BGP Routing Tables Research Articles

Issues with inferring Internet topological attributes

A number of recent studies of Internet network structure are based on data collected from inter-domain BGP routing tables and tools, such as traceroute, to probe end-to-end paths. The goal of these studies is often to infer Internet topological properties. There is growing evidence, however, that the amount and diversity of the data has a significant impact on the conclusions drawn about some of the structural properties. While systematic data collection from a number of network vantage points can reduce certain ambiguities, thus far, no methods have been reported for fully resolving these issues. The goal of our study was to quantify the effects of these anomalies on key Internet structural attributes. We report on our analysis of over 290,000 measurements from globally distributed sites. We contrast results obtained from router-level measurements with those obtained from BGP routing tables, and offer insights as to why certain inferred properties differ. We use multiple views of the same data to demonstrate that some topological attributes, such as the average path length, are relatively consistent across a variety of data sources. We also illustrate how using the same methodology to model other attributes, such as those based on the actual forwarding path between a pair of nodes, or the level of AS path asymmetry, can produce substantially misleading results.

Towards capturing representative AS-level Internet topologies

Recent studies on AS-level Internet connectivity have attracted considerable attention. These studies have exclusively relied on BGP data from the Oregon route-views [University of Oregon Route Views Project, http://www.routeviews.org] to derive some unexpected and intriguing results. The Oregon route-views data sets reflect AS peering relationships, as reported by BGP, seen from a handful of vantage points in the global Internet. The possibility that these data sets may provide only a very sketchy picture of the complete inter-AS connectivity of the Internet has received little scrutiny. By augmenting the Oregon route-views data with BGP summary information from a large number of Internet Looking Glass sites and with routing policy information from Internet Routing Registry (IRR) databases, we find that (1) a significant number of existing AS peering relationships remain hidden from most BGP routing tables, (2) the AS peering relationships with tier-1 ASs are in general more easily observed than those with non-tier-1 ASs, and (3) there are at least about 40% more AS peering relationships in the Internet than commonly-used BGP-derived AS maps reveal (but only about 4% more ASs). These findings point out the need for continuously questioning the applicability and completeness of data sets at hand when establishing the generality of any particular Internet-specific observation and for assessing its (in)sensitivity to deficiencies in the measurements.

Measuring ISP topologies with rocketfuel

To date, realistic ISP topologies have not been accessible to the research community, leaving work that depends on topology on an uncertain footing. In this paper, we present new Internet mapping techniques that have enabled us to directly measure router-level ISP topologies. Our techniques reduce the number of required traces compared to a brute-force, all-to-all approach by three orders of magnitude without a significant loss in accuracy. They include the use of BGP routing tables to focus the measurements, exploiting properties of IP routing to eliminate redundant measurements, better alias resolution, and the use of DNS to divide each map into POPs and backbone. We collect maps from ten diverse ISPs using our techniques, and find that our maps are substantially more complete than those of earlier Internet mapping efforts. We also report on properties of these maps, including the size of POPs, distribution of router outdegree, and the inter-domain peering structure. As part of this work, we release our maps to the community.

Towards capturing representative AS-level Internet topologies

For the past two years,there has been a significant increase in research activities related to studying and modeling the Internet's topology, especially at the level of autonomous systems (ASs). A closer look at the measurements that form the basis for all these studies reveals that the data sets used consist of the BGP routing tables collected by the Oregon route server (henceforth, the Oregon route-views ) [1]. So far, there has been anecdotal evidence and an intuitive understanding among researchers in the field that BGP-derived AS connectivity is not complete. However, as far as we know, there has been no systematic study on quantifying the completeness of currently known AS-level Internet topologies. Our main objective in this paper is to quantify the completeness of Internet AS maps constructed from the Oregon route-views and to attempt to capture more representative AS-level Internet topology. One of the main contributions of this paper is in developing a methodology that enables quantitative investigations into issues related to the (in)completeness of BGP-derived AS maps.

On network-aware clustering of Web clients

Being able to identify the groups of clients that are responsible for a significant portion of a Web site's requests can be helpful to both the Web site and the clients. In a Web application, it is beneficial to move content closer to groups of clients that are responsible for large subsets of requests to an origin server. We introduce clusters ---a grouping of clients that are close together topologically and likely to be under common administrative control. We identify clusters using a ``network-aware" method, based on information available from BGP routing table snapshots.