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Date: Mon, 5 Sep 2011 14:04:49 +0200
Message-ID: <CANEZrP3Fh=Ffeh5PtcaL4QBKXUzkFYAar4031-wVZOVQOhngrw@mail.gmail.com>
From: Mike Hearn <mike@plan99.net>
To: Bitcoin Dev <bitcoin-development@lists.sourceforge.net>
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Subject: [Bitcoin-development] Adding a pong message to the protocol
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I haven't written a patch for this, I might do so if there's
sufficient interest.

Nodes that are under heavy load exhibit extremely high latency, this
makes downloading the block chain from a node that is itself
downloading the block chain basically useless as it takes 30-60
seconds for the node to respond to clients.

It could be fixed by making nodes not accept connections/advertise
until they feel sure they have the best chain, but a more general fix
is to add a "pong" which is returned by "ping". It could contain some
useful stats about the node for network crawlers, but most importantly
timing the delta between ping and pong would let you order nodes by
responsiveness. Currently if you want to do this, it has to be
indirect, using some message that is guarantee to yield a known
response.

Because old clients ignore messages they don't understand, adding the
pong response would be easy and backwards compatible. Making nodes
prefer responsive servers might need a bit of care to avoid sloshing
load around too much.

Thoughts?