A seven-layer conceptual framework that standardizes the functions of a telecommunication or computing system into universal sets of rules and requirements, facilitating interoperability between diverse products and software.
It helps visualize how different network functions interact, from physical transmission to application-level data handling.
Card 2
OSI Layer 2 (Data Link Layer)
Answer
This layer provides node-to-node data transfer, handling the physical addressing (MAC addresses) and error detection for frames within a local network segment.
Switches primarily operate at this layer, using MAC addresses to forward frames to specific devices on the same LAN.
Card 3
OSI Layer 3 (Network Layer)
Answer
This layer is responsible for logical addressing (IP addresses) and routing packets between different networks, determining the best path for data.
Routers primarily operate at this layer, making forwarding decisions based on destination IP addresses.
Card 4
OSI Layer 4 (Transport Layer)
Answer
This layer provides end-to-end communication services, including connection management, segmentation, flow control, and error recovery, primarily using TCP and UDP protocols.
It ensures data is delivered reliably (TCP) or quickly (UDP) between applications on different hosts.
Card 5
TCP/IP Model
Answer
A four-layer protocol suite that defines how data should be formatted, addressed, transmitted, routed, and received, forming the foundational standard for the internet.
Unlike the theoretical OSI model, TCP/IP is a practical, implementation-oriented model that directly corresponds to internet protocols.
Card 6
TCP (Transmission Control Protocol)
Answer
A connection-oriented protocol operating at the Transport Layer that provides reliable, ordered, and error-checked delivery of a stream of bytes between applications.
It ensures data integrity and delivery by using acknowledgments and retransmissions, making it suitable for web browsing and email.
Card 7
UDP (User Datagram Protocol)
Answer
A connectionless protocol operating at the Transport Layer that provides a fast, unreliable delivery service without error checking or guaranteed delivery.
It is preferred for applications where speed is critical and minor data loss is acceptable, such as streaming video or online gaming.
Card 8
IP Address
Answer
A unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication, serving as both an identifier for the host and a locator for its network.
Without an IP address, a device cannot communicate across networks, similar to how a house needs a street address.
Card 9
Subnet Mask
Answer
A 32-bit number that distinguishes the network portion of an IP address from the host portion, defining the boundaries of a subnet.
It tells a device which part of an IP address refers to the network and which part refers to a specific host within that network.
Card 10
CIDR (Classless Inter-Domain Routing)
Answer
A method for allocating IP addresses and routing IP packets that allows for more flexible and efficient use of IP address space than the older classful addressing system.
CIDR notation (e.g., /24) indicates the number of bits in the network portion of an IP address, enabling custom subnet sizes.
Card 11
Private IP Address
Answer
IP addresses reserved for use within private networks (LANs) and are not routable on the public internet, providing a layer of security and conserving public IP addresses.
Examples include 10.0.0.0/8, 172.16.0.0/12, and 192.168.0.0/16, allowing many organizations to use the same internal address ranges.
Card 12
Subnetting
Answer
The process of dividing a larger network into smaller, more manageable sub-networks (subnets) by borrowing bits from the host portion of an IP address.
It improves network performance, security, and simplifies management by breaking down broadcast domains.
Card 13
Broadcast Domain
Answer
A logical division of a computer network where all nodes can reach each other by broadcast at the data link layer, typically bounded by routers.
Subnetting reduces the size of broadcast domains, which can decrease network congestion and improve security.
Card 14
Router
Answer
A network device that forwards data packets between different computer networks, making decisions based on IP addresses to determine the optimal path.
Routers connect distinct networks, such as your home network to the internet, and are crucial for inter-network communication.
Card 15
Switch
Answer
A network device that connects devices within the same local area network (LAN), forwarding data frames to specific destination devices based on their MAC addresses.
Unlike hubs which broadcast data, switches learn MAC addresses and direct traffic efficiently only to the intended recipient.
Card 16
MAC Address (Media Access Control Address)
Answer
A unique, hardware-embedded identifier assigned to network interfaces for communications within a network segment, operating at the Data Link Layer.
