
 Matches Source IP, Source Port, Destination IP,
Destination Port, and Protocol against those specified
in the rule
 If a match occurs, rule is applied to the packet
 e.g. Block all TCP packets from 23.45.67.* on any
port destined for 78.12.89.3:80

(number after the colon specifies port)
Port Forwarding
 Most home networks don’t need the
complexity of most Firewall rules
 Port Forwarding refers to rules with a specific
kind of format
 Allows traffic received from any Internet host
destined for a specific port to be directed to a
specific local host on the home network
Example
 Typical Ports
Internet
Port Application
21
FTP Server (Control)
24.133.65.78
22
SSH server
23
Telnet server
25
SMTP server
80
Web server
3389 Windows Remote
Desktop
WiFi
Router
PC
Laptop
Media
Center
192.168.1.100 192.168.1.101 192.168.1.102
Xbox
192.168.1.103
Windows File Sharing
Idea
 Now we have our
network set up
 We’d like to able to
easily access file on
other hosts


Media Center could
access media stored
on the PC
Laptop may need a file
from PC
 Windows provides an
easy way to facilitate
this
24.133.65.78
WiFi
Router
PC
Laptop
Media
Center
192.168.1.100 192.168.1.101 192.168.1.102
Xbox
192.168.1.103
Windows File Sharing
 Built into Windows
 Specify Directories to
be shared

Entire contents of
directory and all
subdirectories can be
accessed by other
hosts
 Right-click on Folder
icon
 Go to “Sharing and
Security”
Simple Windows File Sharing
 Click “Share this folder on the
network”
 In most cases, this is all that
needs to be done
 Can change the name other
hosts will see when accessing
the folder
 Can change the access
permissions
 By default, other hosts only
have Read-Only access
 Click “Allow network users
to change my files” to give
write permission
 Also gives permission for
others to store new files into
the folder
Switching to Advanced File Sharing
 Open Folder Options
control panel
 Click “View” Tab
 Uncheck “Use simple
file sharing
(Recommended)”
 Click OK
Advanced Windows File Sharing
 This is “Sharing and
Security” window after
Unchecking the Folder
Options setting
 Advanced File Sharing
allows:
 Different permissions for
different users

Users must have a
user account on this
PC
More fine-tuned access
control per user
 In most cases, Simple File
Sharing is adequate
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Windows Network Organization
 Windows File Sharing organizes hosts into
“Workgroups”
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Originally designed for the workplace
People grouped into same project or team
Their PC could be grouped in the same
workgroup
 Files can be accessed from any PC
regardless of workgroup
 Users can specify any name for their PC’s
workgroup (and hostname)
Setting Workgroup Name
 Open “System” Control
Panel

Or right-click on “My
Computer and go to
“Properties”
 Click “Computer Name”
Tab
 Current Name and
Workgroup are
displayed here
 To change, click
“Change…” button
Setting Workgroup Name
 Change the text in the
given boxes to any
desired name
 Click OK
 Workgroup name
changes don’t take
effect until computer is
restarted
Viewing Files Shared On Other Hosts
 Open “My Network Places” on Desktop
 Usually also in Start Menu or linked on right side of
Explorer window
Viewing Files Shared On Other Hosts
 My Network Places
automatically searches
for shared folders from
any host it can find

Can only search in a
local part of the
network
 To view hosts
 Click “View workgroup
computers” on right
side of window
Viewing Files Shared On Other Hosts
 Shows an icon for each host that (independently)
specified the same workgroup name as your PC
 By clicking the parent directory button, can view all
the workgroups the PC can locate

Displays an icon for each workgroup (See the next
slide)
Viewing Files Shared On Other Hosts
Viewing Files Shared On Other Hosts
 Double click on a host to view its shared resources
 Includes shared folders and shared printers
 From this point, you can view (and possibly changed)
shared files as if they were part of your local file
system
Network Setup Wizard
 Setups up Windows to
properly use its network
connections
 Configures many of the
settings we’ve
discussed
 To get started, Open
“My Network Places”
 Click “Set up a home or
small office network”
Network Setup Wizard
 The screens viewed will vary
 Depends on what kind of network connections
are available
Network Setup Wizard
 To enable the Router-like
capabilities of Windows
 Check the top radio
button
 Allows other hosts on
the local network to
send packets to the
Internet through the
PC
 Most common selection
is the middle radio
button
 If setting up the simple
network (just a switch),
choose “Other”
Network Setup Wizard
 Enter description if
desired

Can be left blank
 Enter desired
hostname
 This sets the same
setting as the
“Computer Name”
tab in the “System”
Control Panel
 Click “Next”
Network Setup Wizard
 Enter Workgroup
name

Can be any
desired name
 Click “Next”
Network Setup Wizard
 Enable the ability
to share folders
and printers from
this computer

Click the top
radio button
 Disable it by
selecting the
bottom radio
button
 Click “Next”
Network Setup Wizard
 Review Settings
you’ve chosen
 Click “Next”
Network Setup Wizard
 Unless you need to
apply exactly the
same settings to
many PCs, check
the last radio
button
 Click “Next”
 You’re done