On 10/25/2016 11:26 AM, Przemek Klosowski wrote: > On Mon, Oct 24, 2016 at 10:42 PM, Stephen Dubovsky <smdubov...@gmail.com> > wrote: >> Why would UDP need resends on a shared ethernet port? There are no >> collisions on a full-duplex port & switch (which is pretty much ALL of them >> now-a-days.) Passive hubs went the way of the dodo. > Of course, but you are assuming an ideal active switch, and that may > or may not be the case. All the switched ports are sitting on an > internal bus, whose bandwidth has to be better than N/2*individual > port bandwidth, because in principle, all port pairs could be active > at the same time; on a cheap switch that 'bisection' bandwidth may not > quite be there. Also, in general, two originators could be trying to > talk to the same receiving port and collide on it---switches of course > must implement some form of 'store and forward' to be able to decide > where to switch the packet to, but cheap switches do not have a deep > store queue---maybe they can handle one or two packets but not more > than that. So, in practice, the collisions and dropped packets are > possible.
Yup. Exactly. Happens even on expensive Big Iron Cisco switches as well, though not as prevalent as on the cheaper switches. Though even the cheap switches are much better than the old fashioned hubs. Mark ------------------------------------------------------------------------------ The Command Line: Reinvented for Modern Developers Did the resurgence of CLI tooling catch you by surprise? Reconnect with the command line and become more productive. Learn the new .NET and ASP.NET CLI. Get your free copy! http://sdm.link/telerik _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
