Otter is a new CAIDA tool for visualizing arbitrary network data that can be expressed as a set of nodes, links or paths. We developed Otter to handle visualization tasks for a wide variety of Internet data we deal with in our research, including data sets on topology, workload, performance, and routing. We have used Otter to visualize: multicast and unicast topology databases, core BGP routing tables, reachability and delay measurements, SNMP data, and web site directory structures. Otter's strength is in its data independence: it can handle any formatted data set consisting of links and nodes.

Otter achieves its versatility in what data it can process by using a data format specification prepended to each input file. This specification stipulates attributes of each object in the data file, which Otter uses to tailor its visualizations and even adapt its user interface to a specific data domain. We describe and provide examples of Otter's visualization features, how it achieves data independence, present case studies of Otter's utility in practice, and outline possible future directions for Otter.