QDDIM-02 Issues - PowerPoint PPT Presentation

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QDDIM-02 Issues

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Issue 3: Algorithmic Droppers ... by the relative placement of the queue and the dropper ... parameters that characterize a dropper: Which queue to drop from ... – PowerPoint PPT presentation

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Title: QDDIM-02 Issues


1
QDDIM-02 Issues
  • Policy Framework WG
  • 49th IETF
  • Bob Moore - remoore_at_us.ibm.com

2
QDDIM-02
  • Previously QDIM, the QoS Device Information Model
  • In order to move the document forward, the scope
    was narrowed to DiffServ
  • Thus QDDIM, the QoS DiffServ Device Information
    Model

3
Issue 1 Derivation of Schedulers
  • Should the class PacketSchedulingService be
    derived
  • from ConditioningService, just as the classes for
    Classifiers, Meters, Markers, Droppers, and
    Queues are?
  • from ForwardingService, because a Scheduler is
    different in an important way from the other
    DiffServ elements?

4
Issue 1 Pictures
Fwd
Cond
Clas
Met
Mark
Drop
Q
Sch
Fwd
Cond
Clas
Met
Mark
Drop
Q
Sch
5
Issue 1 Discussion
  • What would PacketSchedulingService inherit from
    ConditioningService?
  • Being a Conditioning Service -- aligns with the
    DiffServ Informal Model
  • Participates in NextService associations
  • Association with protocol endpoint -- people
    think of a Scheduler as the last Conditioning
    Service on an egress interface

6
Issue 1 Discussion
  • Why should PacketSchedulingService not inherit
    from ConditioningService?
  • A Scheduler is in the control plane, not in the
    data plane thus it doesnt condition traffic
    (although it controls the conditioning of traffic)

7
Issue 2 Scheduling Disciplines
  • Should specific scheduling disciplines be
    represented by
  • subclasses of the SchedulerUsed association?
  • subclasses of PacketSchedulingService?

8
Issue 2 Pictures
SchedulerUsed
Q

0..1
Sched
PrioritySchedulerUsed
0..1

BoundedPrioritySchedulerUsed
0..1

etc.
SchedulerUsed
Q

1
Sched
PriSched
BoundedPriSched
etc.
9
Issue 2 Multi-Discipline Scheduler
Is this combination allowed or not?
Priority
Priority
Scheduler 1
Priority
WRR
WRR
Warning Instance diagram
10
Issue 2 Per-Queue Properties
Where to put the priority values (if not in the
associations, then where)?
Priority
Priority
Scheduler 1
Priority
Warning Instance diagram
11
Issue 3 Algorithmic Droppers
  • Currently in QDDIM HeadTailDropperSvc is a
    subclass of DropperService, but other subclasses
    of DropperService represent the drop algorithm,
    not the drop location
  • The Informal Model is moving towards representing
    head / tail dropping solely by the relative
    placement of the queue and the dropper

12
Issue 3 Algorithmic Droppers
  • There seem to be four (independent?) parameters
    that characterize a dropper
  • Which queue to drop from
  • Where in that queue to drop from (head, tail,
    etc.)
  • Which queue or queues to monitor to make the drop
    decision (often, but not always, this is the same
    queue from which packets are dropped)
  • The parameterized algorithm for making the
    decision whether or not to drop a packet

13
Issue 3 Algorithmic Droppers
  • So long as we dont allow the sequence
    Q--gtDropper--gtQ, the first two are handled by the
    sequence of Conditioning Elements
  • Need a separate association for 3 in the MIB,
    diffServAlgDropQMeasure
  • Subclass of DropperService, with additional
    properties, specifies a drop algorithm and its
    parameters

14
Issue 3 Algorithmic Droppers
  • QDDIM also has a class DropThresholdCalculationSer
    vice, which monitors a set of queues, and
    aggregates information about them into values
    that a Dropper can use in its drop algorithm
  • Currently this service is not modeled in the
    Informal Model, the MIB, or the PIB
  • Is this something that should be added to the
    three DiffServ documents?

15
Issue 4 Representing Filters
  • Packet filtering clearly applies to more than
    DiffServ
  • Currently have several ways to represent filters
  • single-field generic (FilterEntry)
  • single-field specific (examples in IPSP)
  • multi-field specific (e.g., IP6TupleFilter)
  • atoms (defined in QPIM)
  • How much convergence do we need here?

16
Any Other Issues?
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