Network Basics

A Quick Glance at Networking Concepts

Welcome to a compact blog that offers essential and fundamental knowledge about networking, which is essential for future pentesters or SOC (Security Operations Center) analysts as this resource include details about vital ports that are commonly used for communication within computer networks. Grasping this information is pivotal for effectively monitoring and analyzing network traffic which ensures strong security measure and protocols

Network Basics

• Internet Protocol (IP) Address: A numerical value is assigned to any device connected to the network that IP for communication. Layer 3 device.
• IPv4 Made up 32 bits which equals to 4 bytes. The combination of IPv4 address globally will be 2³²=4,294,967,296. IPv6 is hexadecimal and is 128 bits. So the number of IPv6 address there could possibly is 2¹²⁸, which is a lot!!
• NAT (Network Address Translation): It is used to allow multiple devices on local network share single IP address for communication. Public IP address is rented from ISP (Internet Service Provider).
• MAC (Media Access Control) Address: Anything that is using network interface will have MAC Address. It is a unique identifier assigned to NIC (Network Interface Card) for communications at layer. MAC address has 6 different pairs, where first 3 pairs are identifiers.
• TCP v UDP: Transmission Control Protocol v User Datagram Protocol

Comparison between TCP & UDP

• Subnetting: The number of hosts one can have on private network depends on the subnet mask. Usually found in as ‘netmask’.

Subnet Cheat Sheet

• For example, /24 means: 255.255.255.255. Similarly for /28 it will be: 255.255.255.240.
• Hosts double as each increment of CIDR, always subtract 2 from total to find hosts.
• Network ID is first address and Broadcast ID is the last address available to us.

OSI Layers: As we move up from layers 1 to 7, we decapsulate data and as we move down the OSI layers from 7 to 1, we encapsulate data.

1. Physical Layer: Devices repeat whatever they are told.
   Example: Ethernet, Fiber Optic.
2. Data Layer: Forwards traffic to uniquely identifying network with an MAC address and flow control.
   Example: Network Interface Card (NIC), Switches
3. Network Layer: Data is divided into packets and forwarded.
   Example: Routers, IPv4, IPv6
4. Transport Layer: Data is forwarded as segments.
   Example: TCP, UDP, Firewalls
5. Session Layer: This layer is responsible for setting, maintaining and tearing down sessions.
   Example: H.323 (streaming audio and video), NetBIOS
6. Presentation Layer: This layer is responsible for making data translation, compression and securing that data with proper encryption
   Example: HTML, XML, EBCDIC
7. Application Layer: This layer provides application level services. Users communicate with the system.
   Example: Web Browsing, E-mail

• Wireless Access Point: The devices that allow wireless devices to connect to wired network which acts as wireless hub.
• Personal Area Network (PAN): The smallest type of wireless/wired network which covers least amount of network.
  Example: Bluetooth
• Local Area Network: This network connects components in limited distance each within 100 meters.
  Example: Room, Within Building
• Campus Area Network (CAN): Connection between building-centric LAN’s across university, industrial park.
  Example: College campus, Business Parks
• Metropolitan Area Network (MAN): This connection connects to devices which are scattered across city. The connection is larger than CAN, but smaller than a WAN.
  Example: Community college with campuses spread across country
• Wide Area Network (WAN): This connection covers distances around the country or around the world.
  Example: Internet

Ports to Remember
There are 65,535 ports. A port number is 16-bit value and 2¹⁶ = 65536. As the starting port is from 0, so the range ends at 65535.

Basic Definitions

• Bot: Anything that can be controlled and commanded by someone, which can either be software or hardware.
• Doxing: The action of making PII (Personally Identifiable Information) public selling or selling it on the internet.
• Exploit: Taking advantage of the vulnerability is called exploit.
• Vulnerability: A weakness that can be exploited by an attacker.