Reimagining Onion Messages as an Overlay Layer

The discussion focuses on the nuanced understanding of how onion messaging operates within the Lightning Network's architecture, particularly emphasizing the non-mirrored nature of the onion overlay concerning the channel graph topology. This distinction highlights that nodes without direct channels can still establish and broadcast an onion link, contrary to a straightforward mirroring of the existing network structure. This point is underscored by referencing the initial BOLT, which clarifies the necessity for explicit specifications to ensure interoperability across different implementations. The importance of such specifications is to have all nodes operate cohesively, adhering to a unified set of behaviors.

A simplified scenario further elucidates the potential efficiency gains from utilizing distinct TCP or QUIC connections for onion messaging. In this example, Alice and Bob represent two nodes with differing message processing capabilities. Alice has a First-In-First-Out (FIFO) queue with various messages waiting to be sent to Bob, who processes messages sequentially and slowly. Due to Bob's single-threaded processing model, a backlog occurs, significantly delaying the transmission of an onion message from Alice to Bob. This delay is attributed to the limited TCP parameters restricting simultaneous message transmissions. The argument posits that employing a separate TCP or QUIC connection for onion messages could prevent such delays, ensuring more efficient message propagation by circumventing the bottlenecks associated with processing other types of messages.

This conversation underscores a critical insight into the design and operational intricacies of the Lightning Network, advocating for architectural decisions that optimize message transmission efficiency. By suggesting modifications, such as the use of distinct connections for different message types, it aims to mitigate processing delays and enhance overall network performance. The referenced BOLT specification serves as a foundational element in understanding these proposed enhancements, highlighting the ongoing dialogue around network optimization and the technical considerations pivotal to its evolution.