Subject: [Megaco] MSRP switch question - H.248.69

From: Ron Ho <[email-masked]>
Date: Thu, 21 May 2009 16:22:19 -0400

Hi All,

I would like to learn more about the Megaco MSRP extension - H.248.69. I am
confused about the role of the MSRP switch.

1. Does the MG (aka the MSRP switch) has it own msrp uri? I assume it does
because the MG need to populate the a=path attribute in the local descriptor
in SDP. Am I right? I think it is needed for MG to send a message out. It
needs to populate the from-path msrp uri, correct?

2. When an endpoint send a message to another endpoint thru the MG (MSRP
switch), does it put the targeted endpoitn msrp uri or the MG's msrp uri
(the a=path that returned from the MG as the local descriptor in SDP)?

3. In H.248.69, it mentioned the MG is merely to relaying the message
between two or more terminations. Does it mean the message is passed from
one termination to the other termination as is keeping all the headers
identical? Or, does the MG need to create a new message but puting the
content of the receiving message there? Also, is the transaction in the
message to send out by the MG kept the same as in the received message if a
new message is created?

4. H.248.69 allows playing of message from the MG to the termination. I
assume that the MG's msrp uri will be used in the from-path msrp uri field.
Right?

5. In section 13 of the extension (Messageing Filtering package), it
mentioned about incoming message in 13.1.1 and outgoing message in 13.1.3. I
am not entire clear about the defintion of incoming and outgoing message.
And it mentioned "User" in the 13.1.3 description. What is it refering to?
the endpoint? the MGC? or what?

6. Is there any sample MSRP call flows/traces available for MSRP messages
flowing through the MG?

7. Is there any sample Megaco call flows/trace avaiabel for the MSRP call?

Thanks,
Ron

---

From: Christian Groves <[email-masked]>
Date: Fri, 22 May 2009 11:56:22 +1000

Hello Ron,

This work stemmed from the work/requirements that 3GPP produced 
regarding MSRP. 3GPP TS23.333 and 29.333 contains more information 
regarding this:
ftp://ftp.3gpp.org/specs/latest/Rel-8/23_series/23333-830.zip
ftp://ftp.3gpp.org/specs/latest/Rel-8/29_series/29333-841.zip

Regards, Christian

Ron Ho wrote:
> Hi All,
>
> I would like to learn more about the Megaco MSRP extension - H.248.69. 
> I am confused about the role of the MSRP switch.
[CNG] Section 3.2.3 gives a definition of "MSRP switch" its essentially 
a MSRP relay used for conferencing. Thus I would assume what is 
described in RFC4976 would largely apply. I think this should cover the 
question 1-3 below.
>
> 1. Does the MG (aka the MSRP switch) has it own msrp uri? I assume it 
> does because the MG need to populate the a=path attribute in the local 
> descriptor in SDP. Am I right? I think it is needed for MG to send a 
> message out. It needs to populate the from-path msrp uri, correct?
>
> 2. When an endpoint send a message to another endpoint thru the MG 
> (MSRP switch), does it put the targeted endpoitn msrp uri or the MG's 
> msrp uri (the a=path that returned from the MG as the local descriptor 
> in SDP)?
>
> between two or more terminations. Does it mean the message is passed 
> from one termination to the other termination as is keeping all the 
> headers identical? Or, does the MG need to create a new message but 
> puting the content of the receiving message there? Also, is the 
> transaction in the message to send out by the MG kept the same as in 
> the received message if a new message is created?
> 4. H.248.69 allows playing of message from the MG to the termination. 
> I assume that the MG's msrp uri will be used in the from-path msrp uri 
> field. Right?
[CNG] Allows the MGC to request the MG to play a message from a 
termination?  Yes unless the MGC has specified something else in the 
message contents.
> mentioned about incoming message in 13.1.1 and outgoing message in 
> 13.1.3. I am not entire clear about the defintion of incoming and 
> outgoing message. And it mentioned "User" in the 13.1.3 description. 
> What is it refering to? the endpoint? the MGC? or what?
[CNG] Think User = Termination, and that the Termination is a message 
box. Therefore messages that are received from other users (other 
terminations in the Context) are treated as incoming. Vice versa for 
outgoing message.
>
> 6. Is there any sample MSRP call flows/traces available for MSRP 
> messages flowing through the MG?
[CNG] I only know of the 3GPP documents.
>
>
> Thanks,
> Ron
> ------------------------------------------------------------------------
>
> _______________________________________________
> Megaco mailing list
> [email-masked]
> https://www.ietf.org/mailman/listinfo/megaco
>

---

From: Ron Ho <[email-masked]>
Date: Fri, 22 May 2009 12:31:54 -0400

Thanks Christian for your clarification.

I can understand that a device like media/conference server will take the
role of MSRP relay. What about BGF in the IMS network? It plays the role of
a session border controller. It is unlikely that a BGF will be used as a
conference server. It is just an intermediate device a IMS call must flow
through. In that scenario, is the BGF really acting as a MSRP relay as
specified in RCC 4976? Also, RFC 4976 mandated the TLS support. Is it
required for the BGF scenario? What if the endpoint does not support TLS? In
a pure peer-to-peer MSRP communication, TLS is not mandatory. A BGF is a
trusted network element in the IMS network and a user is sending a message
to another user in the network and is being forced to go thru the BGF. Does
it mean that TLS is forced on the connection?

