Subject: [Sigtran] [M2UA, IUA] Stream to be used for ASPTM messages

From: Santhana <[email-masked]>
Date: Wed, 03 Mar 2010 19:26:09 +0530

Hi Brian

            Which stream has to be used for ASPTM messages in M2UA and IUA ?

M2UA RFC(3331) states: 

In section 4.2.1

   All MGMT messages, except BEAT and BEAT Ack, SHOULD be sent with
   sequenced delivery to ensure ordering.  All MGMT messages, with the
   exception of ASPTM, BEAT and BEAT Ack messages, SHOULD be sent on
   SCTP stream '0'.  All ASPTM messages SHOULD be sent on the stream
   which normally carries the data traffic to which the message applies.
   BEAT and BEAT Ack messages MAY be sent using out-of-order delivery,

      and MAY be sent on any stream.

===>As per this ASPTM should be sent on stream (other than 0)

On section 1.5.4.1  SCTP Stream Management
   SCTP Stream '0' SHOULD NOT be used for MTP2 User Adaptation (MAUP)
   messages (see Section 3) since stream '0' SHOULD only be used for ASP
   Management (ASPM) messages (see Section 4.3.3).
And RFC explains all the ASPSM/ASPTM messages as ASPM messages. So there
seems to be a contradiction here in RFC.

===>As per this ASPTM should be sent on stream 0

And for IUA is SCTP stream management aligned(same as) with M2UA ?
 
Pls clarify.
 
Regards
Santhanakrishnan

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 3 Mar 2010 16:42:48 -0700

Santhana,

Please see comments below:

Santhana wrote:                            (Wed, 03 Mar 2010 19:26:09)

---X--snip--X---
> And RFC explains all the ASPSM/ASPTM messages as ASPM messages. So there seems 
> to be a contradiction here in RFC.
> 

Yes, ASPM should read ASPSM in section 1.5.4.1 above.

> And for IUA is SCTP stream management aligned(same as) with M2UA ?

No.

The reasons for sending ASPTM and BEAT/ACK on a traffic stream
are primarily to avoid message loss due to deactivation of the
AS (at SGP or ASP) before the last data message has arrived for
the deactivated traffic.  Sending the messages last and
sequenced on the data stream ensures that, once the acknowledge
is received, no messages are in transit to the peer UA.

This is important to meet SS7's stringently low message loss
requirements.

See http://tools.ietf.org/html/draft-bidulock-sigtran-corid-05
for other procedures that can reduce message loss that are in
fitting with this use of ASPTM and BEAT/ACK.

ISDN has far less stringent requirments and, thus, the procedures
are not necessary for IUA and IUA sends all ASPM messages on
stream 0.

Historically, IUA was written first and M2UA came second
borrowing a lot from IUA.  Section 4.2.1 was updated correctly,
but Section 1.5.4.1 still uses the IUA statements, which do
not apply to M2UA.

Please submit an Errata against RFC 3331 for this.

--brian

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

---

From: Xiangsong Cui <[email-masked]>
Date: Thu, 04 Mar 2010 11:13:08 +0800

Dear folks,

We submitted two drafts about the sigtran extension, 
Although the Sigtran WG has been concluded, I still would like to 
talk about these topics in sigtran list before the discussion in tsvwg list.

The drafts may be found by

http://tools.ietf.org/id/draft-cui-tsvwg-snm-ps-00.txt
Abstract: 
   Sigtran is widely applied in the telecommunication network but there 
   are still some issues. This document briefly describes some concerned 
   scenarios and presents the association changeover and Sigtran routing 
   management problems. The goal of this document is to analyse the 
   existing shortage of Sigtran and discuss the desirable improvements. 

http://tools.ietf.org/id/draft-cui-tsvwg-assoc-changeover-00.txt
Abstract:
   Sigtran specifies association-level reliable transport for signaling 
   using SCTP, but in some scenarios a single association failure's 
   reliability mechanism is not sufficient to achieve telco reliability. 
   This document specifies procedures for an SCTP association changeover 
   solution which will enable applications to meet a higher degree of 
   availability. Two generic changeover solutions are presented in this 
   document. One is implemented inside the SCTP protocol stack and the 
   other requires SCTP and ULP to work in collaboration. 

These extensions are expected to improve the performance of sigtran 
network, especially for telecommunication network, what do you think
about them?

Any comments are appreciated!

Thanks and best regards
Xiangsong