Date: Sat, 22 Jan 2000 22:03:41 -0500 From: "Crist J. Clark" <cjc@cc942873-a.ewndsr1.nj.home.com> To: Soren Dayton <dayton@overx.com> Cc: Majid Almassari <majid@ibroadcast.net>, "freebsd-questions@FreeBSD.ORG" <freebsd-questions@FreeBSD.ORG> Subject: Re: Making a 56K Modem Pool Message-ID: <20000122220341.A5211@cc942873-a.ewndsr1.nj.home.com> In-Reply-To: <86d7qtiknk.fsf@polo.overx.com>; from dayton@overx.com on Sat, Jan 22, 2000 at 08:31:11PM -0600 References: <015d01bf6544$086547e0$1791ddd1@balfourplace.com> <86d7qtiknk.fsf@polo.overx.com>
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On Sat, Jan 22, 2000 at 08:31:11PM -0600, Soren Dayton wrote: > "Majid Almassari" <majid@ibroadcast.net> writes: > > > Soren Dayton <dayton@overx.com> wrote in message > > news:86u2k5io06.fsf@polo.overx.com... > > > > > Does someone know what's going on here (or know of a pointer to that > > > kind of information)? I just don't understand what the issues are, > > > and I'm going to need to understand these to buy new modems, phone > > > lines, etc. > > > > Unfortunately there is nothing that you can do about it except calling the > > phone company and complain about noise so they can dispatch a technician to > > check the wiring in your location at least. Remote testing based on Signal > > to Noise ratios are not that accurate anyway. There might be wiring problems > > in your location that a phone tech can determine (like a cross-over > > wiring-Phone guys know this better that I do?). If everything is OK then you > > are basically limited and need to switch to a different Technology such as > > ISDN, XDSL, Cable,...etc. > > Hmm. Either I don't understand your answer, or I asked the question > badly. The setup is two analog modems talking to each other. Both > can separately achieve ~51k connections on their respective phone > lines to various 56k services (such as USR's 56k test line and various > Chicago ISPs). However when connecting to each other, they always get > 33k. One explanation is that one is configured to max out at 33k in > one direction. > > The USR/3com guy said, basically, that this is true. BUT also that > there are funny protocol issues that require that one of the modems be > in a "server mode" and speak a "server protocol". And that these > kinds of devices only come in ISDN flavors (thus requiring digital > lines, etc) > > So my question: is this true? What's the story? What are references > that I can look at? > > Does this disagree with what you are saying? Does it agree? Did I > state the question clearly enough? I am not a modem expert. However, I became aquainted with this issue when people (including the company GM) whined about how they could never do better than 33 Kb/s when they dialed into our network. The 56 Kb/s download and 33.6 Kb/s is an inherent limitation to an analog connection. There is no way around it. The real reasons the limit exists are complicated, and I have not sought to fully understand them. It basically comes down to the fact that a digital line can talk to an analog line at 56 Kb/s (using the V.90 standard), but analog can only talk to digial (or another analog) at 33.6 Kb/s (V.34 I think). It's not intuitively obvious, but it's been a while since I did any RF signal work. This URL is a _really_ non-technical overview, but its the best I could do really quickly. All of the references I previously dug up are written on paper at the office (that's not very like me...). -- Crist J. Clark cjclark@home.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-questions" in the body of the message
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