home networking. objectives understand the basics network addressing learn the basic hardware needed...
TRANSCRIPT
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
Laptop
Xbox
PDAMediaCenter
Simple Network
Can specify IP address manually for each device PC (or laptop) can act as a DHCP server to assign IP
addresses
PC
Laptop
Xbox
PDAMediaCenter
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
PC
Laptop
Xbox
PDAMediaCenter
RouterInternetInternet
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
PC
Laptop
Xbox
PDAMediaCenter
InternetInternet
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
PC
Laptop
Xbox
PDAMediaCenter
RouterInternetInternet
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
PC
Laptop
Xbox
PDAMediaCenter
RouterInternetInternet
WAP
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
PC
Laptop
Xbox
PDAMediaCenter
RouterInternetInternet
WAP
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
PC Laptop Xbox
PDA
MediaCenter
WiFiRouter
InternetInternet
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
RouterN
IC N
IC
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?
PC Laptop XboxMediaCenter
WiFiRouter
InternetInternet
192.168.1.100 192.168.1.101 192.168.1.102 192.168.1.103
24.133.65.78
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
RouterN
IC N
IC
InternetInternet
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
RouterN
IC N
IC
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
Port Application
21 FTP Server (Control)
22 SSH server
23 Telnet server
25 SMTP server
80 Web server
3389 Windows Remote Desktop
PC Laptop XboxMediaCenter
WiFiRouter
InternetInternet
192.168.1.100 192.168.1.101 192.168.1.102
24.133.65.78
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
PC Laptop XboxMediaCenter
WiFiRouter
192.168.1.100 192.168.1.101 192.168.1.102
24.133.65.78
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
Windows Network Organization
Windows File Sharing organizes hosts into “Workgroups” 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