64b/66b Encoding

64b/66b Encoding

In data networking and transmission, 64b/66b is a line code that transforms 64-bit data to 66-bit line code to provide enough state changes to allow reasonable clock recovery and facilitate alignment of the data stream at the receiver.

The overhead of the 64b/66b encoding is 3.125%, which is considerably less than the more common 8b/10b encoding scheme which has a 20% overhead. At the time 64b/66b was deployed, it allowed 10Gb Ethernet to be transmitted with the same lasers used by SONET OC-192, rather than requiring 12.5 Gbit/s lasers, which were not expected to become available for several years.