Re: [Bitcoin-development] Bitcoind-in-background mode for SPV wallets

[Peter Todd <pete@petertodd.org>]

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On 10 April 2014 07:32:44 GMT-04:00, Pieter Wuille <pieter.wuille@gmail.com> wrote:
>There were earlier discussions.
>
>The two ideas were either using one or a few service bits to indicate
>availability of blocks, or to extend addr messages with some flags to
>indicate this information.
>
>I wonder whether we can't have a hybrid: bits to indicate general
>degree of availability of blocks (none, only recent, everything), but
>indicate actual availability only upon actually connecting (through a
>"version" extension, or - preferably - a separate message). Reason is
>that the actual blocks available are likely to change frequently (if
>you keep the last week of blocks, a 3-day old addr entry will have
>quite outdated information), and not that important to actual peer
>selection - only to drive the decision which blocks to ask after
>connection.

Why not just put an expiration date on that information and delay deletion until the expiration is reached?

Also, its worth noting how the node bit solution you proposed can be done as a gradual upgrade path for SPV client. From the perspective of nodes that don't know about it they just see the pruned nodes as SPV nodes without any chain data at all. The only issue would be if large numbers of uses turned off their full nodes, but that's a possibility regardless. Done with partial UTXO set mode this may even result in an eventual increase in the number of full nodes.
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