Bandwidth Measurement of Pakistan

1

• Bandwidth Measurement of Pakistans Internet
  Topology

2
Motivation

• Available Bandwidth impacts application
  performance, VoIP, Video Conferencing
• Load balancing, Multi-Homing
• To choose alternate paths in overlay networks

3
Definitions

• Available Bandwidth
• The spare or unused capacity of a link during a
  certain time period.
• Dispersion
• The time difference between the last bit of the
  first and last packet in train of packets.
• Transmission Rate
• The total number of bits sent in a time unit

4
Measurement Techniques
5
Packet Pair Algorithm

• Two packets of known length (L) are sent with
  fixed inter-packet interval.
• The receiver measures dispersal (?D) of received
  pair
• Bandwidth (B) is calculated by
• B L / ?D
• Assumption
• Link does not carry other traffic because it
  could effect dispersion

6
Packet Train Dispersion Probing

• Similar to Packet Pair Algorithm but uses many
  packets instead just one pair
• Dispersal calculated between first and last
  packet in train
• Cross traffic delays are amortized

7
Self-Loading Periodic Streams

• Send a stream of packets at constant rate and
  measure one way delay of each
• If successive packets have same delay (See Fig a)
  then transmission rate lt bandwidth
• If successive packets have increasing delay then
  they themselves causing congestion (See Fig b)

Fig 1a
Fig 1b
8
SLoPS (Continued)

• This implies transmission rate gt bandwidth
• If transmission rate gt bandwidth then receive
  rate bandwidth
• We find the transmission rate that just causes
  congestion
• A binary search mechanism is used to vary
  transmission rate

9
Tailgating

• Send a train of very small packets and measure
  end-to-end latency
• Send a very large packet with TTL 1 followed by a
  small packet of high TTL.
• The large packet will slow the small tailgate
  packet behind it (for one hop).
• Size of large packet divided by change in latency
  can be used to estimate link bandwidth
• Repeat experiment many times, increasing TTL
  every time to calculate bandwidth of successive
  links

10
Tools
Technique Tools
Packet Pairs Trains B-Probe, C-Probe, Nettimer, Pathrate, Spruce
SLoPS Pathload, PathChirp
Tailgating STAB
11
References

• Locating Available Bandwidth Bottlenecks Vinay
  J. Ribeiro, Rudolf H. Riedi, and Richard G.
  Baraniuk. IEEE Internet Computing Sept 2004
• Lecture Slides, EEC274, UC Davis Chen-Nee Chuah
• A measurement Study of Available Bandwidth
  Estimation tools Jacob Strauss, Dina Katabi,
  Frans Kaashoek