Subject: [Sigtran] SUA Address Indicator

From: Warren Anthony Briggs <[email-masked]>
Date: Wed, 17 May 2006 07:56:48 -0400

Hi All,

Could you please clarify the following:

Q.713. section 3.4.1   states that bit 8 of the SCCP Address Indicator 
parameter is reserved for national use.   RFC 3868 appears to indicate 
that this bit is spare and always 0.  Am I interpreting this correctly 
or should this bit have a 1 to 1 mapping  when encoding from SUA to SCCP 
and vice versa?

thank you,
warren briggs.

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 17 May 2006 10:49:58 -0600

Warren,

Do you know of a case where bit 8 has a national assignment that is
actually in use?

--brian

-- 
Brian F. G. Bidulock    ¦ The reasonable man adapts himself to the ¦
[email-masked]    ¦ world; the unreasonable one persists in  ¦
http://www.openss7.org/ ¦ trying  to adapt the  world  to himself. ¦
                        ¦ Therefore  all  progress  depends on the ¦
                        ¦ unreasonable man. -- George Bernard Shaw ¦

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From: Warren Anthony Briggs <[email-masked]>
Date: Wed, 17 May 2006 13:21:28 -0400

Hi Brian,

no I do not know of any current applications using bit 8.  But I think 
its quite possible that it is in use somewhere. I am really attempting 
to get some consensus on how it should be interpreted. I think it makes  
to follow the SCCP specs as bit 8 of the Address Indicator is spare in 
SUA but I could not see this stated explicitly in RFC 3868.

regards,
warren

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From: Chris Benson <[email-masked]>
Date: Wed, 17 May 2006 11:38:27 -0700 (PDT)

Hi Warren,

It is my understanding that bit 8 of the SS7 SCCP Address Indicator is 
used to distinguish between a National and the International encodings of 
the SS7 SCCP Address (including the rest of the Address Indicator bits) 
and applies to the SS7 encoding only.

For example, SSN and PC indicator positions are swapped between Telcordia 
T1.112.3 Section 3.4.1 and ITU-T Q.713 Section 3.4.1 specifications. This 
is indicated by bit 8 being 1 or 0 respectively.  SUA has no such 
difference of encoding. Bit 8 of the SUA Address Indicator is spare 
because there is only one SUA Address and Address Indicator format 
specification (i.e. RFC 3868).

This is easy for SCCP --> SUA. I think that the SUA --> SCCP direction 
requires a priori knowledge of SCCP's National or International scope and  
thus SS7 encoding format.

This is only my understanding, and I would sure like to
know if it is incorrect.

With thanks, from Chris Benson.

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From: Warren Anthony Briggs <[email-masked]>
Date: Wed, 17 May 2006 15:22:17 -0400

Hi Chris,

Agreed and thanks, that is my understanding also. However I see no 
reason why bit 8 of the SUA Address Indicator is not encoded as per the 
SS7 SCCP's Address Indicator. At a minimum it would remove the 
requirement, as you pointed out, for the SG to have prior knowledge of 
the SCCP's NI.

regards,
Warren

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From: "Brian F. G. Bidulock" <[email-masked]>
Date: Wed, 17 May 2006 17:01:48 -0600

Chris,

This use of bit 8 has not been in use in the NA network since about 1988.

I know of no vendor equipment, even IGW switches, that support that use.
No local, tandem or domestic toll switch in the NA network has supported
it since.

As the use of bit 8 is long deprecated, it must coded zero regardless of
whether it maps to the ancient application or not (see SS7 interoperability
rules).  So I think the matter is moot and no change is needed to SUA.

--brian