Network mapping is the study of the physical connectivity of networks e.g. the Internet. Network mapping discovers the devices on the network and their connectivity. It is not to be confused with network discovery or network enumeration which discovers devices on the network and their characteristics such as operating system, open ports, listening network services, etc. The field of automated network mapping has taken on greater importance as networks become more dynamic and complex in nature.
Large-scale mapping project Images of some of the first attempts at a large scale map of the internet were produced by the Internet Mapping Project and appeared in Wired magazine. The maps produced by this project were based on the layer 3 or IP level connectivity of the Internet (see OSI model), but there are different aspects of internet structure that have also been mapped. More recent efforts to map the internet have been improved by more sophisticated methods, allowing them to make faster and more sensible maps. An example of such an effort is the OPTE project, which is attempting to develop a system capable of mapping the internet in a single day. The "Map of the Internet Project" maps over 4 billion internet locations as cubes in 3D cyberspace. Users can add URLs as cubes and re-arrange objects on the map. In early 2011 Canadian based Internet service provider (ISP) PEER 1 Hosting created their own Map of the Internet that depicts a graph of 19,869 autonomous system nodes connected by 44,344 connections. The sizing and layout of the autonomous systems was calculated based on their eigenvector centrality, which is a measure of how central to the network each autonomous system is. Graph theory can be used to better understand maps of the internet and to help choose between the many ways to visualize internet maps. Some projects have attempted to incorporate geographical data into their internet maps (for example, to draw locations of routers and nodes on a map of the world), but others are only concerned with representing the more abstract structures of the internet, such as the allocation, structure, and purpose of IP space.
Enterprise network mapping Many organizations create network maps of their network system. These maps can be made manually using simple tools such as Microsoft Visio, or the mapping process can be simplified by using tools that integrate auto network discovery with Network mapping, one such example being the Fabric platform. Many of the vendors from the Notable network mappers list enable you to customize the maps and include your own labels, add un-discoverable items and background images. Sophisticated mapping is used to help visualize the network and understand relationships between end devices and the transport layers that provide service. Mostly, network scanners detect the network with all its components and deliver a list which is used for creating charts and maps using network mapping software. Items such as bottlenecks and root cause analysis can be easier to spot using these tools. There are three main techniques used for network mapping: SNMP based approaches, active probing and route analytics. The SNMP based approach retrieves data from Router and Switch MIBs in order to build the network map. The active probing approach relies on a series of traceroute-like probe packets in order to build the network map. The route analytics approach relies on information from the routing protocols to build the network map. Each of the three approaches have advantages and disadvantages in the methods that they use.
Internet mapping techniques There are two prominent techniques used today to create Internet maps. The first works on the data plane of the Internet and is called active probing. It is used to infer Internet topology based on router adjacencies. The second works on the control plane and infers autonomous system connectivity based on BGP data. A BGP speaker sends 19-byte keep-alive messages every 60 seconds to maintain the connection.
Active probing This technique relies on traceroute-like probing on the IP address space. These probes report back IP forwarding paths to the destination address. By combining these paths one can infer router level topology for a given POP. Active probing is advantageous in that the paths returned by probes constitute the actual forwarding path that data takes through networks. It is also more likely to find peering links between ISPs. However, active probing requires massive amounts of probes to map the entire Internet. It is more likely to infer false topologies due to load balancing routers and routers with multiple IP address aliases. Decreased global support for enhanced probing mechanisms such as source-route probing, ICMP Echo Broadcasting, and IP Address Resolution techniques leaves this type of probing in the realm of network diagnosis.
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