Subject: Cisco SG16: Preconditions on commands

From: Chip Sharp <[email-masked]>
Date: Tue, 25 Jan 2000 19:52:01 -0500

Section:        D.1
Category:       Technical
Issue:          The current draft text does not support the concept of
preconditions that must be established in order for a command to be
successful. For example, the MGC and the MG can get out of synch on the
hook state. Consider a MG that just cold-started. Before the gateway
generates a restart ServiceChange, the user picks up the handset. The
gateway detects the off-hook transition, but since it does not have an
EventsDescriptor, it does not generate Notify. Soon after, the gateway
generates a restart ServiceChange. After the MGC receives the message, it
generates a Modify to the gateway to request off-hook detection. However,
since the off-hook transition has happened, the gateway does not generate
Notify. Since the gateway does not play any tone to the user, the user
hangs up the phone. Since the MGC has not requested the gateway to detect
on-hook transition, the gateway does not generate Notify either. If
preconditions were defined and supported, e.g. to require that a request
for off-hook detection would only succeed if the line state was currently
on-hook, such errors could be avoided.
Proposal:       It is strongly recommended, that preconditions as described above
are added to the draft.

v13 Status:     OPEN. No relevant text changed.

Note that this topic has already generated discussion on the list.

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Chip Sharp                 Consulting Engineering
Cisco Systems              Telco Bio-region
Reality - Love it or Leave it.
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