Two thoughts:

A) Doing 2 should be easy using the new MessageExtensions in a PING or PROBE. 

B) I think that 1 might run into serious problems as the messages growing and 
all the fragmentation issues around something in the forwarding header growing. 


 
On Feb 9, 2010, at 12:54 AM, Jouni Mäenpää wrote:

> Hi,
> 
> In the draft “Self-tuning DHT for RELOAD”
> (http://www.ietf.org/id/draft-ietf-p2psip-self-tuning-00.txt), which is
> nowadays a WG item, we specify how a P2PSIP overlay can adapt to
> changing operating conditions. The main idea is that each peer collects
> statistical data about the network and dynamically adjusts its
> stabilization rate, neighborhood set size, and finger table size based
> on the analysis of the data. In order to do this, each peer produces an
> estimate of the current network size, leave rate, and join rate. In the
> simulations we (the authors of the draft) have run, we have observed
> that an easy way to improve the accuracy of these estimates is to allow
> peers to share their estimates. We can imagine at least two ways to do this:
> 
> (1) Peers piggyback their estimates in RELOAD messages.
> 
> (2) Each peer asks a subset or all of the peers in its routing table to
> return their current estimates.
> 
> In alternative (1), a new ForwardingOption could be used for instance in
> messages sent as part of the Chord stabilization routines (e.g., Ping).
> Every peer forwarding such a request or response could add a new
> ForwardingOption containing its current estimates to the message. The
> source node, intermediate nodes, and the destination node would store
> all estimates carried in the ForwardingOptions structures. When the
> stabilization timer fires, each peer would calculate the final estimate
> by taking an average (or median) over the estimates received during the
> stabilization interval and its own estimate.
> 
> In alternative (2), when the stabilization timer fires, every peer sends
> a request (e.g., Probe or Inspect) to all or a subset of the peers in
> its routing table (e.g., to all fingers), asking them to return their
> current estimates. This would require extending the Probe/Inspect
> messages. Again, the average or median of the received estimates and the
> peer's own estimate would be used to calculate the final estimate.
> 
> Any opinions on which alternative would be the preferred one? We would
> like to propose using (1) since it does not add any additional messages
> to the overlay. Also, if using (1), peers can most likely obtain more
> shared values and thus be able to produce more accurate estimates than
> by using (2). However, it might also be interesting to allow both
> approaches.
> 
> Cheers,
> Jouni
> _______________________________________________
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Cullen Jennings
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