router: Use aggregate capacity for first-hop fragmentation check #2
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
The routing fragmentation mitigation heuristic requires each channel to contribute at least `payment_amount / max_path_count` to avoid excessive path splitting. This makes sense for network paths where each additional path incurs base fees and increases failure probability. However, for first hops this is overly restrictive. Multiple channels to the same peer converge immediately at the first hop - there's no actual network-level fragmentation. A 2M sat channel and a 48M sat channel to the same peer should be usable together for a 50M sat payment, but currently the small channel gets rejected (threshold would be 5M sat with default max_path_count=10), leaving only 48M available. This change checks the aggregate capacity across all first-hop channels to a peer. If the aggregate meets the contribution threshold, individual channels are allowed regardless of their size.
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
The routing fragmentation mitigation heuristic requires each channel to contribute at least
payment_amount / max_path_countto avoid excessive path splitting. This makes sense for network paths where each additional path incurs base fees and increases failure probability.However, for first hops this is overly restrictive. Multiple channels to the same peer converge immediately at the first hop - there's no actual network-level fragmentation. A 2M sat channel and a 48M sat channel to the same peer should be usable together for a 50M sat payment, but currently the small channel gets rejected (threshold would be 5M sat with default max_path_count=10), leaving only 48M available.
This change checks the aggregate capacity across all first-hop channels to a peer. If the aggregate meets the contribution threshold, individual channels are allowed regardless of their size.