Linux-Hams archive - September 1997: Re: SCC: TXerrors...

Re: SCC: TXerrors...

Richard Adams (zcwufr.tcumelgd@gchs.com)
Wed, 3 Sep 1997 00:18:13 +0000 (GMT)


According to Luca Palazzo, While burning my cpu.:
>
> Hallo Everyone,
> I finally solved the problems with my S5PCC...
> Everything works near right nw... (note NEAR!)
>
Wonder what is was,? if you share the secret then the next person who trys
will know what to do..

> Now last problem:
> i'm trying to make it to work with xfbb and other progs of ax25-utils...
> When SCC begins to send the first groups of packets everything is
> right.... After a while i can see TXerrors in sccstat and the link begin
> tits way to fail ....
> Ive changed the standard_window_size to 7... The difference between 7 and
> the defaul (2).. is that with 2 no problem for more time... but at the end
> the same thing......

7, huum, if it is a point to point link at high speed fine, but 7 packets
on a shared qrg is to many. Also if you are using 1200 baud your maxkeyup
will expire before all the packets are sent, for example.
7 pings with an MSS of 472 at 9600 baud takes 7083.1 ms in total to return,
ping used as..
ping -c7 -l6 -s472 -i5 <host> returns;
7 packets transmitted, 7 packets received, 0% packet loss
round-trip min/avg/max = 4456.7/5769.9/7083.1 ms

My maxkeyup is set to 7 seconds, if i was to ping with 8 packets the eight
one will not be sent. You might say ok i will increase my maykeyup time,
try but dont forget, most scc modems have a watchdog timer and that will
break the keying of after +/- 10 seconds.
So think what will happen at 1200 baud, even with an MTU of 256.

> I tried to change rxbuff and txbuff.... nothing changes,...
>
The most relavant information can be found in /proc/net/z8530drv
What mode, DG or VC.? send along with this a print out of "netstat -or".

> With scc working in this way it's not possible to make a file transfer or
> something that needs long txing...
> I'm using 2.0.30 + mod14c + z8530utils 2.4c....
>

Does a file transfer work ok with standard_window_size of 2 or even 4?.

> Exept this everything is right...
> I tried it on both 486dx2/66 and p55/133... the same....
>
> What may be?? (i tried defininf SCC_DELAY...)

Read z8530drv/FAQ lines 50 to 70. If you cant solve your problem send us the
info which i asked for above.

> Thanks in advance
> Luca

-- 
Regards Richard, 73.              | "I see" said the blind man to his
AX25  pa3gcu@pi8mid.#zld.nld.eu   |  deaf en dumb daughter, who replyed,
smtp  vqyncl@conxion.net      | "Yes" Linux AX25. NET/ROM, "I have heard
inet  xicpprvz.fkaexju@intertel.net.pl |  that what you see is what you get".