Date: Mon, 11 Jan 1999 08:25:47 -0500 (EST) From: Bill Vermillion <bill@bilver.magicnet.net> To: freebsd-isp@FreeBSD.ORG Subject: Re: Connect speed on FreeBSD. Message-ID: <199901111325.IAA23372@bilver.magicnet.net> In-Reply-To: <Pine.LNX.3.96.990111131058.4256A-100000@orion.smlt.com> from Quintin Oliver at "Jan 11, 99 01:16:41 pm"
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Quintin Oliver recently said: > Greetings! > > We run a local ISP powered by FreeBSD 2.2.8 and 3.0, our users > connect to FreeBSD on 2.2.8 on modem dial. The modems are Modular > Technologies V.90 compliant, however, many of our users have > reported that they can only connect at about 31k to 35k a second, > that is there actuall connect speed NOT BANDWIDTH from the net. > I've checked our configuation over and over again, we are using > Mgetty and we are asking it to connect the users at 57600?? > Does anyone have any ideas on fixing this and/or running > diagnostics on the modems and hardware themselfs? You don't understand how 56K connections work. Two 56K modems talking to one another, will only conncect at the 33.3K rate. That is because of the line encoding. Going back to "Shannon's Law" a classic on information transmission, the theoretical limit on analog lines is only about 35-36K. 56K is possible to RECEIVE with an add-on modem >>IF<< the transmitting side has a device that is connected digitally to the phone company, and that will mean a PRI connection to your device. On the ISP's side, the signal will leave the device that is attached to the PRI (something along the lines of a Max Ascend or similar) and will remain in a digital format until it reaches the customer modem. This is also the reason you can't uplink to a 56K compliant site. The process of convernting the computers digital signal to an analog signal by the modem (mod stands for modulate where the digital signal is converted to analog form), and the has to be reconverted at the target. You'll really need a device that connects with a PRI, and install a PRI. Locally PRIs are in the high hundreds $800+ month. One line will get you 23 modems and a control channel, or 11 128k ISDN lines, or any combination. I'm not familiar with the Modular Technologies devices - but you did say "modem". If, OTOH, you do have a digital connection and you are not seeing anything fast, there are certain places where telcos cluster phones, and then connect these mini-clusers back to the main CO. In those instances the maximum you can ever expect is 33K as there are addtioinal DA and AD conversions in the line. 56K can only have ONE DA in the line. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-isp" in the body of the message
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