Subject: [Sigtran] Which ASP shall answer in Traffic Mode = Multicast?

From: "Sedlak Michael" <[email-masked]>
Date: Thu, 7 Sep 2006 16:02:43 +0200

Hello,

After studying the rfc, I could not find an answer on how to proceed
after a multicast-message was sent to several ASP.

consider a case where 3 ASP are active in an AS, traffic mode type =
multicast.
When an SGP sends a message to all 3 ASP, how do the ASP know which one
shall transport the message to the upper layer? And further on, which
upper layer shall answer the message?

What could be a real-life scenario where multicast is needed?

thanks,
Michael Sedlak

Solution Architect | All-IP Data Core
KapschCarrierCom

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---

From: "Lee Dryburgh" <[email-masked]>
Date: Thu, 7 Sep 2006 15:09:23 +0100

I was told from a very good source, assume that multicast (broadcast)
did not exist in the specs! I was told that it is never used!

So I'd be interested if other SigTran folks had something else to say
on the topic.

Regards

Lee

On 07/09/06, Sedlak Michael <[email-masked]> wrote:
>
>
>
> Hello,
>
> After studying the rfc, I could not find an answer on how to proceed after a
> multicast-message was sent to several ASP.
>
> shall transport the message to the upper layer? And further on, which upper
> layer shall answer the message?
>

---

From: "Barry Nagelberg" <[email-masked]>
Date: Thu, 7 Sep 2006 10:18:46 -0400

Lee,

If your source is correct, then this is a sad comment on the RFC.

Nevertheless, if it's in the RFC, then I would say ignore it at your peril. Someone may use it, and then anyone who
doesn't will be non-compliant and non-interoperable.

Barry Nagelberg
Adax, Inc.

-----Original Message-----
From: Lee Dryburgh [mailto:[email-masked]]
Sent: Thursday, September 07, 2006 10:09 AM
To: Sedlak Michael
Cc: [email-masked]
Subject: Re: [Sigtran] Which ASP shall answer in Traffic Mode =
Multicast?

Regards

Lee

---

From: "Haresign Lincoln" <[email-masked]>
Date: Thu, 7 Sep 2006 10:18:35 -0400

One possible use for multicast would be if you are trying to build some
redundancy mechanism in.  For example:
 
A message gets sent to all ASPs within an AS.  By some agreed mechanism
within the AS, the ASPs would know who is responsible for responding to
that message.  However, if a particular ASP died in the middle of a
call, all the state was being maintained by the other ASPs, so another
ASP could take over the call.
 
This is probably over engineered, and we are not doing it, but it would
be one scenario that you might use this capability.
 
Regards,
Lincoln

________________________________

From: Sedlak Michael [mailto:[email-masked]] 
Sent: Thursday, September 07, 2006 10:03 AM
To: [email-masked]
Subject: [Sigtran] Which ASP shall answer in Traffic Mode = Multicast?

Hello, 

thanks, 
Michael Sedlak 

informed that he may not use, disclose or reproduce the contents
thereof.

---

From: "Lee Dryburgh" <[email-masked]>
Date: Thu, 7 Sep 2006 15:24:43 +0100

On 07/09/06, Haresign Lincoln <[email-masked]> wrote:
> within the AS, the ASPs would know who is responsible for responding to that

Added complexity comes to mind. But I am sure this has all been
thrashed out many times in the past.

> message.  However, if a particular ASP died in the middle of a call, all the
> state was being maintained by the other ASPs, so another ASP could take over
> the call.

Ditto.
>
> This is probably over engineered, and we are not doing it, but it would be
> one scenario that you might use this capability.
>

Does any vendor actually provide the ASP broadcast option?

Regards

Lee

---

From: "Barry Nagelberg" <[email-masked]>
Date: Thu, 7 Sep 2006 10:31:22 -0400

Lee,

Adax supports it on the SGP.

Barry Nagelberg
Adax, Inc.

-----Original Message-----
From: Lee Dryburgh [mailto:[email-masked]]
Sent: Thursday, September 07, 2006 10:25 AM
To: Haresign Lincoln
Cc: [email-masked]
Subject: Re: [Sigtran] Which ASP shall answer in Traffic Mode =
Multicast?

Ditto.

Regards

Lee

---

From: "Lee Dryburgh" <[email-masked]>
Date: Thu, 7 Sep 2006 15:37:30 +0100

That is were the little effort is. Anybody support it at the real end (AS/MGC)?

