Edward Russell wrote:
> I was seeing this with the default -t u1 flag so doesn't that mean
> everything is UDP?  Therefore no TCP keep-alive, probes, etc.? With UDP,
> the sender has no way of knowing if the receiver is full (and doesn't
> care), it just keeps sending.  That mean the only way you could get
> EAGAIN is if the send buffer was full of its own accord.  That is the
> application is stuffing packets in faster than the OS can send them.
> Absolutely nothing to do with the reciever.  
> 
> True?

Seems to be - although I'd make that "faster than the OS/NIC can send 
them."

Depending on the networking stack, you may never see an error (at least 
one due to overflow) on a send() against a UDP socket.  Even when/if the 
send() call resulted in the UDP datagram being dropped somewhere down 
the stack.

Linux does have _intra-stack_ flow control for UDP, but I've only 
experienced it with netperf UDP_STREAM, which uses a blocking socket.

rick

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