On Transmission Scheduling in a Serverless VideoonDemand System

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On Transmission Scheduling in a Server-less
Video-on-Demand System
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Outline

• Background
• Transmission Scheduling
• Performance Evaluation
• Summary

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Server-less VoD System
? Transmission Scheduling is required
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Transmission Scheduling

• On Request Scheduling
• Staggered Scheduling
• Randomized Scheduling

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On Request Scheduling

• At receiver side
• Initiate a video session
• Send requests to all nodes at the same time
• At sender side
• Admit requests
• Reserve a timeslots for each request
• First come, first serve

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On Request Scheduling
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On Request Scheduling

• Simple algorithm
• Minimize start-up latency
• However,
• Timeslots assigned by different nodes to the same
  request are usually close together
• Bursty traffic at the receiver side
• Congestion and packet loss

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Staggered Scheduling

• Why not spreading out the transmission in
  advance?
• Non-overlapping timeslots for each request
• Pre-allocation of timeslots
• Algorithm
• Node i serves node j at timeslot (i j 1) mod
  N

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Staggered Scheduling
Node i serves node j at timeslot (i j 1) mod N
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Staggered Scheduling

• Assumption
• Nodes are clock synchronized
• Two implications
• Performance depends on clock synchronization
  accuracy
• Assumptions may not always be feasible

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Randomized Scheduling

• Motivation
• Eliminate the requirement of synchronization
• Decorrelate the transmission time
• Randomized
• Timeslots to each request
• Timeslots in each round

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Performance Evaluation

• Cluster Size
• Router Buffer Size
• Queueing Delay

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Simulation Model
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Cluster Size
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Router Buffer Size
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Queueing Delay
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Summary

• Transmission scheduling is required to resolve
  the congestion
• Staggered scheduling
• can achieve near-zero packet loss rate with small
  network delay variation and clock synchronization
• Randomized scheduling
• can achieve consistent performance for any delay
  variation
• Without clock synchronization ? suitable for
  serverless system

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Current and Future Works

• Deterministic scheduling
• Optimal schedule for any given delay profile
• Using QQP
• Stochastic scheduling
• Schedule based on stochastic information
• Receiver messaging feedback