Explain how to instantiate various sharding protocols with IBC

[cwgoes]

Most of them are some variant of proxy client & master-slave security.

Message passing architectures also vary, TBD whether that can be instantiated accurately.

• Eth 2.0
• Polkadot

cc @Chjango If there are any others which would be helpful here, let me know.

[cwgoes]

Approximately:

• Polkadot: proxy clients on all parachains, main clients on relay chain of all parachains.
• NEAR: trivial clients, almost like loop-back but asynchronous between block parts.
• Eth 2.0: still underdefined, possibly the same as Polkadot. "Shard pairing" is something special.

[cwgoes]

Should these be blog posts? Documents in this repository? Ideally they would outlive specific protocol comparisons and instead serve as a more general reference, especially for future cross-chain staking topologies. Emphasizing the "continuum of sharding" would be helpful, I have done this in person but never in written form as far as I can recall.

[brentxu]

Blog post and docs both sound reasonable. I want to make a note to find folks who would be interested in this sort of task. Exploring the "continuum of sharding" and how that applies to IBC could be an entire curriculum. Wondering if it is worthwhile to go into some of the academic research as well: https://www.comp.nus.edu.sg/~hungdang/papers/sharding.pdf

[cwgoes]

Also the proxy client topology, e.g. this.

[hxrts]

Worth including one or more Rollup schemes here as well. For instance, LazyLedger plans to provide data availability services to Ethereum-secured Optimistic Rollups, might these transactions be specified via IBC? Or Rollup-to-Rollup communication.