OSI Reference Model Practice Flashcards

Vocabulary flashcards based on the OSI Reference Model lecture notes, covering all seven layers, the DoD model, and data encapsulation processes.

Network Reference Model

A blueprint detailing how communication between network devices should occur, preventing proprietary lock-in to a single vendor's equipment.

Protocols

Rules that govern end-to-end communication between devices on a network.

TCP/IP suite

The most prevalent protocol suite and the foundation of the Internet.

OSI Reference Model

Developed by the International Organization for Standardization ($ISO$) and formalized in $1984$, it consists of $7$ layers governing network information transfer.

Layer-7 - Application layer

The top-most layer that provides the interface between the user application and the network, identifies communication partners, and determines resource availability.

Layer-6 - Presentation layer

Controls the formatting and syntax of user data (such as $GIF$, $JPG$, or $MP3$) and can perform encryption and compression.

Layer-5 - Session layer

Responsible for establishing, maintaining, and terminating sessions between devices, managing communication types like Full-Duplex or Half-Duplex.

Full-Duplex

A category of session communication that allows for simultaneous two-way communication.

Half-Duplex

A category of session communication that allows for two-way communication, but not simultaneously.

Simplex

A category of session communication consisting of one-way communication only.

Layer-4 - Transport layer

Ensures the reliable transfer of data so it arrives error-free and in order, utilizing either connection-oriented or connectionless communication.

Segmentation and sequencing

A Transport layer service where data is broken into smaller pieces and assigned a sequence number for reassembly at the receiving device.

Flow control (or windowing)

The negotiation of the data transfer rate to prevent network congestion.

Transmission Control Protocol (TCP)

A connection-oriented protocol in the $TCP/IP$ suite that ensures reliable delivery of data.

User Datagram Protocol (UDP)

A connectionless protocol in the $TCP/IP$ suite.

Layer-3 - Network layer

Controls internetwork communication with two key responsibilities: logical addressing and routing.

Logical addressing

The provision of a unique address identifying both the host and the network the host exists on.

Routing

The process of determining the best path to a particular destination network.

Layer-2 - Data-Link layer

Responsible for transporting data within a network and packaging higher-layer data into frames.

Logical Link Control (LLC) sublayer

An intermediary between the physical link and higher layer protocols that ensures protocols like $IP$ function regardless of the physical technology used.

Media Access Control (MAC) sublayer

Controls access to the physical medium, using methods like $CSMA/CD$ for Ethernet.

Encapsulation (Framing)

The process of packaging higher-layer data into frames so it can be put onto the physical wire.

Layer-1 - Physical layer

Controls the signaling and transferring of raw bits onto the physical medium, including cabling, connectors, and hubs.

Protocol Data Units (PDUs)

Headers (and sometimes trailers) added by each layer containing protocol information specific to that layer.

Segments

The name of the $PDU$ at the Transport layer.

Packets

The name of the $PDU$ at the Network layer.

Frames

The name of the $PDU$ at the Data-Link layer.

Decapsulation

The process on a receiving device where a $PDU$ header is processed and stripped away before being sent to the next upper layer.

DoD Model

A four-layer networking model consisting of the Application, Host-to-Host, Internet, and Network Access layers.