Subject: About Megaco Message Parser

From: Titty Thomas <[email-masked]>
Date: Sat, 5 Feb 2000 12:09:47 +0530

Hi all

    I have read the Megaco Protocol Sep 21, 99 Draft and have some
doubts about it.

1. Can Megaco be used for an implementation currently?.
2. Are there any reference implementations available?.

About Megaco Message Parsing.
1. Do we need to use lex/yacc or can we do it with any other simple
mechanism.
2. Also for embedded systems how will we do it.

Do we need to do both binary and text encoding of the protocol.

Thanks,
    Titty.

---

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 7 Feb 2000 09:29:13 -0500

> 1. Can Megaco be used for an implementation currently?.
Yes, several people are implementing Megaco now.  There is some
instability in a few areas, but nothing that prevents starting.

> 2. Are there any reference implementations available?.
Not that I know of.  Volunteers accepted!!

> 1. Do we need to use lex/yacc or can we do it with any other simple
You can use lex/yacc, or build another kind of parser.  I've had
some discussions with people doing LALR and LL(1) parsers.  In
some cases, very small changes may be needed in the grammar
depending on the exact rules of the parser.

> 2. Also for embedded systems how will we do it.
Depends on what facilities are available in your OS, and what
parser tools you have.

> Do we need to do both binary and text encoding of the protocol.
No, you need text, binary is optional.  A PERSONAL opinion, sure to
be scorned by some, is that binary will never make it in this protocol.  The
really interesting thing is that, given one text and
one binary implementation, and some example messages, we can put
the size/efficiency argument to rest, as long as you don't care
about the last couple percent (for which we can endlessly argue
about implementation quality!)

Brian

---

From: Matt Holdrege <[email-masked]>
Date: Mon, 7 Feb 2000 09:10:00 -0800

At 12:03 PM 2/7/00 -0500, Rosen, Brian wrote:

> > Please don't mix personal versus "official" comments. The MGC
> > MUST do both
> > binary and text per your agreement as captured by the meeting
> > minutes and
> > published so. An MG may do either.
>I labeled my comments as "Personal".  The document says that
>MGCs SHOULD implement binary, not MUST.  That is the agreement,
>and it has been that way since binary was in.

Wrong. Please go back and read the minutes at
http://www.ietf.org/proceedings/99jul/index.html

> >
> > In the real world, some vendors of MG's will implement binary
> > and some
> > text. Some vendors will likely do both. Binary for carrier
> > class platforms
> > and text for SOHO. So it would behoove universal MGC's to
> > support both.
>That would be your opinion.  Mine would be that once we discover
>that binary gets you nothing, binary will wither, even for
>"carrier class" platforms.  Although an MGC may need the ASN.1
>tools, an MG, even the biggest trunk gateway, won't (I can think
>of one reason why they would - some of us think CAS should be
>interworked to Q.931.  If we really do Q.931, you need ASN.1)
>One encoding for both residential and trunk gateways would be
>preferable.

MG's already do ASN.1 for H.323, but that's beside the point. We've already
had enough debate about the two so there's no point in going into it again.

---

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 7 Feb 2000 12:03:33 -0500

I'll agree that until the market sorts this out, we are condemned to
"both" in most MGCs.

Brian

---

From: Matt Holdrege <[email-masked]>
Date: Mon, 7 Feb 2000 10:43:51 -0800

H.245 being what we now call the Native descriptors used in binary encoding
of H.248. Whatever. In this case I guess it doesn't matter what the
document says.

At 01:38 PM 2/7/00 -0500, Rosen, Brian wrote:
>I did.  There is a statement about encoding of local and remote
>"The MGC must support both SDP and SG16-determined encoding of H.245. An MG
>may support either and this reserves the possibility of migration to a new
>syntax".  That's 245, not 248.  This meeting was
>the coin toss meeting (Oslo), and the result at that point was
>text only encoding, as the following paragraph indicates.
>
>The "should" agreement was reached in Red Bank as I recall, subsequent to
>Oslo.
>
>Brian
>
> > -----Original Message-----
> > From: Matt Holdrege [mailto:[email-masked]]
> > Sent: Monday, February 07, 2000 12:10 PM
> > To: Rosen, Brian
> > Cc: [email-masked]
> > Subject: RE: About Megaco Message Parser
> >
> >

---

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 7 Feb 2000 13:38:02 -0500

Brian

---

From: "Rosen, Brian" <[email-masked]>
Date: Mon, 7 Feb 2000 13:50:21 -0500

Just to finish this thread for those who weren't there,
"Native", or Annex C, media descriptors were, at Oslo, MG-either,
MGC-both.  Subsequently, it was agreed to change it such that it
was Annex C for binary and SDP for text.  That simplified
everyone's implementation.  That is the way text reads now.

Brian

> Sent: Monday, February 07, 2000 1:44 PM
> To: Rosen, Brian