  While increasingly more application-specific blockchains, or ledgers, are
being implemented and deployed, exchanging information between these ledgers
remains an open problem. Existing cross-ledger protocols (XLPs) exhibit a
variety of limitations such as scalability, liveness, efficiency, among others.
This paper proposes a new XLP, namely XLPN-22, which introduces a global
topology for the consortium of ledgers to achieve better efficiency and
scalability of cross-ledger data exchanges. In this work, we prove the safety
and liveness of XLPN-22 and analyze its theoretical complexity. We also
implement XLPN-22 on SciChain ledgers and evaluate it on up to 128 nodes, 8
ledgers, and 16,000 transactions. Experimental results show that XLPN-22
outperforms two baseline protocols, namely VLDB-20 and PODC-18, by 18--50\% and
64--84\%, respectively.
