Followup from discussions with Agoric

[cwgoes]

• Timeouts should close ordered channels

• Implement unordered channels, with causally independent packet timeouts

• Investigate feasibility of DAG ordering on individual packets (including cross-chain)
  Hunch: more reliable channel ==> efficient acknowledging for multiple messages
  Unordered channel ==> selective acknowledgement with message hash
  Packet identities are hash of contents & predecessors, can assume ordering of receipt

• Think about possible fairness guarantees across channels on a connection (maybe for v2)
  Fairness across set of connections
  Fairness across set of channels on a connection
  We can at most restrict validator ordering choices
  Priority of given message determined by sender

• Clarify IBC relayer module interface, note that it is recommended to users

• Optional acknowledgements of success / failure for packets
  Module can choose whether or not to register acknowledgement handler
  Can tell that no reaction will take place, so don't bother acknowledging

• Close "reason" for channels
  Reason as bytestring for voluntary closure provided by channel
  System-level reasons for closure (maybe modules can register hooks)
  Think about cryptoeconomics

• Think about multi-hop case, construct data structures accordingly (e.g. channels are end-to-end)
  Distinguish between multi-hop, single-hop in data structures, multi-hop not yet supported
  Maybe trivial "IBC routing" module, maybe it handles loopback

• Review IBC interface for use "slotting in" as VatTP in Agoric's protocol

• Write specification-compliance testsuite with full spec coverage
  Some level of "binary datagram" -> "binary datagram[s]"
  How to define testsuite, parse JSON

[erights]

For reference, here's the recordings of my two presentations at the summit, with discussion:

Relative Routing
https://www.youtube.com/watch?v=a0Wr2BvIixk

ERights Pegging
https://www.youtube.com/watch?v=nNImbry1HLM

[cwgoes]

Split into:

• ICS 5: Port Allocation #130
• https://github.com/cosmos/ics/issues/131
• Ordered / unordered channels #132
• https://github.com/cosmos/ics/issues/133
• Clarify interface, recommend usage of IBC relayer module #134
• Optional acknowledgements of success / failure for packets #135
• Channel closing handshake alterations #136
• Review/align with Agoric's VatTP and CapTP #50
• Specification compliance testsuites #137
• https://github.com/cosmos/ics/issues/138