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What are the 7 layers of the OSI Model?
- 7. Application
- 6. Presentation
- 5. Session
- 4. Transport
- 3. Network
- 2. Data Link
- 1. Network
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Functions of the Application Layer 7
- End user interacts with the network
- Authentication happens at this layer
- Ensures remote communication partner is available
- Ensures needed communication resources exist (ie modem)
- Both parties agree on procedures of data integrity, privacy and error recovery
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What device and application protocols run at Layer 7?
- Firewalls
- Email protocols ie SMTP and POP3
- Telnet
- HTTP
- FTP File Transfer Protocl
- SNMP Simple Network Managment Protocol
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Funcitions of Presentation Layer 6
- Formats Data
- Encrypts data
- Compatability with operating system
- Proper encapsulation of data for network transmission
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File types associated with Presentation Layer
JPEG, MPEG, ASCII, and TIFF
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Functions of Session Layer 5
- Manages 2 way communication between 2 remote hosts
- Handles the creation, maintence and teardown of communications between 2 hosts
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Functions of the Transport Layer 4
- Establishes a logical end-to-end connection between 2 systems
- segments data received from the upper layers of the OSI model
- Makes sure that data gets to the destination in the correct order and free of errors
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Two methods of transporting data
Connection-oriented (TCP) and Connectionless (UDP)
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Functions of Network Layer 3
- Runs IP at this layer
- Routes at this layer (routers run at this layer)
- Finds valid paths from local router to destination
- Selects best path
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Devices that run at Data Link Layer 2
- Switches run at this layer
- Wireless Access Points (WAP) run at this layer
- Modems and DSL run at this layer
- HDLC
- Ethernet
- PPP Point-to-Point Protocol
- Frame Relay
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Functions of Data Link Layer
- Performs error detection (does not perform error recovery) using Frame Check Sequence
- Also known as MAC address Layer
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Functions of Physical Layer 1
- Translates 1s and 0s
- Concerns itself with cabling, pins, connectors, voltages
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