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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-1
Building a Simple Network
Understanding theHost-to-HostCommunications Model
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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-2
Understanding Host-to-HostCommunications
Older model
Proprietary
Application and combinations software controlled by onevendor
Standards-based model
Multivendor software
Layered approach
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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-3
OSI Model
Reduces complexity
Standardizes interfaces
Facilitates modular engineering
Ensures interoperable technology
Accelerates evolution
Simplifies teaching and learning
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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-4
The Seven Layers of the OSI Model (Cont.)
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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-5
The Seven Layers of the OSI Model (Cont.)
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2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-6
The Seven Layers of the OSI Model (Cont.)
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7/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-7
The Seven Layers of the OSI Model (Cont.)
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8/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-8
The Seven Layers of the OSI Model (Cont.)
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9/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-9
The Seven Layers of the OSI Model (Cont.)
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10/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-10
The Seven Layers of the OSI Model
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11/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-11
Data Encapsulation
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12/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-12
Data De-Encapsulation
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13/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-13
Peer-to-Peer Communication
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14/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-14
Summary
The OSI reference model defines the network functions that occurat each layer.
The physical layer defines the electrical, mechanical, procedural,and functional specifications for activating, maintaining, and
deactivating the physical link between end systems.
The data link layer defines how data is formatted for transmissionand how access to the physical media is controlled.
The network layer provides connectivity and path selectionbetween two host systems that may be located on geographically
separated networks.
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15/17 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.01-15
Summary (Cont.)
The transport layer segments data from the system of the sendinghost and reassembles the data into a data stream on the systemof the receiving host.
The session layer establishes, manages, and terminates sessions
between two communicating hosts. The presentation layer ensures that the information sent at the
application layer of one system is readable by the applicationlayer of another system.
The application layer provides network services to the
applications of the user, such as e-mail, file transfer, and terminalemulation.
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Summary (Cont.)
The information sent on a network is referred to as data or datapackets. If one computer wants to send data to another computer,the data must first be packaged by a process called encapsulation.
When the remote device receives a sequence of bits, the physical
layer at the remote device passes the bits to the data link layer formanipulation. This process is referred to as de-encapsulation.
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