DiffServ WG March DiffServ Model - open issues Andrew Smith March, 2000

DiffServ WG March General tidying-up Closer alignment with DiffServ MIB and PIB terminology (which is correct? - other drafts need to change) “counter” or “monitor”? “discarder” or “algorithmic dropper”? Structure shapers: still some residual text that treates these as Actions, not part of Queuing -> clean this up move most of the discussion stuff from MIB to Model Fred’s n x 2-port = n-port router discussion from 3.1 to Hierarchical Model 3.2 Meter discussion from 3.3 to Meters 5.1 Kwok’s RED discussion from 3.4 to Discarders Kwok’s Queuing example from 3.5 to Schedulers 7.1.2

DiffServ WG March Model: open issues (1) 1. There is a difference in interpretation of token bucket behavior between this document (Appendix A) and [DSMIB]. Specifically, [DSMIB] allows a packet to conform if any smaller packet would conform. (discuss) 2. Should a classifier be part of a TCB? We argue yes. This allows a TCB to be a one input/one output black box element. MIB assumes not why can’t we feed discarders from existing classifier blocks? What if I want to discard based on something other than DSCP? 3rd discarder example in does not make sense and is inconsistent with previous examples (uses DSCP, not PHB) (no) 3. Should we discuss MPLS (a) more or (b) less? (b) 4. Include support for non-DSCP markers? (allow but no explicit discussion)

DiffServ WG March Model: open issues (2) 5. The meter in [SRTCM] cannot be precisely modeled using two two- parameter token buckets because its two buckets do not accumulate credits independently. Do we need to show how the [TRTCM] meter could be implemented? If so, someone please supply text. Should the Model include examples of each or just describe a general n- rate meter? (discuss) 6. Are the current examples for queues, scheduling and buffer management sufficient? (yes) FIFO with thresholds Schedulers (work-conserving and non-work-conserving) with min/max/priority Discarder with triggers (e.g. queue-threshold feedback) and classifiers Should we add a “Precedence PHB” example? (no) 7. Is the description of a shaper sufficient (section 7.2)? Is it overbroad?

DiffServ WG March Model: open issues (3) 8. Does the Queue/Queue-Set concept belong in the model (and the MIB and PIB?), or should the model stick to the abstract PHB representation and leave the implementation details to the MIB and PIB (and other work in this area)? (discuss)