Date: Fri, 11 Jul 1997 11:10:28 -0400 From: dennis <dennis@etinc.com> To: Robert Shady <rls@mail.id.net> Cc: isp@freebsd.org Subject: Re: T1/T3 Upgrade Options? Message-ID: <3.0.32.19970711111025.00c96100@etinc.com>
next in thread | raw e-mail | index | archive | help
At 08:59 AM 7/11/97 -0400, you wrote: >>>> Well, I wasn't going to do this, and probably shouldn't have, but here's >>>> the situation. We all know that you can use the ET-Inc card or the >>>> SDL card for T1 routing... But does FreeBSD have ANYTHING available with >>>> a HSSI interface yet? We've already bought one Cisco 7010 and the $60,000+ >>> >>>Yes. Both SDL and DEC have cards available. If you need particulars, or >>>are not a system integrator, you may email for more particulars. > >Yes, I would like more information please... Does FreeBSD have drivers >available for these cards already? Or would we have to code one... > >> Just to know that we can do at least 10Mbs on a clocked down T3 via V.35 >> (Digital link make a CSU)...if you're metered and running full T3 we can't >> do it (yet). > >This completely contradicts what you say below... If a PCI bus can't do >T3, why would you make a card that could? 10Mb/s is a lot different than 43Mb/s.... I didnt say it can't be done, I said its difficult without special technology. Please read another message I send answering David for details.... Dennis > >> A major factor to consider is that its very difficult to do 86Mbs (T3 is >> full duplex) with an addon card on the PCI bus because the sustained >> throughput rate is often pretty low. Other bus masters (ethernets, for >> example) will futhur reduce the burst capability. While PCI bursts to >> 128MB/s, very few PC products have sustained throughput rates over 100Mb/s. >> If you have a 100Mbs ethernet card on the same bus (you'd have to) the >> number is cut in half. plus bus masters can't be controlled so you have >> contention issues. > >Contention issues I'll agree with for the most part, however.. My calculations >are (correct me if I'm wrong): > >T3 Card = ~12Mbytes/sec [ 45Mbits/sec (each direction), or 90Mbits/sec total] >Ether = ~25Mbytes/sec [100Mbits/sec (each direction), or 200Mbits/sec total] > ============= > ~37Mbytes/sec > > 132 Mbytes/sec - PCI bus >- 37 Mbytes/sec - Interfaces >================ > 95 Mbytes/sec - Left to play with. Because you have no clue how the PCI bus really works (and that burst rates are not sustainable), your Math is totally invalid. Remember that ISA is a 64Mb/s medium and if you get 30Mb/s you are lucky....the numbers are even more dramaticly worse when you add bursts to the formula as with PCI. Ah, if life was only as easy as your trivial account of the world! Dennis
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?3.0.32.19970711111025.00c96100>