Subject: [Sigtran] SP Status double endpoint

From: [email-masked]
Date: Mon, 20 Aug 2007 16:17:36 +0800

hi,
in MTP3 Protocol, signal link test is used for check link status of the
other endpoint;and in SCCP protocol,IT test for sccp connect

section is used for check section's status of the other endpoint .

why not M3UA hasn't ASP Status test for checking the status ,it is very
important to correct the status error when the other endpoint has not the
identical status.

thanks a lot!

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Mon, 20 Aug 2007 06:05:41 -0600

chen.puran,

M3UA has both BEAT and BEAT Ack as well as HEARTBEAT at SCTP level, which
is as much as MTP3 has.

--brian

[email-masked] wrote:                 (Mon, 20 Aug 2007 16:17:36)

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

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Tue, 21 Aug 2007 06:46:49 -0600

chen.puran,

It knows because it knows the state when the association was formed (DOWN)
and all of the exchanges since (SCTP is reliable, will not lose a message).

Still better.  Stupid MTP3 loses messages and so has to audit ever so often.

--brian

[email-masked] wrote:                        (Tue, 21 Aug 2007 08:59:46)
> thanks£¬
> 
> but£¬HEARTBEAT of M3UA can not distinguish every SP Status in every AS
> ,when SP is contained by more than one AS.
> 
> it just can konw SP is BAD OR GOOD,can not konw SP is DOWN,INACTIVE,ACTIVE
> In every AS.
> 
> maybe HEARHBEAT Message need to be extended,contain some parameter(s) to
> distinguish SP Status in every AS ?
> 

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

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 22 Aug 2007 04:20:45 -0600

chen.puran,

[email-masked] wrote:                      (Wed, 22 Aug 2007 08:59:12)
> thanks£¬brain
> 
> but£¬because of a distributed software system & Client/server Mode,When
> Server change The ASP Status
> 
> unexpectedly,it(RFC4666) can not inform Client to Change SP Status in the
> same way or Restore to correct Status.
> 
> it may cause Server to be In DOWN/INACTIVE ,Client to be In ACTIVE,And Can
> not restore to correctly Status.

Oh, yes it can: the unsolicited ASP-INACTIVE-ACK and unsolicited ASP-DOWN-ACK
procedures.  The SGP sends ASP-INACTIVE-ACK to push the ASP to the inactive
state for an AS and ASP-DOWN-ACK to push an ASP down.
> 
> maybe,SCTP is reliable,but interface between M3UA and SCTP is not.
> MTP3 have change and change back ,it is maybe more reliable than M3UA.

SCTP does not misorder messages delivered to the User, MTP does.  SCTP does
not drop messages in the middle, MTP does.

> 
> so,i think check every ASP STATUS in AS is very necessary,and in fact,we
> have encounter the ASP Status ERROR.

Not necessary.

--brian

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

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 23 Aug 2007 05:06:05 -0600

chen.puran,

[email-masked] wrote:                 (Thu, 23 Aug 2007 09:19:22)
> 
> chenpr£ºbut when Server  Changes SP Status unexpectedly,it can send:the
> unsolicited  ASPSM or
> ASPTM Message?  RFC4666 does not contain the actions ,and,i have asked you
> about the unexpect ASPSM/ASPTM Message several weeks ago

RFC 4666

4.3.4.2.  ASP-Down Procedures

   ...

   If the ASP receives an ASP Down Ack without having sent an ASP Down
   message, the ASP should now consider itself to be in the ASP-DOWN
   state.

4.3.4.4.  ASP Inactive Procedures

   ...

   ...                 If the ASP receives an ASP Inactive Ack without
   having sent an ASP Inactive message, the ASP should now consider
   itself to be in the ASP-INACTIVE state.  If the ASP was previously in
   the ASP-ACTIVE state, the ASP should then initiate procedures to
   return itself to its previous state.

> 
> ,but from your answer,we think your means is :if ASP have not sended
> ASPSM/TM,SGP does not send unsolicited ASPSM/TM.

Read the passages above from the RFC.

> 
> if SGP Send ASP_INACTIVEACK,But ASP is In ASP_DOWN,it will go to
> ASP_INACTIVE? your answer is ASP Must Be In ASP_ACTIVE?

No.  Any message received by an ASP in the ASP_DOWN state is unexpected.
Until ASP-UP-ACK is received, the SGP is not allowed to send messages.

> £££££££££££££££¡·please see this section,so your means is
> ASPSM/TM not SGP'S Error ,Just is ASP'S Message's Sort Error? but SGP may
> enter into  unexpected SP Status beacause of software
> exception.

Broken results can be expected from broken software regardless of the
protocol.  Solution: fix the software.

> 
> but M3UA have not change and change back,so when ASP is bad,Mesage will
> lost,MTP does not.
> and M3UA have Middle Point,so M3ua Drop The Messge. SCTP is equal to
> MTP2,so SCTP Can not Compare with MTP3.

See draft-bidulock-sigtran-corid-05.txt for equivalent procedures.

--brian

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

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From: [email-masked]
Date: Fri, 24 Aug 2007 09:02:57 +0800

>protocol.  Solution: fix the software.

--->(jacky chen) sorry,i do not agree with you ,i think protocol should be
perfect to deal with it
,because it will cause traffice failure ,not automatic restoration.it can
not be receptible to the people using the equipment.

>See draft-bidulock-sigtran-corid-05.txt for equivalent procedures.

------->(jacky chen) it is so complex,i think RFC4666 MAY use change and
changeback procedure like MTP3, maybe it will be easy,
just add news messages and procedure like MTP3 does.

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From: "Asveren, Tolga" <[email-masked]>
Date: Fri, 24 Aug 2007 07:55:13 -0400

> just add news messages and procedure like MTP3 does.
I was wondering when this will come up again :-) . I did not follow this
thread in full but could you summarize shortly why you believe that this
is needed?

  Thanks,
  Tolga