Many thanks,
Ron

On Thu, May 21, 2009 at 9:56 PM, Christian Groves <
[email-masked]> wrote:

> Hello Ron,
>
> This work stemmed from the work/requirements that 3GPP produced regarding
> MSRP. 3GPP TS23.333 and 29.333 contains more information regarding this:
>> I would like to learn more about the Megaco MSRP extension - H.248.69. I
>> am confused about the role of the MSRP switch.
>>
> [CNG] Section 3.2.3 gives a definition of "MSRP switch" its essentially a
> MSRP relay used for conferencing. Thus I would assume what is described in
> RFC4976 would largely apply. I think this should cover the question 1-3
> below.
>
>>
> termination?  Yes unless the MGC has specified something else in the message
> contents.
>
>>
> [CNG] Think User = Termination, and that the Termination is a message box.
> Therefore messages that are received from other users (other terminations in
> the Context) are treated as incoming. Vice versa for outgoing message.
>
>>

---

From: "Schwarz Albrecht" <[email-masked]>
Date: Sat, 23 May 2009 07:11:58 +0200

Ron,
your questions are independent of H.248.69, they are more related to
engineering IMS/NGN/... *networks* than H.248 package capabilities.
 
MSRP vs BGF: some functions may be shifted between MSRP & BGF, like e.g.
voice transcoding. 
H.248.69 could be supported by a BGF, - why not? 
H.248.69 is not yet integrated in any H.248 BGF profile, that's why not
covered by BGF.
 
However, a BGF may be already positioned in between a MSRP client and
MSRP relay, - TISPAN Ia profiles do support the handling of TCP bearer
connections (IM-over-MSRP/TCP ... with or w/o TLS).
 
That said, you should raise your questions in 3GPP, TISPAN, ITU-T ...
 
Albrecht

________________________________

	From: [email-masked] [mailto:[email-masked]]
On Behalf Of Ron Ho
	Sent: Freitag, 22. Mai 2009 18:32
	To: megaco
	Subject: Re: [Megaco] MSRP switch question - H.248.69

	I can understand that a device like media/conference server will
take the role of MSRP relay. What about BGF in the IMS network? It plays
the role of a session border controller. It is unlikely that a BGF will
be used as a conference server. It is just an intermediate device a IMS
call must flow through. In that scenario, is the BGF really acting as a
MSRP relay as specified in RCC 4976? Also, RFC 4976 mandated the TLS
support. Is it required for the BGF scenario? What if the endpoint does
not support TLS? In a pure peer-to-peer MSRP communication, TLS is not
mandatory. A BGF is a trusted network element in the IMS network and a
user is sending a message to another user in the network and is being
forced to go thru the BGF. Does it mean that TLS is forced on the
connection?
	
	Many thanks,
	Ron

	On Thu, May 21, 2009 at 9:56 PM, Christian Groves
<[email-masked]> wrote:

		Hello Ron,
		
		This work stemmed from the work/requirements that 3GPP
produced regarding MSRP. 3GPP TS23.333 and 29.333 contains more
information regarding this:

		
		Regards, Christian 

		Ron Ho wrote:

			Hi All,
			
			I would like to learn more about the Megaco MSRP
extension - H.248.69. I am confused about the role of the MSRP switch.

		[CNG] Section 3.2.3 gives a definition of "MSRP switch"
its essentially a MSRP relay used for conferencing. Thus I would assume
what is described in RFC4976 would largely apply. I think this should
cover the question 1-3 below. 

			1. Does the MG (aka the MSRP switch) has it own
msrp uri? I assume it does because the MG need to populate the a=path
attribute in the local descriptor in SDP. Am I right? I think it is
needed for MG to send a message out. It needs to populate the from-path
msrp uri, correct?
			
			2. When an endpoint send a message to another
endpoint thru the MG (MSRP switch), does it put the targeted endpoitn
msrp uri or the MG's msrp uri (the a=path that returned from the MG as
the local descriptor in SDP)?
			
			3. In H.248.69, it mentioned the MG is merely to
relaying the message between two or more terminations. Does it mean the
message is passed from one termination to the other termination as is
keeping all the headers identical? Or, does the MG need to create a new
message but puting the content of the receiving message there? Also, is
the transaction in the message to send out by the MG kept the same as in
the received message if a new message is created?
			4. H.248.69 allows playing of message from the
MG to the termination. I assume that the MG's msrp uri will be used in
the from-path msrp uri field. Right?

		[CNG] Allows the MGC to request the MG to play a message
from a termination?  Yes unless the MGC has specified something else in
the message contents. 

			5. In section 13 of the extension (Messageing
Filtering package), it mentioned about incoming message in 13.1.1 and
outgoing message in 13.1.3. I am not entire clear about the defintion of
incoming and outgoing message. And it mentioned "User" in the 13.1.3
description. What is it refering to? the endpoint? the MGC? or what?

		[CNG] Think User = Termination, and that the Termination
is a message box. Therefore messages that are received from other users
(other terminations in the Context) are treated as incoming. Vice versa
for outgoing message. 

			6. Is there any sample MSRP call flows/traces
available for MSRP messages flowing through the MG?
			7. Is there any sample Megaco call flows/trace
avaiabel for the MSRP call?

			Thanks,
			Ron