Date: Thu, 19 Sep 1996 11:56:43 -0400 From: dennis@etinc.com (Dennis) To: Joe Greco <jgreco@brasil.moneng.mei.com> Cc: hackers@freebsd.org Subject: Re: Routers - hardware received wisdom Message-ID: <199609191556.LAA12631@etinc.com>
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>> > I think that Dennis' comment & what Joe said in his note answered a question >> > that I've had lurking in the back of my mind, "Just what is sufficient to run >> > a FreeBSD T-1 capable router?" >> > >> > Granted that a no-name MB & 133Mhz 486 is running around $120, but I >> > "happen to have" a 386/33, 8mb, 300mb disk sitting in the corner, with >> > an ethernet card in it (isa only :^,). And I have a need for a T-1 capable >> > box soon. Since it would be a fairly un-saturated T-1, I suspect that >> > I will be able to get away with it for a while... Then the question becomes, >> > how many 56/64k/128/256k frame relay links could a "little" box like that >> > handle? (Must be the Scots in me, I hate to throw away anything!) >> >> Let's think about this logically people.. We're only talking about a MAX >> of 187 Kilo-Bytes per second for a single T1 line... I've got calculators >> that could max that out! Now.. When you start throwing multiple ethernet >> devices in there, and you want to provide wire-to-wire speed acrossed those, >> that is another story.. We're using a 486DX4-120Mhz w/32MB of RAM here, and >> it is running 3 100Mb Intel Etherexpress cards, and 2 10Mb SMC Elite Ultra >> cards.. It does a decent job, although I don't know that I would expect to >> be able to get full wire speeds on all ethernet cards simultaneously.. But >> luckily, we have enough segments and switches that we don't need to worry >> about that, yet. > >Rob, > >With all due respect it is not that simple. > >I suspect that with MTU-sized packets, I can easily go wire to wire >with 10baseT at peak speeds even on a 386DX/40 with SMC ISA cards. >Actually I was doing that at one point, IIRC, and it worked fine. > >I suspect that with very small packets, the same machine will have >abysmal performance. > >Dennis' T1 sync serial cards are most similar to an Ethernet card, and >I will flat out state that I can saturate your DX4/120 CPU before I hit >T1 saturation if I attempt to saturate that T1 link with miniature packets. >I have saturated a DX5/133 with this test and it is ugly. Joe, with all due respect.... It depends on "why" the packets were dropped. With our product, they can be dropped only if.... 1) The recieve process cannot get a buffer 2) The on-board buffers become overrun. Only 2 is a CPU issue, and there is virtually no way the you can get that situation on a single T1 unless your machine is off doing something else for long periods of time...like processing ethernet packets. With 2 byte packets, yes, but not with IP size packets (44 or more bytes). This is so highly unusual that it shouldnt be considered. Dennis Dennis
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