Subject: MG-MGC association for redundant MGC

From: Sarika Gupta <[email-masked]>
Date: Sat, 3 Feb 2001 17:26:34 +0530

Hi,
   We are trying to develop fault tolerant platform(with 1+1 redundancy) over
which multiple MGC applications can run.
     MG is an external entity which is from a different vendor and  we don't
have any control over its implementation.
     For switchover from active to standby node, in case the active fails, we
are using the Floating IP concept, so that only one IP address is visible to the
external world. Thus for MG there is only one MGC visible with this Floating IP
address configured in its primary MGC IP address parameter.
Now since MGC acts as server and the MG acts as a client, so whenever  we do the
switchover, the MGC server shall be established again.
But MG shall have to connect as a client to this server again which implies it
shall have to create a new n/w association.
My query is is there any way to avoid this creation of a new association by MG?
If yes then how?
Plus is there any standard which can give us some exact figueres as to what
should be the value of retransmission timers  for MG and the number of retries
before it tries to make a new association.

Regards
Sarika

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From: Tom Taylor <[email-masked]>
Date: Sat, 3 Feb 2001 11:43:34 -0500

Let's see if I understand you correctly.  The same IP address will be used for
both the primary and secondary MGC.  If UDP/ALF is being used and primary and
secondary are sharing state, I would think it would be unnecessary to
reestablish the association.  If those conditions are not met, reestablishment
is necessary.  As Amy Pendleton and I have argued in the past, switchover would
come more quickly if it could be triggered by the newly active MGC.  Otherwise
the MG has to infer the need for switchover from a loss of communications with
the primary (probably using a heartbeat mechanism like the proposal in draft
H.248 Annex N -- see
ftp://standards.nortelnetworks.com/megaco/docs/Current/ITU-SG16/
).