Subject: [Megaco] ASN.1 Notations used in Megaco

From: "Tom-PT Taylor" <[email-masked]>
Date: Mon, 02 Apr 2007 08:48:37 -0400

Here's another one.

Subject:
RE: ASN.1 Notations used in Megaco
From:
"Rambabu Gajula" <[email-masked]>
Date:
Mon, 2 Apr 2007 17:09:37 +0530
To:
"Rambabu Gajula" <[email-masked]>, <[email-masked]>

Resending....

Thanks with regards,
Rambabu Gajula

________________________________

From: Rambabu Gajula
Sent: Saturday, March 31, 2007 8:23 PM
To: [email-masked]
Subject: ASN.1 Notations used in Megaco

Hello,

In Megaco (H.248) ASN.1 Syntax Specifications, Many elements are
"Sequence of ".

But there is no Minimum-Maximum numbers of times these elements can be
send/receive.

This may cause a bit ambiguity some times at least in case of minimum
value is it zero or one.

In case of the minimum value to zero (May be optional element).

Can some one help me to understand the history behind this? (No minimum
and maximum value).

Thanks in advance for your time.

Thanks with Regards,

Rambabu Gajula

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---

From: Paul Long <[email-masked]>
Date: Mon, 02 Apr 2007 11:14:16 -0500

I actually mention this in my guidelines for writing standards:  
http://www.packetizer.com/standards/stdguide.html. It's at the bottom of 
the page.

Paul

---

From: Christian Groves <[email-masked]>
Date: Tue, 03 Apr 2007 13:59:04 +1000

Hello Rambabu,

There's no single reason for this as the information elements are 
different. In some cases message size provides the limit on the maximum 
number e.g. number of transactions, other time the size is alluded to 
via comments in the ASN.1 e.g. number of descriptors in a command. In 
other cases sequence of zero is used to indicate choose or optionality. 
If we look for historical reasons i'd say a primary driver was the 
flexibility of H.248. People saw use cases for H.248 to control IP 
phones others were talking about large trunking gateways. Each would 
have their own restrictions on size. This is why some bodies have used 
profiles as a means of indirectly affecting the maximum sequence size. 
e.g. limiting the number of commands per message.

Regards, Christian