Subject: RE: [Diffserv] Proposal for Diffserv MIB - droppers

From: Andrew Smith <[email-masked]>
Date: Thu, 1 Jun 2000 14:59:13 -0700

Fred,

Maybe the diagram I just sent will clarify. Else, if I may plagiarise your
C-code:

>          switch (ip_header->dscp) {
>          case AF11:
                  do_specific_AF11_stuff();
                  do_commonstuff();
                  break;
>          case AF12:
                  do_specific_AF12_stuff();
                  do_commonstuff();
                  break;
>          case AF13:
                  do_totally_different_AF13_stuff();
>                 break;
           etc.
>          }

The issue is that we want to re-use the do_commonstuff() building blocks and
that needs a "go to" because we do not have procedure calls in the model (or
MIB syntax).

Andrew

_______________________________________________
diffserv mailing list
[email-masked]
http://www1.ietf.org/mailman/listinfo/diffserv
Archive: http://www-nrg.ee.lbl.gov/diff-serv-arch/

---

From: Fred Baker <[email-masked]>
Date: Thu, 01 Jun 2000 16:00:38 -0700

>that needs a "go to" because we do not have procedure calls in the model (or

I have to say that this doesn't have a very strong image match with my 
model of how the MIB works. It seems to me that some combination of 
classifiers and meters selects a set of actions and a queue, neatly 
described in some kind of table, and at that point there is no need to know 
how you arrived at the table - you mere need to know the contents of the 
table. My queuing code doesn't even know that IP called it, or that it is 
queuing an IP datagram, much less that the code was worried about the fact 
that the DSCP contained the number 67. It knows that it has been given a 
message and a set of parameters, and that it is putting the message into a 
queue. It doesn't know anything else, and it doesn't need to know anything 
else.

I'll ask the question I have asked a number of times concerning the model - 
why do I have this layer violation here? Why can I not put IPX traffic, 
which has no DSCP, into the same queuing system if the network operator 
configures IPX routing?

Seems like a phenomenally poor architectural decision to make the queues 
and actions know anything about the classification or the meters. 
Classification is separate because it is another question entirely, 
something that good implementation design separates completely away.