Routing, Telnet, RLogin and Secure Shell(SSH)

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Routing, Telnet, RLogin and Secure Shell(SSH)

Router

In packet-switched networks such as the internet router in a device that determines the next network point to which a packet should be forwarded towards its destination. A router may create or maintain a table of the available route and their conditions and use this information along with distance and cost algorithms to determine the base route for a given packet. Typically, a packet may travel through a anumber of network points with routers before arriving at its destination. Routing is a function associated with the Network Layer(Layer 3) in the standard model of netqwork programming, the Open Systems Interconnection (OSI) model. A layer-3 switch is a switch that can perform routing dunction
An edge router is a router that interfaces with an asynchronous transfer mode(ATM) network.


Every router maintains a routing table in its software to quickly determine the next router to send the message to with
  • the minimum cost
  • high performance and throughput
  • lack of latency,etc.
The routing table is updated at equal intervqals of time like every half an hour.
Suppose after half an hour it recognises that a node point is broken, it quickly clears that data row associated qith the routing table and searches for the next best way to reach the destination.

Gateway:

A gateway is a software that connects two different server networks.

Telnet:

Telnet is an application that is used to run commands on a remote machine. Generally, the command to telneting to a site is:
telnet gaurav.com
or with port numbers: telnet gaurav.com 23

rlogin:

In a system, if all users log into teh central sever and uses its resources, it is known as Local login. In time-sharing systems, it works well. But sometimes, a user may have to access an application program that is located on a different computer.For this user logs onto the remote computer in process called remote login. A user specifies the IP Address for selecting a remote server. It establishes a Telnet session
The mode of operation in a Telnet session is as below:-
  1. At the Telnet client, a chracter that is typed is not displayed on the monitor, but instead , is encoded as an ASCII character and transmitted to a remote Telnet server
  2. At the server, THe ASCII character is interpreted as if the user had typed the chracter on the machine
  3. If the keystroke results in any output, this output is encoded as (ASCII) text and sent to the Telnet client, which disopplay it on its monitor
The Secure Shell set of protocols provides application layer serviced for remote login and file transfer servvices,similar to FTP, Telnet,rlogin,rsh,rcp but ensures secure enecrypted communications between hosts. All components of secure shell provide authentication,confidentiality, and integrity of data, using a avariety of encryptiona nd authentication algorithms, and protect against common attacks on the security and integrity of communications between hosts. On the Internet, Sesure shell is run as a client-server protocol over a TCP connection and secure shell servers use the well-known TCP port 22. In Linux Ubuntu,
for generating certificates you need to install package ssh(*secure shell) from the apt repository using a superuser privileges the following steps: 
$sudo apt-get install ssh
The linux system will ask for the username and password which will not be echoed on the screen as you type for confidentiality After the ssh is installed to can use it for an web framwork like laravel 8.1 of PHP7.1
So, next step is to go to the the directory where ssh is installed. A .ssh file will be automatically created that folder. Just cd into thar folder and type ssh-keygen
This will generatea certificate for your code to run your code locally ans securely as if it were real server SSH internally uses RSA(Rivest-Shamir-Adleman) algorithnm to generate the key
In the /home/gaurav/id_rsa.pub directory in Linux Ubuntu. The SSH is also helpful when you are having two or more operating sytems installed in your machine. Suppose if your amchine is Linux Ubuntu and you have two operating systems inside it through VMWare virtualization server.
If the name of one of the operating system is "vagrant" to enter that system use sudo -su
You will be prompted for username and password and if both of them are correct, you just need to type the following commands: 
$vagrant init # Bootstraping the machine
$vagrant up #Starting the machine i.e.,booting the machine
$ssh vagrant #Going to access the terminal console window of the virtual machine
$vagrant down # Shut down the virtual machine
Note: Not all the features will be avaiable as it has some software and hardware limitaions and security concerns

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