Subject: [Sigtran] M3UA: Broadcast traffic Mode

From: "Goel, Soni" <[email-masked]>
Date: Wed, 20 Feb 2002 15:58:36 -0800

Hi,

(Lyndon, this is in reference to the mail I sent to you earlier)

Please clarify the following -
1) What was the exact requirement for Broadcast mode ? 
Was it to prevent message loss/mis-sequencing/duplication ? If yes, then why
not the procedures similar to MTP3 be defined at M3UA using message
retrieval procedures of SCTP ?
As per the procedure described in a mail in SIGTRAN mailing list archive
(dated 6/1/2001) for thread "M3UA: Changeover between ASPs" if there are  10
ASPs for an AS in Broadcast mode, SGP will send each DATA message to all the
10 ASPs. And the ASP  which is master of a traffic flow, will need to inform
(or checkpoint) 9 slave ASPs with the Correlation Id and  Stream Id of each
message it processed. 
Such type of procedure will multiply the network traffic and processing load
at ASP & SGP manifold. This will  definitely effect the network performance
and lead to a lesser reliable network. Do we really want this ?

2) Moreover, M3UA Draft 12 also doesn't clearly define the functionality of
ASP in Broadcast mode nor the usage of correlation id. It leaves too many
implementation dependent assumptions. Can anybody who is working on this,
give me some reference ?

- Soni

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 20 Feb 2002 20:52:50 -0600

Goel,

Goel, Soni wrote:                            (Wed, 20 Feb 2002 15:58:36)

> 1) What was the exact requirement for Broadcast mode ? 

See the thread "M2UAv0, M3UAv8, SUAv7: Traffic Mode Type" from
July-August 2001, the thread "M3UA-07: Broadcast mode changes" from July
2001 and "m2ua AS broadcast mode" from July.

Also note that this question was again addressed in "m2ua v10: Broadcast
Mode" in October.

Can you tell me what is the use of active/standby mode?  It is just 1+m
loadsharing after all.

> Was it to prevent message loss/mis-sequencing/duplication ?

No.  draft-bidulock-sigtran-corrid-00.txt is to prevent message
loss/mis-sequencing/duplication.  Use of Correlation Id with Broadcast
mode is so that an ASP joining a broadcast AS knows where in the
dataflow it is joining.

> If yes, then why not the procedures similar to MTP3 be
> defined at M3UA using message retrieval procedures of SCTP ?

See draft-bidulock-sigtran-corrid-00.txt for a detailed answer to that
question.  SCTP retreival is not sufficient in of itself.  Coordination
between peers is also required and acheived in this corrid draft by
applying similar techniques as provided for broadcast to loadshare
and override.

> As per the procedure described in a mail in SIGTRAN mailing list
> archive (dated 6/1/2001) for thread "M3UA: Changeover between ASPs" if
> there are  10 ASPs for an AS in Broadcast mode, SGP will send each
> DATA message to all the 10 ASPs.
>
> And the ASP  which is master of a traffic flow, will need to inform
> (or checkpoint) 9 slave ASPs with the Correlation Id and  Stream Id of
> each message it processed.  Such type of procedure will multiply the
> network traffic and processing load at ASP & SGP manifold. This will
> definitely effect the network performance and lead to a lesser
> reliable network.  Do we really want this ?

See the last note in that thread dated Jun 5/2001.  It is the
reponsibility of the ASP to communicate with its other ASPs using an
unspecified implementation dependent ASP to ASP protocol concerning the
state of the ASP's internal processing of received MSUs.

Neither the spec nor the traffic mode require any such onerous
checkpointing.

I suggest you don't use broadcast groups of 10 if you are worried about
network bandwidth.  See also draft-bidulock-sigtran-loadsel-00.txt for
more reasonable scenarios.

> 
> 2) Moreover, M3UA Draft 12 also doesn't clearly define the
> functionality of ASP in Broadcast mode nor the usage of correlation
> id. It leaves too many implementation dependent assumptions. Can
> anybody who is working on this, give me some reference ?

The behavior of the SGP with regard to the ASP is clear and specified.
ASP to ASP communication and coordination of state is outside the
scope of the specification.  Consult the cited threads and drafts
if you are interested in implementation-dependent considerations.

--brian

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