RE: [Seamoby] CT Requirements Comments from IESG

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Hi James,

I do think that this is the issue the IESG was after in the first point.

The reason might simply be a wording of the requirement that is kind of 
confusing. Words like 'meaning' certainly don't help. Further, the
statement that 'a context update MUST preserve the integrity' didn't tell
me in the first place what it is about. 

Let's assume (and we have to agree on this first) that the requirement is about
the following:
If a context has been transferred from old AR to new AR, and the context changes
after this operation, the CT protocol MUST preserve the integrity through updating
the context with its current value, i.e., sending the context again. 

Why this proposal? Assume a context for a state counter (Gary mentioned a policing meter).
In case, that the counter at old AR changes after the context has been transferred, it 
MUST re-send the context in the first place, according to the wording above.

Personally, I think this is enough, although it does not cover cases (how BTW?) in which 
those updates would come too late, and the old (stale) value is used at the new AR. 

So here's my proposal for the wording:

5.5.2 A CT solution MUST minimize inconsistencies in the context's integrity at 
each receiving AR. For that, any changes of context at the supporting AR MUST be 
reflected at those ARs that have already received the context for that MN, i.e.,
a context update MUST be performed through re-sending the context to those ARs.

Regards,


Dirk

>-----Original Message-----
>From: ext James Kempf [mailto:[e-mail]]
>Sent: Thursday, July 11, 2002 6:32 PM
>To: Gary Kenward; Trossen Dirk (NRC/Boston); [e-mail]
>Subject: Re: [Seamoby] CT Requirements Comments from IESG
>
>
>Gary/Dirk,
>
>I think you may be on to something here. I think this might be 
>what the IESG was talking about it the first point, namely the
>lack of discussion of dynamic changes in the context.
>
>Is there some way we could cook this idea down into a 
>paragraph that we could insert for this requirement?
>
>            jak
>
>----- Original Message -----
>From: "Gary Kenward" <[e-mail]>
>To: <[e-mail]>; <[e-mail]>; 
><[e-mail]>
>Sent: Thursday, July 11, 2002 1:56 PM
>Subject: RE: [Seamoby] CT Requirements Comments from IESG
>
>
>> 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
>> >
>> >
>>
>>
>
>

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