head of bus (DQDB) (HOB)

In city networks using Distributed Queue Dual Bus( DQDB), the cells are generated in a cell or frame generator.

DQDB structure

This cell generator, located at the beginning and end of a DQDB bus, is the Head of Bus (HOB). The cells then run from the beginning HOB through the DQDB bus to the end HOB, where they are destroyed. Alternatively, there may be only a single Head of Bus that performs the functions of both.