Subject: Re: ForCES model

From: "Yang, Lily L" <[email-masked]>
Date: Fri, 27 Feb 2004 07:38:43 -0800

That seems impossible to do -- because the metadata that an LFB passes
transparently really depend on the other LFBS in the datapath, that is,
the LFBS before and after this LFB in question. So the LFB itself does
not have that knowledge at all prior to run time. But that is the kind
of information the LFB itself (or the CE) can infer at run time, once
the LFB topology is known. 

For example, if LFB A, B, C (in that order) form the datapath, B has to
pass whatever metadata that is produced by A and expected by C. 

Right? 

-----Original Message-----
From: Forwarding and Control Element Separation
[mailto:[email-masked]] On Behalf Of Anurag Bhargava
Sent: Friday, February 27, 2004 7:31 AM
To: [email-masked]
Subject: ForCES model

Hello,

 I see that we have metadata Expected and metadata Produced in the
schema
in draft-ietf-forces-model-02.txt.

 I was wondering if we should also add an additional information which
will give an idea that the metadata should be passed transparently. It
will still be part of the above classes but will provide the LFB
implementor
that this metadata should be passed unmodified. This will impose the
needed
restricion. And in my mind could be part of the standard FE model

Any comments..

--
anurag

---

From: Anurag Bhargava <[email-masked]>
Date: Fri, 27 Feb 2004 10:52:10 -0500

I see your point. But if we look at it from the LFB's perspective. For
example, LFB A expects metadata 1 and at the same time also needs to be
passed on or produced so that it can be consumed at a later stage, having
this information will be helpful. I don't know the topology but yet know
that it will be used by later LFBs.

For example,
Meter LFB will use the frame length and also the Queue LFB. So, when we
define Meter LFB, atleast in that definition, we can say that length
metadata should be passed by this Meter LFB. But if the model doesn't
provide this information, how will each LFB know.

--
anurag

---

From: Zsolt Haraszti <[email-masked]>
Date: Fri, 27 Feb 2004 11:09:11 -0500

Anurag,

It is a default behavior of any LFB to pass all "un-interesting"
metadata transparently.  Any metadata that is not explicitly or
implicitly used (read/produced) by the LFB fall into this category.
This should be in the draft somewhere.

Some implementations will have inherent physical limitations and
will not be able to provide this default behavior.  We are currently
looking into if and how such limitations should be expressed by via
the model.  Suggestions are welcome.

/zsolt