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Same layer interaction on different computers
The two computers use a protocol to communicate with the same layer on another computer. The protocol defined by each layer uses a header that is transmitted between the computers to communicate what each computer wants to do.
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Adjacent layer interaction on the same computer.
On a single computer one layer provides a service to a higher layer. The software or hardware that implements the higher layer requests that the next lower layer perform the needed function.
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List the layers of the OSI model.
- Physical
- Datalink
- Network
- Transport
- Session
- Presentation
- Application
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Application layer
Interfaces between network and application software. Includes authenticatin services.
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Presentation layer
Defines format and organization of data. Includes encryption.
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Session layer
Establishes and maintains end-to-end bidirectional flows between end points. Includes managing transaction flows.
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Transport layer
Provides a variety of services between two host computers including connection establishement and termination, flow control, error recovery, and segmentation of large data blocks inter smaller parts for transmission.
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Network layer
Logical addresssing, routing and path determination.
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Datalink layer
Formats data into frames appropriate for transmission onto some physical medium. Defines rules for when medium can be used. Defines means by which to recognize transmission errors.
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Physical layer
Defines electrical, optical, cabling, connectors and procedural details required for transmitting bits represented as same form of energy passing over a physical medium.
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List the benefits of a layered network model
(See notes for full definitions)
- Less complex
- Standard interfaces
- Easier to learn
- Easier to develop
- Multivendor interoperability
- Modular engineering
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OSI layer compared to TCP/IP (4 and 5 layer)
- OSI TCP/IP 4layer TCP/IP 5layer
- 7. Presentation
- 6. Session
- 5. Application Application Application
- 4. Transport Transport Transport
- 3. Network Internetwork Internetwork
- 2. Dataling Datalink
- 1. Physical Network Access Physical
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Adjacent layer interaction
The general topic of how on one computer, two adjacent layers in a networking architectural model work together, with the lower layer providing services to the higher layer.
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Decapsulation
On a computer that receives data over a network, the process in which the device interprets the lower-layer headers and, when finished with each header, removes the header revealing the next higher PDU.
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Encapsulation
The placement of data from a higher layer protocol behind the header (and in some cases between a header and a trailer) of the next lower layer protocol. For example an IP packet cold be encapsulated in an ethernet header and trailer before being sent over and Ethernet.
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