RE: SG view of the ASP

Few comments inline.

  Alcatel USA, Inc.                  Internet: <userid>@ssd.usa.alcatel.com
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On Thu, 9 Feb 2006, Munnaluru, Krishna wrote:

> The ASP is currently sending the ASP UP message with the same ASP Id to
> both SGPs. 
> 
> As per the SG guys suggestion we temporarily changed the ASP trafficmode
> in the ASP ACTIVE message to loadsharing and this problem goes away. But
> we see another problem.
> 
> The administrator on the ASP side decides to take down the SCTP
> association with SGP2. The ASP sends ASP DOWN message to the SGP2. Then
> the SGP2 responds with ASP DOWN ACK. So far everything looks good. But
> then immediately the SGP1 sends a NOTIFY with the status=ASP Failure and
> includes the Routing Context value. Why is the SGP1 sending this NOTIFY
> and what is the expected behavior of the ASP upon receiving the NOTIFY
> from the SGP1? The SG is sending the NOTIFY because it treats the ASP as
> two separate ASPs and so it thinks that it is notifying to the other
> ASP.
> 
> I think it came down to the way SG was designed - "The SG treating each
> association as a separate ASP as supposed to just one ASP with two
> associations".  Is this the general way a SG behaves (or designed)?
> Should it not treat an ASP as just one rather than two?
> 
> Please provide some input so that I can confirm my understanding of the
> M3UA protocol.
It seems to be a problem with SG's implementation. following are the
drawbacks with the SG you are using.

1.SG views two physical ASPs, eventhough you have one physical ASP.
  In override traffic mode,as per your mail an ASP has registered with
  two SGPs(SGP1 and SGP2) using the same ASP id in the ASP_UP message
  then ASP sends ACTIVE message to SGP1 so whole AS becomes active at SG.
  
  When SGP2 receives ACTIVE message, SGP1 sends NTFY(ALT_ASP_ACT) with
  the same ASP id. This is not a correct behaviour of handling override 
  traffic mode. If the complete physical ASP goes down, then
  alternate(standby) ASP should be able to send ACTIVE message but you can
  not achieve this with your current configuration. 
 
2.NTFY messages ALT_ASP_ACTIVE and ASP_FAILURE have ASP id but the same
  ASP id is used in other SGPs.

--Samuel



> 
> Thanks,
> Krishna
> 
> -----Original Message-----
> From: Brian F. G. Bidulock [mailto:[email protected]] 
> Sent: Thursday, February 09, 2006 12:21 PM
> To: Munnaluru, Krishna
> Cc: [email protected]
> Subject: Re: [Sigtran] SG view of the ASP
> 
> Krishna,
> 
> I suppose you could try adding ASP Id to the ASP Up message and see
> if the SG recognizes the ASP as one.
> 
> However, as Ille suggests, perhaps the problem is the SG's traffic
> mode (rather than the AS's traffic mode).
> 
> If the SG really believes that the ASP is two distinct ASPs, it should
> be sending a NOTIFY("Alternate ASP Active") from SGP1.  If it does not,
> IMO it is just a bug, so, perhaps the SG does not truly support Active/
> Standby mode.
> 
> --brian
> 
> 
> Munnaluru, Krishna wrote:                    (Thu, 09 Feb 2006 11:34:46)
> > Brian,
> > 
> > This is how it is affecting my expected behavior.
> > 
> > Note: Currently I have only one ASP but in future I intend to add a
> > standby ASP. Hence I use the trafficmode=override in the messages.
> Also
> > the desired behavior is that the ASP to laodshare the traffic going to
> > the SG among the two SGPs.
> > 
> > The problem showed up during the following scenario:
> > 
> > The ASP comes up, establishes associations and sends ASP UP message
> > (ASPIdentifier = 10007) to both SGPs for which the SGPs respond with
> ASP
> > UP ACK. 
> > 
> > The ASP sends ASP ACTIVE (trafficmode=override) with a routing context
> > for the AS to the SGP1 and the SGP1 responds with ASP ACTIVE ACK. The
> > status on the SG shows that the AS is active on SGP1 and inactive on
> > SGP2.
> > 
> > Later the ASP sends ASP ACTIVE (trafficmode=override) with the same
> > routing context to the SGP2 and the SGP2 responds with ASP ACTIVE ACK.
> > The status on the SG shows that the AS is active on SGP2 and inactive
> on
> > SGP1. I was expecting the AS to be active on both SGPs since the ASP
> had
> > sent ASP ACTIVE to both SGPs.  This was not what I was expecting.
> > 
> > The explanation given by the Third party SG team is that since they
> > treat association from SGP1 to ASP as one ASP (ASP1) and the
> association
> > from SGP2 to ASP as a separate ASP (ASP2), they are over writing the
> > status when the SGP2 received the ASP ACTIVE message from the ASP.
> They
> > suggest that I put the trafficmode=loadshare and that would solve the
> > problem.  So I am really confused.
> > 
> > Hope this helps.
> > 
> > Thanks,
> > Krishna
> > 
> 
> -- 
> Brian F. G. Bidulock
> [email protected]
> http://www.openss7.org/
> 
> 
> 
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