Re: setup priority in draft-ietf-tewg-diff-te-proto-

[Francois Le Faucheur <flefauch@cisco.com>]

Dimitry,

At 16:58 22/04/2002 -0400, Dimitry Haskin wrote:
>Francois,
>
>As fairly minor comment, there is seemingly no reason to restrict the setup
>priority values in the same way the holding priorities value are restricted
>(i.e. to form configured TE Class). What you try to achieve will work
>without such a restriction.

Hmm. Interesting point. I think you're right that it could work without the 
restriction.

My first reaction, though, is that we should keep the restriction in, because:
         - Removing it would make configuration somewhat confusing to users 
(ie user can configure setup to any value and holding only to a subset; 
user would inevitably wonder why it is so and will be frustrated not to be 
able to use any value for holding)
         - In practise, it appears that SPs have little practical use for 
different setup and holding priorities (to date at least), and end up using 
the same value for both.

>Such a restriction on the setup priority value
>only adds more error checking and failure cases.

but removing the restriction would make Constraint BAsed Routing and CAC 
more complicated. They would have to be able to handle a setup priority for 
which they have no current "available bandwidth" information in the 
topology database, and in that case they would have to consider the 
"available bandwidth" of next higher priority or the advertised Bandwidth 
Constraint (instead of a dynamic IGP value) in case there is no higher 
priority in that CT.


So to me it seems that keeping the restriction would :
         - keep configuration simpler for the end user
         - keep implementation easier
         - not lose anything really useful in practise

What do you think?

Thanks

Francois

>Regards,
>  Dimitry
>