Subject: [Megaco] Specifying values in AuditCapabilities responses

From: Nigel Williams <[email-masked]>
Date: Fri, 19 Jul 2002 14:47:00 +0100

Hello List,

When auditing capabilities it is possible that the MG supports multiple
values for a property or parameter.  The RFC says the following on this.

  7.2.6 AuditCapabilities

   [...] Descriptors may be repeated where there are multiple possible
values. 

If the AuditCapabilities reply only includes a single property or parameter
with a value then this is practical.  For example, it would be possible to
return one Media Descriptor with Echo Cancellation (from the TDM Circuit
Package) set to "On" and another with it set to "Off".  However, if there
are many possible values or many properties and parameters then there seem
to be two issues.

1. If the value type is a number then an unfeasibly large number of
descriptors would be required.

2. If there is more than one property or parameter that takes a value then
it would be necessary to enumerate the different combinations of the
supported values.  This could lead to an even larger number of descriptors
being required.

The obvious solution to this is to use ranges or lists of values.  However,
the RFC says the following on this.

   Values assigned to Properties may be simple values 
   (integer/string/enumeration) or may be underspecified, where more 
   than one value is supplied and the MG may make a choice: [...]

This does not mention AuditCapablities.  Does anyone have an opinion on
whether using lists and/or ranges for AuditCapabilities should be considered
valid?

Another possible solution would be to use the CHOOSE wildcard ("$") in cases
where all values are valid.  This could save sending a long list of
enumerated type values or a range such as [0:4294967295].  Does anyone have
any comments on whether this should be considered valid?

Thanks in advance
Nigel

Nigel Williams
Voice Networking Group
Data Connection Ltd
Tel: +44 20 8366 1177
Fax: +44 20 8363 1039
Email: [email-masked]
Web: http://www.dataconnection.com

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From: Christian Groves <[email-masked]>
Date: Mon, 22 Jul 2002 17:11:57 +1000

G'Day Nigel,

I don't recall any text forbidding you to use ranges in this respect, so thus I
would consider this valid. The text you refer to in 7.2.6 is only relevant in
the case that you audit different descriptors in the one audit.

Regards, Christian

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From: Christian Groves <[email-masked]>
Date: Mon, 22 Jul 2002 17:11:57 +1000

G'Day Nigel,

Regards, Christian