SDR Global Session Monitoring Effort

Written by Kamil Sarac ( and Kevin Almeroth (

(Our monitoring effort has been finalized)

Project Desciption

The Sdr Global Session Monitoring Effort is an effort to track, manage, and present information about the availability of world-wide sdr sessions. The basic idea is that if a number of people in topologically and geographically diverse places around the world send email to the system with their sdr cache entries we can put together a WWW page showing what sdr entries are being seen by what parts of the world. This type of service has provided many useful functions. For example, if someone is trying to advertise a session they can check the "sdr-monitor" WWW page to see what percentage of sdr-monitor sites around the world see their session.

Sdr-monitor has been used by the multicast community to track and manage multicast session announcement availability as well as to detect potential multicast reachability problems since April 1999. At this point in time (October 2003), we feel that sdr-monitor has completed its mission and we have decided to discontinue our monitoring effort. For multicast users interested in monitoring multicast connectivity in the Internet, we refer them to Multicast Beacon Project  which is a follow up project performing active measurements among a large number of multicast enabled user sites in the Internet.

During our monitoring effort, sdr-monitor had over 100 participants helping us to collect multicast reachability information by running a piece of script in their sites. We thank all of our participants for their help in realizing this project.


Sdr-monitor architecture and the results of our monitoring effort (analysis of long term multicast reachability monitoring data collected with sdr-monitor) has appeared in the following publications:

For more information, please contact Kamil Sarac.