Data Encryption Standard (DES ALGORITHM) in Cryptography - PART 1- simple steps-Network Security

Information technology Subject: CRYPTOGRAPHY AND NETWORK SECURITY Data Encryption Standard (DES) is a block cipher algorithm that takes plain text in blocks of 64 bits and converts them to ciphertext using keys of 48 bits. It is a symmetric key algorithm, which means that the same key is used for encrypting and decrypting ​data. Encryption and decryption using the DES algorithm. Source: https://www.educative.io Comment below the answers to the following questions: 1. What is the name of the DES function which operates on RHS and Key? 2. How many rounds happen in DES? 3. Is permutation necessary? why?