Date: Tue, 23 May 2006 20:31:53 +0100 From: Brian Candler <B.Candler@pobox.com> To: Mike Tancsa <mike@sentex.net> Cc: freebsd-net@freebsd.org, Ian Smith <smithi@nimnet.asn.au> Subject: Re: improving transport over lossy links ? Message-ID: <20060523193153.GA38312@uk.tiscali.com> In-Reply-To: <6.2.3.4.0.20060523140627.10b27dd8@64.7.153.2> References: <6.2.3.4.0.20060521154616.11bd1d60@64.7.153.2> <Pine.BSF.3.96.1060523200509.6317C-100000@gaia.nimnet.asn.au> <6.2.3.4.0.20060523140627.10b27dd8@64.7.153.2>
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On Tue, May 23, 2006 at 02:10:39PM -0400, Mike Tancsa wrote: > It looks like its an issue with the USB serial device and or driver. > Whether the driver or the actual device (or both) not sure. If I put > the same 2 modems put on 2 regular serial ports, ppp is able to see > the carrier is down and drop the connection from the bundle. Same > init strings, only difference is the ports they were on. That matches my experience with USB dongles. The basic functionality of sending and receiving characters is there, but flow control and call handshaking tends to be either non-existent or flaky. I expect this is either because the drivers are reverse-engineered, but the person doing the reverse-engineering wasn't thorough enough to toggle all the control lines, in and out; or because these chipsets are actually not full RS232 implementations. Either way it makes them pretty useless for anything more than a 9600bps console (and even then, they're risky if you want to squirt a string of bytes at the target device) It's a real shame, because most laptops don't have COM ports these days. If someone knows of a USB serial dongle which is widely available, documented by the manufacturer, and has a full robust implementation of all the RS232 control lines in an open-source driver, I'd like to buy one. For some laptops a PCMCIA COM port is an option, but many modern laptops don't have that slot either these days. Regards, Brian.
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