Date: Thu, 22 Jun 1995 18:58:26 -0700 (PDT) From: "Rodney W. Grimes" <rgrimes@gndrsh.aac.dev.com> To: tom@uniserve.com (Tom Samplonius) Cc: jkh@freebsd.org, evanc@synapse.net, hackers@freefall.cdrom.com Subject: Re: FreeBSD as a router Message-ID: <199506230158.SAA09235@gndrsh.aac.dev.com> In-Reply-To: <Pine.BSF.3.91.950622182452.5835B-100000@haven.uniserve.com> from "Tom Samplonius" at Jun 22, 95 06:29:36 pm
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> > > On Thu, 22 Jun 1995, Rodney W. Grimes wrote: > > > The bottleneck is that you have to wait for full frame reception > > before you get an interrupt to tell you to go look at the header > > to decide what to do with the packet. > > > > In dedicated router hardware they use the trick of interrupting > > the CPU after N bytes have been recieved (N is programmable) so > > they can actually decide what to do with the packet before it is > > even completly received. > > A bit of extra delay shouldn't affect throughput, especially with TCP large > window support, or does it? It won't effect long TCP streams, but it sure as heck raises cane with UDP traffic (NFS for example) which has no window and must wait for round trip times for packet acks. > > Can't PC ethernet cards also be handled in the same matter? Or are > there none available with that feature? I have never seen a PC ethernet card with that feature, and the only NIC chip I have seen with it was a custom one done specifically for this purpose (also used in Ethernet Switches). > From looking in Netblazer ST around here, it appears to have a SMC > ethernet card in it..... A Netblazer ST is a far cry from a real router!!! We are talking about ethernet to ethernet routers, not modem pool to ethernet routers. FreeBSD does a fine job as a slip/ppp modem pool to ethernet router, just ask the 100 or so people doing just that with it all over the place (or is that now 1000's doing that :-)). -- Rod Grimes rgrimes@gndrsh.aac.dev.com Accurate Automation Company Reliable computers for FreeBSD
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