> From: Henning Schild [mailto:henning.sch...@siemens.com] > Sent: Wednesday, 21 September 2022 14.59 > > Am Wed, 21 Sep 2022 14:22:07 +0200 > schrieb Morten Brørup <m...@smartsharesystems.com>: > > > > From: Henning Schild [mailto:henning.sch...@siemens.com] > > > Sent: Wednesday, 21 September 2022 13.27 > > > > > > Am Wed, 21 Sep 2022 11:43:13 +0200 > > > schrieb Morten Brørup <m...@smartsharesystems.com>: > > > > > > > > From: Felix Moessbauer [mailto:felix.moessba...@siemens.com] > > > > > Sent: Friday, 2 September 2022 10.46 > > > > > > > > > > Dear DPDK community, > > > > > > > > > > this patch provides the l2reflect measurement tool > > > > > which will be discussed in our 2022 DPDK Userspace Summit talk: > > > > > "Using DPDK OVS for deterministic low latency communication" > > > > > > > > > > While the code still might need some polish, we believe it is > > > > > a good starting point for discussions about low latency > > > > > networking in DPDK. > > > > > > > > > > The tool can also be used in a CI environment to contineously > > > > > measure latencies across the evolution of DPDK and Linux. > > > > > > > > > > Best regards, > > > > > Felix Moessbauer > > > > > Siemens AG > > > > > > > > Dear Felix and Henning, > > > > > > > > Great to meet you at the 2022 DPDK Userspace conference. > > > > > > > > Have you considered using the Configuration Testing Protocol > > > > (CTP), described in chapter 8 of the Ethernet specification from > > > > 1984 [1], instead of your own packet format and the Local > > > > Experimental Ethertype? > > > > > > No we have not, first time i hear about that. First type we used > > > must have been 0xaffe or 0xdead, would have to dig through version > > > control. > > > > You seem to be using the correct EtherType for an experimental > > protocol like this. I was not opposing to that. > > > > > > > > > [1]: http://decnet.ipv7.net/docs/dundas/aa-k759b-tk.pdf > > > > > > > > The CTP an obsolete protocol, and not part of the IEEE standards > > > > for Ethernet, but I think Wireshark is able to parse such > > > > packets. > > > > > > Yes ... does not seem to be a train one wants to hop on. > > > > > > Maybe you can explain how one would use CTP to measure roundtrip > > > times, and go into detail on how that would add value. > > > > I would only change the packet format, not the way of measuring. > > > > > > > > I had a quick look at the spec and did not clearly see whether the > > > protocol could be used at all ... maybe "abused". And being a CTP > > > server one would need to implement more than just "reply". And i do > > > not see any value, except maybe "wireshark support" ... but i am > > > not sure how that would add value. The packets we send are trivial, > > > headers are ethernet and the content does not matter ... so > > > wireshark support is there for all relevant fields. > > > > The primary - and probably only - advantage would be that the > > EtherType 0x9000 is officially allocated for CTP, so you don't need > > to use one of the EtherTypes allocated for experimental purposes, > > which might also be used for other purposes. > > Yes that is something i thought about as well. In case there would be > some sort of conflict with 88B5 i would rather include some sort of > "magic start" or sub-protocol id if you want. > But until we see such a conflict i would simply stick with 88B5 which > seems to be a good fit, but not "clearly standardized". I would not > envision people running l2reflect on a very busy/big network, as the > results would become increasingly fuzzy and meaningless and other > latency benchmarks would probably be a better fit. > > Any confusion with another 88B5 application is "highly unlikely". And > when jumping on 9000 we switch from one "unlikely number" to another > one ... or in fact we are now on one that is "more likely"? From what i > read cisco equipment might start acting on those 9000 packets.
Yes, 9000 are "more likely". Also good point about the Cisco risk. > > I think a "highly unlikely" conflict does not justify a rewrite. For a > not well defined protocol it would not be a "conflict" really. While > 9000 would be "more likely" and dictate a corset to try and fit in. > Even if we can make it fit today, future extensions might not work out. > > So i think i would stay away from CTP. > > Henning Thanks for sharing your thoughts and analysis. I agree, then. Series-Acked-by: Morten Brørup <m...@smartsharesystems.com>
