Subject: [Megaco] doubt about "failover" because of MG failure?

From: [email-masked]
Date: Fri, 19 Apr 2002 19:27:38 +0900

hi, list.

Can "failover" only be applied when redundant MGs used?
what redundant MGs implies that two(or more) MGs have same states(about
active contexts, terminations and so on).
Is that correct? 
Could please teach me what "redundant" exactly means?

In other words, if MG fails and there no MG which is running as standby
having same states as failed one
(even though there could be other MGs),
Shall the failed MG send ServiceChange command with graceful/forced?
If MG fails and there is a MG which is running as standby having same
states as failed one,
Eventaully, this time Can we use "failover"?

Anyway, another question arises.
In RFC 3015, 11.4 Failure of an MG reads
"If a MG fails.... ..... ......
[
Allowing the MGC to send duplicate messages to both MGs accomodates pairs
of MGs that are capable of redundant failover of one of the MGs. Only the
Working MG shall accept or reject transactions. 
]
...
...."

                    ---------------------
                          MGC
                    ---------------------
                      |  <-----------|-------------------  1) 
                      |               |                              1), 2)
MGC send same messages, MG1 and MG2 do something  
                      |               |<------------------ 2)
but only MG1 replies?
             ---------------        ---------------
              MG1(active)       MG2(standby)
             ---------------        -----------------

Above paragraph means that redundant MGs configuration is assisted by MGC
which duplicates messages.
Is that correct?
Should MGC support duplicating messages for this kind of configuration?

Do redundant MGs have same mIds?
Does not MGC send message to failed one until recovering completed?

Duplicating message makes me puzzled. 
Is it not better leave all redundancy mechanism to MG sides?

Last question)
If ,as a result of failover, now MG2 becomes active one and a little bit
later MG1 recovers from error,
Which MG issues ServiceChange with "restart"? MG1 or MG2?

Anyway, what is the effect of "restart"? 
Does "restarted MG" seem to be initial state which means there's no context?

thanks in advance.