On Thu, Nov 29, 2018 at 3:41 PM Christian Huitema <[email protected]> wrote: > > On 11/29/2018 1:05 PM, Templin (US), Fred L wrote: > > > iperf3 is a real Internet application in the same way that ping, traceroute, > > tcpdump, etc. are real applications. It is a well-known tool that network > > engineers use on a daily basis and demonstrates that UDP performance > > is highly correlated with UDP datagram size (i.e., even for sizes that > > exceed the PMTU). > > AFAIK the main difference between large and small UDP packets is doing > the fragmentation/reassembly in the application instead of in the > kernel's UDP stack. For an 8K packet, that means 6 socket calls in the > application case, versus 1 in the kernel case. That is indeed some > overhead. It is not a big deal for medium speed application like video, > but i can see how it will get in the way of running QUIC at several > Gbps, for instance. But then, the overhead could be trivially eliminated > with API improvements, such as passing several packets in a single call.
sendmmsg and recvmmsg do that. > We can ponder why we have not seen such improvements yet, the main > explanation being lack of demand. I fully expect that this will change > if QUIC gets widely used. In fact, it would be good if the fragmentation > draft discussed this API issue. > > -- Christian Huitema > > > > _______________________________________________ > Int-area mailing list > [email protected] > https://www.ietf.org/mailman/listinfo/int-area _______________________________________________ Int-area mailing list [email protected] https://www.ietf.org/mailman/listinfo/int-area
