Why is it important to study the Feistel Cipher?

                Feistel cipher using the concept of a product cipher, which is the performing of   two  or  more  basic  ciphers  in  sequence  in  such  a  way  that  the final  result or product is cryptographically stronger then any of the component ciphers.

            Feistel proposed the use of a cipher that alternates substitutions and permutations. So Feistel cipher is considered to be an important one.