SSH protocol and Telnet protocol telnet

Telnet

What is Telnet protocol?

Telnet Server Software is our most commonly used Telnet Server software and is a typical client/server model service that uses the Telnet protocol to work. So, what is the Telnet protocol? What features does it have?

Telnet is a protocol located at layer 7th of the OSI model---application layer, a TCP/IP protocol that provides connectivity to remote host terminal emulation by creating a virtual terminal. That means he's a TCP-based application-layer protocol. This protocol needs to be authenticated by username and password and is the standard protocol for Internet remote Login service. The application of the Telnet protocol can turn the computer used by the local user into a terminal of the remote host system. It provides three basic services:

1) Telnet defines a network virtual terminal to provide a standard interface for a remote system. Client programs do not need to know the remote system in detail, they only need to construct a program that uses standard interfaces;

2) Telnet includes a mechanism to allow client and server negotiation options, and it also provides a set of standard options;

3) Telnet handles both ends of the connection symmetrically, that is, Telnet does not force the client to enter from the keyboard, nor does it force the client to display output on the screen.

What's the use of Telnet?

Telnet provides remote login capability so that users can log on to the remote Telnet server by running the Telnet client on the local host. Commands that are entered locally can be run on the server, and the server returns the results locally as if it were operating directly on the server console. This allows remote operation and control of the server locally.

1) Establish an effective connection between the user terminal and the remote host;

2) can share the software and data resources on the host;

3) can use the information Query service provided on the remote host for information inquiry;

Telnet system composition?

Telnet consists of three parts: client software, Server software, and Telnet communication protocol.

The Telnet client software runs on the user's computer. When a user performs a telnet command to Telnet, the client software completes the following functions:

1) Establish a TCP connection to the remote host. It opens a socket on a known TCP port number 23rd, and if the Telnet Server software on the remote host has been listening for connection requests on this known port, the connection will be set up.

2) to provide user interface by terminal mode.

3) Transfer the user input information to the remote host via the Telnet protocol.

4) Accept the information sent by the remote host and the appropriate conversion is displayed on the screen of the user's computer.

The remote host must be running Telnet Server software to provide Telnet telnet service. The Telnet Server software will complete the following functions:

1) inform the network that the system is ready to provide remote connection services.

2) Continuously listen for the user's connection request on the TCP port # 23rd, which is known for weeks.

3) processing the user's request.

4) Return the processed results to the client program via the Telnet protocol.

5) Continue to listen for user requests.

Telnet itself is a protocol, so between Windows and Linux can be remote from each other

SSH:

The Telnet service is easy to use, but because of its low security, it is often used instead of Telnet for remote administration using SSH (Secure Shell). SSH is a protocol that provides secure communication in an application, which allows secure access to the server via SSH, because SSH encrypts all transmitted data based on a mature public key encryption system, ensuring that the data is transmitted without malicious damage, leakage, or tampering. SSH also uses a variety of encryption and authentication methods to solve the transmission of data encryption and identity authentication problems, can effectively prevent network sniffing and IP spoofing attacks.

Using Telnet, the TCP/IP protocol used to access the remote computer to control your network device is equivalent to shouting your username and password when you leave a building. Someone will be listening soon, and they will take advantage of your lack of security awareness. Traditional Web services such as FTP, pop, and telnet are inherently insecure because they transmit passwords and data in plaintext on the network, and it's very easy for someone with ulterior motives to intercept the passwords and data. Moreover, the security authentication methods of these service programs also have their weaknesses, that is, it is very easy to be attacked by the "man in the Middle" (man-in-the-middle) way. The so-called "middleman" attack means that the "middleman" is impersonating a real server to receive your data to the server, and then impersonating you to pass the data to the real server. The data transfer between the server and you is a very serious problem after the hands and feet of the "middleman".
SSH is an industry standard for replacing Telnet and other remote console management applications. SSH commands are encrypted and are kept secret in several ways.
When using SSH, a digital certificate authenticates the connection between the client (your workstation) and the server (your network device) and encrypts the protected password. SSH1 uses the RSA encryption key, SSH2 uses the digital Signature Algorithm (DSA) key to protect the connection and authentication. Cryptographic algorithms include Blowfish, Data Encryption Standard (DES), and Sanchong DES (3DES). SSH protects and helps prevent spoofing, "man-in-the-middle" attacks, and packet snooping.
By using SSH to encrypt all transmitted data, the "man-in-the-middle" attack is not possible, and it can prevent DNS and IP spoofing. An additional benefit is that the transmitted data is compressed so that the transfer speed can be speeded up. SSH has a number of features that can replace Telnet and provide a secure "channel" for FTP, pop, and even PPP.

SSH protocol and Telnet protocol telnet