Subject: RE: [Megaco] supplied address and ServiceChangeAddress

From: "Kevin Boyle" <[email-masked]>
Date: Thu, 28 Apr 2005 11:00:18 -0400

There is additional text in that section: "Note that the use of
ServiceChangeAddress is not encouraged."  This is advice that ought to be
followed.
 
That aside, to answer your question, the paragraph is discussing the
SCAddress parameter alone.  It only indicates that if the SCAddress
parameter is present, then the recipient of the SC command must switch to
that new address.
 
Note that if the MGC wishes to change its address, it should use Handoff and
the SCMGCID to announce that change.
 
Kevin

  _____  

From: [email-masked] [mailto:[email-masked]] On Behalf Of
Jan Lindquist (AL/EAB)
Sent: Thursday, April 28, 2005 10:35 AM
To: [email-masked]
Subject: [Megaco] supplied address and ServiceChangeAddress

Hello,
 
I would like assistance in the interpretation in the text in H.248
specifically in section 7.2.8 relating to ServiceChangeAddress.  Here is a
copy of the text in question:

"The MG may specify the transport ServiceChangeAddress to be used by the MGC
for sending messages in the ServiceChangeAddress parameter in the input
ServiceChangeDescriptor. The MG may specify an address in the
ServiceChangeAddress parameter of the ServiceChange request, and the MGC may
also do so in the ServiceChange reply. In either case, the recipient must
use the supplied address as the destination for all subsequent transaction
requests within the association."
 
The H.248 transport to be used is UDP/IP.
 
The question relates to the last sentence in the above paragraph.  A common
technique with UDP transport of H.248 is to copy the source IP address in
the IP header that is in the first ServiceChange from the MG.  So all
subsequent message to the MG will use that MG IP address.  There is no need
for a ServiceChangeAddress.
 
The question is in the reverse direction.  If I want to change the IP
address that the MG should use for any subsequent messages to the MGC.  The
MGC sends a ServiceChange reply with a new IP address to itself.  Shouldn't
the MG use that IP address for subsequent messages?
 
There is a subtle implication in the text that this is acceptable but what
does "supplied address" mean.  For ServiceChange coming from the MG the IP
address in the IP header is the supplied address.  If this accepted
technique for indicating supplied address it is possible to interprete the
ServiceChange reply could indicate the supplied address for the MGC.
 
Is this interpretation correct?
 
Regards,
JanL

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---

From: [email-masked]
Date: Fri, 29 Apr 2005 12:02:16 +0200

Hi Jan,

just an additional comment to the sentence:
"A common
technique with UDP transport of H.248 is to copy the source IP address in
the IP header that is in the first ServiceChange from the MG."

I don't know how to handle such a argument. This seems to be an assumption,
or a specific interpretation, or a "best current practice" because it is
not mentioned in any H.248 Rec. Right?

My question is: do you want to make this implicit assumption as an explicit
proposal, e.g., for ETSI H.248 Profiles? ["because the subsequent
argumentation bases on this hypothesis"]

Best rgds/Albrecht

                      "Kevin Boyle"                                                                                                 
                      <[email-masked]         To:      "Jan Lindquist (AL/EAB)" <[email-masked]>, [email-masked]      
                      om>                      cc:                                                                                  
                      Sent by:                 Subject: RE: [Megaco] supplied address and ServiceChangeAddress                      
                      megaco-bounces@i                                                                                              
                      etf.org                                                                                                       

                      28.04.2005 17:00                                                                                              

Note that if the MGC wishes to change its address, it should use Handoff
and
the SCMGCID to announce that change.

Kevin

  _____

Hello,

"The MG may specify the transport ServiceChangeAddress to be used by the
MGC
for sending messages in the ServiceChangeAddress parameter in the input
ServiceChangeDescriptor. The MG may specify an address in the
ServiceChangeAddress parameter of the ServiceChange request, and the MGC
may
also do so in the ServiceChange reply. In either case, the recipient must
use the supplied address as the destination for all subsequent transaction
requests within the association."

Regards,
JanL