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 <website or IP>	Ping device for connectivity or use a common server like Google's DNS (8.8.8.8).
	traceroute <website or IP>	Show routers packet interacted with. Use for troubleshooting.
	nslookup <website name>	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.