Connecting to the
Network
Networking for Home and Small Businesses – Chapter 3
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What is a network?
 The ability to connect people and equipment no matter
where they are in the world.
– telephone
– computers
– television
 How does your body work as a network??
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Networking and Its Benefits
A CONVERGED NETWORK!!!
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Networking and Its Benefits
 SOHO Network
– Small Office/Home Office
– sharing of resources
• Internet
• Printer
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Networking and Its Benefits
Schools,
Corporations
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Networking and Its Benefits
 Define the components of an Information network
 Hosts
– PCs
– send and receive information across the network
–connected to a network device
 Peripherals
– not directly connected to the network, but connected to hosts
 Network devices
– hub, switch, router
 Network media
– used to connect hosts/devices
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Networking and Its Benefits
 Clients and servers
– software installed determines the role of a client or a server
 Server software
– enables the server to provide information to other hosts
 Client software
– enables the client to request and display information from the
server
– Example: Internet Explorer
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Networking and Its Benefits
 Build computer peer-to-peer network and verify
 The ability to act as both a client and server
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Network Topologies
 Physical topology
– created to record where each host is on the network
– shows how each host is connected (media, devices, etc)
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Network Topologies
 Logical topology
– how the host uses the network
– host names, addresses, groups, applications
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Communication Protocols
 Primary purpose of a network – to communicate
 Elements of communication
– Sender (source)
• has a need to communicate
– Receiver (destination)
• receives message and interprets it
– Channel
• pathway for information to travel
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Successful delivery of the message
 Rules (protocols) must be followed:
– Identification of the sender and/or receiver
– Channel in which to communicate (face-to-face)
– Mode of communication (written or spoken)
– Language
– Grammar
– Speed or timing
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Communication Protocols
 Encoding vs. Decoding
 Encoding
– Humans
• converting thoughts into language, symbols, or sounds
– Computers
• messages converted into bits by sending host
• each bit encoded into sound, light, or electrical impulses
• destination host then decodes the signal
 Decoding
– reverse of encoding
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Communication Protocols
 Message formatting and encapsulation
 Message needs a specific format
 Compare to parts of a letter
– Identifier (recipient)
– Salutation
– Message
– Closing
– Identifier (sender)
 Encapsulation
– placing the letter into the envelope
 De encapsulation
– letter removed from the envelope
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Communication Protocols
 Messages have size restrictions depending on the
channel used
 If the message is broken into smaller pieces, it is easier
to understand
 If the message is too long or too short, will be
considered undeliverable.
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Communication Protocols
 Timing
– when to speak; how fast or how slow
– how long to wait for a response
 Access Method
– determines when someone is able to send a message
– can speak when no one else is talking, otherwise a COLLISON
occurs
 Flow Control
– timing for negotiations
– sender might transmit messages faster than the user can handle
 Response Timeout
– how long should you wait for a response and what action to take
 Acknowledgment
– may be required to ensure message was delivered
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Communication Protocols
 Message Patterns
 Unicast – single destination
 Multicast – same message to a group
 Broadcast – all hosts need to receive the message
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Communication Protocols
PROTOCOLS = RULES TO FOLLOW
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Communication Across a Local Ethernet
Network
 Computers must speak the same language in order to
communicate!!
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Standards in technology
 Standards – rules by which equipment from different
vendors operate
 Benefits of standards:
– Facilitate design
– Simplify product development
– Promote competition
– Provide consistency
– Facilitate training
– More vendor choices for customers
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Communication Across a Local Ethernet
Network
 IEEE (Institute of Electrical and Electronic Engineers)
– maintains networking standards
– 802.3 – Ethernet standard
 A breakdown of terminology
– 100 Base-T
– 100 = Speed in Mbps
– Base = Baseband transmission
– T = Twisted Pair
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Communication Across a Local Ethernet
Network
 Physical addressing
 MAC address (Media Access Control)
 Ethernet communication
– each interface has a MAC address
– each device may look at the data, but only the interface that
matches the destination MAC will respond
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The Ethernet Frame
 Preamble – beginning of the timing
 SFD (Start Frame Delimiter) – marks the end of the timing, but
beginning of the frame
 Destination MAC
 Source MAC
 Length/Type
– Length – tells which protocol receives the data
– Type – number of bytes of data
 Encapsulation – packet of information
 FCS (Frame Check Sequence) – checks for damaged frames
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The Hierarchical Design Structure
 Smaller, more manageable groups allow traffic to
remain local on the networks
 Divided into three layers
– Access Layer
• connection to the hosts
– Distribution Layer
• interconnects smaller networks
– Core Layer
• high speed connection between
distribution devices
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Logical Addressing
 MAC vs. IP
 IP Address (Logical Address)
– assigned based on where the host is located
– assigned by the administrator
 Parts of an IP address
– Network – same for all hosts connected to the LAN
– Host – unique to each host on the network
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Access Layer Devices
 Most basic level
 Made up of:
– host devices
– first line of networking devices
– hub, switch, workstations
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Access Layer Device – A HUB
 Accepts data signal from one port and sends it
(regenerates) out all ports
– multiport repeater
 Collisions
– results in message being garbled and unreadable
– occur when two or more hosts send a message at the same
time (undesirable in a network)
 NOT VERY SMART
– a hub will not recognize there is a collision and send it all
ports
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Hubs And Collision Domains
 Collision domain – area where the collision has
occurred.
