Topics in Internet Research: Project Scope

1
Topics in Internet Research Project Scope

• Mehreen Alam
• 04030053

2
Contents

• Objective
• Issues
• Cell Switching
• From Cell to Packet Switching
• Packet Switching
• Facts to Study

3
Objective

• Study and do throughput analysis of cell based
  and packet based switches, in terms of the
  scheduling algorithm and the switch architecture.

4
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

5
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 packets deadline expires
• Retry for unsuccessful packets
• transmission may be preempted and restarted from
  the beginning later.

6
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

7
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

8
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

9
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

10
Q A