Re: Empty stream-level statistics descriptor

Hello Mike,

This issue has been dealt with in the latest Implementors' Guide. i.e.

6.22 Empty Statistics Descriptor

Description: The text of clause 7.1.15/H.248.1 indicates that the MGC 
may send an empty Statistics Descriptor to the MG: “The receipt of an 
empty descriptor means that no statistics shall be collected for the 
specified termination”.
Sending an empty Statistics Descriptor is possible using the binary 
encoding of Annex A; but impossible using the text encoding of Annex B. 
The text encoding needs to be fixed to allow an empty Statistics Descriptor.

Reference: Subject: RE: H.248.1 Sub-series IG for review
Date: Sun, 27 Apr 2008 21:35:56 +0100
From: Elad Chomsky <[email protected]>

[Begin Correction]
B.2 ABNF specification

; Time = hhmmssss
Time = 8(DIGIT)

statisticsDescriptor = StatsToken [LBRKT statisticsParameter 
*(COMMAstatisticsParameter) RBRKT]

;at-most-once per item
statisticsParameter = pkgdName [EQUAL VALUE /
(LSBRKT VALUE *(COMMA VALUE) RSBRKT)]
…
[End Correction]

Regards, Christian

Michael Dell wrote:
>
> Hi there
>
> We have a quick question about the correct syntax for returning an 
> empty stream-level statistics descriptor on an audit response. This is 
> permitted at termination-level, but does not seem to be possible at 
> stream-level, given the ABNF below. We can see two possible solutions:
>
> 1. This is a clear omission in the ABNF, and it needs to be updated to 
> allow just SA (without brackets), probably by adding auditReturnItem 
> to the list of allowable entries in the streamParm field.
>
> 2. This is by design, and the response should not contain a statistics 
> descriptor at stream level if there are no statistics to return, even 
> if they were requested in the audit.
>
> Could the list please advise how best to proceed, or point out how we 
> have misunderstood the ABNF.
>
> Regards
>
> Mike Dell
>
> ---
>
> __
>
> _Termination level audit response_
>
> The following ABNF shows that we are allowed to return either a 
> statisticsDescriptor or a StatsToken on a AuditValue response. It also 
> shows that "SA{}" is not valid. Therefore the correct Megaco syntax 
> for a response with no statistics is SA.
>
> *
>
> Version 3 ABNF
>
> *
>
> auditReturnParameter = (mediaDescriptor / modemDescriptor / 
> muxDescriptor /
>
> eventsDescriptor / signalsDescriptor /
>
> digitMapDescriptor / observedEventsDescriptor /
>
> eventBufferDescriptor / *statisticsDescriptor* /
>
> packagesDescriptor / errorDescriptor /
>
> *auditReturnItem*)
>
> auditReturnItem = (MuxToken / ModemToken / MediaToken /
>
> DigitMapToken / *StatsToken* / ObservedEventsToken /
>
> PackagesToken)
>
> statisticsDescriptor = StatsToken LBRKT statisticsParameter *(COMMA
>
> statisticsParameter) RBRKT
>
> __
>
> _Stream level audit response_
>
> Things are less clear here. The following ABNF shows that SA is not 
> valid but neither is SA{} (as statisticsDescriptor ABNF does not allow 
> this).
>
> streamDescriptor = StreamToken EQUAL StreamID LBRKT streamParm *(COMMA
>
> streamParm) RBRKT
>
> streamParm = (localDescriptor / remoteDescriptor /
>
> localControlDescriptor / *statisticsDescriptor*)
>
> ------------------------------------------------------------------------
>
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