Shortcuts through Colocation Facilities

TL;DR

This study evaluates the effectiveness of colocated relays in reducing Internet path latencies, finding that strategically placed Colo-based relays significantly outperform other relay types in most cases, with substantial latency improvements.

Contribution

It provides the first large-scale measurement analysis of Colo-hosted relays' performance in latency reduction, identifying optimal locations and quantifying their benefits.

Findings

Colo-based relays achieve latency reductions in 76% of cases.

75% of latency improvements require only 10 relays in 6 large Colos.

Relays in Colos outperform other relay types in latency reduction.

Abstract

Network overlays, running on top of the existing Internet substrate, are of perennial value to Internet end-users in the context of, e.g., real-time applications. Such overlays can employ traffic relays to yield path latencies lower than the direct paths, a phenomenon known as Triangle Inequality Violation (TIV). Past studies identify the opportunities of reducing latency using TIVs. However, they do not investigate the gains of strategically selecting relays in Colocation Facilities (Colos). In this work, we answer the following questions: (i) how Colo-hosted relays compare with other relays as well as with the direct Internet, in terms of latency (RTT) reductions; (ii) what are the best locations for placing the relays to yield these reductions. To this end, we conduct a large-scale one-month measurement of inter-domain paths between RIPE Atlas (RA) nodes as endpoints, located at eyeball networks. We employ as relays Planetlab nodes, other RA nodes, and machines in Colos. We examine the RTTs of the overlay paths obtained via the selected relays, as well as the direct paths. We find that Colo-based relays perform the best and can achieve latency reductions against direct paths, ranging from a few to 100s of milliseconds, in 76% of the total cases; 75% (58% of total cases) of these reductions require only 10 relays in 6 large Colos.