A telecommunications system can include a network device with a layered protocol architecture for allowing transfer of upper layer Protocol Data Units using a shared medium. A data block includes a plurality of Protocol Data Units and a data block header, which includes a delimiter as a length indicator (LI). Any last protocol data unit of the data block has no delimiter. When a Protocol Data Unit fills the balance of the data block, the length indicator is zero having no data for a first link indicator in any next in sequence data block.