• Networking protocols define the rules and conventions for communication across a network.
  • Protocols define speed of transmission, error checking, async/sync etc.


  • The protocols are established between sender and receiver before starting communication.
  • This is done via a handshake.
  • Data packets are exchanged between various routers.

TCP 3-way handshake

IP vs Mac address

  • A Mac address is provided by the NIC manufacturer and cannot be changed, but can be spoofed.

  • An IP address is typically assigned by a router, and allows for easier communication across the internet and within your local network.

  • IP addresses are more commonly used in networking applications.



  • 32-bit IP addresses
  • Around 4 billion possible IPs
  • 8 bits form an octet. Each octet may represent any number between 0 to 255.

Reserved IP Ranges

A β†’ 10.x.x.x /8 B β†’ - / 16 C β†’ 192.168.x.x /24

Link local

x.x.x.0 is a network address rather than a device address

Broadcast address x.x.x.255


  • 128-bit IP addresses
  • fc00:bbbb:bbbb:bb01::34:4e8e

Classful Addressing

  • Initially, a network consisted of different classes
  • Each class has a different structure of addressing
  • Consider a large organisation; it will require class A addressing. In a single network, 2^24 hosts can be used. In total, only 2^7 such organisations can be addressed.

Classless Addressing

  • In classless addressing, an IP address has an 8-bit suffix that specifies the number of bits allocated for network ID.
  • For example, if the 8-bit suffix represents the number 14 and the remaining 18 bits represent the host ID.
  • For example, is represented in binary as given.

Subnet masking

  • A subnet mask is used to identify the two parts of an IP address.
  • For example, a subnet mask represents a network ID of 8 bits and a host ID of 24 bits. This is equivalent to a suffix /8 in classless addressing. (CIDR)
  • When AND operation is performed between an IP address and its subnet mask, its network ID is obtained.

Public and private


  • These addresses need not be registered on the internet registry.
  • Private addressing for internal networks saves unique IPv4 addresses that can be used for routers and web servers that connect to the internet daily.


  • Some public IP addresses are also identified using domin names.
  • A DNS server translates the domain name to an IP address.

Static and Dynamic addressing

Static Addressing

  • Static IP addresses are assigned by the network administrator. When the device is in use, this address remains unused.

Dynamic IP Addressing

  • An IP addressing can be used when the device is not used.
  • The protocol responsible for this is dynamic host control protocol (DHCP)

Dynamic Host Control Protocol (DHCP)

  • DHCP also provides subnet masks and other automatic configuration details. This eliminates the problem of manual configuration.

  • Takes care of frequent changes in an IP address

  • Allocates private addresses within an internal network

  • Broadcast to all DHCP servers requesting an IP

  • A DHCP server offers an IP for a particular duration

  • Broadcasts a message confirming the request for IP

  • DHCP server that offered the IP address sends an acknowledgement and assigns the DHCP client the IP address.

Port Numbers

  • A port number is a 16-bit number attached to the IP address that is used to identify a process or application on a computer
  • Using this number, an application running in the client system is accessed.

I am familiar with ports, so some information has been omitted.

NATβ€”Network Address Translation

  • A network address translator provides external access to a privately addressed network as shown in the figure.
  • 1 public IP is shared between all private IPs.
  • Adds a layer of security
  • Private IP addresses are not available to external servers
  • Router tracks requests and reassigns them to the appropriate host
  • Port numbers are assigned with a specific time frame

Port Forwarding

  • Port forwarding is an application of NAT where port mappings are explicitly defined, allowing you to talk to services behind non-standard ports.


  • TCP/IP is a suite of communication protocols used to interconnect network devices of different manufacturers on the internet.

  • Source β†’ Sender of the message

  • Destination β†’ Receiver of the message

  • Packet sequence β†’ The order of the message in which it should be reassembled

  • Data β†’ Contents of the message

  • Error checking β†’ Bits to make sure that the message has been received correctly

User Datagram Protocol (UDP)

  • A protocol similar to TCP but operates at a faster rate
  • UDP: message is sent in the form of chunks or called datagrams
  • TCP: message is sent as segments
  • Used for gaming and video calling over the internet



C β†’ Create β†’ POST R β†’ Read β†’ GET U β†’ Update β†’ PUT D β†’ Delete β†’ DELETE

Email Communications: SMTP, POP3, IMAP


  • Send emails


  • Retrieve mail from server
  • Delete mail from server


  • Retrieve message from server
  • Leave mail on the remote server

SSH (Secure Shell Protocol)

  • Remotely access a terminal on another computer through a text interface

  • SSH is used by network administrators and developers

  • Typically runs on port 22

FTP (File Transfer Protocol)

  • FTP defines the set of rules for transferring large files on the Internet
  • The files required for a website are organised on a web server using this protocol.
  • Users may have private access to upload the files. Other users may be given access to download these files.

VoIP (Voice over Internet Protocol)

  • A set of protocols that enable you to make voice calls over the internet using UDP.