[nos-bbs] MAXFRAME

kd6oat kd6oat at gmail.com
Mon Jun 9 21:20:15 EDT 2014

According to my old PK-232 operating manual, "MAXFRAME limits the number of
unacknowledged packets the tnc permits on the radio link, and the number of
continguous packets your tnc will send in a single trnasmission. The "best"
value of MAXFRAME depends on your local channel conditions. In most cases
of local keyboard operation, the default value of MAXFRAME of 4 works well.
When the amount of traffic is heavy, the path in use is poor or you are
using many digipeaters, you can actually impove your throughput by reducing
MAXFRAME. Use MAXFRAME 1 for best results on HF packet."

I believe MAXFRAME works in concert with FRACK and RETRY commands. My other
old packet handbook explanes that when a MAXFRAME setting of 4 is exceeded,
"additional packets will not move into the TNC or controller until awaiting
messages area acknowledged or their path has been discontinued."

While the exact "why" remains somewhat elusive, I hope that is helpful.


On Mon, Jun 9, 2014 at 5:54 PM, Michael E Fox - N6MEF <n6mef at mefox.org>

> Charles,
> Yes, the manual states the optimal value is 1 but gives no reason or
> explanation of why.
> My email asked for the why.
> Michael
> -----Original Message-----
> From: nos-bbs-bounces at tapr.org [mailto:nos-bbs-bounces at tapr.org] On Behalf
> Of Charles Hargrove
> Sent: Monday, June 09, 2014 3:28 PM
> To: nos-bbs at tapr.org
> Subject: Re: [nos-bbs] nos-bbs Digest, Vol 118, Issue 1
> I have been using a value of 1 ever since I first set up my system back in
> the
> late 90's.  The JNOS manual was my guide and it makes sense.
> From the JNOS manual:
> ax25 maxframe [<count>]
> Establish the maximum number of frames that will be allowed to remain
> unacknowledged at one time on new AX.25 connections. This number cannot be
> greater than 7. Without <count> it will display the current setting. Note
> that
> the maximum outstanding frame count only works with virtual connections. UI
> frames are not affected. Also note that for optimal performance, a value of
> 1
> should be used.  Default is 1 frame.
> and
> 1.2. Maxframe
> This parameter controls the number of I-frames that may be send on an AX.25
> connection before it must stop and wait for an acknowledgement. Since the
> AX.25/LAPB sequence number field is 3 bits wide, this number cannot be
> larger
> than 7. It can be shown that the optimal value is 1.
> Since unconnected-mode (datagram) AX.25 uses UI frames that do not have
> sequence numbers, this parameter does not apply to unconnected mode.
> > I'm trying to optimize the value of MAXFRAME.
> >
> > I've seen statements on the web such as "for best efficiency, use
> =
> > 1", but no evidence or explanation is provided.  In fact, a window size
> of
> > just one is usually the LEAST efficient way to go.
> >
> > So, what are you guys using for MAXFRAME out there?
> >
> > Why?
> >
> > How did you decided on that value?
> >
> > Do you have any evidence (experimental, annectdotal, or otherwise) that
> led
> > you to use that value?
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