Latency is a concern if your application is sending one packet at a time and waiting for a reply. If you are streaming large blocks of data, the first packet is delayed by the network latency but after that you will receive a 10Gbps stream continuously. The latency for jumbo frames vs 1500 byte frames depends upon the switch type. On a cut-through switch there is very little difference but on a store-and-forward switch it will be proportional to packet size. Most modern switching ASICs are capable of cut-through operation.
Subhachandra On Wed, Mar 21, 2018 at 7:15 AM, Willem Jan Withagen <w...@digiware.nl> wrote: > On 21-3-2018 13:47, Paul Emmerich wrote: > > Hi, > > > > 2.3µs is a typical delay for a 10GBASE-T connection. But fiber or SFP+ > > DAC connections should be faster: switches are typically in the range of > > ~500ns to 1µs. > > > > > > But you'll find that this small difference in latency induced by the > > switch will be quite irrelevant in the grand scheme of things when using > > the Linux network stack... > > But I think it does when people start to worry about selecting High > clock speed CPUS versus packages with more cores... > > 900ns is quite a lot if you have that mindset. > And probably 1800ns at that, because the delay will be a both ends. > Or perhaps even 3600ns because the delay is added at every ethernet > connector??? > > But I'm inclined to believe you that the network stack could take quite > some time... > > > --WjW > > > > Paul > > > > 2018-03-21 12:16 GMT+01:00 Willem Jan Withagen <w...@digiware.nl > > <mailto:w...@digiware.nl>>: > > > > Hi, > > > > I just ran into this table for a 10G Netgear switch we use: > > > > Fiberdelays: > > 10 Gbps vezelvertraging (64 bytepakketten): 1.827 µs > > 10 Gbps vezelvertraging (512 bytepakketten): 1.919 µs > > 10 Gbps vezelvertraging (1024 bytepakketten): 1.971 µs > > 10 Gbps vezelvertraging (1518 bytepakketten): 1.905 µs > > > > Copperdelays: > > 10 Gbps kopervertraging (64 bytepakketten): 2.728 µs > > 10 Gbps kopervertraging (512 bytepakketten): 2.85 µs > > 10 Gbps kopervertraging (1024 bytepakketten): 2.904 µs > > 10 Gbps kopervertraging (1518 bytepakketten): 2.841 µs > > > > Fiberdelays: > > 1 Gbps vezelvertraging (64 bytepakketten) 2.289 µs > > 1 Gbps vezelvertraging (512 bytepakketten) 2.393 µs > > 1 Gbps vezelvertraging (1024 bytepakketten) 2.423 µs > > 1 Gbps vezelvertraging (1518 bytepakketten) 2.379 µs > > > > Copperdelays: > > 1 Gbps kopervertraging (64 bytepakketten) 2.707 µs > > 1 Gbps kopervertraging (512 bytepakketten) 2.821 µs > > 1 Gbps kopervertraging (1024 bytepakketten) 2.866 µs > > 1 Gbps kopervertraging (1518 bytepakketten) 2.826 µs > > > > So the difference is serious: 900ns on a total of 1900ns for a 10G > > pakket. > > Other strange thing is that 1K packets are slower than 1518 bytes. > > > > So that might warrant connecting boxes preferably with optics > > instead of CAT cableing if you are trying to squeeze the max out of > > a setup. > > > > Sad thing is that they do not report for jumbo frames, and doing > these > > measurements your self is not easy... > > > > --WjW > > > > _______________________________________________ > > ceph-users mailing list > > ceph-users@lists.ceph.com <mailto:ceph-users@lists.ceph.com> > > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com > > <http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com> > > > > > > > > > > -- > > -- > > Paul Emmerich > > > > croit GmbH > > Freseniusstr. 31h > > 81247 München > > www.croit.io <http://www.croit.io> > > Tel: +49 89 1896585 90 > > _______________________________________________ > ceph-users mailing list > ceph-users@lists.ceph.com > http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com >
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