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Topics in Internet Research: Project Scope. Mehreen Alam 04030053. Contents. Objective Issues Cell Switching From Cell to Packet Switching Packet Switching Facts to Study. Objective.

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Presentation Transcript
contents
Contents
  • Objective
  • Issues
  • Cell Switching
    • From Cell to Packet Switching
  • Packet Switching
  • Facts to Study
objective
Objective
  • Study and do throughput analysis of cell based and packet based switches, in terms of the scheduling algorithm and the switch architecture.
issues
Issues
  • Packet vs. Cell switching
  • Delays – packet delays & average finite delays
  • throughput
  • Speed up
  • traffic pattern
    • admissible, uniform, distributions, law of large numbers, efficiency, stability
  • algorithms
    • Matching (maximal, maximum)
    • scheduling
  • simplicity and practical feasibility
  • Complexity (time, space and cost)
  • hardware implementation
  • performance evaluation
cell switching
Cell Switching
  • Packets
    • Have variable lengths - are divided into cells of unit length
    • Switch operates on variable-size data units at their interfaces, but internally operating on cells
  • Each Packet
    • given deadline by which it must traverse the switch
  • Successful Packet
    • if the sequence of cells comprising it is contiguously transmitted out of the switch before the packet’s deadline expires
  • Retry for unsuccessful packets
    • transmission may be preempted and restarted from the beginning later.
cell switching1
Cell Switching
  • To Study
    • Scheduling Policy - decides at each time step which packets to serve
      • use competitive analysis to measure the performance of the following scheduling policies with goals to maximize
          • the total number of successfully transmitted packets
          • the total value of successfully transmitted packets (priority)
    • pseudo-packet switching
      • Proof
        • Maximum throughput by IQ is identical to that achievable with CIOQ cell switches.
        • By simulation – IQ have performance advantages OQ
from cell to packet switching
From Cell to Packet Switching
  • Main problem in the IQ switches
    • scheduling
    • In real traffic dividing the variable packets into cells at the input side of the switch and then re-assembling these cells into packets on the output side achieve it.
  • Downside
    • bandwidth is lost as division of a packet may generate incomplete cells
    • additional overhead of segmentation and reassembling cells into packet
  • Solution
    • Send variable length packets
  • …….. Packet Switching
packet switching
Packet Switching
  • Do packet scheduling in
    • units of arriving packet sizes, and
    • non-preemptive fashion
  • Study how packet Scheduling is
    • Stable for any admissible Bernoulli iid. arrival traffic using a simple modification of Maximum Weight Matching (MWM) algorithm, like cell-based MWM
    • Extended to general re-generative traffic model instead of just admissible traffic
    • A scenario where packet based MWM is unstable
      • But has admissible traffic pattern for any work-conserving (that is maximal type) scheduling algorithm
    • …. A new proposed waiting” MWM algorithm - stable for any admissible traffic using fluid limit technique
facts to study
Facts to Study
  • Maximum throughput by IQ packet is identical to that achievable with CIOQ cell switches
  • For packet switches
    • IQ have performance advantages OQ
  • Stability of modified maximum weight matching for packet based switches
    • admissible traffic
    • general admissible arrival traffic
    • general re-generative traffic model
  • The Unstable scenario for packet based MWM
ad