I E E E E C O M M U N I C a T I O N S Internet Topology Discovery: a Survey

his survey focuses on measurements of the network topology, i.e., the representation of the interconnection between directly connected peers in the network. While some of this information can be gleaned from passive measurements, researchers largely obtain the topology and its characteristics from active measurements. There are three different levels at which to describe the network topology: the link layer topology, the network layer topology, sometimes referred to generically as the internet topology, and the overlay topology. The link layer topology, as defined by Breitbart et al. [1], refers to the characterization of the physical connectivity relationships that exist among entities in a communications network. In other words, it is the description of how data link layer devices, switches and bridges, are interconnected and how the different hosts are connected to them. Maintaining an accurate and complete knowledge of the link layer topology is a prerequisite to many critical network management tasks such as network diagnostics and resource management. There is considerable scientific literature devoted to techniques for the discovery of link-layer topology. Interested readers might refer to Robertson [2], Tang and Sugla [3], Wood et al. [4], Breitbart et al. [1], Lowekamp et al. [5] and, more recently, Bejerano [6]. However, a deep description of link layer topology discovery mechanisms is beyond the scope of this article as link-layer topology discovery is an intra-domain task and this survey focuses on topology discovery at the scale of the internet. A typical overlay topology would be the topology of a peer-to-peer system. An overlay topology can be unstructured or structured. Structured overlays are exemplified by distributed hash tables, such as Chord [7] or CAN [8]. As explained by Stutzbach et al. [9], " peers select neighbors through a predominantly random process. An overlay topology is influenced by peer participation (i.e., join and leave mechanisms) as well as the protocol behavior (i.e., neighbor selection). Characterizing an overlay topology can be done by examining properties of snapshots of the overlay. " These snapshots can be gathered using a topology crawler, an engine that queries peers for a list of their neighbors ([9, 10]). As stated by Stutzback et al. [11], " a deep understanding of the topological characteristics in overlay systems is required to meaningfully simulate and evaluate the actual performance of the proposed search and replication techniques. " The overlay topology has drawn the attention of the net-ABSTRACT Since the beginning of the …