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Communicating over the
Network
Network Fundamentals – Chapter 2
Version 4.0
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Network Structure
 Three elements of communication
• Message source
• The channel
• Message destination
– Data or information networks capable of carrying many different
types of communications
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 How are messages communicated?
– Data is sent across a network in small “chunks” called segments – known as
segmentation
– Multiplexing – describes the process of interleaving multiple digital data
streams into ONE signal (see example in online curriculum 2.1.2)
– It increases the reliability of network communications
– Disadvantage is the amount of encapsulation that must occur with every
segment, especially for large amounts of data!
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Network Components
• Hardware (includes devices and media)
• Software (services and processes)
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End Devices
– End devices form interface with human network &
communications network
– Originate data flow!
– Examples: Computers, printers, VoIP Phones,
cameras, cell phones, etc. (End user devices)
– Commonly referred to as hosts (source or destination
of a message)
– Each host has an address that will identify it on the
network
– Role of end devices:
• Client (software installed so they can request & display info from the
server)
• Server (provide information and services to other hosts)
• Both client and server
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Intermediary Devices
–Role of an intermediary device
• Examples: Hubs, switches, access points, routers,
modems, firewalls, etc.
• Provides connectivity and manages data flows
across network
• Works behind the scenes
• Determines the path data will travel to get from
source to destination
• Knows all the paths that exist
• Informs other like devices about errors or
communication failures
• Retimes & retransmits signals as necessary
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Network Media
– This is the channel over which a message travels
– Encoding is different for each type, i.e. electrical
impulses, light pulses, wave patterns
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Network Types
 Local Area Networks (LANs)
– A network serving a home, building or campus is considered a
Local Area Network (LAN)
– Single geographic area, usually a common organization
– Administered by a single organization
– Provides network services to a common organization
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Network Types
 Wide Area Networks (WANs)
– LANs separated by geographic distance are connected by a
network known as a Wide Area Network (WAN)
– Be able to identify a LAN and a WAN given a similar diagram
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Network Types
 Define the Internet
– The internet is defined as a global mesh of interconnected
networks
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Network Symbols – be able to recognize
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Function of Protocol in Network Communication
– A protocol is a set of predetermined rules
– Implemented in software that is loaded on each host and
network device
– View them as a stack – from low to high in a hierarchy
– Outline the functions necessary to communicate between
layers
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Network Protocols
– Network protocols are used to allow devices to communicate
successfully
– Protocols agree on structure of message (specific to PDU’s)
– Protocols agree on the process of sharing, error handling, and
termination procedures – all functions necessary for
communication
– Require layer dependent encapsulations
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Protocols and Industry standards
– A standard is a process or protocol that has been endorsed by
the networking industry and ratified by a standards organization
– Ensures all protocols (open or proprietary) will work together
– IEEE (Institute of Electrical and Electronic Engineers)
– IETF (Internet Engineering Task Force)
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Function of Protocol in Network Communication
Examples of Protocols
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Function of Protocol in Network Communication
 Technology independent Protocols
– Many diverse types of devices can communicate using the
same sets of protocols
– This is because protocols specify network functionality, not the
underlying technology to support this functionality
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Layers with TCP/IP and OSI Model
 Benefits of using a layered model
•
•
•
•
Assists in protocol design
Fosters competition (different vendors can work together)
Changes in one layer do not affect other layers
Provides a common language
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Layers with TCP/IP and OSI Model
All
People
Seem
To
Need
Data
Processing
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Layers with TCP/IP and OSI Model
 TCP/IP Model – created in early 1970s – KNOW what
each layer is responsible for!
 Open Standard
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Layers with TCP/IP and OSI Model
 Protocol data units (PDU) and encapsulation
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Key functions of encapsulation
 Ensure that data pieces get from sending to receiving
device
 Ability to re-assemble the data packets correctly
 Ability to identify data packets that belong together with
the same communication package
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Comparing TCP/IP and OSI Model
Know these layers and how they compare between the
two models
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Addressing and Naming Schemes
 Explain how labels in encapsulation headers are used
to manage communication in data networks
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Addressing and Naming Schemes
 Describe examples of Ethernet MAC Addresses, IP
Addresses, and TCP/UDP Port numbers
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Addressing and Naming Schemes
 Think about a computer that has only one network
interface on it. All the data streams created by the
applications that are running on the PC enter and leave
through that one interface, yet instant messages do not
popup in the middle of word processor document or email showing up in a game.
 This is because the individual processes running on the
source and destination hosts communicate with each
other. Each application or service is represented at
Layer 4 by a port number.
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