 More collision domains = better performance
 How many collision domains exist in the graphic
shown?
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Access Layer Device – A SWITCH
 SMARTER THAN A HUB
 dedicated bandwidth out each port
 no need to share with other ports (unlike a hub)
 Can forward messages to a specific host by looking in
its MAC table
 If destination MAC is not in its MAC table, floods the network out
all ports looking for a response
 Only the host with the correct MAC address will respond
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More Stuff on Switches
 How does the MAC table get built?
– keeps track of frames being sent between hosts
– records the information when there is a response
 Collision Domains
– each port on a switch is its own collision domain
– 8 port switch = 8 collision domains
 Online Activity 3.4.3
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Broadcasts
 If there is only one destination MAC in a message, how
can you contact everyone else?
– send a broadcast MAC
– hexidecimal digits
– FFFF.FFFF.FFFF
 Useful when hosts need to send information but don’t
know what hosts are to receive it
 Switches and hubs send the broadcast out to everyone
on their network. (Broadcast Domain)
ONLINE ACTIVITY 3.4.5
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ARP Request
 Sent when the sending host knows the destination IP,
but not the MAC
 Will discover the MAC address of any local host on the
network
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Distribution Layer Devices and
Communication Methods
 Responsible for making sure local traffic stays local on the
network
 Traffic destined for other networks will be passed on.
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Distribution Layer Devices—The Router
 Routers – directs traffic based on the destination IP
address
 Routers build routing tables; switches build MAC
tables
 Routers decode packets, switches decode frames
 Look only the network portion of the IP address
– finds the best path to take to get to the destination
 Routers do not forward broadcasts!!!
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Default Gateway
 Used when a host wants to send data to a host on a
different network.
 Must be set on the workstation connected to the routing
device – the router interface connected to the PC
Activity 3.5.3
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Routing Tables and ARP tables
 Used by routers to store information
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Types of Routing
 Dynamic
– information is obtained from neighboring routers
 Static
– manually entered by the network administrator
 What happen to a message that is not in the routing table?
– It is dropped unless . . .
 A default route is set
– “last resort” type of router
– will send it to the router it thinks may be have the destination IP
ONLINE ACTIVITY 3.5.4
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Distribution Layer Devices and
Communication Methods
 LAN – Local Area Network
 Under the same administrative control
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Distribution Layer Devices and
Communication Methods
 Packet Tracer
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Plan, Implement and Verify a Local Network
 Consider the following before beginning:
– Number and type of hosts
– Applications to be run on the network
– Data and devices to be shared
– Speed requirements (bandwidth)
– Level of security
– Reliability of the network
– Connectivity requirements
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Building the Network
 Physical environment
– temperature control
– availability/placement of outlets
 Physical configuration
– location of devices
– how are devices connected
– location/length of cable runs
– hardware configurations (hosts, servers)
 Logical configuration
– size of broadcast & collision domains
– IP addressing scheme
–Naming
–Permissions
–Sharing
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Multifunction Devices
 Integrated routers
– Linksys wireless router
– problem = single point of failure
 Cisco Integrated Services Router (ISR)
– performs services of three different devices
• router
• switch
• wireless access point
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Implement and Document the Network
 Develop a prototype
– tests network design
 PACKET TRACER – ACTIVITY 3.6.2
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Sharing Resources
 Main reason for networking – sharing resources
– File sharing
– Print sharing
 Consider this before sharing:
– security issues
– permissions granted
 Windows XP users
– use Simple File Sharing
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