Paul,
Please see my email posted today on this issue describing the implications.
- Logan
Paul Long wrote:
Bancroft,
These components are in a CHOICE type, so the clause that you specify has nothing to do with our discussion. I think your response assumes they are in a SEQUENCE type.
Also, by "do not use," I meant that, upon receipt, these choices are to be semantically treated as another, generic choice, undefinedReason and that they are to no longer be transmitted. Again, these are CHOICE, not SEQUENCE components.
Paul Long Smith Micro Software, Inc.
-----Original Message----- From: Bancroft Scott [mailto:baos@OSS.COM] Sent: Friday, October 06, 2000 4:17 AM To: ITU-SG16@MAILBAG.INTEL.COM Subject: Re: Error in H.323v3 ASN.1
On Thu, 5 Oct 2000, Paul Long wrote:
<snip>
Unless I am misunderstanding what you are saying, the "-- do not use" will not work if the receiver is using an earlier version in which the "-- do not use" type is defined, for it violates X.680 clause 24.14:
24.14 A value for a given extension addition type shall not be specified unless there are values specified for all extension addition types not marked OPTIONAL or DEFAULT that lie logically between the extension addition type and the extension root.
NOTE 1 -Where the type has grown from the extension root (version 1) through version 2 to version 3 by the addition of extension additions, the presence in an encoding of any addition from version 3 requires the presence of an encoding of all additions in version 2 that are not marked OPTIONAL or DEFAULT.
Omitting OPTIONAL and DEFAULT from an extension addition definition means that an extension addition value is mandatory in messages that are originated by an implementation in which such extension additions are defined, which implies that an encoding cannot have a missing mandatory extension addition value followed by any other component.
The only way that interoperability can be achieved here is by the older version H.225 spec being changed to add OPTIONAL to those items marked with "-- do not use". It will have no effect on the bits on the wire, other than to make such encodings valid.
Bancroft Scott Toll Free :1-888-OSS-ASN1 OSS Nokalva International:1-732-302-0750 baos@oss.com Tech Support :1-732-302-9669 x-1 1-732-302-9669 x-200 Fax :1-732-302-0023
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