‹new breed› of infrastructure maps are dynamic in nature, constructed with live data gathered from the Internet every time the map is requested by a user.

Maps for Operational Internet Management

Maps can summarise and present complex, rapidly changing data on the operational state of a network in a single visual image, providing an easy-tointerpret overview of the system and thereby aiding problem diagnosis and solving. For example, in NOCs (network operations centers) of large ISPs just a handful of skilled operations are responsible for keeping a complex and geographically distributed hardware infrastructure running smoothly and maps are essential (see AT&T display).[4] As a New York Times story noted on the huge stress on the U.S. telecommunications systems immediately following the attacks of the 11th September 2001, “By watching computerized maps of the United States, [operators] can tell in an instant whether there are any jams in longdistance traffic.”[5] However, the detailed network monitoring maps and tools used by operators in NOCs are not made public for reasons of security and commercial

confidentiality. Some Internet networks, particularly those serving the research and education communities, do make summary network performance data publicly available using map interfaces. These interfaces are popularly referred to as ‹network weather maps.› These maps represent public-spirited information dissemination tools, providing network customers (usually universities and research labs) with useful information, especially to identify trouble spots, as well as having a marketing function (see next section). Two examples of network weather maps—the Abile network in the US and NORDUnet serving Scandinavia [Figure 3]—are updated frequently (for example the Abilene map is updated every five minutes), allowing users a ‹peak inside› the network cloud. Both maps provide a summary of overall network performance with links colour coded by their traffic flows, but importantly they also provide an interactive, visual interface through which to browse more detailed performance statistics available as tables and statistical charts. These two maps are also illustrative of the two major cartographic archetypes employed to represent computer networks – showing linkages and nodes