Computer networks Data transmission systems Computer science Data communication Computer programming Cryptography Networking C (Computer program language) C++ (Computer program language) Computer Science Data link layer Data structures (Computer science) Security measures Structured programming Application layer Business communication C COMPUTER NETWORKS Cipher-Decipher Cryptography-- Telephone Data Security Data Communication and Networking Data Encryption Data Link Protocol Data communications Data communications and networking Interfacing&communications Local area networks (Computer networks) Mathematics-Cryptography NETWORK LAYER