Subject: Re: [Megaco] ServiceIncompleteFlag in case of ASN

From: Christian Groves <[email-masked]>
Date: Tue, 01 May 2007 16:24:18 +1000

Hello Rambabu,

Please see my response below.

Regards, Christian

Rambabu Gajula wrote:
>
> Hi,
>
> I am trying to understand the Service Incomplete flag (Described in 
> Specification H.248 Version 3 section: 7.2.8.1.10).
>
> As per the H.248 Specification, Initial Service Change Request message 
> should go in Version-1 format. The newly added element should go now 
> in “X-SC”.
>
> Extension Containers Service Change request.
>
> The Name: SIC Type: Boolean Possible Values: ON
>
> 1) The type mentioned here is BOOLEAN, but the ASN.1 Syntax in 
> “NonStandardIdentifier” is experimental “IA5String”. How we will map 
> the Boolean to IA5String.
>

[CNG] As the section says the value is encoded as per the given ABNF, so 
its a simple string mapping.
>
> 2) Possible Values: ON, As per my understanding in case of Boolean 
> value means: 0 or non zero(1). How this is mapping string to digit here?
>
[CNG] The ASN.1 "/experimental IA5String(SIZE(8))/" contains "X-SC" as 
this is the name of the parameter.
The ASN.1 "/data OCTET STRING/" contains "SIC=ON"

> 3) The maximum length allowed for extension containers is 
> “experimental IA5String (SIZE(8))” Maximum size allowed is=8, In ABNF 
> grammar the maximum length mentioned as = 64 octets.
>
[CNG]
The name of the extension parameter in the ABNF is defined as:
/ extensionParameter = "X" ("-" / "+") 1*6(ALPHA / DIGIT)/
This gives 8 characters max.
The name of the extension parameter in the ASN.1 is defined as:
/ experimental IA5String(SIZE(8))/
This also gives 8 characters max.

With regards to the data aspect the form of the ASN.1 is:
/ data OCTET STRING/
the ABNF is:
/parmValue /
these both give plenty of room for data.
>
> Can please help me if my understanding is incorrect.
>
> Thanks with Regards,
>
> Rambabu Gajula
>
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