Date: Fri, 3 Oct 1997 21:16:22 -0400 (EDT) From: "John T. Farmer" <jfarmer@sabre.goldsword.com> To: gurney_j@resnet.uoregon.edu Cc: freebsd-hardware@freebsd.org, jfarmer@goldsword.com Subject: Re: Multiple serial ports Message-ID: <199710040116.VAA07559@sabre.goldsword.com>
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On Thu, 2 Oct 1997 18:54:13 -0700 John-Mark Gurney said: >John T. Farmer scribbled this message on Oct 2: >> Uh, actually, I've had good success with with several different brands >> for multiple terminals/printers/front-end system consoles all active at >> the same time. Granted, I don't try to run the ports at greater than >> 56kbps. Frankly, you don't need to. > >why exactly?? a friend was dialed into my machine (using a 14.4k >internal!!) and we were sending some text down the line.. and he was >able to get 8kbytes/sec+ over the link.. and this is with a zoom 14.4k, >and a zoom 28.8k modem... if I wasn't running the zoom at 115.2kbps, we >wouldn't of been able to do that... and instead would of slowed a >14.4kbps call... (think if it was a 28.8k??) > >plus also, there is a MAJOR reduction in the latency of a connection >when you run the speed faster.. for example, when another friend >upgraded to a Supra 288kbps modem, and I was still on my Supra 14.4k >modem.. the latency dropped 50ms JUST because his modem->computer rate >increased... and then when I went to 28.8k also (both of these are >external), we dropped another 70-100ms in latency... Ah, increasing the line speed does not necessarily mean that latency will go down. The latency of a 32k synchronous digital link (FR connection, for example) is usually less than the latency of a 33.6k analog modem connection. A lot of the latency reduction in your example is due to difference between 14.4 & 28.8 modems. Modem brnad will also play a factor, not to mention the effect of flow control on each leg... >this also brings up that kernel ppp (pppd) is usually much lower latency >than iij-ppp... the friend with his internal 14.4k (first example) and >my extern zoom 28.8k, we were able to knock off at least 20ms off ping >times because he went from iij-ppp over to ppp... the last time we had >the connection up (he's moved, and much better connected) we were able >to do 140ms ping times over the 14.4k connection... Yes, this is a known factor that can be accounted for & tuned for. >these may not seem much, but when your used to do typing of a wireless >ricochet modem, when at BEST will give you 350ms, mostly 400-450ms, you >REALLY becom aware of the problems with latency... > >of course, then you just need to go FR or ISDN, and it'll be much >better.. > Which brings me to this question: To whit, What the devil does any of this have to do with the issue/problem that was being discussed? The issue was dealng with multiple consoles on servers, routers, etc. located locally and/or remotely. The basic "plug a terminal into the console serial port" of your cisco(s), but for multiple devices. Anyway, this discussion has wandered far, far afield of freebsd-related hardware issues. I propose to declare it buried... John ------------------------------------------------------------------------- John T. Farmer Proprietor, GoldSword Systems jfarmer@goldsword.com Public Internet Access in East Tennessee dial-in (423)470-9953 for info, e-mail to info@goldsword.com Network Design, Internet Services & Servers, Consulting
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