Subject: M3UA: Loss of SGP connectivity

From: Amish Chana <[email-masked]>
Date: Wed, 29 Aug 2001 11:03:46 +0100

Hi all,

In section 1.4.4.2 ("Signalling Gateway Redundancy"), the text of the first 
paragraph states "Should an SGP lose all or partial SS7 connectivity and 
other SGPs exist, the SGP MUST terminate the SCTP associations to the 
concerned ASPs."

I think the above action is a bit extreme. Wouldn't a DRST be more 
appropriate in the event of partial SS7 connectivity loss or a DUNA if a SGP 
has lost all its SS7 conections?

Are any messages exchanged when the SGP tries to terminate an association?
Is there a routing key deregistration process?
Wouldn't we get a cyclic situation where the affected ASPs continuously try 
to re-establish their associations until the SS7 connectivity is 
re-established to its normal state?

Amish

_________________________________________________________________
Get your FREE download of MSN Explorer at http://explorer.msn.com/intl.asp

---
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, 29 Aug 2001 06:43:15 -0500

Amish,

We discussed this quite a lot.

Amish Chana wrote:   (Wed, 29 Aug 2001 11:03:46)
> other SGPs exist, the SGP MUST terminate the SCTP associations to the 

This was raised as an issue some months ago.  Yes, it is too extreme in
the case of partial loss of SS7 connectivity at an SGP.

> has lost all its SS7 conections?

A good case has been made for reserving DRST and DUNA for indicating
routing situations in the SS7 network at the SG level only (not at the
SGP level).  A proposal for using ASPIA Ack at the SGP to indicate loss
of connectivity on a per-SGP basis has been proposed on the thread:

 [M3UA /SUA] Gracefull shutdown of SGP

It would consist of the SGP sending unsolicited ASPIA Ack to all active
ASPs for the RCs which are affected by the partial SS7 outage and the SGP.
This permits the ASPs to alternately route traffic.

> Are any messages exchanged when the SGP tries to terminate an association?

If all traffic on the association is affected, rather than terminating the
association, the SGP can use the unsolicited ASPDN Ack procedure to force
the ASP to a down state.  Upon attempts or reattempts of the ASP to perform
the ASPUP procedure, the SGP could responsd with ERR("Management blocking").

> Is there a routing key deregistration process?

All routing keys are deregistered in response to forcing the ASP to the
down state with ASPDN Ack or upon loss of the association.

> re-established to its normal state?

The wording in section 1.4.4.2 is bad and is at issue.  Certainly the
SGP can allow the association to be formed (or remain) but resist all
further attempts to perform ASPUP or ASPAC by refusing with reason
"Management Blocking".

--brian

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

---

---

From: "Schantz, John" <[email-masked]>
Date: Wed, 29 Aug 2001 07:54:23 -0700

Amish,
	No, a partitioned SG model should be re-examined by those that plan
to implement such a "beastie".  The SNMM can not handle both the node view
and partitioned node view at the same time.  Since the single node view is
required to the SS7 network and the existing nodes migrating to the IP
transport, the draft must return the view for SNMM and its procedures back
to the node view.

	I know this doesn't answer your question since the procedures to
handle a partitioned SG do not exist.

John

> -----Original Message-----
> From: Amish Chana [mailto:[email-masked]]
> Sent: Wednesday, August 29, 2001 5:04 AM
> To: sigtran
> Subject: M3UA: Loss of SGP connectivity
> 
> 
> Hi all,
> 
> You are currently subscribed to sigtran as: [email-masked]
> To unsubscribe send a blank email to 
> [email-masked]
> 

---