Subject: Re: [issue 7] All PL messages addressed to only LFBs?

From: "Khosravi, Hormuzd M" <[email-masked]>
Date: Sun, 28 Nov 2004 21:23:30 -0800

-----Original Message-----
From: Forwarding and Control Element Separation
[mailto:[email-masked]] On Behalf Of Jamal Hadi Salim

So all that you are(or have been) asking for is:

PL level PDU : = MAINHDR <HBexception>|
                        <ASSOCexception>|
                         <LFBselect>+
LFBselect := LFBCLASSID LFBInstance <OPER>+
OPER:= <OPERATION [<path-data>]*>+
HBexception := ...
ASSOCexception := ...

Instead of:

PL level PDU : = MAINHDR<LFBselect>+
LFBselect := LFBCLASSID LFBInstance <OPER>+
OPER:= <OPERATION [<path-data>]*>+

Note, These are two different grammars.
BTW, are you dropping the Association message from that list?

[HK] you are close now..I have assumed that we already have an exception
for HB since we all agreed to that. Other than that I don't think we
need exceptions, I don't see an exception for Association msgs to be
specific...may be just Teardown (but this might not be needed as
well)...I will respond on this specifically in the [issue 1] email on
section 6.2 that you had sent out.

> All the grammar states is that the messages consist of a main header,
> followed by LFB Select TLVs. I am not sure why this is being confused
> with all messages being addressed to LFBs.

The main header + lfb selectors are de/mux points or otherwise known as
addressing entities. There are no LFBs on the CE - other than what is
being proposed for the two core LFBs. No claim has been made anywhere in
this thread that there were LFBs on the CE; i went back and reread all
messages.
Nobody has stated that the fact that LFBselector exists on the PL
message from FE->CE implies LFBs exist on the CE.  That does not equate
there are no LFB mux points on the CE - but thats an implementation
detail which we dont need to discuss here. [correct]

If this is the "confusion" all along (disappointing) then we need to
clarify it in the text. We need to make progress.
I think we may need to add text that when the message comes from the
FE->CE that infact the LFB selector refers to the source LFB+instance
and not destination.  Would this help? 

[HK] Yes, this would clear up the confusion. We should also add text
stating that for CE->FE msgs the LFB selector refers to the destination
LFB, we don't have any text which states that either...but you had
assumed this, thus there was the confusion about FE->CE msgs

>  You had a similar opinion on
> the conf call, it would be helpful if you can clarify this as well.
>

Yes, It is true that Robert did ask for an exception for hearbeats
as well in that concal. But instead we went onto a wildgoose chase of
whether the grammar changes or not in the last 10 emails or so. The
grammar changes. So lets not discuss that any further, please.

We may be back on track - and hopefully we can make progress.
[HK] Yes I think we are back on track, by adding the clarification text
to FE->CE msgs, etc

If you take the LFBSelector out of the message description for certain
specific messages - you are creating an exception in the grammar. My
points against this as i stated earlier (in my first email on this
thread infact) are:
You save almost nothing in terms of parsing in processing cycles by
keeping the exceptions. And you loose in elegance/consistency
departments by having unnecessary exceptions to the rule.
For those reasons i ask that we have no exceptions.

[HK] The only exception is for HB msg, which we have discussed in great
detail before. We have probably exchanged a dozen emails on the protocol
list and even discussed it in one of our conf calls, so if you refer to
those or recall the discussion (it was done for efficiency reasons in
this case), it will be pretty clear.

Anyways I am glad the confusion is sorted out, adding the text
clarification for all the msgs will definitely help avoid any such
confusion in the future. Should we call this issue resolved now ?

Thanks
Hormuzd