> -----Original Message----- > From: Christian Riesch [mailto:[email protected]] > Sent: Tuesday, December 09, 2014 11:37 PM > To: Keller, Jacob E; Richard Cochran; linuxptp- > [email protected] > Subject: RE: [Linuxptp-devel] [PATCH RFC V2 0/4] Time stamp asymmetry > correction > > Jake, > > >-----Original Message----- > >From: Keller, Jacob E [mailto:[email protected]] > >Sent: Wednesday, December 10, 2014 1:00 AM > >To: Richard Cochran; [email protected] > >Subject: Re: [Linuxptp-devel] [PATCH RFC V2 0/4] Time stamp > asymmetry > >correction > > > >In regards to the comment about whether a negative value should be > >acceptable, I think it should not. The reason is because I can't think of > any > >scenario in which hardware timestamps the packet *before* it arrives... > That > >is, there should never be a hardware which negative latency as that is > >physically not possible. > > We did a few measurements of egress and ingress timestamping delays > (see [1]). We actually measured negative delays for some hardware (see > Table III in [1]). Our conclusion was that this hardware must already be > (over)compensating PHY delays, however I did not yet manage to ask > this question to the manufacturer. But it shows that there are cases > where one wants to compensate a negative egress or ingress latency. > > Regards, > Christian >
Fair enough. I had not thought of over-compensated delays. I think we can just modify the configs code to allow negative numbers, as the scanf function should already do it. Just treat numbers which have no sign indicator as positive. Regards, Jake ------------------------------------------------------------------------------ Download BIRT iHub F-Type - The Free Enterprise-Grade BIRT Server from Actuate! Instantly Supercharge Your Business Reports and Dashboards with Interactivity, Sharing, Native Excel Exports, App Integration & more Get technology previously reserved for billion-dollar corporations, FREE http://pubads.g.doubleclick.net/gampad/clk?id=164703151&iu=/4140/ostg.clktrk _______________________________________________ Linuxptp-devel mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/linuxptp-devel
