Hello, Thank's very much for your answer. I don't think the sender uses the whole bandwidth available. My 2 hosts are linked with a 100 Mbit link. On both publisher and subscribers, I have limited the rate (using the ZMQ_RATE socket option) to 20000. This is confirmed by the wireshark IO Graph
Best regards Emmanuel On 13/04/2010 14:04, Martin Sustrik wrote: > Emmanuel TAUREL wrote: > >> Hello all, >> >> I am using zmq 2.0.6 on Ubuntu 9.04 boxes. >> I am using PUB/SUB with the epgm protocol. I have one publisher on host >> A and 2 subscribers on host B. >> The ZMQ_RATE is set to 20000 on both publishers and subscribers. I do >> not filter anything on the subscribers side. On the publisher side, I have >> a ZMQ_HWM set to 100 and ZMQ_LWM set to 50. >> I am sending 4 kbytes messages. The first byte within each message is a >> counter which allows me to check that I haven't lost any message. >> My problem is that I am loosing messages! >> >> I have wireshark on both sides (Host A and Host B). I have studied a >> little bit what happened during my transmission. >> On Host B (the receiver), I notice a hole in the ODATA sequence number >> sent by Host A. Then, Host B send a NAK packet requesting the missing >> datagram. >> Host A reply to this NAK packet by a NCF packet which according to what >> I have read in RFC 3208 is correct. But I do not see any RDATA packet >> sent by the source (Host A) and therefore my subscribers loose the >> concerned messages!! >> >> I agree that the wireshark on host A (the sender) tells me that the >> datagram missing on Host B (the receiver) have been sent but I guess >> these packets have been lost by the >> switch between the 2 hosts. But as far as I have understood PGM, it is a >> reliable protocol and this case should be covered by some >> re-transmission which apparently in my case is only half-done. >> >> Are you aware of some similar cases? >> > One scenario I can think of is that the sender uses whole bandwidth > available (ZMQ_RATE socket option) for sending new data. Thus there's no > bandwidth available for retransmissions. > > If that's the case the behaviour is OK and everything works as expected. > > The rationale is that a single slow consumer should not slow down the > sender and thus all the well-behaved consumers that may be listening to > the same feed. > > Martin > _______________________________________________ > zeromq-dev mailing list > [email protected] > http://lists.zeromq.org/mailman/listinfo/zeromq-dev > _______________________________________________ zeromq-dev mailing list [email protected] http://lists.zeromq.org/mailman/listinfo/zeromq-dev