Regards

Lee

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 7 Sep 2006 10:52:43 -0600

Sedlak,

I presume that you are speaking of broadcast traffic mode under, say,
M3UA, rather that IP "broadcast" or "multicast".  Broadcast is a
mechanism that permits all other traffic modes independent of the SG.
The ASPs serving an AS decide between themselves which one will handle
a given message.  In a typical arrangement, each ASP serving the AS
would be responsible for active processing of 1 range of SLS (M3UA)
and responsible for checkpointing on the remaining ranges of SLS.  ASPs
heartbeat and checkpoint between each other or rely upon ASP Failure
indications from the SGP to detect a failed ASP.  When an ASP fails,
the active ASP in the AS responsible for acting as backup to the failed
ASP takes starts actively processing messages rather than just check
pointing for the range of SLS for the failed ASP.

Of course, other arrangments are possible.  Active-Standby and Loadshare
can also be preformed by ASPs in broadcast mode.

The reason that you do not see much mention of this in the RFCs is because
the RFCs do not dictate how ASPs in a broadcast AS behave because ASP-ASP
communication and coordination is out of scope.  From the ASP-SG protocol
perspective, the SG simply sends the message to each ASP serving the AS and
does not dictate who processes it.

Hope that helps.

--brian

Sedlak Michael wrote:                      (Thu, 07 Sep 2006 16:02:43)
>    When  an  SGP  sends a message to all 3 ASP, how do the ASP know which
>    one  shall  transport  the message to the upper layer? And further on,
>    which upper layer shall answer the message?
> 

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/

---

From: Chris Benson <[email-masked]>
Date: Thu, 7 Sep 2006 10:59:29 -0700 (PDT)

Lee,

I am in another department of Barry's company, and we support 
broadcast mode at an AS implementation of M3UA. The individual
M3UA users (MTP3-users) of each ASP are expected to co-ordinate
ownership etc. This AS broadcast mechanism is just a vehicle to
all instances of the higher layer at each ASP.

You asked whether any vendor supported AS broadcast. Adax does.
You are probably more interested in an example usage, and I
know of no actual usage of broadcast by our customers, except
when they are testing for protocol specification conformance ;-)

With thanks, from Chris Benson,
Adax, Inc.

-- 
Christopher Benson, Software Engineer,
Adax Inc., Berkeley, California, USA.
[email-masked]
+1 510 548-7047 ext. 189

---

From: "Lee Dryburgh" <[email-masked]>
Date: Thu, 7 Sep 2006 19:11:43 +0100

Chris,

Thanks for the interesting info.

As you've pre-guessed I'd be interested to know if anyone knows of a
customer using it?

Regards

Lee

---

From: "Saurabh Jain" <[email-masked]>
Date: Fri, 8 Sep 2006 10:53:44 +0530

Hi,

I have query for Broadcast mode in SUA.

For M3UA, Broadcast mode : the role of SG would be to Broadcast messages to
all ASPs.
                                            the role at ASPs would be to
accept the message.
                                                      Now thru inter-ASP
communication, one of the ASPs may process it and rest would drop it,
                                                      or all ASPs
may process it.

However, will Broadcast mode also be applicable for SUA Class 2 Messages?
Potential issues:

   - This would mean that for a single SCCP Connect request from User,
   SUA would have to maintain multiple connections, one with each Peer ASP.
   - What happens if 1 out of multiple Peer ASPs does not send a COAK,
   (we will not be able to send further messages to this ASP for this
   connection)
   - What happens if a new ASP becomes active, (and some Class 2
   connections had already been established with earlier ASPs), we will not be
   able to send data for earlier connections towards this new ASP.

 RFC 3868, only explains Broadcast Mode in general (in section 4.3.4.3.  ASP
Active Procedures)
*"The algorithm at the SGP for  broadcasting traffic within an AS to all the
active ASPs is a simple broadcast algorithm, where every message is sent to
each of the  active ASPs."*

If we allow Broadcast Mode for Class 2 Messages then there would be a
slight conflict with the above section.

rgds
Saurabh

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Fri, 8 Sep 2006 01:06:01 -0600

Saurabh,

Saurabh Jain wrote:                             (Fri, 08 Sep 2006 10:53:44)
> 
>    Potential issues:
> 
>      * This  would mean that for a single SCCP Connect request from User,

No, just one connection with the AS.

>      * What  happens if 1 out of multiple Peer ASPs does not send a COAK,

Why not?  All messages can still be sent to all active ASPs in the AS.

>      * What  happens  if  a  new  ASP  becomes  active, (and some Class 2
>        connections  had  already  been established with earlier ASPs), we
>        will not be able to send data for earlier connections towards this
>        new ASP.

Again, why not?

--brian

-- 
Brian F. G. Bidulock
[email-masked]
http://www.openss7.org/