Common Networking Terms and What They Mean:
| Title | Description |
|---|---|
| OSI (Open Systems Interconnection) | An ISO Model for networking. Consists of 7 layers. Can be used to structure complex networks by encapsulating them into layers and building on top of abstractions in a standard way. Does not map well to the networking model for the internet. Learn more. |
| Bit | Represents electrical signals (0 = off, 1 = on). |
| Byte | A group of bits (usually represented as 8 bits). 1 byte = 8 bits. |
| Hex | A more concise way to represent computer signals using hexadecimal characters (Base-16) for human readability. 1F is easier to read than 00011111. |
| Host | A computer. Could be a personal computer, a server, or something else. Doesn’t matter. |
| Link | A physical medium (cables or radio waves) connecting two hosts. |
| Physical Port | A physical port where a link can be plugged in. |
| Logical Port | A software construct that allows programmers to tap into the networking stack. Example: TCP ports, UDP ports, etc. Note: TCP Port ≠ UDP Port. |
| Socket | A software interface that connects a process to another process on the same or different host using the protocol family (addressing domain) and the socket type (communication type). Common Protocol Families: IPv4, IPv6, IPC (Inter-Process Communication—Local) Common Socket Types: Stream Socket (TCP), Datagram Socket (UDP), Raw Socket (IP). |
| Network Interface | Network equipment that connects the host to an external link. Used to be a physical card. Nowadays, built into the motherboard of the computer. Uses Ethernet or WiFi. Has a physical port (in the case of Ethernet). Also known as NIC/Interface/Network Adapter/Network Card. |
| Ethernet | A set of network protocols to transmit information from one host to another over a link. |
| WiFi | Extends Ethernet by using radio waves to transfer signals. |
| IP Address | A unique address used to identify devices on the internet. Commonly refers to IPv4 (32 bits, 2³² = 4.2 billion addresses—not enough for all of humanity). Newer is IPv6 (128 bits, 340 undecillion (undecillion = 10³⁶) addresses—hopefully enough for everyone). Example: 192.168.1.1 Numbers separated by dots represent 8 bits each. 8 × 4 = 32 bits. |
| CIDR | Classless Inter-Domain Routing Notation: A human-readable way to represent a series of IP addresses. Example: 192.168.1.0/24 Everything after / represents the number of fixed bits (also referred to as the network prefix). In the example, 24 bits are fixed, which means 8 bits are free. So the CIDR represents 256 IP addresses (2⁸ = 256 combinations). |
| IP Packet | A series of bytes sent from one host to another. |
| MAC Address | Media Access Control Address: A globally unique 48-bit address burned into the network interface for a device. Structure: First 24 bits: Organizational Unique Identifier. Last 24 bits: Identifies the device itself. Example: 00:1A:2B:3C:4D:5E (represented in hex for conciseness). |
| Hub | Has multiple ports. Sends a signal received at one port to every link on the hub. |
| Switch | A hub with intelligence. It incrementally maps physical ports to MAC addresses and only sends signals to relevant ports. |
| Router | A specialized computer that maintains a forwarding table consisting of destinations, sources, and interfaces. When a router receives a packet, it uses the route table to determine where to send the packet. |
| Network | A series of hosts connected through links, hubs, switches, and routers. Represented by a CIDR range, e.g., 10.16.0.0/16. |
| Subnet | A smaller network carved out of a bigger network (sub-network). Represented by a CIDR range, e.g., 10.16.1.0/24. |
| Subnet Mask | Another way of representing a subnet IP range. All the 1s represent the network prefix. Example: Mask: 255.255.255.0 Network Address: 192.168.1.0 Equivalent CIDR: 192.168.1.0/24 The subnet mask is commonly used by routers to determine if the destination IP address for a packet is part of the subnet by performing a bitwise AND operation between the subnet mask and the network address. |
| Network Topology | A map of a connected network. |
| Full-Mesh Topology | Every node is connected directly to every other node in a network. |
| Hub & Spoke Topology | Multiple networks are connected using a central network. |
| Bandwidth | Measured in bits per second, it indicates how much data a certain type of cable can carry over a given period. e.g., 500 Mbps. Units: Mbps: Megabits per second (not the same as MBps) Gbps: Gigabits per second. |
| Latency | The time it takes for a signal to travel from one host to another. Measured in milliseconds (ms). |
| Propagation Delay | The time it takes for a bit to travel along the link. |
| Packet Delay | The time it takes for a packet to travel from one host to another. Formula: Packet Delay = Propagation Delay + Transmission Delay + Queuing Delay. |
Reserved CIDR Ranges
Here are a few reserved CIDR blocks for various purposes:
- 10.0.0.0/8 - Private network addresses (very common)
- 192.168.0.0/16 - Private network addresses (very common)
- 127.0.0.0/8 - This computer, via the loopback device.
- 172.16.0.0/12 - Private network addresses.
- 192.0.0.0/24 - Private network addresses.
- 198.18.0.0/15 - Private network addresses.
- 192.0.2.0/24 - Documentation.
- 198.51.100.0/24 - Documentation.
- 203.0.113.0/24 - Documentation.
- 233.252.0.0/24 - Documentation.
Number Bases
| Base | Base Name | Common Prefix |
|---|---|---|
| 2 | Binary | 0b |
| 8 | Octal | 0o |
| 10 | Decimal | None |
| 16 | Hexadecimal | 0x |