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3: Connecting to the Network
Networking for Home & Small Business
What’s a Network?
• Make a phone call, watching TV, radio,
Internet, Gaming
– All depend on a reliable network
• Group of connected devices able to
communicate with each other
Networks
Basic Network Components
• 4 categories of components
– Hosts
– Shared peripherals
– Networking devices
– Networking media
Hosts
– They send & receive data
– Have an IP Address
Shared Peripherals
– Shared devices that ARE connected to a host
– Print Sharing
Networking devices
• Interconnect hosts
• Move & control traffic
Networking media
• Connects Devices
Activity
Handout
• Complete
Client-Server
• Hosts have an IP
Address
• Can act as a client
or server
– Server provides
services to other
hosts
– One server can
provide many
services
– Clients request &
display info from
servers
Popular Client-Server Network
• World of Warcraft
• Players from all over the world connect &
play
Peer-to-Peer Networks
• One computer can sometimes act as the
server & the client
• Simplest: 2 connected devices
– Uses a crossover cable
• Multiple PC’s connect with a hub
Peer-to-Peer Networks
• Large businesses have lots of traffic
– Dedicated servers to handle requests
Famous Peer-to-Peer
• LimeWire
– Exchanging MP3’s with another device
Client, Server, or Both
Physical Topology
• Layout/Map of network
• Shows where each host is located, wiring,
network devices
Logical Topology
• Groups hosts by how they use the network
– Not physical location
• Host names, addresses, group info &
applications can be recorded
Lab 3.1.5
• Building a Peer-to-Peer Network
Review
• What does SOHO stand for?
– Small office home office
• What interconnects hosts & controls traffic?
– Network devices
• Which cable connects 2 PC’s together?
– Crossover cable
• Hosts are devices that have what?
– IP Addresses
• Describe client-server.
End of Part 1
Principles of Communication
• The Message
• Source or
Sender
• Destination or
Receiver
• Channel or
Pathway
• Protocol or
Rules
Human Communication
• What are our rules of communication?
Protocols
• Rules of Communication over a medium
• Protocols define the details of how the
message is transmitted, and delivered.
• This includes issues of:
Message Encoding
•
Encoding
•
•
Thoughts into words
Proper encoding for that medium
•
•
Light, electricity, or radio waves
Destination will decode the message
Encapsulation
• Putting a letter in an envelope
• Encapsulated in a frame before sent over
the network
– The frame acts as the envelope
– Has addresses of source and destination
• If not formatted correctly, they will not be
delivered!
Handout
• Complete
Review
• What 4 things do you need for
communication?
– Source, destination, channel, protocol
• Describe encoding.
– Bits into electricity, light, or radio waves
• A message is encapsulated in what?
– Frame
• Which 2 address are in the frame?
– Source & destination MAC address
Message Size
• You talk in sentences.
– Length will vary depending on what can be
processed or understood by the listener
• Messages sent across networks are broken
into smaller pieces
– Size of a frame
Message Timing
• People use timing to determine when to
speak, how fast or slow to talk, and how
long to wait for a response. These are the
rules of engagement.
• Access Method
• Flow Control
• Response Timeout
Message Timing
• Access Method
– When to begin sending & how to respond to
errors
– Collision if two talk at same time
• Flow Control
– Sender can transmit messages faster than the
destination can receive & process
– Use flow control to negotiate correct timing for
successful communication
• Response Timeout
– How long to wait for responses & what to do
Unicast Message Pattern
• Unicast
– 1 to 1 single message
Multicast Message Pattern
• Multicast
– 1 to a group message
Broadcast Message Pattern
• Broadcast
– 1 to all
Activity
Review
• What is it called when one message format
is placed in another message format?
– Encapsulation
• Bob is talking to Sally. Which type of
message pattern is this?
– Unicast
• Which address is used in a frame?
– MAC address (source & destination)
Review
• Which message is one to all?
– Broadcast
Importance of Protocols
• Computers need rules to communicate
• Local network devices MUST speak same
language
• Most common wired protocol is
ETHERNET
Early Days of Computing
• Each vendor had their own rules
• Standards had to be created
Standardizing
• IEEE maintains standards approvals
– Assigned a #
– 802.3 is Ethernet
– 100Base-T
• 100 megabit Ethernet
• Baseband Transmission
• Twisted Pair Cabling
Physical Addressing
• Remember encapsulating frames?
