The Open System Interconnection model 7 Layers Flashcards
(19 cards)
What is the role of the Application Layer?
It provides network services directly to user applications like web browsers and email.
Give an example protocol at the Application Layer.
HTTP, FTP, SMTP
What does the Presentation Layer do?
It formats, encrypts, and compresses data for the Application Layer.
Give an example function of the Presentation Layer.
Data encryption, character encoding conversion
What is the main function of the Session Layer?
It establishes, manages, and ends sessions between applications.
What does the Session Layer control?
Communication synchronization and session management.
What does the Transport Layer do?
Segments data and ensures delivery — either reliable (TCP) or fast/unreliable (UDP).
What addressing is used at the Transport Layer?
Port numbers
What devices interact with the Transport Layer?
Firewalls (they filter by port and protocol)
What is the main responsibility of the Network Layer?
Routing packets and assigning IP addresses.
What devices operate at the Network Layer?
Routers, Layer 3 switches
What is the PDU of the Network Layer?
Packet
What does the Data Link Layer do?
Frames data with MAC addresses and handles local error detection.
What devices work at the Data Link Layer?
Switches, bridges, NICs
What is the PDU of the Data Link Layer?
Frame
What does the Physical Layer do?
Transmits raw bits as electrical/optical signals through cables or wireless.
What devices operate at the Physical Layer?
Cables, hubs, Wi-Fi radios, network interface cards
What is the PDU of the Physical Layer?
Bits
Match each OSI layer to its PDU.
Layers 7–5: Data
Layer 4: Segment
Layer 3: Packet
Layer 2: Frame
Layer 1: Bits
