[zeromq-dev] ZMQ_MCAST_LOOP: Control multicast loopback

Steven McCoy steven.mccoy at miru.hk
Thu Jun 24 12:52:39 CEST 2010

I'd like to update this entry in the zmq_setsockopt(3) manpage,

"The *ZMQ_MCAST_LOOP* option shall control whether data sent via multicast
transports using the specified *socket* can also be received by the sending
host via loopback. A value of zero disables the loopback functionality,
while the default value of 1 enables the loopback functionality. Leaving
multicast loopback enabled when it is not required can have a negative
impact on performance. Where possible, disable *ZMQ_MCAST_LOOP* in
production environments."

When enabled multicast loop can completely disable reliable delivery.
 Negative acknowledgements, NAKs, are sent from receiver to sender as
unicast messages; unicast packets are not broadcast to all listening sockets
hence back channel communication is only functional to the first opened

A side note, the more advanced functionality being developed in OpenPGM 5
such as congestion control completely fails on multicast loop.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.zeromq.org/pipermail/zeromq-dev/attachments/20100624/886950e4/attachment.htm>

More information about the zeromq-dev mailing list