Computer Network or Networking
is the interconnection if multiple devices, generally termed as Hosts connected using multiple paths for the purpose of sending or receiving data or media. There are also multiple devices or mediums which help in communication between two different devices which are known as “Network Devices”. For Example: Router, Switch, Hub, Bridge.
The layout pattern using which devices are interconnected is called Network Topology. Such as Bus, Star, Mesh, Ring, Daisy Chain.
OSI stands for “Open System Interconnection.” It is a reference model that specifies standards for communications protocols and also the functionalities of each layer.
Then we have Protocol, it is a set of rules or algorithms which define the way how two entities can communicate across the network and there exists different protocol define at each layer of the OSI model. Few of such protocols are TCP, IP, UDP, ARP, DHCP, FTP and so on.
Unique Identifiers of Network
Hostname
Each device in the Network is associated with a unique device name known as Hostname. In your Windows Operating System open “Command Prompt” and type “hostname” and press “Enter” this displays the hostname of your machine.
IP Address (Internet Protocol Address)
Also, know as the Logical Address, is the network address of the system across the network. To identify each device in the world-wide-web, Internet Assigned Numbers Authority (IANA) assigns IPV4 (Version 4) address as a unique identifier for each device on the Internet. The length of the IP address is 32-bits. (Hence we have 232 IP addresses available.) Type “ipconfig” in the command prompt and press ‘Enter’, this gives us the IP address of the device.
MAC Address (Media Access Control address)
Also known as physical address, is the unique identifier of each host and is associated with the NIC (Network Interface Card). MAC address is assigned to the NIC at the time of manufacturing. Length of the MAC address is : 12-digit/ 6 bytes/ 48 bits Type “ipconfig/all” in the command prompt and press ‘Enter’, this gives us the MAC address.
Port
Port can be referred to as a logical channel through which data can be sent/received to an application. Any host may have multiple applications running, and each of these applications is identified using the port number on which they are running. Port number is a 16-bit integer, hence we have 216 ports available which are categorized as shown below
Well known Ports 0–1023
Registered Ports 1024–49151
Ephemeral Ports 49152–65535
Number of ports: 65,536
Range: 0–65535
Type “netstat -a” in the command prompt and press ‘Enter’, this lists all the ports being used.
Socket
The unique combination of IP address and Port number together are termed as Socket.
Few more concepts
DNS Server
DNS stands for Domain Name System.
DNS is basically a server that translates web addresses or URL (ex: www.google.com) into their corresponding IP addresses. We don’t have to remember all the IP addresses of each and every website. The command ‘nslookup’ gives you the IP address of the domain you are looking for. This also provides the information of our DNS Server.
ARP
ARP stands for Address Resolution Protocol.
It is used to convert the IP address to its corresponding Physical Address(i.e.MAC Address). ARP is used by the Data Link Layer to identify the MAC address of the Receiver’s machine.
RARP
RARP stands for Reverse Address Resolution Protocol. As the name suggests, it provides the IP address of the device given a physical address as input. But RARP has become obsolete since the time DHCP has come into the picture.
The Internet
In simplest words, it is a global network of smaller networks interconnected using communication protocols that are standardized. The Internet standards describe a framework known as the Internet protocol suite. This model divides methods into a layered system of protocols.
These layers are as follows
- Application layer (highest) — concerned with the data(URL, type, etc), where HTTP, HTTPS, etc comes in.
- Transport layer — responsible for end-to-end communication over a network.
- Network layer — provides a data route.
The World Wide Web
The web is a subset of the internet. It’s a system of Internet servers that support specially formatted documents. The documents are formatted in a markup language called HTML(that supports links, multimedia, etc). These documents are interlinked using hypertext links and are accessible via the Internet.
To link hypertext to the Internet, we need
- The markup language, i.e., HTML.
- The transfer protocol, e.g., HTTP.
- Uniform Resource Locator (URL), the address of the resource.
We access the web using web browsers.
URI
URI stands for ‘Uniform Resource Identifier’, it’s like an address providing a unique global identifier to a resource on the Web. Uniform Resource Locator (URL) is the most commonly used form of a URI.
The URL consists mainly of two parts
- The protocol used in the transfer, e.g., HTTP.
- The domain name.
> If you wanna get into IT or Security field you should have good amount of knowledge related to Networking so focus on Networking first 
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