Date: Tue, 21 May 2013 16:36:07 +0200 From: Andre Oppermann <andre@freebsd.org> To: Hooman Fazaeli <hoomanfazaeli@gmail.com> Cc: liujie@263.net, freebsd-net@freebsd.org Subject: Re: netmap bridge can tranmit big packet in line rate ? Message-ID: <519B8657.6070201@freebsd.org> In-Reply-To: <519B82D8.9010508@gmail.com> References: <1369140007.80942.YahooMailClassic@web121602.mail.ne1.yahoo.com> <519B82D8.9010508@gmail.com>
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On 21.05.2013 16:21, Hooman Fazaeli wrote: > AsBarney pointed outalready, your numbers are reasonable. You have almost saturated > the link with 1514 byte packets.In the case of 64 byte packets, you do not achieve line > rate probably because of the congestion on the bus.Can you show us "top -SI" output on the > sender machine? Be aware that "line rate" for small packets is NOT raw link speed divided by packet size. There's also pre- and post-amble bits and inter-frame gap to be considered. Those bits are on the wire too but invisible as they are handled entirely by the ethernet NIC. The minimum size of an ethernet frame is 64 bytes (excluding the additional bits, 84 bytes including them) even though IP packets can be smaller. The difference is padded by the NIC. So the maximum is 14,880,960 pps at 64 bytes and 812,740 at 1500 bytes. There's a number of resources explaining this issue in more detail: http://www.cisco.com/web/about/security/intelligence/network_performance_metrics.html http://ekb.spirent.com/resources/sites/SPIRENT/content/live/FAQS/10000/FAQ10597/en_US/How_to_Test_10G_Ethernet_WhitePaper_RevB.PDF -- Andre
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