On 27/09/15 20:17, xor wrote: > http://www.researchgate.net/publication/280623435_On_the_Impossibility_of_Efficient_Self-Stabilization_in_Virtual_Overlays_with_Churn >> Abstract >> —Virtual overlays generate topologies for greedy rout- >> ing, like rings or hypercubes, on connectivity restricted networks. >> They have been proposed to achieve efficient content discovery >> in the Darknet mode of Freenet, for instance, which provides >> a private and secure communication platform for dissidents >> and whistle-blowers. Virtual overlays create tunnels between >> nodes with neighboring addresses in the topology. The routing >> performance hence is directly related to the length of the >> tunnels, which have to be set up and maintained at the cost of >> communication overhead in the absence of an underlying routing >> protocol. >> In this paper, we show the impossibility to efficiently maintain >> sufficiently short tunnels. Specifically, we prove that in a dynamic >> network either the maintenance or the routing eventually exceeds >> polylog cost in the number of participants. Our simulations >> additionally show that the length of the tunnels increases fast >> if standard maintenance protocols are applied. Thus, we show >> that virtual overlays can only offer efficient routing at the price >> of high maintenance costs. I don't think this applies to Freenet at the moment, at least not directly. Darknet-mode Freenet is an embedding, not a virtual overlay (that is, we change the ID's to make routing based on ID work, rather than establishing tunnels as virtual connections based on ID), and it has relatively low churn.
It might apply to darknet Freenet if we adopted X-Vine for routing rather than using location swapping. This might be necessary if we can't make swapping scale. At the moment it looks like swapping doesn't scale (that is, the stabilisation time is greater than polylog in the size of the network), but Vilhelm Verendel identified several possibilities for improving it. It would be worth reading the wider literature, especially the thing about hyperbolic space. Oskar has mentioned two other location assignment/routing algorithms that try to achieve the same thing as our Metropolis-Hastings swapping mechanism. The paper above dismisses work on embeddings as not sufficiently proven. Right now this is largely academic as there is no large darknet-mode Freenet...
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