GCC (General Communication Channel) was defined by G.709
is in-band channel used to carry management and signaling information within OTN elements.
Two types of GCC are available:
- GCC0 - two bytes within OTUk overhead. GCC0 is terminated at every 3R (Re-shaping, Re-timing, Re-amplification) point and used to carry GMPLS signaling protocol and/or management information.
- GCC1/2- four bytes (each of two bytes) within ODUk overhead. These bytes are used for client end-to-end information and shouldn't be touched by the OTN equipment.
In contrast to SONET where Data Communication Channel (DCC) has constant bandwidth (b/w), GCC b/w depends on line rate. For example GCC0 b/w in case of OTU1 is ~333Kb/s as for OTU2 its b/w is ~1.3Mb/s.