Coordinate

Coordinate represents a point in a Vivaldi network coordinate system.

A coordinate has two components: a Euclidean and a non-Euclidean component.

The Euclidean component represents the distance across the core of the Internet, where link distance typically reflects geographic distance.

The non-Euclidean component is a "height" offset, which represents the distance across an access link to the core Internet. Link distance on access links is typically constrained by bandwidth and congestion, rather than geography.

See "Vivaldi: A Decentralized Network Coordinate System" by Dabek, et al.

struct Coordinate (

size_t dims

double maxError = 1.5

double minHeight = 1.0e-5

double ce = 0.25

double cc = 0.25

double rho = 150.0

) if (

dims > 0 &&

isValid01!ce

isValid01!cc

isFinite(rho)

rho > 0.0

) {

void update(Coordinate other, double rtt, double localAdjustment, double remoteAdjustment);

double distanceTo(Coordinate other);

static bool valid(double d);

double[dims] vector;

double height;

double error;

}

Members

Functions

distanceTo double distanceTo(Coordinate other): Returns the Vivaldi distance to other in estimated round-trip time.
update void update(Coordinate other, double rtt, double localAdjustment, double remoteAdjustment): Given a round-trip time observation for another node at other, updates the estimated position of this Coordinate.

Static functions

valid bool valid(double d)

Variables

error double error;: error is a unitless measure of confidence that this Coordinate represents the true distance from the origin.
height double height;: height is the non-Euclidean component of the coordinate, which represents the distance along an access link to the Internet core in seconds.
vector double[dims] vector;: vector is the Euclidean component of the coordinate which represents the distance from the origin in the Internet core in seconds.

Parameters

dims: Dimensionality of the coordinate system.
maxError: Limit to the error any observation may induce.
minHeight: The minimum height of any Coordinate.
ce: A tuning factor which impacts the maximum impact an observation can have on a Coordinate.
cc: ditto
rho: A tuning factor for the effect of gravity exerted by the origin to control drift. See "Network Coordinates in the Wild" by Ledlie, et al. for more information.