Re: What minimum rates should I use?

Bill Woodland (wcw@bga.com)
Sat, 19 Jul 1997 11:41:11 -0500


At 08:39 PM 7/17/97 +0200, Rolf Hemmerling wrote:
>Bill Williams wrote:

um...that's WOODLAND, Rolf :)

>> >I usually use 10/20 and 10/24 for my min/max transmit and receive rates,
>Bill, why do high rates cause timeouts ? Does the CPU speed has
>any influence on that (P200 =3D fast, 486DX133 =3D slow)
>I can=B4t figure out !

I don't dare try to explain this with what little I know about the
protocols. I CAN tell you that it's not JUST a high rate that causes this,
but a rate that doesn't MATCH your modem's capabilities. I've used 100k
transmit and 300k receive on my LAN connection, and it works just fine.
I'm sure it has something to do with the open-continue packets. Here's
some info I got from Cornell on this:

"The OpenContinue packet is used for connecting, disconnecting, keeping a
connection alive, and tracking information about participants. [Windows:
Connections are kept alive by sending an OpenContinue packet every 2
seconds. If you don't receive an OpenContinue packet for 60 seconds, the
connection has timed out. Mac: An OpenContinue packet is sent every 3
seconds if nothing else has been sent during the last 3 seconds; and
OpenContinue packet is sent every 5 seconds if no OpenContinue packet was
sent in the last 5 seconds. If no packets have been received for 60
seconds, the connection has timed out.]"

My guess is that if the ref is tries to send you 60k for up to 60 seconds
before it sends you another OC packet, but since you can only actually
RECEIVE 28k, it takes twice as long for this data to actually come in.
Naturally this means that the OC packet looks to be a minute late, which
makes it look like the connection timed out.

Bill Woodland (Squeek =A9) PC questions only, please.
URL: http://cu-seeme.cornell.edu/~WCW
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