In 1994, Bill Ostrom was the first to design a canoe/portage pack with an internal frame. An internal frame canoe pack has a rigid back and a hip belt so the weight is transferred to your hips, and the pack moves with you.
Consider an internal frame canoe/portage pack if you want extra comfort, are carrying heavy loads, expect long portages, or have a cranky back. The extra support is well worth it. Click here for a detailed description of the "Internal Frame Canoe/Portage Pack Suspension System".
Ostrom Canoe Pack/Barrel Harness Comparison Chart