Null X.25 cable?

Null X.25 cable?

[un@roo]

Hello linux-x25,

  Hello All!

  Is there any way to connect two X.25 card directly via cable (may be
  NULL MODEM)?
  If yes, what configuration of connectors it must have?
  Will two cards (configured as DTE) work together?

  If anyone knows, please help!
  
  

-- 
Best regards,
 un                          mailto:un@rootelecom.ru

Re: Null X.25 cable?

[Steve Schefter]

Hi.

>   Is there any way to connect two X.25 card directly via cable (may be
>   NULL MODEM)?
>   If yes, what configuration of connectors it must have?
>   Will two cards (configured as DTE) work together?
> 
>   If anyone knows, please help!

The short answer is yes.

But in order for this to work, there are a few things you need to
check.

First, the card must be capable of being internally clocked.  One
side will need to be setup as internal and the other as external.

Second, make sure you use a synchronous null modem cable.  The
more common async null modem won't route the clocks properly between
the two sides (it just crosses the data and control signals).
You'll need to make sure that the "I" side of the null modem goes
to the side that has the clocking set to internal.

Third, there are two concepts of DTE and DCE in X.25: physical and
logical.  The null modem will take care of the fact that you are
connecting two physical DTEs together, but you also need to change
the logical setting (in software) to DCE on one side.

You can find the pinout for null modem cables for various electrical
interfaces on our website under "support".

There's also an application note covering this topic on our website:
http://www.wanware.com/index.php?page=support/app_notes/mach2mach&menu=support

Regards,
	Steve

------------------------------------------------------------------------
Steve Schefter                               phone: +1 705 725 9999 x26
The Software Group Limited		       fax: +1 705 725 9666
642 Welham Road, 			     email: steve@wanware.com
Barrie, Ontario CANADA  L4N 9A1 	       Web: www.wanware.com

Re: Null X.25 cable?

[TProvoni]

Wanware hardware sounds somewhat restrictive in its clock
configurations.  I have worked with several vendors' equipment that
allows symmetric independent clocking.  Transmit clocks are sent from
both sides and the receivers extract the clocks as they receive data.
Of course, even in symmetric clocking setups, one side must be the
logical or protocol DCE and the other must be the logical or protocol
DTE.

Joachim Martillo 

BTW, some specifications provide a third sense of DTE
and DCE in terms of connector definition.

Thus it is possible to use a DCE connector on the interface that is a
DTE in the clock sense and a DCE in the protocol sense.

In a message dated 5/14/04 9:25:32 AM Eastern Daylight Time, 
steve@wanware.com writes:
Hi.

>>   Is there any way to connect two X.25 card directly via cable (may be
>>   NULL MODEM)?
>>   If yes, what configuration of connectors it must have?
>>   Will two cards (configured as DTE) work together?
>> 
>>   If anyone knows, please help!
>
>The short answer is yes.
>
>But in order for this to work, there are a few things you need to
>check.
>
>First, the card must be capable of being internally clocked.  One
>side will need to be setup as internal and the other as external.
>
>Second, make sure you use a synchronous null modem cable.  The
>more common async null modem won't route the clocks properly between
>the two sides (it just crosses the data and control signals).
>You'll need to make sure that the "I" side of the null modem goes
>to the side that has the clocking set to internal.
>
>Third, there are two concepts of DTE and DCE in X.25: physical and
>logical.  The null modem will take care of the fact that you are
>connecting two physical DTEs together, but you also need to change
>the logical setting (in software) to DCE on one side.
>
>You can find the pinout for null modem cables for various electrical
>interfaces on our website under "support".
>
>There's also an application note covering this topic on our website:
>http://www.wanware.com/index.php?page=support/app_notes/mach2mach&menu=suppor
t
>
>Regards,
>    Steve

Re: Null X.25 cable?

[Steve Schefter]

Hi Joachim.

> Wanware hardware sounds somewhat restrictive in its clock 
> configurations.  I have worked with several vendors' equipment that 
> allows symmetric independent clocking.  Transmit clocks are sent from 
> both sides and the receivers extract the clocks as they receive data.  

We support that as well.  It is just more common to have the physical
DCE generate the clock for both sides to use (such as when you are
connected to a modem or DSU/CSU).  I generally only put internal clocking
on both sides when I'm using FM0 line encoding.

> BTW, some specifications provide a third sense of DTE and DCE in terms 
> of connector definition.
>  
> Thus it is possible to use a DCE connector on the interface that is a 
> DTE in the clock sense and a DCE in the protocol sense.

When you say the DCE is "DTE in the clock sense", do you mean it's
externally clocked?  (And you didn't like my arbitrary selection of DTE
as externally clocked above ;-)

Just to be clear, there's the selection of:
	- physical DTE versus physical DCE
	- logical DTE versus logical DTE
	- who will provide the clock
All three of these are independently chosen.  You can mix and match
and get lots of combinations.

	Steve

------------------------------------------------------------------------
Steve Schefter                               phone: +1 705 725 9999 x26
The Software Group Limited		       fax: +1 705 725 9666
642 Welham Road, 			     email: steve@wanware.com
Barrie, Ontario CANADA  L4N 9A1 	       Web: www.wanware.com