LIGHTNING-GETROUTE(7)

NAME
lightning-getroute - Command for routing a payment (low-level).

SYNOPSIS

getroute id msatoshi riskfactor [cltv] [fuzzpercent] [seed]

DESCRIPTION

The getroute RPC command attempts to find the best route for the payment of msatoshi to lightning node id, such that the payment will arrive at id with cltv-blocks to spare (default 9).

There are two considerations for how good a route is: how low the fees are, and how long your payment will get stuck if a node goes down during the process. The riskfactor floating-point field controls this tradeoff; it is the annual cost of your funds being stuck (as a percentage), multiplied by the percentage chance of each node failing.

For example, if you thought there was a 1% chance that a node would fail, and it would cost you 20% per annum if that happened, riskfactor would be 20.

If you didn’t care about risk, riskfactor would be zero.

The fuzzpercent is a positive floating-point number, representing a percentage of the actual fee. The fuzzpercent is used to distort computed fees along each channel, to provide some randomization to the route generated. 0.0 means the exact fee of that channel is used, while 100.0 means the fee used might be from 0 to twice the actual fee. The default is 5.0, or up to 5% fee distortion.

The seed is a string whose bytes are used to seed the RNG for the route randomization. If not specified, a random string is used.

RISKFACTOR EFFECT ON ROUTING

The risk factor is treated as if it were an additional fee on the route, for the purposes of comparing routes.

The formula used is the following approximation:

    hop-risk = num-hops x per-hop-risk
    timeout-cost = blocks-timeout x per-block-cost
    risk-fee = amount x hop-risk x timeout-cost

We are given a riskfactor; expressed as two multiplied percentages is the same as fractions multiplied by 10000. There are 52596 blocks per year, thus per-block-cost x per-hop-risk is riskfactor' divided by 5,259,600,000.

The final result is:

    risk-fee = amount x num-hops x blocks-timeout x riskfactor / 5259600000

Here are the risk fees as a percentage of the amount sent, using various parameters. For comparison with actual fees, we assume nodes charge 0.05%:
Riskfactor | Nodes | Delay per node | Risk Fee % | Route fee %
0.001 | 5 | 6 | 0 | 0.25
1 | 5 | 6 | 0 | 0.25
1000 | 5 | 6 | 0.0029 | 0.25
0.001 | 10 | 72 | 0 | 0.5
1 | 10 | 72 | 0.0001 | 0.5
1000 | 10 | 72 | 0.1369 | 0.5
0.001 | 20 | 1008 | 0 | 1.0
1 | 20 | 1008 | 0.0077 | 1.0
1000 | 20 | 1008 | 7.6660 | 1.0

RECOMMENDED RISKFACTOR VALUES

0.001 is a value for tie-breaking in favor of shorter routes, but not really costing in any risk.

1 is a conservative value for a stable lightning network with very few failures.

1000 is an aggressive value for trying to minimize timeouts at all costs.

RETURN VALUE

On success, a "route" array is returned. Each array element contains

timeout for the payment failure, in blocks.

AUTHOR

Rusty Russell <rusty@rustcorp.com.au> is mainly responsible.

SEE ALSO

lightning-pay(7), lightning-sendpay(7).

RESOURCES

Main web site: https://github.com/ElementsProject/lightning