It's a physical address, often written as six pairs of hexadecimal digits (e.g., 00:1A:2B:3C:4D:5E), that never changes unless the network adapter is replaced.
Card 17
Default Gateway
Answer
The IP address of the router interface on the local network that serves as the entry point for all traffic destined for other networks or the internet.
If a device wants to send data outside its current subnet, it must send it to the default gateway.
Card 18
Routing Table
Answer
A data table stored in a router or networked computer that lists routes to particular network destinations, along with the metrics (costs) associated with those routes.
Routers consult their routing table to decide which interface to use and which next-hop IP address to send a packet to.
Card 19
DNS (Domain Name System)
Answer
A hierarchical and distributed naming system that translates human-readable domain names (like www.example.com) into numerical IP addresses that computers use to identify each other.
It acts like a phonebook for the internet, allowing users to access websites by name instead of memorizing IP addresses.
Card 20
DHCP (Dynamic Host Configuration Protocol)
Answer
A network management protocol used on Internet Protocol (IP) networks for automatically assigning IP addresses and other communication parameters to devices connected to the network.
Without DHCP, administrators would have to manually configure IP addresses for every new device joining a network.
Card 21
DNS Resolver
Answer
A client-side service or application that initiates and sequences the queries that ultimately lead to a full answer to a requested resource, such as an IP address.
Your computer uses a DNS resolver (often provided by your ISP or a public service like Google DNS) to find the IP address for a domain name.
Card 22
Port 80 (HTTP)
Answer
The standard default port used for Hypertext Transfer Protocol (HTTP), which facilitates unencrypted communication between web browsers and web servers.
When you type a URL without specifying a port, your browser typically defaults to port 80 for HTTP requests.
Card 23
Port 443 (HTTPS)
Answer
The standard default port used for Hypertext Transfer Protocol Secure (HTTPS), which provides encrypted communication between web browsers and web servers using SSL/TLS.
This port ensures secure data transmission for sensitive information like login credentials and financial transactions.
Card 24
Port 22 (SSH)
Answer
The standard port for Secure Shell (SSH), a cryptographic network protocol that enables secure remote command-line access, file transfer, and tunneling services.
It provides a secure way to manage servers remotely, encrypting all communication between the client and server.
Card 25
Port 21 (FTP)
Answer
The standard control port for File Transfer Protocol (FTP), used for transferring files between a client and a server.
While still used, FTP is often replaced by SFTP (SSH File Transfer Protocol) or FTPS (FTP Secure) for better security due to its unencrypted nature.
Card 26
Ping
Answer
A command-line utility used to test the reachability of a host on an Internet Protocol (IP) network and to measure the round-trip time for messages sent from the originating host to a destination computer.
A successful ping indicates basic network connectivity; failures suggest issues like an offline host, firewall block, or routing problem.
Card 27
Traceroute (Tracert)
Answer
A network diagnostic tool that displays the path (route) and measures transit delays of packets across an Internet Protocol (IP) network from source to destination.
It helps identify where traffic stops or slows down along the path, pinpointing potential bottlenecks or failures in the network.
Card 28
ipconfig (Windows) / ifconfig (Linux/macOS)
Answer
Command-line tools used to display and manage the TCP/IP network configuration parameters for a system, including IP address, subnet mask, and default gateway.
These commands are essential for quickly checking a device's network settings and verifying if it has obtained an IP address correctly.
Card 29
Netstat
Answer
A command-line network utility that displays network connections (both incoming and outgoing), routing tables, and a number of network interface statistics.
It helps identify which ports are open, which applications are listening, and any active connections, useful for diagnosing connectivity or security issues.
Card 30
Loopback Address (127.0.0.1)
Answer
A special IP address (127.0.0.1 for IPv4) that refers to the local machine itself, used to test network applications or services running on the same host without involving physical network hardware.
Pinging 127.0.0.1 confirms that your TCP/IP stack is functioning correctly, even if your network card is disconnected.