(iv) Channel coding

The Data Link layer performs framing (organizing bits into frames), error control (detecting/correcting errors via checksums/CRC), and flow control (regulating transmission rate between sender and receiver).

Channel coding (adding redundancy to combat channel noise at the signal level, e.g. line coding schemes) is a Physical layer function, not a Data Link layer function — it deals with how bits are represented as signals, which is below the Data Link layer's scope.