Subject: When DEACT Flows are Required

From: "J. G. Dudley (444/4358)" <[email-masked]>
Date: Mon, 27 Nov 95 13:53:46 EST

Section 2-4 of ATM-02 describes DEACT flows used for HPR link
deactivation over ATM.  However, section 2.7.1.1 shows HPR link
deactivation without the use of DEACT.  In light of this discrepancy,
I was asked at AIW9 if the DEACT flows are needed.

When HPR may share SVCs, HPR link activation may or may not trigger
SVC activation depending on whether a suitable SVC is already in use
by other protocols; likewise, HPR link deactivation may or may not
trigger deactivation of the underlying SVC depending on whether other
protocols are using the SVC.

The flows in figures 2-9, 2-10, 2-11, 2-12, and 2-13 are correct for
the case where HPR cannot share or chooses not to share the underlying
SVC with other higher-layer protocols.  An adjacent node learns that
an HPR link has been deactivated when the underlying SVC is deactivated.
The DEACT flows are not needed.  The next version of the HPR/ATM
document will so indicate.

The DEACT flows are used to notify the adjacent HPR node that the HPR
link is being deactivated when HPR may be sharing the underlying SVC.
In the case where the HPR link is deactivated but the underlying SVC (in
use by some other higher-layer protocol) remains active, there is no
other mechanism by which the adjacent node is notified.

Gary Dudley
IBM APPN Architecture Team