[ClusterLabs] corosync in multicast mode produces lots of unicast traffic

Klaus Darilion klaus.mailinglists at pernau.at
Wed Oct 17 06:00:15 EDT 2018

Hi Jan!

Thanks for your answer.

>> I have a Proxmox cluster which uses Corosync as cluster engine.
>> Corosync uses the "default" multicast configuration. Nevertheless,
>> using tcpdump I see much more packets sent by corosync using unicast
>> between the node members than multicast packets.
>> Is this normal behavior? If yes, please point me to some documentation. 
> It really depends. If cluster is quiet (no configuration changes) so it
> basically only heartbeats then it's pretty normal that unicast trafic
> (used for heartbeats) is bigger than multicast one.

Now I am confused. I thought that corosync uses totem and the totem
protocol has implicit keep-alive by passing the token between the ring
members. So, even if there are no messages, the token is passed on in
the ring giving implicit keep-alive. And all this is done using multicast.

So, is my understanding wrong and corosync uses totem only for message
delivery and there is an additonal "heartbeat" feature which sends
unicast keep-alive to all the known members?


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