If the sending machine sets DF in the IP header, then any interstitial machine that must fragment will drop the packet as well.
Best to stick to MTU-sized payloads with UDP, since IP fragmentation is handled poorly in many cases--either due to policy, or bad implementations. On 2015-09-25 15:17, Andy Walls wrote: >> From: David Halls Subject: [Discuss-gnuradio] UDP Sink Size Limit - ERROR: >> send > > error:send_to: Message too long > >> Date: Fri, 25 Sep 2015 09:05:56 +0000 > >> Dear All, When I increase my packet length in a transmission flow graph to >> over 16,000 bits, I get the following error "ERROR: send error:send_to: >> Message too long​" > > This looks like the underlying sendto() system call is returning > EMSGSIZE. From man sendto: > > EMSGSIZE > The socket type requires that message be sent atomically, and > the size of the message to be sent made this impossible. > >> this is from the UDP block which I am using in order to send the transmitted >> bits to the destination in order to perform BER. I am sending the packets in >> bursts, one packet every two seconds. > >> I currently have the Payload size set to 147.2k and Send Null Pkt as EOF set >> to true. > >> Is this some fundamental limit, or can I overcome the issue? > > 16,000 bits is 2000 bytes. The default MTU is usually 1500 bytes (for > IP header, UDP header, and payload together). Try modifying the MTU on > your machine's network interface to something larger, say 4000. > > The MTU of the receiving machine or other network hardware might still > be only 1500, so the the UDP packet could get IP fragmented. I'm not > sure how well UDP works when fragmented. > > -Andy > > _______________________________________________ > Discuss-gnuradio mailing list > Discuss-gnuradio@gnu.org > https://lists.gnu.org/mailman/listinfo/discuss-gnuradio [1] Links: ------ [1] https://lists.gnu.org/mailman/listinfo/discuss-gnuradio
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