H.225.0 says that the extension bit cannot be 0. Setting it to 1 violates the standard. Besides, there may be compliant EPs that justifiably assume this bit to be set correctly. As with all non-compliant behavior, the result is non-determinant. The compliant EP may, for example, accept the transgression, reject the call, or crash. We've been through this before. We'll just have to agree to disagree.
Paul Long Smith Micro Software, Inc.
-----Original Message----- From: Horvath Ernst [mailto:ernst.horvath@SIEMENS.AT] Sent: Wednesday, November 03, 1999 11:39 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: AW: presentationIndicator and Calling Party Number
Paul,
from H.225.0 subclause 7.2.2 it is clear that the general encoding rules of Q.931 apply. Setting bit 8 of octet 3 to 1 was correct as long as octet 3a was forbidden in H.225.0. Now, since octet 3a is allowed, bit 8 must follow the rules for an extension bit.
I recognize your backwards compatibility issue, but a proper implementation of Q.931 encoding and error rules should allow an old implementation to cope with this situation gracefully.
Ernst Horvath Siemens AG
-----Ursprüngliche Nachricht----- Von: Paul Long [mailto:plong@SMITHMICRO.COM] Gesendet am: Mittwoch, 3. November 1999 17:33 An: ITU-SG16@mailbag.cps.intel.com Betreff: Re: presentationIndicator and Calling Party Number
H.225.0 has always required that the octet-3 extension bit in calling party number be set to 1. Regardless of the reason for it being this way, setting it to 0 renders an EP non-compliant and risks interoperability problems. In addition, H.225.0 cannot be changed in this regard in a future version without risking interoperability problems.
Paul Long Smith Micro Software, Inc.
-----Original Message----- From: Horvath Ernst [mailto:ernst.horvath@SIEMENS.AT] Sent: Wednesday, November 03, 1999 10:06 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: AW: presentationIndicator and Calling Party Number
Hi,
see inserted answers below.
Ernst Horvath Siemens AG
-----Ursprüngliche Nachricht----- Von: henri.maenpaa@NOKIA.COM [mailto:henri.maenpaa@NOKIA.COM] Gesendet am: Mittwoch, 3. November 1999 15:55 An: ITU-SG16@mailbag.cps.intel.com Betreff: presentationIndicator and Calling Party Number
All,
First, there seems to be some inconsistency about the use of 3a octet of Q931 CallingPartyNumber field in H.225.0. Hopefully this is just an editorial mistake.
Q931 (05/98) states the following (chapter 4.5.1 Coding Rules): c) An octet group is formed by using some extension mechanism. The preferred extension mechanism is to extend an octet (N) through the next octet(s) (Na, Nb, etc.) by using bit 8 in each octet as an extension bit. The bit value "0" indicates that the octet continues through the next octet. The bit value "1" indicates that this octet is the last octet. If one octet (Nb) is present, also the preceding octets (N and Na) must
be present.
Whereas H.225.0v3 (09/99) seems to do the opposite in Calling Party Number field by telling to set the octet 3 extension bit to 1, and use octet 3a as "encoded following the values and rules of table 4-9/Q931."
[EH:] This can only be an oversight. The correct text must be for bit 8 of octet 3: Set to '1' if octet 3a is not present, set to '0' otherwise.
Second, I am also wondering why H.225.0 currently allows two methods for CLIP/CLIR indication: Octet 3a and the ASN.1 side presentationIndicator IE. OK,
the standard
states strictly that octet 3a overrides the other, and
therefore there
should not be insolvable conflicts at the receiving entity, but still why they were both included?
[EH:] H.225.0 allows two places to include calling party information (both optional): the Calling party number information element and the sourceAddress field in User-user. The presentationIndicator field is intended for the latter one.
-Henri Mäenpää, Nokia