Conference annecy::dcs90erver

Hi,

with the DCS90, we cannot talk of X25 gateway in the same sense as, for
example, the DECNIS.
The DCS90 must be considered as a WAN controller as the DSYT1 and the DNSES.
The only difference with respect to these boards is that is sits on the
ethernet rather than on the internal bus.
Similarly to the DSYT1 and the DNSES,  X25 accesses the DCS90 lines through the
LAPB protocol. All the X25 stuff is done in  the host system.
Then, the limits are those imposed by X25.
For what concerns the DCS90 itself, the driver set a limit of 100 units, which
is in fact a theoretical limit.  The real limit depend on the utilization
context:

for example, if you have 20 DCS90 running both lines simultaneously at 19200
bps (transmit and receive),  that makes 19200*4*20 = 1536000, which is above
10% of the ethernet bandwidth just for the usage of the DCS90's. Whether this
is too much or not, it depends on the total ehernet traffic.

Another limitation  factor is the CPU power.

These are only guidelines; what is the number of DCS90 you would like to
connect to the same host ?

Regard
                Marco

    Hello,
    
    Thank you very much for your information.  I was told that the DCS 90 can 
    be shared by multiple UNIX system on the same LAN, is that true ?
    
    Regards,
    
    LK Lee
    
    	

Hi Lee,

I am sorry for the late answer !  The batch job which watch my notes was not
working, and I have been very busy, so I realize it just now.

Yes, the DCS90 is shareable between multiple systems, including now OpenVMS 7.0.

But note that, in order for a DCS90 line to be taken by a host, it must have
been freed  by the host previously using it. 

On Unix, a line is "taken" by the host in either case:
- a ncl Modem Connect Line entity pointing to that physical line is created;
  or
- if accessing the LLC2 layer interface with the PIFC library API,a PAP        
establish command is sent to reserve a given line.

A line is released by either:
 
- deleting the ncl Modem Connect Line entity pointing to that physical line;
  or
- if accessing the LLC2 layer interface with the PIFC library API, sending a PAP
  stop command followed by a PAP clear command.


On Open VMS, it is sufficient to disable the modem connect line.


Regards
	Marco