[garphunkle]

My attempt at a summary:

Ripple refers to "spatial-reuse": a phenomenon where a train of packets spread from an originator uninterrupted.

With Ripple, nodes can only transmit DATA when they have received the "talking stick" (token) from the upstream originator. A downstream node can request a token with the new MAC frame: ready-to-receive. With their simulation, a node is always in either a TX, RX, or Listen state with equal proportions, so you have 1/3rd spatial-reuse.

This solves a problem in 802.11 where physical layer collision avoidance is sub-optimal for link utilization. Other protocols I am familiar with solve this with beacons to synchronize guaranteed time slots (a mode of IEEE 802.15.4), or they adopt a similar RTS/CTS scheme which can suffer from the hidden node problem.

What I cannot picture in my own head is how a packet can swim upstream: this protocol has a strong notion of upstream/downstream.