OSI Model Flashcards
What does “OSI” stand for?
Open Systems Interconnection
What is the OSI model?
A conceptual framework for how applications communicate over a network
How many layers are there in the OSI model?
7 layers
What are the 7 layers of the OSI model?
7 - Application
6 - Presentation
5 - Session
4 - Transport
3 - Network
2 - Data Link
1 - Physical
What is layer 7 of the OSI model?
7 - Application
What is layer 6 of the OSI model?
6 - Presentation
What is layer 5 of the OSI model?
5 - Session
What is layer 4 of the OSI model?
4 - Transport
What is layer 3 of the OSI model?
3 - Network
What is layer 2 of the OSI model?
2 - Data Link
What is layer 1 of the OSI model?
1 - Physical
The “Application” layer is which level? What does it do?
7 - Application
- Provides work services to the end user
- “Services”: protocols that work with the data that the client is using (HTTP, FTP, etc.)
- Provide a set of services to supply data to and recieve data from the “Presentation” layer
The “Presentation” layer is which level? What does it do?
6 - Presentation
- Does syntax processing. Converts data from one format to another
- Handles transmitting data from the top “Application” layer which is presented in “application format” to “network format” and vice versa
- Information is passed from the “Presentation” layer to the “Session” layer or “Application” layer
The “Session” layer is which level? What does it do?
5 - Session
- The construction, direction, and conclusion about connections between devices
- Supports multiple types of connections
- Responsible for authentication and reconnection if an interruption occurs
- After a session is established, data passes to or from the “Transport” layer
The “Transport” layer is which level? What does it do?
4 - Transport
- Responsible for the transmission of data across network connections
- Coordinates how much data to send, how fast to send the data, where the data goes, etc..
- TCP, UDP, etc.
- Once the transport layer has completed its function, data is passed to or from the “Network’ layer
What is TCP? What is UDP?
TCP - Transmission Control Protocol
UDP - User Datagram Protocol
The “Network” layer is which level? What does it do?
3 - Network
- Handles the routing of the data
- Once data is received at this layer, the data is scanned to determine if it has reached its final destination
- The “Network” layer sends data to the correct destinations on outgoing transmissions and receives incoming transmissions as well
- Manages the mapping between logical addresses and physical addresses
Which protocol is the most common for the “Network” layer?
IP: Internet Protocol
How does address mapping work for IP addresses? What is ARP?
Through ARP (Address Resolution Protocol)
What is TCP/IP
Transmission Control Protocol / Internet Protocol
The “Data Link” layer is which level? What does it do?
2 - Data Link
(most complex layer)
- Sets up links across the physical network
- Checks for transmission errors in data received from the “Physical” layer and then packages bits into data frames
- Manages physical addressing methods for MAC or LLC layers
- Data passes to or from the “Physical” layer
What are the sub-layers of the “Data Link” layer?
MAC (Media Access Control)
LLC (Logical Link Control)
The “Physical” layer is which level? What does it do?
1 - Physical
- Electrical / physical layer
- Encompasses all physical and electrical components of a network
- Transmits the digital data bits from the source/sending device’s physical layer over network communications media
