Networking Cheat Sheet Summarized

Network: A collection of interconnected devices (computers, servers, etc.) that communicate and share resources.
Internet: A global network that connects millions of private, public, academic, business, and government networks, enabling communication and information sharing.
Intranet: A private network within an organization, restricted to authorized users, typically for internal communication and resource sharing.
Extranet: An extension of an intranet that allows limited access to outsiders, typically for business partners or customers.

Server-Bus: A network where multiple devices are connected to a central server or hub, with communication occurring through the server.
Peer to Peer (P2P): A decentralized network where each device can act as both a server and a client, sharing resources directly with others.

Bus: All devices are connected to a single central cable (the bus), with data sent to all devices.
Star: Devices are connected to a central hub or switch, with each device having a direct connection to the hub.
Ring: Devices are connected in a circular fashion, and data travels in one direction around the ring.
Mesh: Devices are interconnected in a way that allows multiple paths between any two devices, offering high redundancy and reliability.
Fastest: Mesh
Lowest cable consumption: Bus
Hardest Troubleshooting: Bus
Easiest Development: Ring

OSI Layers:
- Application: End-user protocols (e.g., HTTP, FTP).
- Presentation: Data formatting, encryption, and compression.
- Session: Manages sessions between devices.
- Transport: Ensures reliable data transfer with segmentation and connection control (TCP/UDP).
- Network: Routing and IP addressing.
- Data Link: Physical addressing, error detection/correction.
- Physical: Transmission of raw data over a physical medium.
TCP/IP Layers:
- Application: Protocols for communication (e.g., HTTP, FTP, Email).
- Transport: Manages end-to-end communication (TCP/UDP).
- Internet: Responsible for routing (e.g., IP, ICMP, ARP).
- Network: Deals with the transmission of data over physical networks (Ethernet, ATM).

Data Center: A facility used to house computing systems and associated components like storage, networking, and security systems.

Benefits:
- Lower cost
- Flexibility and scalability
- Automatic updates
- Unlimited capacity
Disadvantages:
- Requires a stable internet connection
- Relies on high-speed internet for optimal performance

Infrastructure as a Service (IaaS): Provides virtualized computing resources over the internet.
Platform as a Service (PaaS): Provides a platform allowing customers to develop, run, and manage applications.
Software as a Service (SaaS): Software delivered over the internet on a subscription basis.

Pyramids:

Static Routing: Manual configuration, no dynamic adjustments, minimal overhead but lacks flexibility.
Dynamic Routing: Uses algorithms (e.g., OSPF, IS-IS) to automatically adjust routes based on network changes.

Classless and Classful:

Classful: Older system of IP addressing based on predefined classes (A, B, C).
Classless: More flexible system using CIDR (Classless Inter-Domain Routing).

Routing Types:

Distance Vector: Routers share routing tables, and updates happen periodically (e.g., RIP).
Link State: Routers share network topology information, with updates every 30 minutes and use Dijkstra’s algorithm for routing decisions (e.g., OSPF).

Hierarchical network design organizes a network into three layers, each with specific roles to enhance scalability, manageability, and performance.

Core Layer:
- Focuses on high-speed data transfer across the network backbone.
- Provides fault tolerance and redundancy to ensure reliability.
- Designed for fast transport with minimal latency.
Distribution Layer:
- Acts as a mediator between the core and access layers.
- Implements security policies, such as filtering and access control.
- Supports load balancing and enforces policies for traffic management.
Access Layer:
- The layer where end devices (like PCs and printers) connect to the network.
- Supports VLANs (Virtual LANs) for segmenting networks.
- Ensures Quality of Service (QoS) for critical applications.
- Provides Power over Ethernet (PoE) to power devices like IP phones and wireless access points.

This hierarchical approach simplifies network management, improves performance, and enhances fault tolerance.

Switching: The process of directing data from one device to another in a network.

Types of Switching:
- Circuit Switching: Establishes a dedicated path for the entire communication session.
- Message Switching: Entire messages are sent from one point to another, stored and forwarded at intermediate nodes.
- Packet Switching: Data is divided into packets and sent independently, with each packet potentially taking a different path.

Table of IP Headers:
- Version: Protocol version (IPv4 or IPv6).
- IHL (Internet Header Length): Length of the header.
- Type of Service: Specifies quality of service options.
- Total Length: Entire packet size.
- Identification: Unique packet identifier.
- Flags: Control fragmentation.
- Fragment Offset: Fragment position in original packet.
- Time to Live (TTL): Prevents packets from circulating indefinitely.
- Protocol: Defines the protocol used in the payload (e.g., TCP, UDP).
- Header Checksum: Error detection for the header.
- Source Address: Sender's IP address.
- Destination Address: Receiver's IP address.
- Option: Optional data for additional features.

taiwbi/Summerized-Network.md