Subject: Re: [Sigtran] SUA: GTT function placement

From: [email-masked]
Date: Thu, 2 May 2002 16:35:01 +0530

Hi Marc,

Please see some comments below ..

Best Regards,
-Sandeep

"Lamberton, Marc" <[email-masked]> on 05/02/2002 03:30:44 PM

To:   [email-masked]
cc:    (bcc: Sandeep Mahajan/HSS)

Subject:  [Sigtran] SUA: GTT function placement

Hi all,

In the SUA draft the GT Translation function is positioned in the "SG as
relay-point". This is clear for inbound messages coming from the SS7 network
with "route on GT" in their called address.

For outbound messages (from AS/ASP to SS7) it might be possible to perform the
GTT either in the SG or in the ASP. In a multiple SG's configuration, it seems
that GTT is required in the ASP to perform SG selection; if the ASP is connected
to multiple SG's; the ASP can store the availability of remote PC/SSN thru each
SG, and then use this information to perform SG selection. For outbound messages
with "route on GT" in the called address, the ASP must perform the GTT to derive
a PC, and then select a SG capable to reach that PC.
Sandeep >> This sounds reasonable to me, a small comment
According to section 2.3.2 of Q.714 if SCCP receives message from local User
with RI = "Route on GT" and point code included in the called address parameter
is not the local point code, SCCP should send the message to node serving that
point code. If point code is not included in the address parameter or point code
included is the local point code translation should be performed in the local
Node. If we apply the same to SUA also ( which I think we should) GTT may
conditionally be performed at ASP.

If the ASP performs a GTT on outbound messages, it would be nice to add the
derived PC into the SUA message called address, and then the SGP uses that PC
for the MTP3 DPC. Can we assume that a SGP receiving a message from an ASP with
a called address containing [RI="route on GT" , a GT, and a PC] will not perform
its own GTT and will use that DPC value for the MTP3 header ?
Sandeep >> According to section 2.3.1, point 3 of Q.714, if a CR or CL message
is received from MTP3 and RI is set to "Route on GT", Translation must be
performed. If the same is applicable for SUA also, if SUA layer at SG receives
message with RI = "Route on GT", it should perform translation. If the result of
translation is a point code that is accessible in SCCP network, SUA should pass
this message to SCCP layer at SG/SGP, where no translation should be needed as
point code included in the called address will not be the point code of local
Node.

Do you foresee any other issues or advantages to do the GTT in the ASP as well ?

Marc Lamberton
Compaq TPU
[email-masked]
Tel. (33)4 9295 5598

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Thu, 2 May 2002 06:28:38 -0500

Sandeep,

Please see comments below...

[email-masked] wrote:                            (Thu, 02 May 2002 16:35:01)
-X-snip-X-

> conditionally be performed at ASP.

That would be a rather pschyzophrenic GTT function: half performed at ASP,
half performed at SG.  There is no need to perform GTT at the ASP, the CDPA
is sent to the SG and the SG performs GTT.

> point code included in the called address will not be the point code of local

If you check Q.714, you will find that the point code *can* be the point code
of the local node.  There is nothing stopping two SCCP-Users from talking to
each other locally via the SCCP-Provider.

--brian

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