Basic Networking, Cyber Security And Ethical hacking Starting Notes

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 Basic Concept Of Networking 

**OSI Model (open System interconnection ) Model developed by ISO

 

7. Application       Upper Layer

6. Presentation      Upper Layer

5. Session               Upper Layer

4. Transport          Lower Layer

3. Network            Lower Layer

2. Datalink            Lower Layer

1. Physical             Lower Layer



7. Application Layer ( PDU at this level is message or Data)

     This Layer uses for User Interaction

     protocol Uses :- http, https, ftp, smtp, telnet, dns, dhcp, ssh


6. Presentation layer (PDU at this level is data or Message)

   -In this layer it Identify of File types, Compression/                            Decompression, Encryption/ Decryption.

    Protocol uses :- https, sftp, ssh, smtps


5. Session Layer ( PDU at this level is data or Message)

- It maintains the sessions Between Two End Users.  

 Layer: Dialog Control, adds checkbits to data,                         uploading/download.


4. Transport Layer. (PDU at this level is Segment for TCP ,         Datagram for UDP  And  SPX (Sequenced Packet Exchange) Is Data )

- It provides End to End Connectivity

- Segmentation and Reassembly

- A unique number defined for each and every protocol or service which is  defined by IANA (1-65535)

1. Well Known Ports: 1 - 1023

2. Registered Port:

3. Free Ports

Well Known Ports:

20/TCP,21/TCP   -   FTP (File Transfer Protocol)

22/TCP   -    SSH (Secure Shell)

23/TCP   -    Telnet

25/TCP   -     SMTP (Simple Mail Transfer Protocol)

53/TCP  - Transmission Control Protocol

53/UDP   -     DNS (Domain Name Server)

67/UDP   -     DHCP (Dynamic Host Configuration Protocol)

68   -     Bootp

69   -     TFTP (Trival File Transfer Protocol)

80  -     HTTP (Hyper Text Transfer Protocol)

110  -    POP3 (Post Office Protocol)

123  -     NTP (Network Time Protocol)

143  -     IMAP (Internet Message Access Protocol)

161   -     SNMP (Simple Network Management Protocol)

443    -     HTTPS (Hyper Text Transfer Protocol Secure)


Windows :- C:\windows\system32\drivers\etc\services

Linux:-  /etc/services


3.  Network layer ( PDU at this level packet )

 In this Layer Routing, IP Allocation, Query Management/Error   Reporting

Header: Source IP & Destination IP

Protocols: IP (Internet Protocol), IPX (Internet Packet Exchange), ICMP (Internet Control Message Protocol )

, IGMP (Internet Group Message Protocol), ARP (Address Resoltion Protocol), RARP (Reverse Address Resolution Protocol ).


2. Data link layer : ( PDU at this level is Frame )

 i. MAC --> Media Access Control

  MAC is 48 bit address of NIC (Network Interface Card)     written   in Hexadecimal Numbers also known as Physical     Address or Hardware Address

    A1:23:9C:E4:11:9A

    Windows: ipconfig/all 

    Linux/MAC: ifconfig

    Header: Source MAC & Destination MAC Address

    Encapsulation Protocol.

ii. LLC --> Logical Link Control

Adds checksum CRC (Cyclic Redundancy Check) to data frames

. This is the only layer where trailer is added

Protocols: HDLC, SDLC, PPP, FRAME RELAY

 Physical Layer: Identifies topology, media, and send data

 PDU --> Bits

IP Address:->

IPv4 --> It is a 32 bit address written in dotted decimal divided into octats.


1. Physical Layer ( PDU at this level is Bit )

 In this Layer use wired Or wireless to connect to internet.

 - Ethernet






 

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