Downstream synchronous multichannel (DSSM) communications are provided among a plurality of carriers, each being a completely DOCSIS™ 2.0-compliant downstream. The synchronous multichannels support communications with both DSSM-capable communications nodes and non-DSSM-capable communications nodes (e.g., legacy cable modems). Non-DSSM packets are transmitted on a single channel. DSSM packets are split into multiple pieces, which are transmitted simultaneously on all available channels. Since the physical delay variation (e.g., group delay change) across the adjacent carriers is small (on the order of a symbol time), the multiple pieces arrive at the receiving communications nodes at nearly the same time and can be reassembled with minimal buffering and no packet ordering problems. To avoid causing trouble for the non-DSSM-capable communications nodes, the packet pieces are encapsulated with a header that causes the non-DSSM-capable communications nodes to silently discard them.