Methods, apparatus and systems for controlling flow of data between a memory of a host computer system and a data communications interface for communicating data between the host computer system and a data communications network. In an example embodiment, an apparatus includes a descriptor table for storing a plurality of descriptors for access by the host computer system and data communications interface. Descriptor logic generates the descriptors for storage in the descriptor table. The descriptors include a branch descriptor comprising a link to another descriptor in the table.