QoS Approaches and Bandwidth Broker in a Diffserv Environment

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QoS Approaches and Bandwidth Broker in a Diffserv
Environment
Manish Mahajan
TASSL Presentation 09/12/01
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Background

• It means providing consistent, predictable data
  delivery service and satisfying customer
  requirements.
• Needed
• IP provides best effort service and makes no
  guarantees
• about when data will arrive, or how much it can
  deliver.
• New breed applications (Audio/Video) demand high
  data
• throughput capacity and low-latency
  requirements.
• Benefits
• Manage jitter sensitive applications
  (audio/video
• playbacks)
• Manage delay-sensitive traffic (real time voice)
• Control loss in times of inevitable bursty
  congestion

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Continued
All the complexity is pushed out onto the edge
routers. Functions performed by the edge
routers Classification Marking Policing Functions
performed by the core routers Packet forwarding
according to the marking Policing (Necessary) and
Remarking if required The bandwidth broker is an
agent that manages resources. It can be a stand
alone or defined as a part of the edge router.
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Broker Components
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Broker Responsibilities

• allocate bandwidth for end-to-end connections
  with less state and simpler trust relationship
  (SLAs)
• parcel out regions Marked traffic allocations and
  set up leaf routers within the local domain.
• responsible for internal and external admission
  control decisions configures any routers within
  the domain
• responsible for negotiating with bandwidth
  brokers from
• neighboring domains.
• associated with a particular trust region, one
  per domain.

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How it works

• An application signals a bandwidth request to
  the Broker along with estimated traffic profile.
• 2. The Bandwidth Broker should respond to
  application after having set-up the QoS with the
  routers.
• 3. The Bandwidth Broker should be able to reject
  over-booking of bandwidth.          
• 4. The Bandwidth Broker should be able to
  reconfigure routers either via a CLI or by other
  means of communication.
• 5. The Bandwidth Broker should handle the
  application terminating its use of the bandwidth
  and return the bandwidth to the pool

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In Action
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InterDomain Communication
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Multimedia Applications

• conferencing applications (e.g.. Vic, vat)
• streaming applications (client/server based
  e.g.. Real audio)
• Multimedia Network Requirements
• Tight latency/delay bounds
• High throughput
• Low Jitter
• Low loss but tolerable
• 5) Use UDP (hence difficult to control
  congestion)

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Corrective Actions

• Obvious approach Drop offending packets
• Check if packets really are interfering with
  other flows. If not then decrease precedence
• Trade picture quality for network bandwidth
  (compute intensive v/s network intensive)
• E.g.. Can introduce different precedence for
  different MPEG frames. Good idea to drop B frames
  in congested network than audio frames.
• 5) Capable of responding to congestion, e.g., by
  changing the
• parameters of the coding algorithm to
  reduced bandwidth
• 6) Playback buffer at receiver to smooth jitter

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Tools Network Simulator 2 (USC)

• Used to define network topology and simulate
  network conditions.
• Current Diffserv patch provided by Nortel
  Networks.
• Bandwidth Broker class interacts with the policy
  management function implemented in the Diffserv
  policy class.
• Tcl/Tk to interpret commands in foreground and
  C implementation in background.
• Simple and duplicated topology at present

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Need for Improvement Future Work

• To be able to implement GOOD policy decisions
  during both congestion and non-congestion periods
• Study of various multimedia applications and
  their usage profile
• Maintenance of History of Application profile
• Dynamic re-allocation of bandwidth