OSI Model Flashcards

What does OSI stand for?

Open Systems Interconnection — a conceptual model that standardizes communication functions into 7 layers.

How many layers are in the OSI model? and what’s the top-to-bottom order?

7 layers: Application, Presentation, Session, Transport, Network, Data Link, Physical.

What is a common mnemonic to remember OSI layers (top → bottom)?

All People Seem To Need Data Processing.

What is the name and role of OSI Layer 7?

Application Layer – Closest to the end-user, provides network services like email, file transfer, web browsing.

What are examples of Layer 7 protocols?

HTTP/HTTPS, FTP, SMTP, DNS, POP3, IMAP, SNMP.

What is the name and role of OSI Layer 6?

Presentation Layer – Translates, encrypts, and compresses data for the Application Layer.

What are examples of Layer 6 functions?

Data formatting, character encoding (ASCII, EBCDIC), encryption (TLS/SSL), compression (JPEG, MP3, GIF).

What is the name and role of OSI Layer 5?

Session Layer – Establishes, manages, and terminates communication sessions between applications.

What are examples of Layer 5 functions/protocols?

NetBIOS, RPC, SQL session management, establishing check points in data transfer.

What is the name and role of OSI Layer 4?

Transport Layer – Ensures complete data transfer with error-checking and flow control.

What are examples of Layer 4 protocols?

TCP (reliable, connection-oriented), UDP (faster, connectionless).

What is Layer 4 addressing & data unit?

Uses port numbers (e.g., TCP 80 = HTTP). Data unit is called a Segment.

What is the name and role of OSI Layer 3?

Network Layer – Determines the best physical path for data; handles logical addressing and routing.

What are examples of Layer 3 protocols?

IP (IPv4, IPv6), ICMP, IPsec, OSPF, RIP, BGP.

What are Layer 3 devices & data unit?

Devices = Routers, Layer 3 switches. Data unit = Packet.

What is the name and role of OSI Layer 2?

Data Link Layer – Provides error detection, MAC addressing, and controls how data is placed on the medium.

What are the two sublayers of Layer 2?

LLC (Logical Link Control) and MAC (Media Access Control).

What are examples of Layer 2 protocols?

Ethernet (IEEE 802.3), PPP, Frame Relay, ARP.

What are Layer 2 devices & data unit?

Devices = Switches, Bridges. Data unit = Frame.

What is the name and role of OSI Layer 1?

Physical Layer – Defines the physical transmission of raw bits over a medium (cables, voltage, radio frequencies).

What are examples of Layer 1 technologies?

Ethernet cables, fiber optics, Wi-Fi radio waves, hubs, repeaters.

What is the Layer 1 data unit?

Bits (0s and 1s).

Which OSI layers are combined in the TCP/IP model’s Application layer?

Application (7), Presentation (6), and Session (5).

Which OSI layers map to the TCP/IP Network layer?

OSI’s Network layer (3).

Which OSI layers map to the TCP/IP Network Access (Link) layer?

Data Link (2) and Physical (1).