Date: Fri, 11 Jul 1997 08:59:03 -0400 (EDT) From: Robert Shady <rls@mail.id.net> To: dennis@etinc.com (dennis) Cc: rcramer@sytex.net, isp@FreeBSD.ORG Subject: Re: T1/T3 Upgrade Options? Message-ID: <199707111259.IAA19275@server.id.net> In-Reply-To: <3.0.32.19970710175730.00b07380@etinc.com> from dennis at "Jul 10, 97 05:57:33 pm"
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>>> 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?
> 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.
The way I see it, you theoretically could have 3 100 Mbit interfaces AND a
T3 card running simultaneously (specially since it's not likely you'll ever
push a true 45Mbits/sec each direction on a T3). However, the real problem
comes into play trying to find a CPU that can handle that many interrupts
per second effeciently.
-- Rob
===
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