SSH

SSH (Secure Shell) 

SSH is an application layer network protocol designed to provide secure remote access to the operating system and tunnel TCP connections. It allows encryption of all traffic, including passwords, making it a secure alternative to Telnet and rlogin protocols. 

Main SSH features: 

• Secure remote access: SSH allows administrators to securely connect to remote servers and execute commands, which is especially important for managing servers and network equipment. 
• Secure File Transfer: SFTP and SCP protocols running on top of SSH provide secure file transfer between systems. 
• Port Tunneling and Forwarding: SSH can forward traffic between ports by encrypting it, which is useful for creating secure channels for other protocols. 
• Data compression: SSH supports compression of transmitted data, which can improve performance when transmitting data over slow channels. 

How SSH works: 

1. Connection Establishment: Occurs over a TCP connection that starts with a three-way handshake (SYN, SYN-ACK, ACK). 
2. Authentication: Uses various methods, including passwords and keys, to confirm the identity of the client and server. 
3. Key Exchange: Publicly available information is exchanged to create a secret key used to encrypt traffic. 

SSH is the de facto standard for secure remote access and is widely used in DevOps and DevSecOps for automated deployments and system management.