[Pce] ISIS Separate instances [Was: New PCE working group I-Ds]

>>>>> - still unclear to me whether isis pce disc. will or not use a
>>>>>   separate inst. (cf. gen-app discussion at isis working group)
>>>>
>>>> ISIS pce disc relies on procedures defined in 4971.
>>>> This is a deployment issue to use same or separate instances.
>>>
>>> do you assume that you would leave such choice possible ? i
>>> was left with the impression after last isis mtg discussion
>>> that there is a real incentive for making this a recommended
>>> behavior
>>
>> Just to avoid confusion: the PCED is being carried within the ISIS
>> Router Capability TLV, the processing of which is defined in RFC4971.
>
> indeed, i am not referring to 4971 at such, i am referring to the
> fact that if exchanging non-routing info w/ is-is result in recommending 
> separated instance then the ISIS PCE disc. w-g doc becomes a prime 
> candidate for such recommendation. just a matter of consistency.

My understanding of the discussion in the ISIS working group is that:
- They are tending towards believing that there should be a separation 
between
   flooding of IP link-state information and *all* other information
- They think that such a separation might reasonably be handled by using
   multiple (greater than one) instances of ISIS
- They have not yet reached a conclusion as to whether existing extensions
   fall into this category, but there was building opinion that TE 
advertisements
   might be strong candidates for off-loading to a second instance
- The Router Capability TLV would also be up for consideration

No slides for this topic from the ISIS working group in Chicago seem to have 
been posted yet.

The most recent version of the relevant I-D appears to be 
http://www.ietf.org/internet-drafts/draft-ginsberg-isis-genapp-01.txt 
although I know Les was planning some updates as a result of the Chicago 
meeting.

It seems to me that:
1. The ISIS working group is not going to reach a conclusion on this
   in a hurry.
2. When they do reach a conclusion we MUST fall in with it.
3. In the mean time, just as TE and Router Caps are currently
   carried in a single instance, the PCE discovery will be so
   carried.
4. You should all contribute to this discussion on the ISIS mailing list.

Cheers,
Adrian 

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