Network Models & OSI Reference Model

Vocabulary flashcards covering key terms and functions of the OSI reference model, its layers, design principles, and example application protocols.

OSI Reference Model

A seven-layer framework created by ISO for standardizing network communication between open systems.

ISO (International Standards Organization)

The body that proposed and maintains the OSI model to promote international protocol standards.

Layer Abstraction Principle

Guideline stating that a new OSI layer should be created whenever a different level of abstraction is required.

Physical Layer

The OSI layer that transmits raw bits over the physical medium, dealing with signals, timing, and connectors.

Signal Representation

The choice of electrical signals used for ‘1’ and ‘0’ bits at the physical layer to ensure correct reception.

Bit Duration

The time (in nanoseconds) each bit occupies on the medium, a key physical-layer timing parameter.

Transmission Direction

Physical-layer decision on whether data can flow simultaneously both ways (full-duplex) or not.

Connection Management (Physical Layer)

Procedures for establishing and tearing down the physical connection between devices.

Connector Configuration

Specification of the number of pins and their functions in a network connector at the physical layer.

Data Link Layer

The OSI layer that provides error-free transmission between adjacent nodes through framing, acknowledgements, and flow control.

Data Frame

A block of data (hundreds/thousands of bytes) created by the data link layer for sequential transmission.

Acknowledgement Frame

Control frame sent by the receiver to confirm correct receipt of a data frame.

Traffic Regulation (Flow Control)

Mechanism in the data link layer that prevents a fast sender from overwhelming a slow receiver.

Medium Access Control (MAC) Sublayer

Part of the data link layer that controls access to a shared broadcast channel.

Network Layer

The OSI layer responsible for routing packets, handling congestion, QoS, and interconnecting heterogeneous networks.

Routing

Process of selecting a path for packets through a subnet, using static tables or dynamic updates.

Congestion Control

Network-layer technique for managing excess packets that cause bottlenecks.

Quality of Service (QoS)

Network-layer metrics such as delay, transit time, and jitter provided to upper layers.

Transport Layer

End-to-end OSI layer that segments data, ensures reliable delivery, and offers various service types to the session layer.

Error-Free Point-to-Point Channel

Common transport service delivering data in order with a practically negligible error rate.

Session Layer

Layer enabling sessions between machines, offering dialog control, token management, and synchronization.

Dialog Control

Session-layer service that tracks which party’s turn it is to transmit data.

Token Management

Session-layer method preventing simultaneous execution of critical operations by multiple parties.

Synchronization (Checkpointing)

Session-layer feature that inserts recovery points into long transmissions to resume after crashes.

Presentation Layer

OSI layer handling the syntax and semantics of data, providing abstract data structures and standard encoding.

Abstract Data Structure

Presentation-layer definition of data formats independent of machine representation for interoperability.

Application Layer

Top OSI layer containing user-oriented protocols such as HTTP, FTP, email, and network news.

HTTP (HyperText Transfer Protocol)

Application-layer protocol enabling web browsers to request and receive pages from servers.