On 09/28/2015 05:14 AM, David Halls
wrote:
Thanks for your reply Marcus, but does that mean there is no
way around the problem?
Regards,
David
Naked UDP provides no framing overlay, which means you are limited
to MTU-sized packets.
You should perhaps look into either using TCP, and/or ZMQ.
Others can provide guidance on ZMQ usage.
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
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