ITEM: I4208L

SLIP at 38400bps

The following is a description of one set of circumstances where a 
Serial Line IP connection was made with the RS/6000's tty ports set
to a line speed of 38400 baud:

   Mod  590 at 3.2.5   128-port controller
   Mod  340 at 3.2.4   16-port adaptor

The TTY ports were set for 38400 baud.  All refences to IXON, IXOFF, and 
IXANY in TTY program characteristics were removed as specified on page 
4-83 of System Management Guide:  Communications and Networks, GC23-2487-00.
Although this is not always necessary, in this instance, the port was
configured with these attributes.

RTS hardware flow control was added to each tty port.  RTS flow control 
was enabled on the modems by setting the appropriate register in the 
modems.  This was important because the telephone line speed between
the modems was slower than the port speeds.  Whenever there is a
difference between the line and port speeds,some sort of flow control
is needed.

The "enable login" entry in SMIT's TTY program settings were set to
disable.  Enable, share, or delay do not work for slip.  From the command
line, type "pdisable tty14" to disable tty14.

Machine sys_local contactes sys_remote.  Assign appropriate IP addresses.

   sys_local 2.0.0.50       netmask 255.0.0.0 
   sys_remote 2.0.0.51      netmask 255.0.0.0

The address for the SLIP interface is on a separate network from the
Ethernet adaptor which is on 1.0.0.X.  SLIP does not work well if it's
interface and another interface are on the same network.

A script called 'slipup' was run on sys_local:

   /etc/ifconfig sl14 inet 2.0.0.50 2.0.0.51 netmask 255.0.0.0 up
   /etc/slattach tty14 38400 '"" AT OK ATDT5551234 CONNECT ""' 9

The 9 at the end of the second line enabled  diagnostic output so 
that the script could be observed.  The '9' was ommitted after the 
script proved to be reliable.  The baud rate of 38400 corresponded
to a direct entry in the /etc/uucp/Devices file:

   Direct tty14 - 38400 direct

A similar script was run on sys_remote:

   /etc/ifconfig sl16 inet 1.1.1.20 1.1.1.10 netmask 255.0.0.0 up
   /etc/slattach tty16 

Sys_local did an "active" slattach and sys_remote did a "passive"
slattach.

To stop the slattach use "ifconfig sl\# detach" .  Do not do a kill -9
on the slattach's process id.

This customer insisted on jumpering modem pin 5 (CTS) to pin 8 on 16 port
adaptor (CD).  The customer understood what he was doing and it worked
for him but it is not recommend that this be done.

Once the machine is rebooted, the script will need to be run again.  An
alterative to the script, once the connection is found to be reliable
is to define the interface in smit following this path:

Communications Applications and Services
 TCP/IP
  Further Configuration
   Network Interfaces
    Network Interface Selection
     Add a Network Interface
      Add a Serial Line INTERNET Network Interface

For a passive connection, do not specify a baud rate or dial string.  
For an active connection, specify the same dial string that is in the 
single quotes of the slattach command.



Support Line: SLIP at 38400bps ITEM: I4208L

Dated: August 1994 Category: N/A

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