OSI Model & TCP/IP Suite - Vocabulary Flashcards

Vocabulary flashcards covering OSI model layers, encapsulation/de-encapsulation, PDUs, and TCP/IP concepts from the lecture notes.

OSI (Open Systems Interconnection) Model

A conceptual framework by ISO for standardizing networking functions into seven layers.

Seven Layers of OSI

Application, Presentation, Session, Transport, Network, Data Link, and Physical.

Application Layer (Layer 7)

Closest to the end user; interacts with software applications; HTTP/HTTPS are examples of layer 7 protocols.

Presentation Layer (Layer 6)

Translates data between application and network formats; handles data representation and encryption/decryption.

Session Layer (Layer 5)

Manages dialogues (sessions) between hosts; establishes, maintains, and terminates connections.

Transport Layer (Layer 4)

Provides host-to-host delivery; segmentation and reassembly; ensures reliable data transfer.

Network Layer (Layer 3)

Provides connectivity between end hosts on different networks; logical addressing (IP) and path selection; routers operate here.

Data Link Layer (Layer 2)

Provides node-to-node data transfer; frames; layer 2 addressing; switches operate at this layer and data is formatted for the physical medium.

Physical Layer (Layer 1)

Defines physical characteristics of the transmission medium (voltage, cables, connectors); bits are converted to signals.

Encapsulation

Process where each layer adds its own header (and sometimes trailer) as data moves down the OSI stack.

De-encapsulation

Process of removing headers/trailers as data moves up the stack at the receiving end.

PDU (Protocol Data Unit)

Data units used at each layer:

• Data at the Application layer,

• Segment at the Transport layer,

• Packet at the Network layer,

• Frame at the Data Link layer.

Data, Segment, Packet, Frame

PDUs corresponding to OSI/TCP-IP layers:

• Data (Application),

• Segment (Transport),

• Packet (Network),

• Frame (Data Link).

Adjacent-layer interaction

Communication between neighboring layers on the same device as data passes between layers.

Same-layer interaction

Communication between the same layer on neighboring devices across the network.

Upper Layers

Layers 5–7 (Application, Presentation, Session) typically used by application developers; lower layers handle transport and routing.

Lower Layers

Layers 1–4 (Physical, Data Link, Network, Transport) primarily involved in data transport and connectivity,

HTTP/HTTPS

Layer 7 protocols used by web browsers; examples of Application layer protocols.

Layer 2 Addressing

MAC addresses used at the Data Link layer; switches operate here; hardware addressing.

Layer 3 Addressing

IP addresses used at the Network layer; used for routing and path selection.

Routers

Devices that operate at the Network layer (Layer 3) for inter-network routing and path determination.

Switches

Devices that operate at the Data Link layer (Layer 2) for forwarding frames based on MAC addresses.

TCP/IP Suite

A four- to five-layer conceptual model and protocol suite used on the Internet; foundational protocols include TCP and IP; developed by DARPA.

OSI vs TCP/IP

OSI is a seven-layer reference model; TCP/IP is the practical, fewer-layer suite used in real networks; OSI influenced thinking but TCP/IP is deployed.

OSI to TCP/IP mapping

Common mappings align OSI Application with TCP/IP Application, OSI Transport with TCP/IP Transport, and OSI Network with TCP/IP Internet.

Encryption in Presentation Layer

The Presentation layer handles encryption and decryption of data during transmission.

Application Data Format vs Network Format

Data at the Application layer is in application format; the Presentation layer translates it into a network-compatible format for transmission.

Physical Layer Characteristics

Defines physical medium properties (voltage levels, transmission distances, connectors, cables); bits become signals or vice versa.

Data Link Layer Functions

Provides node-to-node connectivity, defines frame structure and MAC addressing; switches operate here; detects/corrects some errors.

PDUs and Headers/Trailers

Headers contain control information; trailers may carry error-detection data; each layer adds its own header/trailer to the PDU.