[messaging] Message order in group chat (attempt at summary)

[Ben Laurie]

On 27 April 2014 18:40, Moxie Marlinspike <moxie at thoughtcrime.org> wrote:
>
>
> On 04/27/2014 07:39 AM, Ximin Luo wrote:
>> I'm not so sure about displaying messages where you haven't yet seen
>> their parents yet. This violates causality, and the principle of
>> delivering messages in-order.
>
> A fundamental premise of asynchronous messaging is that any message can
> be delayed hours or days for some or all recipients, or that any message
> can be lost entirely at any point in time for some or all recipients.

If it is delayed for all recipients, then causality cannot be violated :-)

Here's a crazy idea.

Each client maintains a list of messages it knows each other client
has seen (because that client has told it so). Every time it sends a
message to another client, it also sends all messages it has seen that
it does not know the other client has seen. It also sends a list of
messages it knows the other client doesn't know it has seen.