I'm the network administrator at the Barcelona School of Informatics, in
We are testing a spanish deployment tool, Opengnsys, that uses udpcast
for massive file distribution, via multicast.
In our tests, we have found that udpcast floods our network with
multicast traffic, and this is a big problem for us.
We have other multicast products for many years, like Rembo, and there
is no problem about flooding.
We have been sniffing and analyzing udpcast protocols, and we think that
the problem is in the IGMP signaling. We haven't capture
any IGMP packet. We have analyzed the source code, and we haven't been
able to locate any reference to IGMP.
Usually, the standard solution is generating an IGMP-Group Specific
query, to subscribe the receiver to the group. With this step, you join
a multicast group. Then, when the sender broadcast the multicast
traffic, the network is capable to switch the packets only to the
We have found, that our switches, are not capable of locate multicast
receivers PCs, because they don't see the IGMP packet. IGMP snooping is
enabled, and it allows the switches identify multicast, but, it doesn't
These are our testing scripts:
./udp-receiver --file /tmp/dst.iso --interface eth0 --nokbd
./udp-sender --file /tmp/wi7_pr64_000.iso --full-duplex --interface
eth0 --autostart 30 --nokbd
Sender and receiver are Linux machines, in the same subnet, without any
kind of firewalls. The file arrives fine, but, the multicast traffic
floods other ports. The switch involved is a cisco C3560G-48PS, with
igmp snooping enabled, and there is multicast enabled router (Cisco
3750G-48TS) for querier in this VLAN. Our switches don't make any
Thanks in advance.