[zeromq-dev] Fwd: 0MQ fails when it goes through a switch

[Stephen Hemminger]

On Thu, 09 Apr 2015 13:26:19 +0200
Dorvin <dorvin at tlen.pl> wrote:

> Switch receives frame and tries to forward it. But switch has some 
> queues on each port. These queues are of finite size and if you try to 
> send to much information in one frame then it might be dropped. Second 
> thing is Ethernet standard defines max ethernet payload size to be 1500 
> bytes. If you try to send more then it might not work. There are 
> extensions to this standard which allow for bigger payloads (it's called 
> jumbo frame) but you would have to check with switch documentation if 
> your device supports that and how to enable it. There are also other 
> options that might influence your traffic but embedded switches are 
> usually dumb machines with little capabilities.
> 
> 0MQ is supposed to handle large messages but I don't know why your 
> switches complain. If you have this possibility try to check your code 
> with enterprise-class switches and troubleshoot there. These switches 
> will tell you far more about what's wrong with your code

If it truly is a layer 2 switch.
Make sure the MTU setting is same on all systems connected to the switch.

Also, make sure that that switch is compatible with the frame size you choose.
Some older consumer grade switches only support 1500 byte MTU.  If you set MTU
to correct value (even 1500) then TCP will do the necessary logic to break up
the request into smaller packets and reassemble.