Date: Wed, 16 Oct 1996 15:35:23 -0700 From: Jim Shankland <jas@flyingfox.COM> To: CPELTIER@iectech.com, jgreco@brasil.moneng.mei.com Cc: freebsd-isp@freebsd.org Subject: Re: pppd reliability Message-ID: <199610162235.PAA02673@saguaro.flyingfox.com>
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> Does anybody have any experience using pppd to run > dedicated 115K ppp links (ISDN application) on > 2.1.0 release. My main concern is reliability and > CPU loading experiences. I am considering 16550 > UART based boards and the Cyclades products. > The router platform is Pentium 100-133Mhz. It may > coexist with T1 frame links. I have solid T1 frame reliability > without system crashes. Would I jepordize this situation > by adding serial based ppp links? I am thinking about > using the Motorola Bitsurfer Pro with multilink PPP in > a host mode (if possible) to combine the two B channels > into a 115Kbit single, spoofed ppp stream. Anybody else > trying this? I know that the USR I modems don't support > Multilink PPP in host mode (at least not yet). Any other > good ISDN adapters with Multilink PPP spoofing and host > mode support? I'd think twice about this, personally, and look hard at using Ascend routers (or something similar) for ISDN. I'm not convinced the BitSurfr Pro, for one, is up to snuff for server-side use. Ours periodically took itself out of service, and had to be power-cycled. Also consider that at 115.2 Kbps async, you're doing 11520 BYTES/second, since an async byte is 10 bits, counting the start and stop bits. That means you're doing 92080 bps synchronous, so when you're multilinking, you're really getting only about 1.5 B-channels. And serial ports just tend to be higher maintenance than a router on your Ethernet, in lots of little ways (I've had several just "lose" the carrier-state-change interrupt, for example.) Granted, hanging 4 BSPros off a multiport card in a box running FreeBSD is cheaper than buying a 4-BRI router. Based on my experience, I predict you'll quickly recoup that cost in time saved tinkering with the setup, and dealing with a steady trickle of annoying little failures. Jim Shankland Flying Fox Computer Systems, Inc. (P.S.: What the world really needs is a cheap, ISA-bus BRI card with well-documented programming information, and an interface more like an Ethernet card than a serial card. A PCI-based 4-BRI card would be nice, too :-).)
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