Network fundamentals Original

DNS

also translates IP addresses to hostnames

servers

are commonly used to deliver services that are constantly required, most server are never turned off. Examples of servers - Mail Server, Cloud Server, File Server, Print Server, Web Server, Application Server, Database Server etc .

Firewall:

are usually the first line of defense in network security. They establish a barrier between your secured and controlled internal networks that can be trusted from untrusted outside networks such as the internet. A firewall can be hardware or software or both.

DHCP e)

uses UDP port 67 and 68. DHCP also uses the DORA process (Discovery, Offer, Request, Acknowledge

A wireless router

which is what you might have at home, helps to connect multiple devices without wire.

DNS Records =

1) A record 2) Pointer record 3)MX record , 4)Cname record

An IP address has two portions. The network or LAN portion and the Host portion. For example using IP 192.168.5.2.

192.168.5 = network or LAN portion while .2 represents the Host portion.

OSI

: OSI stands for Open Systems Interconnection. It is a reference model that specifies standards for communication protocols and also the functionalities of each layer

The Structure of an IPV4 Address:

An IPV4 address is a unique 32bit number or a four-octet number X . X . X . X where X = number 8bits 8bits 8bits 8bits = 32bits 1octet 1octet 1octet 1octet =4 octets

Computer Network: .

A connection of multiple devices also known as HOSTS, that are connected using multiple paths, for the purpose of sending/receiving data or information

-Client Server Network :

A group of systems connected together, sharing information from a central server.

-Peer-to-peer Network :

A group of systems connected together, sharing information with no server involved.

DHCP (Dynamic Host Configuration Protocol) :

A network protocol used on IP networks. It enables a server to dynamically assign an IP address and other network configuration information to a computer from a range of numbers (Scope) configured for a given network, upon request.

Firewall: .

A network security device that monitors incoming and outgoing traffic and decides whether to allow or block specific traffic based on a defined set of security rules

Port :

A port can be referred to as a logical channel which data can be sent/received to an application. A computer can have multiple applications running and each app can be identified using the port which they are running

Protocol :

A protocol is a set of rules which define the way how two entities can communicate across the network and there exists different protocols defined at each layer of the OSI model such as TCP, IP, ARP, DHCP, FTP, UDP

DNS (Domain Name System):

A server which translates web addresses or URLs (ex: www.google.com) into their corresponding IP addresses. Like a phonebook which lets you look up the name of a person or business and get their number, DNS lets you type the website address and automatically finds the IP address for the website.

Server :

A software or hardware device that accepts and responds to requests made over a network. The device that makes the request and receives a response from the server is called a client.

Switch: .

A switch is responsible for connecting the computers together. A switch is a major backbone of a Local Area Network as it provides an avenue for different computers to be interconnected

Open system :

A system that is connected to the network and is ready for communication

Closed System :

A system that is not connected to the network and can't be communicated with.

Access Point:

A wireless network device that acts as a portal for devices to connect to a local area network. It can be used to extend wireless coverage of an existing network and for increasing the number of users that can connect to it.

IP Address:

Also known as Logical address, the IP address is the network address of the system across the network. It is a Unique identifier to each device on the network (Like your SS number is unique).

MAC Address :

Also known as physical address. It uniquely identifies each host and is associated with its NIC ( Network Interface Card ) It is assigned to your NIC at the time of manufacturing.

Computer Network

Computer networks can also include multiple devices or mediums which help in the communication between two different devices (Network devices) and include routers, switches, hubs, and bridges.

Hostname :

Each device in a network is associated with a unique device name known as a Hostname. To find out your hostname, open the command prompt and type hostname

Ethernet:

Ethernet refers to the cabling and ports involved in networking. The network cables are referred to as Ethernet cables and they are used to connect a computer to all other networking devices. The most common is the RJ45 connector, CAT5, CAT6 and CAT7 cables.

Router

For two o more LANs to be interconnected, you need a router. Routers operate in layer 3 of the OSI model and it makes use of IP addresses at its interface.

IPV4 Classes

IP Class Subnet Mask First Octet Example Class A 255.0.0.0 1 - 126 10.0.1.1 Class B 255.255.0.0 128 - 191 128.16.1.2 Class C 255.255.255.0 192 - 223 192.168.2.4 Class D Not available 224 - 239 224.14.8.8 Class E Not available 240 - 255 not available

There are 2 versions.

IPV4 (version 4) and IPV6 (version 6). IPV4 is the most commonly used.

Differences :

IPV6 has security built into its stack. IPV4 has no security built into its stack.

Difference between IPV6 and IPV4

IPV6 is a 128 bit number while IPV4 is a 32 bit number.

Difference between IPV6 and IPV4

IPV6 uses the IP Sec ( Security protocol ) hence slower. IPV4 has no security overhead hence it is faster in data transmission.

Switch

It operates at level 2 of the OSI model standard of communication. It allows devices in your network to communicate with each other as well as with other networks.

Types of computer Networks

LAN (Local Area Network) MAN (Metropolitan Area Network) WAN (Wide Area Network)

Subnet Mask :

Only systems with the same network address can talk to each other.

NIC (Network Interface Card):

Sends data, receives data and controls data flow between the computer and the network.

Computer Network

Simply put, computer networking is a means by which computers are interconnected to share data and information, resources and all other network devices such as printers.

TCP/IP:

Stands for Transmission Control Protocol/Internet Protocol. It is a set of rules and methods that are used to interconnect devices on the internet.

DHCP

Suppose you have 500 computers and you need to manually assign each of them and IP address, it would be a tough and time-consuming task. A DHCP server does the work by assigning the IP addresses to the machines automatically.

Differences between TCP and UDP

TCP transmits critical data while UDP transmits non-critical data. UDP broadcasts data TCP is reliable in data transmission while UDP is not reliable in data transmission TCP will guarantee data transmission to receiving systems while UDP will not TCP is a connection-oriented protocol while UDP is a connectionless oriented protocol (TCP will perform a 3-way handshake between sending and receiving systems before data transmission). Read about this -TCP comes with built in Flow Control Mechanism. UDP does not.

Network Topology:

The layout arrangement of the different devices in a network. Common examples include Bus, Star, Mesh, Ring, Daisy Chain (Read about these topologies)

Router : .

Used to connect different networks together

Subnet Mask :

Used to separate the network or LAN portion of an IP address from the Host portion (segments an IP address). It also helps to determine the class of an IP address as it is assigned to computers, routers, or switches.

DNS (Domain Name System):

Without DNS the internet would basically collapse. Computers can only communicate using series of numbers. So DNS was developed as a sort of phonebook that translates the domain you enter in your browser into a computer readable IP. If DNS is down, you would only be able to access a website by typing it's IP address.

VLAN (Virtual Local Area Network):

is a method of logically separating a LAN and making it look like different networks in one. Physically it is one network but logically they are different networks. This is done by a switch that has been configured for this purpose.

Type this command in the command prompt to view ports being used

netstat -a

Well known Ports =

port 0 - 1023

Registered Ports =

port 1024 - 49151

Use cases :

servers that manage network resources. For example; a user may set up a server to control access to a network, send/receive email, manage print jobs, or host a website. Some servers are committed to specific task often referred to as Dedicated Servers but others are shared servers.