OSI MODEL Flashcards
What is the purpose of the OSI model?
To standardize how devices communicate over a network.
Which OSI layer is responsible for end-to-end communication?
Transport Layer.
Which OSI layer is closest to the user?
Application Layer.
Which layer provides encryption?
Presentation Layer.
Which layer assigns logical addresses like IPs?
Network Layer.
Give an example of a Physical Layer device.
Hub, cables, repeaters.
What is transmitted in Layer 1?
Bits (0s and 1s).
True or False: Layer 1 understands IP addresses.
False.
Name a Physical Layer standard
Ethernet, USB, DSL, Bluetooth.
What is modulation?
Converting data into signals for transmission.
What are the two sublayers of the Data Link Layer?
LLC (Logical Link Control) and MAC (Media Access Control).
What address type does Layer 2 use?
MAC address.
What unit of data does Layer 2 use?
Frame.
What is the purpose of CRC in Layer 2?
Error detection.
Name a Layer 2 device.
Switch.
What is the PDU (Protocol Data Unit) for Layer 3?
Packet.
What is a protocol used at the Network Layer?
IP (Internet Protocol).
What Layer does a router operate on?
Layer 3 (Network Layer).
What is fragmentation?
Splitting data into smaller packets for transmission.
What is TTL (Time to Live)?
A field that limits the lifespan of a packet.
What is the main protocol for reliable delivery in Layer 4?
TCP (Transmission Control Protocol).
What is the main protocol for fast, connectionless delivery?
UDP (User Datagram Protocol).
What is a port number?
An address for a specific process or service.
What is segmentation?
Dividing large data into smaller pieces.
What is flow control?
Managing data speed between sender and receiver.
What’s the main job of the Session Layer?
: Start, manage, and end sessions between apps.
Is the Session Layer responsible for sync checkpoints?
Yes, to allow recovery if sessions are interrupted.
Example of a session-based activity?
Logging into a remote server (SSH).
What is session multiplexing?
Managing multiple sessions over one connection.
: Does the Session Layer handle encryption?
No, that’s the Presentation Layer.
What does the Presentation Layer do to data?
Translates, encrypts, and compresses it.
Example of format translation?
JPEG to BMP, or text to HTML.
What is data serialization?
Converting structured data into a format to send over a network.
Does the Presentation Layer work directly with users?
No, that’s the Application Layer.
Give one encryption protocol handled at this layer.
SSL/TLS.
Name a protocol at the Application Layer.
HTTP, FTP, SMTP, DNS.
What does the Application Layer provide?
Services for software and user interaction.
What’s the difference between the App Layer and applications?
The App Layer provides network services, not the actual apps.
Example of an Application Layer service?
Web browsing (HTTP), email (SMTP/IMAP).
Which layer do DNS and DHCP work on?
Layer 7 – Application Layer.
the 7 layers of the OSI model in order (top to bottom):
“All People Seem To Need Data Processing”
1 Application
2 Presentation
3 Session
4 Transport
5 Network
6 Data Link
7 Physical
