Date: Sat, 22 Aug 1998 21:39:26 -0700 (PDT) From: Doug White <dwhite@resnet.uoregon.edu> To: Lee.David@oscsystems.com Cc: Freebsd-questions@FreeBSD.ORG Subject: Re: Multicast Packet size problem Message-ID: <Pine.BSF.4.00.9808222137320.20446-100000@resnet.uoregon.edu> In-Reply-To: <85256666.0066A145.00@smtpgt2.oscsystems.com>
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On Thu, 20 Aug 1998 Lee.David@oscsystems.com wrote: > I developed an application that does multicasting.....I am trying to send > packet sizes ranging from 1000 bytes to 12,500 bytes. My test > configuration consist of a receiver on one and a sender both FREE BSD ver > 2.2.6. I can successfully send and receive a packet size of 1400 bytes or > less, using the system calls sendto and recvfrom. However, I cannot seem > to get it to work for packets larger than 1400 bytes. The symptoms of the > sender are as follow - after a hundred or more packets the sendto system > call returns an error code via the perror call of such "sendto: can not > route to host". In addition the receiver never receives any packets at > all!! Are the sender and receiver on the same network? What happens if you immediately restart the program? Run a traceroute to the other host? > FYI, I also found that if run the test with packet size greater than 1400 > bytes, starting the same sender and receiver mention above in different > process windows on the same machine, the sender behaves the same. However > the receiver does indeed receive all packets generated by the sender!!! > > I have set up an SGI IRIX UNIX machine as the sender and the receiver a > FREEBSD and am able to run both of the above test successfully. > > Your help would be greatly appreciated, I have spent a few days looking > into this problem and am stumped. I'd also set up tcpdump and see where the ICMP No Route To Host message is coming from. Your router may be dropping such a message to shut up the sender. I'm not sure 12k packets are kosher -- they're going to fragment _badly_ since Ethernet can only send 1500 bytes at once. Doug White | University of Oregon Internet: dwhite@resnet.uoregon.edu | Residence Networking Assistant http://gladstone.uoregon.edu/~dwhite | Computer Science Major To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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