Physical Layer
Handles the transmission of raw bits over physical media like cables and wireless signals. Deals with voltage levels
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| Term | Definition |
|---|---|
| Physical Layer | Handles the transmission of raw bits over physical media like cables and wireless signals. Deals with voltage levels |
| Data Link Layer | Provides node-to-node data transfer and handles error detection/correction. Uses MAC addresses and is where switches operate. Includes LLC and MAC sublayers |
| Network Layer | Responsible for logical addressing and routing packets between different networks. This is where routers operate and IP addresses are used |
| Transport Layer | Ensures reliable data transfer between hosts with error checking and flow control. Handles segmentation and can provide connection-oriented or connectionless communication |
| Session Layer | The Session Layer (Layer 5) of the OSI model is responsible for establishing, managing, and terminating dialogues (sessions) between applications on different devices. |
| Presentation Layer | Translates data between application and network formats. Handles encryption |
| Application Layer | Closest to end users and provides network services directly to applications. Where protocols like HTTP |
| TCP/IP Application Layer | Combines OSI layers 5-7. Provides network services and protocols that applications use to communicate |
| TCP/IP Transport Layer | Provides end-to-end communication services. Uses TCP for reliable |
| TCP/IP Internet Layer | Handles logical addressing and routing of packets across networks. IP protocol operates here along with ICMP and ARP |
| TCP/IP Network Access Layer | Combines OSI layers 1-2. Handles physical transmission of data and local network protocols like Ethernet and WiFi |
| Class A IP Range | 1.0.0.0 to 126.0.0.0 with default mask 255.0.0.0. First bit is 0 |
| Class B IP Range | 128.0.0.0 to 191.255.0.0 with default mask 255.255.0.0. First two bits are 10 |
| Class C IP Range | 192.0.0.0 to 223.255.255.0 with default mask 255.255.255.0. First three bits are 110 |
| Private IP Ranges | 10.0.0.0/8 |
| Subnet Mask | Binary pattern that determines which portion of an IP address represents the network and which represents the host |
| CIDR Notation | Shorthand method using a slash followed by the number of network bits. Example: 192.168.1.0/24 means first 24 bits are network |
| Default Gateway | Router IP address that devices use to send traffic destined for other networks. Acts as the exit point from the local network |
| IPv6 | 128-bit addressing system using hexadecimal notation separated by colons. Designed to replace IPv4 due to address exhaustion |
| TCP | Connection-oriented protocol that guarantees delivery with error checking |
| UDP | Connectionless protocol that sends data without establishing a connection or guaranteeing delivery. Faster but less reliable |
| HTTP | Port 80 protocol for transferring web pages and resources. Uses request-response model between clients and servers |
| HTTPS | Port 443 protocol that adds encryption to HTTP using SSL/TLS. Secures data transmission between client and server |
| DNS | Port 53 service that translates domain names into IP addresses. Operates hierarchically with root |
| DHCP | Port 67/68 protocol that automatically assigns IP addresses and network configuration to devices on a network |
| ARP | Protocol that maps IP addresses to MAC addresses on a local network. Maintains a cache of recent mappings |
| ICMP | Protocol used for diagnostic and error-reporting purposes. Powers tools like ping and traceroute |
| FTP | Port 21 protocol for transferring files between systems. Sends credentials and data in cleartext |
| SFTP | Port 22 protocol that provides secure file transfer over SSH with encryption. Not related to FTPS |
| SSH | Port 22 protocol providing secure remote access and command execution. Uses encryption and supports key-based authentication |
| Router | Operates at Layer 3 and forwards packets between different networks based on IP addresses. Makes routing decisions |
| Switch | Operates at Layer 2 and forwards frames within a network based on MAC addresses. Creates separate collision domains |
| Hub | Operates at Layer 1 and broadcasts all traffic to every connected device. Creates one large collision domain |
| Firewall | Security device that monitors and filters traffic based on predetermined rules. Can operate at multiple layers |
| Access Point | Device that allows wireless devices to connect to a wired network. Broadcasts SSIDs and manages wireless connections |
| Modem | Device that modulates and demodulates signals to connect a local network to an ISP. Converts between analog and digital |
| Load Balancer | Distributes network traffic across multiple servers to optimize resource use and prevent overload |
| MAC Address | 48-bit physical address burned into network interface hardware. Consists of 6 hexadecimal octets separated by colons or hyphens |
| Port Numbers | 16-bit numbers that identify specific processes or services on a host. Range from 0-65535 with well-known ports below 1024 |
| Common Ports | HTTP:80 |
| Broadcast | Transmission sent to all devices on a network segment. Uses MAC address FF:FF:FF:FF:FF:FF or IP ending in .255 |
| Unicast | One-to-one transmission sent from one source to one specific destination. Most common traffic type |
| Multicast | One-to-many transmission sent to a group of interested recipients. Uses special IP address range 224.0.0.0 to 239.255.255.255 |
| Collision Domain | Network segment where data packets can collide. Switches create separate collision domains for each port |
| Broadcast Domain | Network segment where broadcast traffic is propagated. Routers separate broadcast domains while switches don't |
| NAT | Technique that translates private IP addresses to public ones for internet communication. Conserves public IP addresses |
| VLAN | Logical segmentation of a network at Layer 2 that creates separate broadcast domains on the same physical switch |
| VPN | Encrypted tunnel that allows secure communication over public networks. Creates a virtual private connection |
| Bandwidth | Maximum data transfer rate of a network connection. Measured in bits per second |
| Throughput | Actual data transfer rate achieved in practice. Usually lower than bandwidth due to overhead and congestion |
| Latency | Time delay for data to travel from source to destination. Measured in milliseconds and affects responsiveness |
| Half-Duplex | Communication mode where data flows in both directions but only one direction at a time. Example: walkie-talkies |
| Full-Duplex | Communication mode where data flows in both directions simultaneously. Modern switches and NICs use this |
| Packet Structure | Data unit consisting of header (source/destination info |
| Three-Way Handshake | TCP connection establishment process using SYN |
| command - ipconfig | Displays IP configuration information |
| command - ping | Tests Connections to other IP ports |
| command - netstat | Displays network connections. |
| command - tracert | Displays the route taken to the destination |
| command - nslookup | Directly queries the name server for information on a destination domain. |