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Conference noted::decnis

Title:	DEC Network Integration Server (DECNIS)
Notice:	Please read note 1 to use this conference effectively
Moderator:	MARVIN::WELCH

Created:	Wed Sep 18 1991
Last Modified:	Thu Jun 05 1997
Last Successful Update:	Fri Jun 06 1997
Number of topics:	3660
Total number of notes:	15082

3518.0. "NSP flow control ?" by ZUR01::FEER (Peter Feer, MCS Zurich) Fri Jan 24 1997 09:13

	In DECnet/OSI we have for NSP two possibilites of
	flow control policy

	SEGMENT FLOW CONTROl   resp.   NO FLOW CONTROL (= XON/XOFF)

	On a DECnis, NSP seems to have only XON/XOFF flow control.


1.  What whould be the correct configuration for DECnet/OSI on OpenVMS
    when I have heavy data traffic over an DECnis (i.e. X.25)
    to an OpenVMS system ?


2.  What happens if the OpenVMS has SEGMENT FLOW CONTROL and the DECnis
    has XON/XOFF configured and the VMS can not accept any new data.
    Does the DECnis understand the way how OpenVMS says "stop" ?
    Or in other words: do the two mechnism understand each other ?


	Grateful for any comments,
	Peter

T.R Title User Personal
Name Date Lines

3518.1 MARVIN::SIMS Andrew Sims, IPEG Reading. Fri Jan 24 1997 11:11 29

T.R	Title	User	Personal Name	Date	Lines
3518.1		MARVIN::SIMS	Andrew Sims, IPEG Reading.	`Fri Jan 24 1997 11:11`	29
	>>> 1. What whould be the correct configuration for DECnet/OSI on OpenVMS >>> when I have heavy data traffic over an DECnis (i.e. X.25) >>> to an OpenVMS system ? I don't really have a good answer for this one, however personally I would use no flow control (XON/XOFF) as there have been various problems with DECnet/OSI segment flow control in the past (I don't know the current state of these problems). I don't believe that the setting of NSP flow control policy has a significant effect on connections to the DECNIS. This is because the only heavy user of NSP on DECNIS is X.25 GAP which has its own flow control mechanisms which I would expect to kick in before NSP flow controls. However you will need to consider what effect changing the OpenVMS system NSP flow control will have on other applications. >>> 2. What happens if the OpenVMS has SEGMENT FLOW CONTROL and the DECnis >>> has XON/XOFF configured and the VMS can not accept any new data. >>> Does the DECnis understand the way how OpenVMS says "stop" ? >>> Or in other words: do the two mechnism understand each other ? NSP allows you to use different flow control mechanisms for the Tx and Rx paths. Although DECNIS's NSP implementation will never request segment flow control it does understand segment flow control and will act on segment flow control messages generated from the remote system, in your case the OpenVMS system. Andrew.

>>> 1.  What whould be the correct configuration for DECnet/OSI on OpenVMS
>>>     when I have heavy data traffic over an DECnis (i.e. X.25)
>>>     to an OpenVMS system ?

I don't really have a good answer for this one, however personally I would use
no flow control (XON/XOFF) as there have been various problems with DECnet/OSI
segment flow control in the past (I don't know the current state of these
problems).

I don't believe that the setting of NSP flow control policy has a significant
effect on connections to the DECNIS.  This is because the only heavy user of
NSP on DECNIS is X.25 GAP which has its own flow control mechanisms which I
would expect to kick in before NSP flow controls.

However you will need to consider what effect changing the OpenVMS system NSP
flow control will have on other applications.

>>> 2.  What happens if the OpenVMS has SEGMENT FLOW CONTROL and the DECnis
>>>     has XON/XOFF configured and the VMS can not accept any new data.
>>>     Does the DECnis understand the way how OpenVMS says "stop" ?
>>>     Or in other words: do the two mechnism understand each other ?

NSP allows you to use different flow control mechanisms for the Tx and Rx
paths.  Although DECNIS's NSP implementation will never request segment flow
control it does understand segment flow control and will act on segment flow
control messages generated from the remote system, in your case the OpenVMS
system.

Andrew.