OSI Model Flashcards
Background network info. Not required for exam but helps with understanding Sec+ topics.
- Physical Layer
Concerned with transmission and reception of the unstructured raw bit stream over the physical medium.
Physical structure:
- Cables
- Hubs
Primary device - hub
- Data Link Layer
Provides node-to-node data transfer over the physical layer.
Frame - primary protocol data unit, container for single n/w packet and contains MAC address.
2 sublayers:
- Medium Access Control (MAC) Layer - controls a device’s access to n/w and permission to transmit data.
- Logical Link Control (LLC) Layer - identifies and encapsulates n/w layer protocols
Central devices: Switch, Bridge, WAP
Central protocols: PPP/SLIP
- Network Layer
Controls the operations of the subnet, deciding which physical path the data takes.
Provides functional and procedural means to xfr packets from one node to another network’s node.
Central device: Router
Central protocol: IP/IPX/ICMP
- Transport Layer
Ensures that messages are delivered error-free, in sequence, and with no lossess or duplications.
TCP - Host to Host, Flow Control
Central protocols: TCP/SPX/UDP
- Session Layer
Controls dialogue between computers
Establishes, manages and terminates connections between a local and remote machine
Synch & send to ports (logical ports)
Central device: logical ports
Central Protocols: RPC/SQL/NFS/NetBIOS names
- Presentation Layer
Formats the data to be presented to the Application layer. Viewed as the translator for the network.
Syntax layer - encrypt & decrypt (if needed)
Central protocols: JPEG/ACII/EBDIC/TIFF/GIF/PICT
- Application Layer
Serves as the window for users and application processes to access the network service.
End User Layer - program that opens what was sent or creates what will be sent.
Protocols: (E)SMTP/Telnet/FTP/DNS/DHCP/SNMP
OSI Model
Open Systems Interconnection model
Conceptual model that standardizes communications functions of telecom or computing systems.
Goals:
- Interoperability of diverse systems
- Standardized communications protocols
Comprised of 7 layers
OSI Model Layers
- Application layer
- Presentation layer
- Session layer
- Transport layer
- Network layer
- Data layer
- Physical layer