Hypernets -- Good (G)news for Gnutella

Red Roo writes: "This online article addresses the recent criticism of Gnutella network scalability by pointing out that it is a Cayley tree. As a viable candidate for massively scalable P2P bandwidth, all trees are dead! But by going to higher dimensional virtual networks (aka "hypernets") e.g., hypercubes or hypertori, near linear scalability can be achieved for P2P populations on the order of several million peers each with only 20 open connections. This concept seems to have been entirely overlooked by critics and developers alike."

Comments

Trouble: this network topology requires authority

[shimmin]

While the article is interesting in the sense that it shows that efficient p2p network topolgies are possible (for suitably small definitions of efficient), actually implementing it on a network of untrusted peers could be problematic.

This is because it assumes the peers are already arranged in the network in the topology one wants.

If a central addressing authority exists, it is no problem to simply give new peers addresses and the addresses of their neighbors in such a way that the network acquires any topolgy the authority wants. The authority can even cope with peers leaving the network more or less arbitrarily.

However, a real question is -- how do you get peers to "self-assemble" into the desired topology in such a way that a small population of peers that choose not to play by the generally accepted rules cannot dramatically effect the outcome. In other words, how can peers be persuaded to place themselves on the points of a cubic hyperlattice solely by contacting a few already installed peers, some of which may not be telling the truth?

This paper's math is flawed

[jeske]

The author is using bandwidth calculations intended for physical network topologies and applying them to virtual networks. This is flawed and renders his analysis invalid.

In layman's terms. If you are a node in one of his example networks, and you're sitting on a DSL connection, does the available bandwidth you contribute to the net change whether you have 20 outbound TCP connections or 2? No. It is constant. The author incorrectly computes the "bandwidth" of these different network topologies like you are stringing a separate DSL to each person you open a TCP connection to.

Available network bandwidth in a peer network like Gnutella is related only to the physical interconnect of the nodes. (i.e. whether they are on an SBC DSL line or sitting a North American OC-3)

The only useful analysis is that which determines the amount of data-transfer required between each node (and all nodes) for common operations when using different topologies. When performing this study, you are looking for the topology which will transfer the smallest amount of data over the smallest number of nodes when performing searches. For a great analysis, see the Gnutella Performance Paper by Ritter, referenced by the above paper.

Careful analysis will tell you the same thing that common sense does -- that the best architecture involves centralized dedicated servers (supernodes), located on machines with the largest physical bandwidth available. (i.e. eactly what Napster did. )

In order to create an efficient peer network which scales, Gnutella 'merely' needs to 1) order the network by physical topology, 2) identify the nodes with the best combination of physical bandwidth, longevity, and CPU/disk resources, and 3) fully utilize those machines as supernodes.

Good luck. :)