Subject: M3UA: Impact of missing changeover

From: "MOUILLAUD,FRANCOIS (Non-HP-France,ex2)" <[email-masked]>
Date: Wed, 12 Sep 2001 18:42:19 +0200

Hello,

Some time ago (July 11, but I lost the initial mail), the
issue of missing changeback in M3UA (thread: Changeback Issue)
was raised. I am wondering what happens in the changeover.
Sorry if I missed previous debates on this, but I wonder 
what will happen with the current draft text.

In a paralell combined linkset arrangement, SP has SS7 links
to two distinct SG/STP, each connected by an ASP to the same SPMC.
The paralell linkset is between the SP and the SPMC.
Say each SG/STP has two SS7 links to the SP. Link 1 of SG1 fails.
Some of the traffic that was handled by the link say SLS=0010 will
be diverted to one of SG2 links. A COO message is sent to the SG2.

How do you expect SG2 to react and have this SLS traffic diverted
by the ASP? I would currently expect SG2 to acknowledge the COO,
but no message being sent to the ASP, traffic inbalance will occur
and the SP will keep sending messages with that SLS 0010 for SG1.
This means SG1 needs a link to SG2 (and if this link is down,
the messages with SLS 0010 from the ASP will be lost: clearly not
an acceptable situation).

If now the second link fails as well on SG1, the situation is
probably better because I expect SG1 to send a DUNA to SP, and so
the SP will know what to do. SG2 will also acknowledge the new COO,
but the ASP will have its traffic diverted. 

Is the conclusion that SLS arrangements in a combined linksets
with M3UA MUST be such that SLS can only be diverted within a linkset?

Thanks,
Francois Mouillaud.

---
You are currently subscribed to sigtran as: [email-masked]
To unsubscribe send a blank email to [email-masked]

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 12 Sep 2001 12:36:39 -0500

Francois,

What you describe is part of the issue raised.  M3UAv8 has no
provisions for exchanging anything like COO between SGP and
ASP, either within or between associations.

It was discussed briefly again in the thread "IPSP cases" (which
was a little out of place).

I believe that Correlation Id/Ack has been added to the draft
to permit this, however, we have not seen the text yet.

Greg/Janvier?

--brian

MOUILLAUD,FRANCOIS (Non-HP-France,ex2) wrote:  (Wed, 12 Sep 2001 18:42:19)
> You are currently subscribed to sigtran as: [email-masked]

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

---

---

From: Greg Sidebottom <[email-masked]>
Date: Thu, 13 Sep 2001 00:53:50 -0400

Hi Brian,

I added your text for the Correlation Id parameter in the Iss9 draft to
support the Broadcast traffic mode.  I'm not yet aware of a Correlation Ack
proposal.  I haven't read the "IPSP cases" thread yet though - I am still
catching up.  Can you fill me in on the proposal?

Thanks,

   Greg

----- Original Message -----
From: "Brian F. G. Bidulock" <[email-masked]>
To: "sigtran" <[email-masked]>
Sent: Wednesday, September 12, 2001 1:36 PM
Subject: Re: M3UA: Impact of missing changeover

> > To unsubscribe send a blank email to
[email-masked]
>
> --
> Brian F. G. Bidulock
> [email-masked]
> http://www.openss7.org/
>
>
> ---
> You are currently subscribed to sigtran as: [email-masked]
> To unsubscribe send a blank email to
[email-masked]

---

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 13 Sep 2001 00:41:05 -0500

Greg,

See the thread "M3UA: Changeover between ASPs" for the initial
proposal (back in May).

However, I don't believe that it is really necessary to add a
Correlation Ack.  Correlation Id could be used for other than
Broadcast modes to acheive better failover loss, duplication and
missequencing between SGP on SCTP CDI.  When switching traffic
between SGs, controlled rerouting procedures are more applicable
than changeover procedures and the ASP is always at its discretion
to perform them.

M3UA still lacks acceptable procedures for changeover and changeback
between ASPs and SGPs in all modes but Broadcast.

I can think of several approaches to using the existing Correlation
Id to assist with changeover between SGP or between ASPs.  The
best peforming and least complicated one is to tag the first DATA
in each association with a Correlation Id/ASP Id.  When and SGP
switches traffic from one ASP to another, it tags all data which
was sent by SCTP but not acknowledged with the corresponding
Correlation Id/ASP Id.  The receiving ASP can then determine which
messages are duplicates and which are not.  The same in the SGP
direction.

--brian

Greg Sidebottom wrote:                             (Thu, 13 Sep 2001 00:53:50)

---

---

From: Greg Sidebottom <[email-masked]>
Date: Thu, 13 Sep 2001 00:53:50 -0400

Hi Brian,

Thanks,

   Greg

----- Original Message -----
From: "Brian F. G. Bidulock" <[email-masked]>
To: "sigtran" <[email-masked]>
Sent: Wednesday, September 12, 2001 1:36 PM
Subject: Re: M3UA: Impact of missing changeover

---