FW: Remarks on H.450.x and H.225.0

Orit Levin orit at RADVISION.COM
Tue Dec 2 16:18:55 EST 1997

Scott Petrack wrote:
> This problem has bothered me for a long time. I considered many times
> introducing into the VoIP Forum an OID which would be used precisely as Jim
> suggests, so that the entire industry could signal a SEQUENCE of
> NonStandardParameter.

So do you mean something like this?:

    NonStandardParameter ::=SEQUENCE
        nonStandardIdentifier NonStandardIdentifier, -- e.g., VoIP OID
        data OCTET STRING

where data contains the following:

    SET SIZE (1..256) OF NonStandardParameter

BTW, I believe that it should be a SET OF and not a SEQUENCE OF, because
SEQUENCE OF implies that the order is important, and I don't think that
is the intent here. Or is it?

One way to handle this for _future_ syntax is to define a type that is
itself a set of NonStandardParameters, as in:

    NonStandardParameters ::=SEQUENCE
        nonStandardParameters SET SIZE (1..256) OF NonStandardParameter

> One example of why this is necessary is so that when someone else uses our
> stack we can both pass non-standard parameters.

Just to play devil's advocate, can you give an example of a specific
need for this? A quick review of H.245 didn't turn up very many
situations where aggregation isn't handled already at a higher level or
where it just doesn't make sense in the first place.

Here is an example of where iteration is expressed at a higher level.
The capability table contains multiple capabilities, so there is no need
for a single capability containing multiple NonStandardParameters--just
add more nonStandard capabilities. Case in point: it makes no sense,
IMO, for UserInputCapability to have a nonStandard CHOICE of multiple
NonStandardParameters, when multiple nonStandard UserInputCapabilities
would have served just as well. I agree with Dykstra--_I don't like more
than one way of doing the same thing._

An example of where multiple NonStandardParameters may not make sense in
the first place is in the NonStandardMessage type. Is there ever a need
to combine several NonStandardParameters in the same RequestMessage, for
example? IOW, these uses are atomic.

Paul Long___________________________http://www.cmpu.net/public/plong
Smith Micro Software, Inc.__________http://www.smithmicro.com/

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