[comp.dcom.modems] Zmodem over X.25

paul@csnz.co.nz (Paul Gillingwater) (05/27/89)

Hi;
I am trying to use an X.25 connection for an international file
transfer link between New Zealand and Spain.

I can establish the link just fine, which is between two Unix
boxes.  It doesn't work as a normal terminal, i.e. the remote
PAD does not send a line until it is terminals, which I assume is
due to the setting of the data forwarding signal (X.3 PAD parameter
SET 3:2).  I tried setting SET 3:126 which should make all ASCII
control characters and DEL become forwarding characters, but 
this does not fix the problem - it seems that I am only setting
the parameters in my local PAD.  How can I set the parameters
in the PAD in Spain remotely?

I should say that I am using a dial-up X.25 PAD via a V22bis modem
(asynch).  Maybe I should make the connection first, then set my local 
PAD parameters - does this automatically get passed on to the remote
PAD ??

Now file transfer - I have got Kermit working, since it uses CR to
terminate its packets.  It's SLOOOOOOW, especially because it has
no windowing and slow turn-around.  I want to get ZMODEM working,
but of course I have never done this before.  Can some kind soul
tell me the optimum tricks/settings for Zmodem and the PAD X.3 profile
for this to succeed?

Thanks.
(mail and I will summarize).



-- 
Paul Gillingwater, Computer Sciences of New Zealand Limited
Bang: ..!uunet!dsiramd!csnz!paul    Domain: paul@csnz.co.nz
Call Magic Tower BBS V21/23/22/22bis 24 hrs +0064 4 767 326

jas@goya.dit.upm.es (Jose Ramon Alonso Sotorrio) (05/29/89)

In article <35@csnz.co.nz> paul@csnz.co.nz (Paul Gillingwater) writes:
>Hi;
>I am trying to use an X.25 connection for an international file
>transfer link between New Zealand and Spain.
>
>I can establish the link just fine, which is between two Unix
>boxes.  It doesn't work as a normal terminal, i.e. the remote
>PAD does not send a line until it is terminals, which I assume is
>due to the setting of the data forwarding signal (X.3 PAD parameter
>SET 3:2).  I tried setting SET 3:126 which should make all ASCII
>control characters and DEL become forwarding characters, but 
>this does not fix the problem - it seems that I am only setting
>the parameters in my local PAD.  How can I set the parameters
>in the PAD in Spain remotely?
>
>I should say that I am using a dial-up X.25 PAD via a V22bis modem
>(asynch).  Maybe I should make the connection first, then set my local 
>PAD parameters - does this automatically get passed on to the remote
>PAD ??
>
The trouble arises from you both having PAD's, ie: none has native
x25 access. You can't (with a minimal probability of success) set
remote PAD's parms from a local dialup PAD. No x29 working between
them.

You can try this:
get the (local :-) spanish party to set the profile you need on
one of the PAD's ports, say #3. Suppose their x25 address is
12345.  Then tell them to set up an x25 subaddress, say 1234502
that inmediately switches incoming calls to port#3.  This port will
have the profile you needed.

As to your local setup, in the dialing script, or whatever, when
hooked to your dialup PAD, issue a ^P, followed by the profile you
wish.  CALL then 1234502 and off you go.

Alternatively, get native x25 access on the (called) spanish side,
and let them ioctl the x25 board and set both local and (throu x29)
remote settings. This is (I presume...) what goes on when you call
Compu$erve or Bix: they set everything. That's why you see inmediate
echo normaly: they set local (your pad) echo. When you go into 
chat/party/whatever (raw mode) it's their host that echoes, and it
takes *several* seconds for each char.  Just an example.

>Now file transfer - I have got Kermit working, since it uses CR to
>terminate its packets.  It's SLOOOOOOW, especially because it has
>no windowing and slow turn-around.  I want to get ZMODEM working,
>but of course I have never done this before.  Can some kind soul
>tell me the optimum tricks/settings for Zmodem and the PAD X.3 profile
>for this to succeed?
>
A setup like the one described above brings mail and news to
Spain from mcvax in Holland every day. We use f-proto uucp, and
(once we solved some flow control problems) it works flawlessly.
While I love Zmodems throuput and restarting capabilities, you
can be on the air quickly with uucp, and then explore zmodem.
I seem to recall it was originaly developed under contract from
Tymnet (or was it Telenet??) for use in their x25 lines.  The
autor is on the net and can certainly be of help.

Beware that f-proto expands binaries a lot. Not sure about the
exact expansion, but I know it's much worst than uuencode/btoa.
?Someone knows the method?

I'll be glad to help the spanish side, if they contact me.

>Thanks.
>(mail and I will summarize).
>
I thought this of general interest.

>Paul Gillingwater, Computer Sciences of New Zealand Limited
>Bang: ..!uunet!dsiramd!csnz!paul    Domain: paul@csnz.co.nz
>Call Magic Tower BBS V21/23/22/22bis 24 hrs +0064 4 767 326
>
Or, if on the other side of the world,
Foro BBS, v22,22bis +34 1 449 31 74 :-))

Dept. of Telematic Systems Engineering. Technical U of Madrid.
jas@dit.upm.es         jas@goya.uucp            mcvax!goya!jas
ETSI Telecomunicacion.               tlf. +34 1 449 5762, x325
Ciudad Universitaria                 fax  +34 1 243 2077
28040 Madrid Spain                   telex       47430 ETSIT E

piet@cwi.nl (Piet Beertema) (05/30/89)

	>I tried setting SET 3:126 which should make all ASCII
	>control characters and DEL become forwarding characters, but 
	>this does not fix the problem - it seems that I am only setting
	>the parameters in my local PAD.  How can I set the parameters
	>in the PAD in Spain remotely?
No way to do that with the vast majority of PAD's that are on
the market. Only a few PAD's (e.g. Micom) allow you to "escape
to X.29 control mode" making it possible to read/set the remote
PAD's X.3 parameters.

	>Now file transfer - I have got Kermit working, since it uses CR to
	>terminate its packets.  It's SLOOOOOOW, especially because it has
	>no windowing and slow turn-around.
Between Spain and New-Zealand X.25 links will go via satellite,
possibly even via 2 satellites. That's causing massive delays.
Furthermore it's not unusual that there is some fancy gateway
involved that by default limits your link speed to 1200 bps...
And even without satellites involved, X.25 is slow, as was proved
long ago here in Europe with uucp: the standard (packet) g-proto
was about 3 times slower than the (non-packet) f-proto; with the
latter we obtain effective speeds around 2500 bps (on a 4800 bps
line) between Holland and Japan and around 2000 bps to Australia.

-- 
Opinions expressed above reflect those of my employer, except when they don't.

	Piet Beertema, CWI, Amsterdam	(piet@cwi.nl)