> For the complete documentation index, see [llms.txt](https://sallam.gitbook.io/sec-88/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://sallam.gitbook.io/sec-88/network-sec/networking-fundamentals.md). # Networking Fundamentals ## Network Security Notes ### Basic Definitions Related to Networking 1. **Network**: A collection of **interconnected devices** (e.g., computers, servers) for **communication** and **resource sharing**. 2. **Protocol**: Rules and standards governing communication in a network. 3. **IP Address**: Unique numerical identifier for devices on a network. 4. **Router**: Device forwarding data between different networks, directing traffic. 5. **Switch**: Connects devices on a local network, forwarding data based on MAC addresses. 6. **Firewall**: Monitors and controls network traffic, enforcing access policies. 7. **DNS** (Domain Name System): Translates domain names to IP addresses. 8. **DHCP**: Assigns IP addresses and network configuration automatically. 9. **LAN** (Local Area Network): Connects devices in a limited area. 10. **WAN** (Wide Area Network): Spans large distances, connecting LANs. 11. **Ethernet**: Standard for wired connections, defining OSI model layers. 12. **Wi-Fi**: Wireless networking allowing cable-free connections. 13. **VPN** (Virtual Private Network): Secure connection over a public network. 14. **Bandwidth**: Maximum data transmitted over a network in a given time. 15. **Latency**: Time delay in data transmission over a network. 16. **Clients**: Devices requesting services/resources from servers. 17. **Server**: Stores and manages resources, responding to client requests. 18. **Request-Response**: Client-server interaction: request, process, respond. 19. **Resource Sharing**: Servers share resources with multiple clients. 20. **Scalability**: Capability for multiple clients to connect to a server. 21. **Client Responsibility**: Clients handle services/resources received. ### Most Common Protocols | Protocol | Port Number | Description | | -------- | ----------- | ------------------------------------- | | HTTP | 80 | Hypertext Transfer Protocol | | HTTPS | 443 | HTTP Secure | | FTP | 21 | File Transfer Protocol | | SSH | 22 | Secure Shell | | Telnet | 23 | Telnet Protocol | | SMTP | 25 | Simple Mail Transfer Protocol | | DNS | 53 | Domain Name System | | DHCP | 67/68 | Dynamic Host Configuration Protocol | | POP3 | 110 | Post Office Protocol 3 | | IMAP | 143 | Internet Message Access Protocol | | RDP | 3389 | Remote Desktop Protocol | | NTP | 123 | Network Time Protocol | | SNMP | 161 | Simple Network Management Protocol | | LDAP | 389 | Lightweight Directory Access Protocol | | SMTPS | 465 | SMTP Secure | | SIP | 5060/5061 | Session Initiation Protocol | | FTPS | 990 | FTP Secure | ### Network Types * **Local Area Network (LAN)**: Connects devices in a limited geographical area. * **Wide Area Network (WAN)**: Spans large distances, connecting multiple LANs. * **Metropolitan Area Network (MAN)**: Covers a larger geographic area than a LAN. * **Campus Area Network (CAN)**: Interconnects LANs within a university campus or large organization. * **Personal Area Network (PAN)**: Connects devices in close proximity to an individual. * **Wireless Local Area Network (WLAN)**: LAN using wireless communication technologies. * **Virtual Private Network (VPN)**: Provides a secure, encrypted connection over a public network. * **Storage Area Network (SAN)**: Dedicated network providing high-speed access to shared storage devices. * **Cloud Computing Network**: Infrastructure used in cloud computing environments. * **Internet**: Global network of interconnected networks. ### 7 Layer OSI Model | Layer | Name | Function | Typical Use | Protocols | | ----- | ------------ | --------------------------------------------------------------------- | -------------------------------- | ------------------------------------ | | 7 | Application | Interface between software applications and the network | End User Layer | HTTP, FTP, SSH, DNS | | 6 | Presentation | Translates data into a format understood by the application layer | Syntax Layer | SSL, SSH, IMAP, MPEG, JPEG | | 5 | Session | Establishes, manages, and terminates connections between applications | Sync & Send Layer, APIs, Sockets | | | 4 | Transport | Ensures reliable delivery of data between hosts | End-to-end Connections | TCP, UDP | | 3 | Network | Handles routing of data packets between networks | Packets | IP, ICMP, IPSec, IGMP | | 2 | Data Link | Manages data transmission over a physical link | Frames | Ethernet, PPP, Switch | | 1 | Physical | Transmits raw data bits over a physical medium | Physical Structure | Fiber, Access Points, Copper Cabling | ### Network Topologies * **Bus Topology**: All computers connected to a single cable. * **Star Topology**: Each node connected to a switch. * **Ring Topology**: Each node connected to one other, reducing packet collision. * **Mesh Topology**: Each node has an independent connection to every other node. ### Network Cables - Copper | Cable Type | Max Data Transfer Speed | Max Operating Length | | ---------- | ----------------------- | -------------------- | | CAT5 | 100 Mbps | 100 Meters | | CAT5e | 1 Gbps | 100 Meters | | CAT6 | 10 Gbps | 55 Meters | | CAT6a | 10 Gbps | 100 Meters | | CAT7 | 10 Gbps | 100 Meters | | CAT8 | 40 Gbps | 30 Meters | ### Network Cables - Fiber | Cable Type | Max Speed/Distance | Typical Use | | ------------------- | --------------------- | ---------------------------------------------------------------------------------------- | | OM1 - Orange Jacket | 10 Gbps/33 Meters | 100 Mbps Ethernet | | OM2 - Orange Jacket | 10 Gbps/82 Meters | 1 Gbps Ethernet | | OM3 - Aqua Jacket | 10 Gbps/300 Meters | 10 Gbps Ethernet | | OM4 - Aqua Jacket | 10 Gbps/400 Meters | 100 Gbps Ethernet @ 150 meters | | OM5 - Green Jacket | 10 Gbps/400 Meters | Improvements on OM4. Efficient light wavelength breakdown. | | OS1 - Yellow Jacket | Up to 100 Gbps/10 km | Single-mode fiber for indoor nodes. Used in fiber internet connections and data centers. | | OS2 - Yellow Jacket | Up to 100 Gbps/200 km | Single-mode fiber for outdoor infrastructure. Used for MANs, ISPs, or MSPs. | ### OSI Troubleshooting | Layer | Command | Purpose | | ------------ | ---------------------------- | -------------------------------------------------------------------------------- | | Physical | `ip -br -c link` | Check physical interface status. Detailed NIC and virtual NIC information. | | Data Link | `ip neighbor show` | Display ARP table showing IP and MAC addresses of reachable devices. | | Network | `ip -br -c address show` | Check NIC connection status, IP address, and CIDR. Ensure valid IP on LAN NIC. | | | `ping ` | Ping device for connectivity or use a common server like Google's DNS (8.8.8.8). | | | `traceroute ` | Show routers packet interacted with. Use for troubleshooting. | | | `nslookup ` | Check DNS entries on your server. Ensure IPs match ping results. | | Transport | `ss -tunlp4` | Show socket statistics. Verify connections and ports on the server. | | Session | `ssh` or `rtp` | Establish SSH session or initiate RTP session for testing. | | Presentation | `html`, `rtsp` | Connect to a camera's webpage or query a camera stream through VLC. | | Application | Using the program | Interact with a webpage or view DS logs to confirm the application is running. | ### Network Hardware * **Network Interface Controller (NIC)**: Ethernet jack on a computer. * **Wireless Network Interface Controller**: Uses radio waves to connect to an access point.