CompTIA Network+ N10-009 Lesson 1: OSI Model

Vocabulary flashcards covering OSI layers, PDUs, devices, protocols, and encapsulation flow based on CompTIA Network+ N10-009 Lesson 1 study notes.

OSI Layer Mnemonic (Layer 7 to 1)

"All People Seem To Need Data Processing" (Application, Presentation, Session, Transport, Network, Data Link, Physical).

Layer 1 - Physical

The OSI layer responsible for moving raw 1s and 0s across a physical or wireless medium using cables, signals, connectors, transceivers, hubs, and repeaters.

Physical Layer PDU

Bits.

Layer 2 - Data Link

The OSI layer associated with MAC addresses, Ethernet, switches, frames, and VLANs.

Data Link Layer PDU

Frame.

FCS (Frame Check Sequence)

A field in an Ethernet frame used for error detection.

CRC (Cyclic Redundancy Check)

The error-checking calculation associated with detecting frame corruption.

Layer 3 - Network

The OSI layer responsible for IPv4/IPv6 addresses, routers, routing tables, and default gateways to move traffic between different IP networks.

Network Layer PDU

Packet.

Layer 4 - Transport

The OSI layer responsible for end-to-end communication management using TCP, UDP, and port numbers.

TCP PDU

Segment.

UDP PDU

Datagram.

TCP (Transmission Control Protocol)

A connection-oriented and reliable transport-layer protocol that uses a three-way handshake (SYN -> SYN-ACK -> ACK).

UDP (User Datagram Protocol)

A connectionless transport-layer protocol with less overhead that does not provide built-in delivery acknowledgments and retransmission behavior.

Three-Way Handshake

The TCP connection setup process consisting of SYN -> SYN-ACK -> ACK.

Layer 5 - Session

The OSI layer that establishes, manages, and terminates communication sessions.

Layer 6 - Presentation

The OSI layer responsible for data formatting, encoding, encryption/decryption, and compression/decompression.

Layer 7 - Application

The OSI layer providing network services and protocols used by applications.

Encapsulation

The process of moving data down the OSI stack: Data -> Segment/Datagram -> Packet -> Frame -> Bits.

De-encapsulation

The process of moving data up the OSI stack: Bits -> Frame -> Packet -> Segment/Datagram -> Data.