Subject: [Din] New SCP draft

From: David Mazieres <[email-masked]>
Date: Wed, 13 Jun 2018 14:33:35 -0700

Hi, everyone.  We've posted a new draft of the SCP protocol spec in the
usual place:

        https://datatracker.ietf.org/doc/draft-mazieres-dinrg-scp/

In addition to a bunch of clarifications, the new draft addresses a bug
or serious ambiguity in how nodes may exit the NOMINATION phase.
Previously, nomination effectively had to go on in perpetuity.  Now, we
just run the NOMINATION and PREPARE phases concurrently, and allow a
node to accept a prepared ballot even before it has completed the
nomination phase.  This makes it possible for a node that has
externalized a slot to remember only the externalize message and no
longer have to participate in nomination.

To make this all clearer, we also added a new section with a table
summarizing the phase transitions.

Thanks for any comments and feedback.

David

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From: Piers Powlesland <[email-masked]>
Date: Thu, 14 Jun 2018 12:09:09 +0100

Hi David,

A couple of thoughts.

I think SCPQuorumSet could be renamed to SCPScliceSet or SCPQuorumSliceSet.
As it is, the naming implies that the set contains quorums when in fact it
may not.

Also does echoing a peer involve forwarding messages from a peer to other
peers? My usual understanding of the word "echo" is that a message sent is
sent back, in this context my immediate understanding of "echoing a peer"
would be that messages from a peer are forwarded on or redistributed to the
network, but the definition of echoing a peer makes no mention of that.

'To echo "v", the node merges any valid values from "v"’s "voted" and
"accepted" sets into its own "voted" set.'

On Wed, Jun 13, 2018 at 10:33 PM, David Mazieres <
[email-masked]> wrote:

> _______________________________________________
> Din mailing list
> [email-masked]
> https://www.irtf.org/mailman/listinfo/din
>

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From: David Mazieres <[email-masked]>
Date: Thu, 14 Jun 2018 08:12:33 -0700

> As it is, the naming implies that the set contains quorums when in fact it

That's a good idea.  I think maybe just SCPSlices is clear enough and
shorter.

> "accepted" sets into its own "voted" set.'

Since the messages are broadcast, technically the sending node may hear
its votes echoed back, but I agree this could provide the wrong
intuition.  Similarly "mirroring" might convey the wrong thing.  Maybe
"relaying" or "repeating" or "following"?  Any other ideas?

David