RE: [Seamoby] CT Requirements Comments from IESG

["Gary Kenward" <[e-mail]>]

Dirk: 
 
  A valid point. There is a certain atomic level of granularity which has to
be
dealt with - that is, there's no protocol in the world that can synchronize
changes in
information that occur at the source while the information is "in-flight" or
being
received at the destination. If changes in context while the context is
being transferred
make a different to the successful performance of CT, then there is no hope.
 
  The problem is most significant for state context transfer. E.g. counters
will continue
to count while CT is moving the context to the destination. Either these
changes have no
significant impact upon the forwarding service provided at the new AR (e.g.
it may not 
matter that a policing meter misses a few packet counts), or a different
mechanism
has to be defined for re-establishing the state context.
 
  The handover is real and unavoidable. Mitigating the disruption to the
service at the new
AR is the challenge. It would be nice if the disruption was nil, but
unlikely.
 
Gary

-----Original Message-----
From: [e-mail] [mailto:[e-mail]]
Sent: July 11, 2002 16:30
To: Kenward, Gary [WDLN2:AN10:EXCH]; [e-mail];
[e-mail]
Subject: RE: [Seamoby] CT Requirements Comments from IESG


Hi all,
 
jumping in as somebody who has been an observer so far, struggling with the
current discussion on
'integrity'.
 
When I look at the current wording, i.e., 
"5.5.2 A context update MUST preserve the integrity, and thus the meaning,
of the context 
at each receiving AR. The context at the AR actually supporting an MN's
traffic will change with time. 
For example, the MN may initiate new microflow(s), or discontinue existing
microflows. Any change of context 
at the supporting AR must be replicated at those ARs that have already
received context for that MN.", 
 
and compare this to the plain integrity of the actually transmitted data
(i.e., its bits and therefore its semantics)
that has been brought to the table as a replacement now, I'm quite confident
that this is not what the requirement 
is talking about. 
 
If we remove the word 'meaning' (which is very vague and free for
interpretation for me as well), it is still the word
'integrity' left, which is more than plain integrity of the transmitted
data, in particular if we look at the following sentences
in the requirement, which state what kind of integrity is meant (which
probably also builds the bridge to the vague 
term 'meaning'), namely that the integrity of a context must be preserved in
the sense that a received context at new 
AR at some point t must be the same as the context at old AR at the same
time t. This is by far more than plain data 
integrity of the transmitted data. Even if your data has been transmitted
correctly, the context might be stale (and therefore 
its integrity is lost) because it had changed at old AR in the meanwhile.
The action to be taken is also given in the text, 
namely the change of context has to be replicated to the new AR. As you can
(hopefully) see this is by far more than
preserving the 'meaning' of each bit. It mandates that changes in the bit
values at one end are reflected at the other
end, i.e., it talks about distributed data integrity in my interpretation of
the requirement text.
 
Hence, the actual concern might have been (just guessing) whether or not it
is the task of the CT protocol to 
preserve the abovementioned integrity. Maybe, the IESG wants to see this
functionality left to the replication logic that resides
within each AR. Or on the contrary, they do not see this important topic
covered appropriately. 
 
Regards,
 
 
Dirk 

-----Original Message-----
From: ext Gary Kenward [mailto:[e-mail]]
Sent: Thursday, July 11, 2002 3:48 PM
To: 'James Kempf'; [e-mail]
Subject: RE: [Seamoby] CT Requirements Comments from IESG



You call it fidelity, I call it data integrity. 
I've seen "data integrity" used in publications 
(no, I cannot quote references). 

What we need is a term that everyone, including the 
IESG, can agree upon. 

> -----Original Message----- 
> From: James Kempf [ mailto:[e-mail]
<mailto:[e-mail]> ] 
> Sent: July 11, 2002 12:22 
> To: Kenward, Gary [WDLN2:AN10:EXCH]; [e-mail] 
> Subject: Re: [Seamoby] CT Requirements Comments from IESG 
> 
> 
> > Perhaps the actual answer is to state exactly what was intended 
> > originally: that the bit order and bit values have to arrive exactly 
> > as they were transmitted. 
> > 
> 
> So this requirement is talking about transmission fidelity? I 
> sure would not have guessed that from reading it. I thought it 
> intended to talk about usability. 
> 
> I would suggest that the wording you have above is really a 
> lot more precise that what is currently in the spec. 
> 
> Any other comments? Could we substitute Gary's wording above 
> for "meaning" in the current requirement. 
> 
>             jak 
> 
>