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RNP used multicast to transmit courses from Impa

From January 28th to February 1st, the Institute of Pure and Applied Math (Impa) offered the course " Professional Development to Middle School Math Teachers. " The classes, which took place in Impa's building, in Rio de Janeiro, were transmitted to several Brazilian states via RNP's network. The students from other regions could attend the course live and participate in it sending questions by means of a chat tool.

In order to transmit the event, multicast technology was used directly on RNP2 backbone, without the need to implant new links. No band reserve was made either due to a technical limitation of the router that transmitted Impa's data to RNP's Point of Presence in Rio de Janeiro (PoP-RJ). Nevertheless, according to Sidney de Lucena, RNP's technician who participated in the experiment, it also should not be necessary since multicast technology is a great "band saver." He explains that "in multicast, only one flow of information is sent whenever there is a coincidence of routes among the receivers. Only when there are bifurcations in these routes does the replication of the traffic to these different routes take place."

Lucena claims that "RNP took care of the multicast infrastructure as far as the PoPs, which collaborated extending this infrastructure to the classrooms or auditoriums where the lectures delivered at Impa could be watched on a wide screen and with the sound of the auditorium, for instance, or on single machines." The math institutes of the University of Campinas (Unicamp) and of the federal universities of Ceará (UFC), Pernambuco (UFPE), Minas Gerais (UFMG) and Rio Grande do Sul (UFRGS) participated in this experiment. The dedication of the technicians in the PoPs was vital to the success of the transmission.

Problems and virtual applauses

In spite of the tests carried out the week before the event, there were problems during the transmission. In some peak moments of use of Impa's network, the sound and the image failed, causing a few complaints. The transmission rate ended up being reduced from 250 Kbps to 150 Kbps, which did not significantly affect the audio and video quality but greatly minimized the flaws. According to Roberto de Beauclair Seixas, Impa's researcher and one of the organizers of the experiment, even with the problems, "intrinsic to the transmission via Internet," " there was complete success and acceptance on the part of the universities: " the professors loved participating in the experiment and sent their virtual applauses to the technical staff and to the organizers of the course. The classes were recorded and made available for download in Impa's FTP server: ftp://200.17.63.184:5001/.

The evaluation of the technicians involved in the transmission was also positive, and they are eager to repeat the experiment. That was what could be realized in the debates that happened, via network, during the event. Through the same chat tool used by the professors, the technicians informed how the reception was and looked for the solution to any problem that might occur.

[RNP, 02.04.2002]