Measurements of the Internet topology in the Asia-Pacific Region

Bradley Huffaker (bhuffake@sdsc.edu)
CAIDA, Univ. of California, San Diego, USA
USA

Marina Fomenkov (mfomenkova@ucsd.edu)
CAIDA, Univ. of California, San Diego, USA
USA

David Moore (info@caida.org)
CAIDA, Univ. of California, San Diego, USA
USA

Evi Nemeth (evi@caida.org)
CAIDA, Univ. of Colorado, USA
USA

k claffy(kc@caida.org)
CAIDA, Univ. of California, San Diego, USA
USA



Abstract

CAIDA, the Cooperative Association for Internet Data Analysis, has done a study of network connectivity in the Asia-Pacific region. The focus is on network latency and performance, autonomous system (AS) and country peering, and third party transit. Using ICMP packets from nine geographically diverse monitors we collect data that includes the forward IP path and the round-trip delay to about 2000 destinations (mostly web servers) in the Asia-Pacific region. From these IP paths and delay values we gather statistics about transit providers, peering, and the appropriateness of our metrics to measure the Internet.



1. Introduction

As the Internet grows relentlessly, so do the difficulties in monitoring and understanding its complexity. Studies are available that rely upon theoretical models or simplified assumptions in order to emulate certain features of Internet behavior. However, the actual macroscopic dynamic characteristics of the global Internet have not been studied in any detail. Our work seeks to narrow this gap. By monitoring the performance of a large set (many tens of thousands) of end-to-end paths over a period of time, we obtain empirically-based insight into macroscopic Internet topology dynamics.

We apply active probe measurements to capture and track relevant cross-sections of global Internet topology. CAIDA developed the skitter tool to continuously measure the forward IP path and round trip time (RTT) from a source to many thousands of destinations. In this paper we focus specifically on Internet connectivity and topology measurements of the Asia-Pacific region, using data obtained from nine skitter hosts located in North America (4), Asia (3), Europe (1), and New Zealand (1). Each source queries the same database of more than 21,000 destinations from all over the world, including about 2000 destinations in the Pacific Rim countries. By augmenting this data with both routing tables and geographical data, we can see large components of Internet topology at multiple logical and geopolitical levels: from individual hops, to Autonomous Systems (ASes), to countries traversed.

The paper is organized as follows. We review related work in Section 2. Section 3 briefly describes the design and implementation of the skitter measurement tool, lists the sites that host skitter sources, and gives an overview of the raw data. We discuss the data analysis methodology and present results in Section 4. Section 5 concludes the paper.



2. Related work

Internet mapping studies typically focus on characterizing and delineating Internet topology and/or performance. Characterizing topology requires collecting data on Internet nodes and links to create a graph-like map of parts of the Internet. Characterizing performance typically involves measuring RTTs between pairs of hosts and studying how the RTT varies depending on the path, time of day, traffic type, and other parameters.

One of the most extensive attempts to map the Internet is the Mercator project [1], which uses UDP packets in the same manner as traceroute, to discover Internet topology at the router level. Unlike skitter, Mercator maps the Internet starting from a single host, and does not use any external database to guide selection of its probe destinations. Instead, Mercator selects probe targets using a heuristic called "informed random address probing" to guess which portions of the IPv4 address space are likely to contain addressable nodes. The algorithm builds a graph rooted at the Mercator source host, and uses source-routing to try to discover cross-links. Mercator also has heuristics for resolving aliases, i.e., identifying multiple interfaces (IP addresses) that belong to the same router. After running for three weeks in the summer of 1999, Mercator had discovered nearly 150,000 interfaces and nearly 200,000 links. In five days of data collected in November 1999, skitter running on 18 source hosts saw about the same number of nodes and nearly 270,000 links.

There are other Internet mapping projects [2, 3, 4] that attempt to obtain router and/or AS level maps. From skitter data we can derive both router maps and AS maps.