AW: H.225.0 v4 inconsistencies/errors found

Horvath Ernst ernst.horvath at SIEMENS.AT
Thu Jun 8 04:42:56 EDT 2000


having been through it a number of time does not solve a problem at all
unless we fix it.

Facts are:
1) Octet 3a is an optional octet in calling party number IE. It may or may
not be present.
2) Q.931 clause 4.5.1, which is mandatory for H.225.0 (see clause 7.2.2),
specifies the use of the extension bit to indicate presence or absence of
optional octets.
3) My interpretation of of H.225.0 is that Q.931 clause 4.5.10
applies for the coding of calling party number, including the use of octet 3
bit 8 as extension bit.
4) As octet 3a was not allowed in H.323v1, bit 8 in octet 3 was correctly
set to '1'.
5) Octet 3a, when present, poses a problem for v1 in any case, independent
of bit 8 of octet 3!
6) Clearing the call if an optional information element is flawed is not
correct - it should be ignored. Clearing is only correct for erroneous
mandatory or 'comprehension-required' optional IEs. Calling party number is
not 'comprehension-required'.

Ernst Horvath
Siemens AG

> -----Ursprüngliche Nachricht-----
> Von: Paul Long [mailto:Plong at SMITHMICRO.COM]
> Gesendet am: Donnerstag, 08. Juni 2000 05:03
> An: ITU-SG16 at
> Betreff: Re: H.225.0 v4 inconsistencies/errors found
> Karl,
> We've been through this before. Allowing the extension bit in
> octet 3 to be
> set to 0 causes H.225.0v4 to be inconsistent with earlier versions and
> potentially causes insurmountable backwards-compatibility
> problems between
> v4 EPs and v1, v2, and v3 EPs. For pre-v4 EPs, this bit shall
> not be set to
> 0 under any circumstances. Since the calling EP cannot know
> the version of
> the called EP before it sends Setup, it would be sending an
> IE that would
> contain invalid content for a pre-v4 EP. According to Q.931,
> the receiving
> EP would then be required to terminate the call with
> ReleaseComplete. A safe
> solution would be to add a new Calling Party Number field
> where this bit is
> allowed to be set to 0.
> Paul Long
> Smith Micro Software, Inc.
> "Primum non nocere"
> -----Original Message-----
> From: Klaghofer Karl ICN SIB NL D1
> [mailto:Karl.Klaghofer at ICN.SIEMENS.DE]
> Sent: Wednesday, June 07, 2000 10:29 AM
> Subject: H.225.0 v4 inconsistencies/errors found
> Rich, and others
> Please find below comments I have in the area of Calling
> Party Number IE
> and
> the ASN.1 elements ScreeningIndicator and PresentationIndicator.
> Comments no. 1-4 should be corrected by the editor in v4, since these
> are
> inconsistencies/errors. Comment 5 could be solved later.
> 1) Calling Party Number IE (octet 3 extension bit 8)
> The H.225.0v4 definition looks as follows:
> -       Set to '1'
> This is not compliant with the extension bit handling used in
> Q.931 and
> H.225.0. It should be corrected in v4 (v3 impl guide) to read:
> -       Set to '1' if octet 3a is not present; set to "0" if
> octet 3a is
> present.
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