Networking Fundamentals
Network Security Notes
Basic Definitions Related to Networking
Network: A collection of interconnected devices (e.g., computers, servers) for communication and resource sharing.
Protocol: Rules and standards governing communication in a network.
IP Address: Unique numerical identifier for devices on a network.
Router: Device forwarding data between different networks, directing traffic.
Switch: Connects devices on a local network, forwarding data based on MAC addresses.
Firewall: Monitors and controls network traffic, enforcing access policies.
DNS (Domain Name System): Translates domain names to IP addresses.
DHCP: Assigns IP addresses and network configuration automatically.
LAN (Local Area Network): Connects devices in a limited area.
WAN (Wide Area Network): Spans large distances, connecting LANs.
Ethernet: Standard for wired connections, defining OSI model layers.
Wi-Fi: Wireless networking allowing cable-free connections.
VPN (Virtual Private Network): Secure connection over a public network.
Bandwidth: Maximum data transmitted over a network in a given time.
Latency: Time delay in data transmission over a network.
Clients: Devices requesting services/resources from servers.
Server: Stores and manages resources, responding to client requests.
Request-Response: Client-server interaction: request, process, respond.
Resource Sharing: Servers share resources with multiple clients.
Scalability: Capability for multiple clients to connect to a server.
Client Responsibility: Clients handle services/resources received.
Most Common Protocols
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
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
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
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
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.
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