Johan Torås Halseth [ARCHIVE] on Nostr: 📅 Original date posted:2017-09-04 📝 Original message: I haven’t looked too ...

📅 Original date posted:2017-09-04
📝 Original message:
I haven’t looked too closely at your proposal, but the first thing that hit me (2 weeks ago, sorry for not answering right away), is that instead of the basic flood-the-network-about-channels algorithm that currently is being used, this makes each route discovery request behave more or less like flooding (ask everybody within your local topology)?
Also it will be interesting to see when the network starts developing, I suspect that if you keep every node within 3 hops in your local topology, you end up storing most of the network anyway. So I think the routing algorithms will be far easier to optimize and analyze after some real world data :)
That being said, interesting idea, I’m not dismissing it :D

On Tue, Aug 22, 2017 at 3:08, Billy Tetrud <billy.tetrud at gmail.com> wrote:
Hey Guys,
I'm testing this mailing list out for the first time, so I'm probably gonna be doing it wrong.
I want to talk about route discovery and route generation in the lightning network. It seems there's a couple types of things going on with routing: * Super basic flood-the-network style routing to get things up and running, as I believe is implicitly proposed here: https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md [https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md]

* More involved research projects that may not reach fruition any time soon. Eg this: http://bitfury.com/content/5-white-papers-research/whitepaper_flare_an_approach_to_routing_in_lightning_network_7_7_2016.pdf [http://bitfury.com/content/5-white-papers-research/whitepaper_flare_an_approach_to_routing_in_lightning_network_7_7_2016.pdf]


I'd like to discuss a near-term approach that can replace the basic flood-the-network style route discovery, but isn't so complicated that it needs a ton of study and work. This won't be the end-all solution to route discovery, but should take us a lot further than flood-the-network.
I propose a protocol where each node knows about its own local network topology, and to find a final route, a transaction originator queries a number of its connections for routes to the intended destination. By doing this, it means that nodes are *not* receiving or storing the entire network topology, which makes route discovery a lot less taxing on the network (in terms of bandwidth and storage space).
To go into more detail...
When a node joins the network: 1. it broadcasts its information to all its channels (pretty much as proposed here [https://github.com/lightningnetwork/lightning-rfc/blob/master/07-routing-gossip.md] ) announcing its relevant channel information 2. it requests local network topology information from all its channels for information about channels 1 hop beyond its direct connection (ie it will receive information about which addresses those channels are connected to, and their related fee info / etc) 3. it then requests topology information for channels 2 hops beyond, etc until it has filled its cache to its satisfaction (the user can choose some amount of megabytes as its limit of network topology data to store) 4. it also subscribes to topology changes for nodes at those distances (eg if a node has requested information from 3 hops away, it will receive info about any new channels or removed channels that fall within that distance)
When a node receives an announcement message from a node joining the network: 1. it will store that node's info in its cache 2. it will also forward that info to any node that's subscribed to topology changes that fall within the relevant distance
When a node wants to construct a route for a transaction: 1. It checks to see if it has a path to that node in its cache. If it does, it finds the cost of the cheapest path it has. 2. It asks all the channels on the edge of its cached local view for their cheapest path (however you want to define cheapest), specifying that it only care about paths with a maximum cost of the cheapest path it has already found in its cache. For example, if the node has nodes up to 3 hops away in its cache, it will *only* ask the nodes 3 hops away (it will not ask its direct connections, nor nodes 2 hops away, since it already has enough information to ignore them) 3. When it gets all its responses, it constructs a path
When a node receives a path request from a node: 1. It checks its cache for its cheapest cache-only path 2. It asks nodes on the edge of its cached local view for their cheapest path, specifying that it only cares about paths with a maximum cost of either its cheapest cache-only path or the max-cost specified by the requesting node minus the channel cost between it and the requesting node (whichever is cheaper). A node on the edge of its cached local view is *not* asked for route information if the cost to that node exceeds the max-cost this relay node would specify. 3. It reports the results that satisfy the max-cost requirements of the requesting node
And that's it. All the route information can be encrypted and signed so relaying nodes can't read the information inside, and so the requesting source node can verify which nodes sent that information.
This protocol should keep both node-announcement messages *and* route request messages highly localized.
Thoughts?
~BT
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