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• select the best_ni to send from, by going through all the local_nis that can reach any of the networks the peer is on
  • consider local_ni health in the selection by selecting the local_ni with the best health value.
  • If this is a resend do not select a local_ni that has already been used.
• select the best_peer_ni that can be reached by the best_ni selected in the previous step
  • If this is a resend and the resend peer_ni is specified, then select this peer_ni if it is healthy, otherwise continue with the algorithm.
  • If this is a resend and the resend peer_ni is not specified do not consider a peer_ni that has already been used for sending.
• send the message over that path.

...

• find peer_ni using dst_nid (non-MR, so this is the only peer_ni candidate)
  
  • no issue if peer_ni is healthy
  • try this peer_ni even if it is unhealthy if this is the 1st attempt to send this message
  • fail if resending to an unhealthy peer_ni
• pick the preferred local_NI for this peer_ni if set
  • otherwise pick a healthy If the preferred local_NI is not healthy, then find a healty local NI and make set it to be the preferred local_NI for this peer_ni
• send over this path

B2D - src any, route dst, nmr dst

• • find the router you can reach the dst_nid on (router selection already considers router health using the existing mechanism. Currently a router is alive or dead, discovered via router pings and controlled by tunables such as asynchronous route failure)
    • If this is a resend and the peer_ni is unhealthy fail the send
    • If this is an original send, then use the peer_ni even if it's not healthy.
  • select the best_ni to send from by going through all the local nis that can reach the router NID
    • consider local_ni health in the selection by selecting the local_ni with the best health value.
    • If this is a resend do not select a local_ni that has already been used.
  • send over that path

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• • this NMR peer.
    • TODO: What are the impact of switching the preferred NI?
      • The NMR peer might think that this message is coming from a different peer. Would that lead to the failure of the RPC message?
      • IF so, should we fail the re-sending the message if the preferred NI is set and not healthy?
  • otherwise if preferred local_NI is not set, then pick a healthy local NI and make it the preferred NI for this peer_ni
• send over this path

B2D - src any, route dst, nmr dst

• find route to dst_nid
• find peer_ni of router
  • no issue if peer_ni is healthy
  • try this peer_ni even if it is unhealthy if this is the 1st attempt to send this message
  • fail if resending to an unhealthy peer_ni
• pick the preferred local_NI for the dst_nid if set
  • TODO: Same question as above.
  • otherwise pick a healthy local NI and make it the preferred NI for this dst_nid
• send over this path

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