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iip title author discussions-to status type category created requires
40
ICON BTP Message Fragmentation
Heonseung Lee (@leeheonseung)
Draft
Standards Track
IRC
2020-06-14
25

Simple Summary

If the size of the relay message containing the block proof of the SRC chain exceeds the transaction size allowed by the target chain, define and add logic to fragment the BTP message from the BMC to handle this.

Abstract

If the size of Relay Message containing Block Proof larger than Transaction size of target chain, a problem occurs. To solve this, add the logic to fragment and assemble the Relay Message.

Motivation

Block proof of the ICON chain can be verified in the BMV of the chain using only the parts related to BTP. However, in certain chains, it is sometimes necessary to receive and verify the entire Block Proof.

At this time, the ICON Relay Sender fragments the RelayMessage and delivers it to the ICON BMC, and it is necessary to assemble and verify it.

For this reason, there is no issue for ICON Block Proof verification on target chain, so BTP 1.1 implements it only on the ICON BMC.

Specification

BMC

Interface

handleFragment

void handleFragment(String _prev, String _msg, int _idx);
  • Params
    • _prev: String (BTP Address of the previous BMC)
    • _msg: String (Fragmented base64 encoded string of serialized bytes of Relay Message)
    • _idx: Integer (Index of fragment)
  • Description:
    • Concat the fragments of the Relay message that come with _idx in the order of _idx.
    • If _idx is negative, it is determined as the first message, and if _idx is zero, it is determined as the last fragmentaion message.
      • For example, if the number of fragments is 4, then _idx should be -3, 2, 1, 0 sequentially
    • Instead of verifying each time each fragmentation message is processed, it is assembled and verified when the last fragmentation message arrives.
    • Assemble fragments of the Relay Message and call by BMC.handleRelayMessage.
    • It's allowed to be called by registered Relay.

Implementation

TBD

Copyright

Copyright and related rights waived via CC0.