– Source & destination address needed
• Each host on Ethernet has a physical
address (MAC Address)
– Burned into NIC
• NIC encapsulates source & dest. MAC
• Host that receives frame reads dest. MAC
– If it contains its own MAC, it will process it
– If not, it ignores it
Example
Lab 3.3.3
• Determine the Mac Address
• Ipconfig /all
Ethernet Frame Structure
• Frames are also called PDU’s
– Protocol Data Units
Activity
Hierarchical Design Structure
• MAC Address is like your name
– Doesn’t tell where you are on the network
– Not efficient by itself
– Imagine if all hosts on Internet could only be
identified by a MAC address
• Ethernet is a broadcast technology
– Sent to all in a network
– Too much traffic & collisions
• Separate into smaller networks
Hierarchical in Life
Hierarchical Design in Networks
• Dividing your network into smaller groups or
layers
– Keeps local traffic local
– Only data intended for other networks will move on to
other layers
• Access Layer
– Provides connections to hosts in a local Ethernet
network.
• Distribution Layer
– Interconnects the smaller local networks.
• Core Layer
– A high-speed connection between distribution layer
devices.
3 Layer Model
IP Addressing
• Your name doesn’t change but where you
live might
– MAC stays on NIC
– Doesn’t change no matter where you move
• IP Address is like your address
– It is logical, not physical
• Needed to go beyond your network
– Stay local or go elsewhere???
IP Addressing
• 2 parts
– Identify the network
– Identify the host
• Network portion is same for all devices on a
local network
• 209.120.5.72
IP Network Example
Lab 3.3.6
• Determine the IP Address of the Computer
• Let’s do this together
• How do we find the IP Address through the
command prompt?
– Ipconfig /all
• Why is an IP address important?
Handout
• 3 Layer Model & Addressing Activity
Review
1. What is the process of placing one format
into another (like a letter into an envelope
to be sent in the mail)?
– Encapsulation
2. Which device is typically at the
Distribution Layer?
– Router
3. When a PC receives a message, which
address is used to determine if it for that
PC?
– Destination MAC
Review
1. Which organization creates & maintains
the standards?
– IEEE
– Why?
2. A frame contains which 2 addresses?
– Source & Destination MAC
3. What does FCS stand for & what does it
do?
– Frame Check Sequence, checks for errors
Hubs
• At Access Layer
• Simple Device (DUMB)
– Message in one port, out all others
– Does not send to specific device
– Sends one message at a time
•
•
•
•
Collisions can occur
They wait for silence, & then resend randomly
Too many collisions slow the network
Keep these collision domains SMALL
Pictures of Hubs
Hub Example
Hub & Collision Domain
Handout
• Hubs
Switches
• Access Layer
• Connects multiple hosts like a hub
– Forwards a message to a specific host!
– Reads the destination MAC
• Has a MAC address table
– Ports & MAC addresses on them
• Creates a virtual circuit to destination
• No bandwidth sharing between hosts
• No collisions!
How a switch works
More about Switches…
• What if destination MAC is NOT in the
table?
– Floods message out all ports, except one it
came in on
– Compare the destination MAC in frame
– Correct one processes the message
Switch Table
• How does the switch add the MAC address
to its table?
– It examines the source MAC & port it came in
on
– When it responds to a message, it adds it
• Updates table for every message
Example
• Go to Slide 3.4.3-2
• Look at example
What else about Switches?
• Hub attached to switch port scenario
• Separate collision domains for each switch port
Switch Handout
Review
1. Hubs & Switches are at which design
layer?
– Access Layer
2. Which device creates a virtual circuit from
the source to destination?
– Switch
3. Which device sends data in one port &
out all ports regardless of the destination?
– Hub
Review
1. Which address does a NIC read when
deciding if the message is for itself?
– Destination MAC
2. In 100Base-T, what does the 100 mean?
– 100Mbps
– How about the T?
•
Twisted Pair Cabling
3. If a switch receives a frame & doesn’t have
the dest. MAC in its table, what happens?
