OSI Model – 7 Layer

Question 1

Layer 7 – Application

Answer 1

** Key Functions:**
Interface between user and network

Provides network services to applications (e.g., browsers, email)

Example protocols: HTTP, FTP, SMTP

PDU: Data

**Example device: **Application software (e.g., Zoom, Chrome)

Question 2

Layer 6 – Presentation

Answer 2

** Key Functions:**
Translates data formats (e.g., character encoding, encryption, compression)

Ensures data is in a usable format for the Application Layer

PDU: Data

Example: Encryption engines, codecs

Question 3

Layer 5 – Session

Answer 3

** Key Functions:**
Establishes, manages, and terminates sessions between applications

Controls communication synchronization and dialog

PDU: Data

Example: Session managers, APIs

Question 4

Layer 4 – Transport

Answer 4

** Key Functions:**
Breaks data into segments

Adds port numbers for application-specific routing

Ensures reliable delivery (TCP) or faster but unreliable delivery (UDP)

Firewalls filter based on transport protocols and ports

PDU: Segment

Example: TCP, UDP, Firewalls

Question 5

Layer 3 – Network

Answer 5

** Key Functions**
Adds IP addresses to create packets

Determines the best path across networks using routing

Routes packets between different networks

PDU: Packet

Devices: Routers, Layer 3 switches, firewalls

Question 6

Layer 2 – Data Link

Answer 6

** Key Functions**
Adds MAC addresses to form frames

Handles error detection for local transmission

Controls access to the physical medium

PDU: Frame

Devices: Switches, bridges, network interface cards (NICs)

Question 7

Layer 1 – Physical

Answer 7

** Key Functions**
Transmits raw bits over the physical medium (cables, wireless, etc.)

Converts data into electrical, optical, or radio signals

Concerned with connectors, voltage, frequencies, and physical standards

PDU: Bits

Devices: Cables, hubs, Wi-Fi radios, network cards