I think the question of just what is being exposed and what is being
kept private does turn on how the SLS is expected to be used. If
it is something that is communicated between a customer and a provider,
then it seems quite reasonable that a provider should NOT necessarily
exposed PHBs used nor even certain quality measures that are not
those that the customer is being "guaranteed". Brian and I have said
repeatedly that what PDB a provider is using is not really expected
to be exposed; a PDB is an additional part of the diffserv toolkit that
it supposed to give a recipe for putting pieces together in a certain
way and ending up with a certain treatment (generally quantified by
metrics) that a packet of the traffic aggregate using that PDB can
expect. One can envision various ways of using this. The two that
occur to me immediately is: 1) I want to offer a certain "service level"
to a customer class. I browse existing PDBs to see how to find one
that can let me select the parameter of interest. Maybe I get some
other attributes, too, but I don't want to sell those features, so
I don't talk about them. Or 2) I decide I want to offer a particular
sort of treatment that some PDB can be configured to provide (VW may
be an example of this). I read the PDB document to figure out how to
set up my network for this and what behavior I should expect. I sell
something that is spec'd lower than the "expected" behavior to be
on the safe side. In either case, I don't necessarily want to say
what PDB I'm using, at least in part because I don't want customers
demanding the other measureable properties of that PDB in case I
want to use a different PDB that offers the same measure that I sold
them, but not the others. Also, it may be a proprietary PDB.
I think Brian's point about exposing PHBs has more to do with *if*
premarking is part of your agreement. I believe he used the word "may".
I'm not all that certain myself how people expect to use an SLS.
If it doesn't "hide" the implementation details for the particular
"service" from a customer then it seems like it may not differ
from the RFC2475 term Service Provisioning Policy. I also think, on
rereading rfc2475, that "service" in that document is generally used as
we are using PDB "the service provided to a traffic aggregate" though
the PDB notion is specific to a single domain.
Kathie
This archive was generated by hypermail 2b29 : Fri Feb 09 2001 - 00:22:50 CET