Meridian

	A Lightweight Approach to Network Positioning

Meridian Query Language

This prototype allows submitting custom routing queries to the 413 deployed Meridian nodes. The query language is similar to C, and provides a flexible interface to experiment with the routing protocol. The text area by default loads an implementation of the closest node discovery protocol as an illustration.

A more detailed description of the language can be found here.

Meridian query:

Measurement closest(double beta, Node t[]) {
    Measurement self = get_distance_tcp(t, -1);
    double avg_lat = array_avg(self.distance);
    double min_lat = array_min(self.distance);
    double max_lat = array_max(self.distance);
    Node ring_m[] = array_intersect(
        ring_ge((1.0 - beta) * min_lat), ring_le((1.0 + beta) * max_lat));
    if (array_size(ring_m) == 0) {
        return self;
    }
    Measurement r_lat[] = get_distance_tcp(ring_m, t, 
        ceil((2.0 * beta + 1.0) * max_lat));
    int min_index = -1; 
    min_lat = avg_lat;
    for (int i = 0; i < array_size(r_lat); i = i + 1) { 
        double cur_lat = array_avg(r_lat[i].distance);
        if (cur_lat < min_lat) {
            min_index = i;
            min_lat = cur_lat; 
        }
    }
    if (min_index == -1) {
        return self;
    }
    Measurement min_n = r_lat[min_index];    
    if (min_n.addr != 0 && min_lat < (avg_lat * beta)) {
        Measurement ret_n = rpc(ring_m[min_index], closest, beta, t);
        if (ret_n.addr != 0) {
            return ret_n;
        }
    }    
    return min_n;
}

int main() {
    Node t1 = {dns_lookup("www.cs.berkeley.edu"), 80, 0, 0};
    Node ts[] = {t1};
    Node e = {dns_lookup("planetlab1.csail.mit.edu"), 3964, 0, 0};    
    Measurement r = rpc(e, closest, 0.5, ts);
    if (r.addr == 0) {
        r.addr = e.addr;
        r.port = e.port;
    }
    print("Closest node is ");
    println(dns_addr(r.addr));
    for (int i = 0; i < array_size(r.distance); i = i + 1) {
        print("--> ");
        print(r.distance[i]);
        print(" from ");
        println(dns_addr(ts[i].addr));
    }
    return 0;
}

Meridian Query Language

Meridian Project

Computer Science Department
Cornell University

Meridian Query Language

Meridian Project

Computer Science Department Cornell University

Computer Science Department
Cornell University