Subject: [Sigtran] SUA Question - Trasaction ID based Routing

From: "Doss, James" <[email-masked]>
Date: Thu, 10 Jul 2003 12:27:16 -0700

Hi John,
 
In SUA spec draft version 15.
 
With reference to Page 112 . SCTP Associations Fig 2 Signaling Gateway Architecture.
 
Will the transaction ID based routing the responses to the ASP originated the transaction.
 
Ex scenario:
 
ASP1 from AS3 originated a transaction using SG1 towards SS7 network.
 
The Response for this  QUERY hits SG2 (Assuming SG1 and SG2 are mated).
 
Question 1:
 
At this condition will SG2 route this message back to ASP1.
 
Question 2: 
 
Will SG1 and SG2 share the information about Open Transactions originated from the ASPs(1..n).
Or Else how the Transaction ID based routing (key ) will work.
 
Please correct me if I understood the routing in a wrong way.
 
Thanks and regards
James Doss
Sr Software Engineer
VeriSign Inc,
Norcross, GA

---

From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 10 Jul 2003 14:13:28 -0600

James,

Doss, James wrote:                                                                   (Thu, 10 Jul 2003 12:27:16)
>    With reference to Page 112 . SCTP Associations Fig 2 Signaling Gateway

Page 112 would be the Author's Addresses...

>    Please correct me if I understood the routing in a wrong way.

The TID Label approach described in 4.7.2 and 4.7.3 and A.3.1 will work for
simple (and correct) Query/Response pairs in protocol class 0 with operations
class 3 (no return on error and no rejects or aborts) if you have sufficient
control of the TCAP application that you can control the range of TIDs that
it assigns per ASP.  Protocol class 0 or 1 and operations class 1 or 2 (return
on error, rejects and aborts) will fail because the returned error does not
have sufficient information to determine the ASP from TID (because the ASP's
TID is not present in the message), or if you cannot strictly control the way
that the TCAP layer assigns TIDs at an ASP.

So, it works for only the most trivial of applications.  For more
sophisticated applications, see draft-bidulock-sigtran-tua-01.txt

A superior registration procedure was proposed whereby the ASP could inform
both SGs of the ASP ownership of a TID on the BEGIN/QWP/QWOP, but the broken
TID Label approach slithered its way into SUA.

The DRN Label approach is broken worse.  For serious TCAP applications, use
TUA.

The last thread was "SUA-09: SCCP Connections and TCAP Transactions" from
Jan 2002.  (At that time it was too late to make changes--hah!)

Before that there is a discussion in "SUA Decision needed - handlin multiple
SGs" where it was determined that broken procedures are ok if those broken
procedures have a couple of people to nod their heads at each other.

See especially "[SUA Issue 14] Changes and addtions required for decoupled
operation."  These problems go back to August 2001.

Perhaps Verwimp is still around to defend the Label approach, or perhaps
not.

--brian

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

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