Transcript The OSI Model`s Seven Layers Defined and Functions

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Let’s start with a little example of how we
communicate in relation to how
computers communicate.
 Please shake the hand of the person
next to you.

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Layer 1
Physical (The Handshake): defines the electrical and physical specifications
(maybe some of you got a shock when you first touched).
1 byte
1 byte
1-2
bytes
Variable
2 bytes
1 byte
Flag
Address
field
Flag
Control field
Data/
Information
FCS
Example of a Frame
(Data Link layer protocol)
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
Even though the NIC (Network Interface Card) is typically associated as
part of the Data Link layer (MAC address – Media Access Control) so is it,
in a manner of speaking, part of the Physical layer – accepts frames from
the Data Link layer and generates signals.
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Layer 2
Data Link (Hand-Eye Contact): the actual linkage and mechanisms to move
data about the network such as topology, Ethernet or Token-Ring, basically
how data is transmitted.
Example of a Frame
(Data Link layer protocol)
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
Data Link layer and its sublayers
The LLC (Logical Link Control) sublayer provides an interface with the
Network layer protocols which appends the physical address of the
destination computer onto the data frame.
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Layer 3
Network (GPS): defines the process used to route data across the network
(logical addressing).
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
Used to translate network addresses into their physical counterparts and
decides how to route data from the sender to the receiver.
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Layer 4
Transport (Satellite): provides for reliable transmission of data segments
(disassembly and assembly of data before and after transmission).
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
Ensures data is transferred for one computer to the next reliably, in the
correct sequence, and hopefully without error.
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Layer 5
Session (GPS & Satellite People): establishes, maintains, and manages
communications between computers.
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
Refers to a connection for ongoing data exchange between two parties.
Sort-of like making a phone call and having a conversation.
(can you hear me now?)
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Layer 6
Presentation (You, your appearance): concerned with data representation
and code formatting.
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
May be referred to as the translator. Accepts Application layer data and
formats it so one application/host can understand another
application/host.
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Layer 7
Application (Web Page): provides services to the software and your request
for network services like the browser and email client(s)
(like a negotiator).
Courtesy Course Technology/Cengage Learning
Network+ Guide to Networks, 6th Edition
Serves as the window for users and application processes to access
network services. This layer contains a variety of commonly needed
functions.
(Microsoft Support - Article ID: 103884 - Last Review: February 27, 2002 - Revision: 1.0)
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
Does anyone have an idea of about
when OSI Model (Open Systems Interconnection
Reference Model) came about?
› (Think about when the personal computer
made an appearance)

Do you recall hearing all this talk about
standardization?
› (Remember OSHA – Occupational Safety
and Health Organization).
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
Well ISO (International Organization for Standardization)
developed the OSI model in an effort to
set a standard by suggesting, proposing,
and recommending the steps to transfer
data from one network device to
another.
› Another words an open platform for the
world to communicate from one computer
to another over a network.
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

You can probably see how important having
some kind of standard today especially with all
the various computer manufacturing
companies there are, all the components that
are used in a single computer, and of course
the massive internet system and resources
available.
Even all the social networking tools out there
that are free to explore and manipulate you
need some kind of standard to help keep it all
together and hopefully safe from those that
take advantage of the innocent.
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

You always hear how important location,
location, location is, yet communication is also
quite critical and important.
Here’s an interesting way to look at this
concept; Doug Lowe (an author for Dummies.com)
puts it “These layers are kind of like the layers
of an onion: Each successive layer envelops
the layer beneath it, hiding its details from
the levels above. The OSI model is also like
an onion in that if you start to peel it apart
to have a look inside, you’re bound to shed
a few tears.”
I believe his intentions where to represent the onion as tears of joy.
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Dean, T. (2013). Network+ Guide to Networks. (6th ed.).
Boston, MA: Course Technology, Cengage Learning.
Microsoft Support (2002, February 27). ID: 103884 . The OSI Model's Seven Layers
Defined and Functions Explained. Retrieved July 23, 2013, from
http://support.microsoft.com/kb/103884
Dummies.com (n.d.). Getting to Know the OSI Model for the CCNA Exam. Reasons for
a layered model. Retrieved July 23, 2012, from
http://www.dummies.com/how-to/content/getting-to-know-the-osi-model-forthe-ccna-exam.html
Dummies.com (n.d.). Network Basics. The Seven Layers of the OSI Reference Model.
Retrieved July 23, 2012, from
http://www.dummies.com/how-to/content/network-basics-the-seven-layers-ofthe-osi-referen.html
Microsoft Support (2002, February 27). ID: 103884 . The OSI Model's Seven Layers
Defined and Functions Explained. Retrieved July 23, 2013, from
http://support.microsoft.com/kb/103884
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