OSI Model and Networking Fundamentals

Vocabulary flashcards covering OSI model concepts, layer responsibilities, network signals, and related terminology from the Networking 1 fundamentals notes.

OSI model

Open Systems Interconnection reference model; a universal standard for networking formulated in the 1970s to standardize network communications between different types of networks.

OSI seven layers

Bottom to top: Physical (Layer 1), Data Link (Layer 2), Network (Layer 3), Transport (Layer 4), Session (Layer 5), Presentation (Layer 6), Application (Layer 7).

Stack

A set of OSI layers; can be referred to by layer names or by their numeric stack.

Physical Layer (Layer 1)

Bottom layer responsible for transmitting raw bit streams; handles hardware, cables, signals (analog or digital) and voltage levels.

Data Link Layer (Layer 2)

Second layer responsible for node-to-node data transfer; detects and may correct errors; contains LLC and MAC sublayers.

Network Layer (Layer 3)

Third layer that regulates the passage of packets across routes; handles routing and addressing (physical and logical paths).

Transport Layer (Layer 4)

Fourth layer responsible for reliable end-to-end data delivery and fragmentation of messages.

Session Layer (Layer 5)

Fifth layer that establishes, maintains, and terminates communication sessions; controls duration and recovery from transmission errors.

Presentation Layer (Layer 6)

Sixth layer that formats, translates, encrypts, and compresses data; handles character encodings like ASCII and EBCDIC.

Application Layer (Layer 7)

Top layer that provides user access to applications and network services (e.g., HTTP, SMTP) and interfaces for remote access.

Frame

A unit of data at the Data Link Layer used for transmitting data across a single link.

Packet

A discrete unit of data at the Network Layer used for routing across networks.

Bit

A binary digit; the most basic unit of data in computing and digital communications.

MAC address

Media Access Control address; a unique 48-bit hexadecimal identifier assigned to a network interface; first half identifies the vendor.

LLC (Logical Link Control)

Sublayer of the Data Link Layer responsible for flow control, error control, frame synchronization, and avoiding network traffic.

MAC sublayer

Sublayer of the Data Link Layer that handles addressing based on MAC addresses.

CRC (Cyclic Redundancy Check)

An error-detection method used to detect accidental changes to raw data in transmission.

EBCDIC

Extended Binary Coded Decimal Interchange Code; an 8-bit character encoding used by IBM and some older systems.

ASCII

American Standard Code for Information Interchange; an 8-bit character encoding supporting 128 characters, widely used in modern systems.

Analog signal

A continuous signal with varying voltage or amplitude; examples include voice, light waves, and radio signals.

Digital signal

A signal that encodes information in discrete binary values (0s and 1s); commonly used in LANs and high-speed WANs.

EMI

Electromagnetic Interference; interference caused by magnetic fields from electrical devices.

RFI

Radio Frequency Interference; disturbance caused by radio waves from devices like radios or TVs.

TWA (half-duplex)

Two-way alternate mode where only one direction transmits at a time (e.g., walkie-talkie).

TWS (full-duplex)

Two-way simultaneous mode where sending and receiving occur at the same time; more efficient than half-duplex.

Network topology

The arrangement of devices and connections in a network, affecting performance and scalability.

LAN and WAN

Local Area Network and Wide Area Network; OSI model supports internetworking between different network types.

HTTP, DNS, SMTP (Application Layer examples)

Protocols and services used at the Application Layer for web browsing, email, and name resolution.

OSI as foundation

The 7-layer OSI model is the foundation of LAN and WAN communications and guides inter-networking.

Physical Layer responsibilities (examples)

Manages data through physical media (wired and wireless); includes network connectors and conversion between analog and digital signals.

Data Link Layer responsibilities

Ensures proper data transmission, detects errors, and uses CRC; includes LLC and MAC sublayers.

Correlation of layers

Higher layers prepare data (formatting, encryption) and lower layers handle transmission and physical signaling.