– Floods it out all ports, except one it came in on
Broadcasts
• One host can send messages to all other
LOCAL hosts
– Find info from others
– Tell others something
• One destination MAC in a frame only
– There’s a special MAC address that all hosts
will receive & process
– 48 bits, all binary 1’s
– In hexadecimal, FF:FF:FF:FF:FF:FF
• Look at 3.4.4
Broadcast Domain
• Too many hosts in a domain, causes traffic
backup
– This is why you divide into smaller LAN’s
Let’s Practice Together
• Slide 3.4.5
MAC & IP
• What if you want to send data, but only know their
IP address and not their MAC?
– ARP (Address Resolution Protocol)
ARP
• Host sends out a broadcast frame w/ the IP
address of the destination host
– FF:FF:FF:FF:FF:FF
• Each host receives & compares the IP
address to see if it is their own
• Matching host sends its MAC address back
to source
• Source then adds it to its ARP table
• Then it can send the message
ARP Example
ARP Example
Review
1. A broadcast frame contains which MAC
address?
– All F’s
2. How many bits is a MAC address?
– 48
3. Describe a broadcast
4. What separates broadcasts?
Distribution Layer
• Separates & connects your small networks
– Connects your Access Layer networks
– Can filter traffic & provide security
Routers
• Distribution Layer
• Connects different local networks
• Reads the packet encaps. in frame
– Destination IP Address (network portion)
– Subnet Mask
• Finds best path to that destination network
Routers- The Path…
• Each port connects a different local
network
• Rips open to find destination IP
• Looks in Routing Table
– In the table:
• Encapsulates in new frame
• Sends it out port towards or connected to that
destination
• Routers DO NOT forward broadcasts!
Path Example- H1 to H4
Default Gateway
• When sending a message on your local
network you use ARP to find dest. MAC
• When sending a message on another
network
– You encapsulate:
•
•
•
•
•
•
Source IP
Source MAC
Destination IP
You don’t know the destination MAC!
So you include the MAC of the router port!
Router will receive & process this MAC, BUT NOT
THE ARP MAC broadcast!
Default Gateway
• This IP is set in TCP/IP settings
• Router port that your host connects to- same local
network
– If the host knows the IP, it will use ARP to find out the
MAC address on router port
– Example on next slide
Default Gateway
Default Gateway
Lab
• Complete 3.5.3-2
Routing Tables
• Networks & best path to reach them
• Knows this info by:
– Dynamically learned from other routers
– Manually entered by admin
• No route in table?
– Drop it OR
– Default Route is set by admin
Routing Tables
Where does data go?
• Directly to the network destined for
• To another router
• When router forwards the frame, it MUST
include a destination MAC
– If it is connected, it will use the dest MAC from
its ARP table
– If not, it will sub MAC address of connected
router’s port
• ARP table for each port/local network
Look at…
• 3.5.4.2
• 3.5.4.3 activity
LAN
• Network over a small area
– Under one administration
– Router will separate
How many local networks?
Adding hosts to a LAN
• Advantages/Disadvantages?
Adding hosts to a LAN
• Advantages/Disadvantages?
Planning a Network
• Ethernet is most popular
• Planning is key!
• First, gather this info:
– The number & type of hosts to be connected
– The applications to be used
– Sharing & Internet connectivity requirements
– Security & privacy considerations
– Reliability & uptime expectations
– Connectivity requirements including, wired and
wireless
Plan & Document
• Maps of topology
• Physical environment
– Temperature
– Power
• Physical configuration
– Location of network devices
– Length of cables
– Hardware config
• Logical Configuration
– Broadcast & collision domains
– IP & Naming Scheme
Physical Topology
• How many broadcast, collision & networks?
Review
1. Describe a default gateway.
2. Each router port has an _______ table
that hold the MAC addresses of devices
connected to each port.
– ARP
3. Which one device will separate or
segment a network?
– Router
4. Describe a routing table.
Multifunction Devices
• Integrated Routers
– Usually for SOHO
– Switch/router/access point in one
– Single point of failure
• Cisco ISR
– Separate components to add/replace
Linksys
Linksys
Connecting the Linksys
• All connected to switch ports MUST be in
same IP network to communicate
• Display IP configuration settings
– Ipconfig
– Ipconfig /all
Lab
• 3.6.4
Sharing Resources
• XP has simple file sharing
– You can set more specific
– Full Control
– Modify
– Read & Execute
– List Folder Contents
– Read
– Write
• Look at 3.6.5
3: Connecting to the Network
Networking for Home & Small Business