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Towards Policy-Enabled Multi-Hop Routing for Cross-Chain Message Delivery

Amin Rezaei, Solomon L. Davidson, Bernard Wong

Abstract

Blockchain ecosystems face a significant issue with liquidity fragmentation, as applications and assets are distributed across many public chains with each only accessible by subset of users. Cross-chain communication was designed to address this by allowing chains to interoperate, but existing solutions limit communication to directly connected chains or route traffic through hubs that create bottlenecks and centralization risks. In this paper, we introduce xRoute, a cross-chain routing and message-delivery framework inspired by traditional networks. Our design brings routing, name resolution, and policy-based delivery to the blockchain setting. It allows applications to specify routing policies, enables destination chains to verify that selected routes satisfy security requirements, and uses a decentralized relayer network to compute routes and deliver messages without introducing a trusted hub. Experiments on the chains supporting the Inter-Blockchain Communication (IBC) protocol show that our approach improves connectivity, decentralization, and scalability compared to hub-based designs, particularly under heavy load.

Towards Policy-Enabled Multi-Hop Routing for Cross-Chain Message Delivery

Abstract

Blockchain ecosystems face a significant issue with liquidity fragmentation, as applications and assets are distributed across many public chains with each only accessible by subset of users. Cross-chain communication was designed to address this by allowing chains to interoperate, but existing solutions limit communication to directly connected chains or route traffic through hubs that create bottlenecks and centralization risks. In this paper, we introduce xRoute, a cross-chain routing and message-delivery framework inspired by traditional networks. Our design brings routing, name resolution, and policy-based delivery to the blockchain setting. It allows applications to specify routing policies, enables destination chains to verify that selected routes satisfy security requirements, and uses a decentralized relayer network to compute routes and deliver messages without introducing a trusted hub. Experiments on the chains supporting the Inter-Blockchain Communication (IBC) protocol show that our approach improves connectivity, decentralization, and scalability compared to hub-based designs, particularly under heavy load.

Paper Structure

This paper contains 52 sections, 8 figures.

Table of Contents

  1. Introduction
  2. Background
  3. Inter-Blockchain Communication (IBC)
  4. Relayers
  5. Multi-Hop Extension
  6. Limitations
  7. Architecture
  8. xRoute Application Services -- App Layer
  9. xRoute Transport -- Transport Layer
  10. Relayer Control Plane (RCP) -- Network Layer
  11. Relayer Data Plane (RDP) -- Link and Physical Layers
  12. Policy Enforcement Module
  13. Security Requirements
  14. Message Delivery Fees
  15. Message Delivery Time
  16. ...and 37 more sections

Figures (8)

  • Figure 1: Sequence Diagram illustrating a multi-hop packet's flow
  • Figure 2: xRoute architecture. xRoute Core modules run on-chain (application services, policy enforcement, governance, and multi-path). Relayers run off-chain control/data planes for route computation and packet forwarding.
  • Figure 3: Relayer Network Architecture. The coordination network is a BFT blockchain where relayers stake tokens and collaborate on route computation and packet delivery. Management contracts on source/destination chains hold escrowed fees and verify relayer signatures. Relayers specialize in specific chains, each monitoring only the chains they stake for and holding gas tokens only for those chains, reducing per-relayer operational burden.
  • Figure 4: Effect of utilizing xRoute on Connectivity, when chains with smaller than required Nakamoto coefficient are avoided
  • Figure 5: Effect of Taking out Top-X chains (sorted by number of connections) on connectivity.
  • ...and 3 more figures