# Networking Refresher

![Networking Refresher](https://cdn.hashnode.com/res/hashnode/image/upload/v1680988451729/c0e902af-b1d4-4fa5-8d2e-721ce29271e4.jpeg)

Networking is the exchange of information and ideas among people with a common profession or special interest, usually in an informal social setting. I recently felt like I had trouble remembering some of the stuff related to networking. Thus, I decided to take a small refresher and write stuff down so that they would stick with me better! What better way than to blog about it? 😏

* * *

IP Addressing (Layer 3)
=======================

**IPV4**
--------

*   Decimal notation
*   32 bits

**IPV6**
--------

*   Hexadecimal notation
*   128 bits

**Network Address Translation (NAT)**
-------------------------------------

*   Network address translation is a method of remapping one IP address space into another by modifying network address information in the IP header of packets while they are in transit across a traffic routing device.

****Classful Network****

![Networking Refresher](https://cdn.hashnode.com/res/hashnode/image/upload/v1680988452995/41317c06-c143-4dc7-90b0-15a3e35f959f.png)

A classful network is a network addressing architecture used in the Internet from 1981 until the introduction of Classless Inter-Domain Routing in 1993. The method divides the IP address space for Internet Protocol version 4 into five address classes based on the leading four address bits.

****Private / Public IP Address classes****

![Networking Refresher](https://cdn.hashnode.com/res/hashnode/image/upload/v1680988454224/d4fc614c-91e1-4c1d-9659-6c10a972fafe.png)

MAC Addresses (Layer 2)
=======================

A media access control address is a unique identifier assigned to a network interface controller for use as a network address in communications within a network segment. This use is common in most IEEE 802 networking technologies, including Ethernet, Wi-Fi, and Bluetooth.

*   Related to switching
*   48 bits
*   Contains 6 pairs of twos \[00:0c:29:78:a2:a2\]
*   First 3 pairs/half = Identifier \[Able to identify the vendor of the NIC\]

TCP, UDP and the Three-Way Handshake
====================================

****TCP (Transmission Control Protocol)**** is a standard that defines how to establish and maintain a network conversation through which application programs can exchange data. \[Connection oriented protocol\]

****UDP (User Datagram Protocol)**** is an alternative communications protocol to Transmission Control Protocol (TCP) used primarily for establishing low-latency and loss-tolerating connections between applications on the internet. \[Connection-less protocol\]

****A three-way handshake**** is a method used in a TCP/IP network to create a connection between a local host/client and server

TCP
---

*   Connection-Oriented Protocol
*   High Reliability
*   HTTP
*   HTTP
*   FTP
*   SSH

How does the TCP Three-way handshake work?

To Initiate a connection:

SYN → SYN, ACK → ACK

To gracefully terminate a connection:

FIN → FIN, ACK → ACK

UDP
---

*   Connection-less Protocol
*   Less Reliable
*   Streaming
*   DNS
*   VOIP

Common Ports and Protocols
==========================

*   ****TCP (Transmission Control Protocol)****
*   FTP | 21
*   SSH | 22
*   Telnet | 23
*   SMTP | 25
*   DNS | 53
*   HTTP | 80
*   HTTPS | 443
*   POP3 | 110
*   SMB | 139 + 445
*   IMAP | 143
*   ****UDP (User Diagram Protocol)****
*   DNS | 53
*   DHCP | 67 . 68
*   TFTP | 69
*   SNMP | 161

The OSI Model
=============

The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology.

1 | ****Physical → data cables, Cat6****

****2 | Data link → Switching, MAC Addresses****

****3 | Network → IP Addresses, Routing****

****4 | Transport → TCP, UDP****

****5 | Session → Session Management****

****5 | Presentation → WMV, JPEG, MOV****

****6 | Application → HTTP, SMTP****