The underlying network topology is an important piece of information that currently is mostly ignored in the development of large distributed applications. However, there are multiple contexts when using this knowledge can greatly optimize the running time and reduce the usage of the necessary resources. Another field of interest in topology monitoring is the process of network monitoring itself. Knowing the topology can help in reducing the network load from distributed measurements, i.e. avoiding measuring multiple times a region of the network.

A global view of raw image of the network
as it is retrieved by traceroute/tracepath.

Each MonALISA service in executing a set of monitoring modules which are based on standard tools (traceroute, tracepath, ping) to collect basic information on connectivity and hop delay.

Realtime view of 16 hops trace
from Caltech-test.kek.jp to monalisa2.cern.ch

Then, this data is used by dedicated services, to get information like location, Autonomous System number (AS), Network Name, a short description about the domain in which each hop resides and its location.

History of the trace between Purdue-Physics and citgrid2
with hops delays over the last 6 hours

Another specialized MonALISA service to determine whether two IPs are on the same device (router) and serve this information to topology mapping clients or other services.

This service is dynamically building a dictionary with all the IPs identified by measurements performed by all the monitoring services and is using several techniques to identify all the IPs which are on the same router.

IPs belonging to the same router have been identified

Based on this data, complex algorithms can be developed to discover problems in the network interconnections or for optimization purposes.

Actual distance and path together with minimum compputed distance and path
between two farms.