[Din] draft-mazieres-dinrg-scp-05 nomination, reasons for peer selection process

Piers Powlesland <pierspowlesland@gmail.com> Mon, 17 December 2018 15:10 UTC

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From: Piers Powlesland <pierspowlesland@gmail.com>
Date: Mon, 17 Dec 2018 15:10:00 +0000
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Subject: [Din] draft-mazieres-dinrg-scp-05 nomination, reasons for peer selection process
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Section 3.4 on page 10, describes the nomination protocol, where nodes
suggest and agree on values to begin balloting with. A node limits
itself to accepting suggestions from only certain validators, such
that validators that appear in many of a node's quorum slices are
favoured over those that appear in less quorum slices.

It's not clear from the draft why this step is necessary.

If the intent is to ensure that peers that appear in many of a node's
quorums have more influence than those that don't, then the peer
selection process seems redundant since nodes that appear in many
quorums implicitly have more influence than those that don't, because
they appear in more quorums.

It also seems that, by limiting the peers that a node accepts
suggestions from, the set of values that make it to balloting will
also be limited. Values that didn't make it to balloting this slot
will have to wait till the next slot to have a chance to be agreed
upon. If this is the case then it seems that the peer selection
process is limiting the responsiveness or throughput or both of the

What would be the problem with not performing peer selection and each
node simply accepting all suggestions from all of its validators
during nomination?