Mice and Elephants Ioannis Giannoualtos Master in System and - - PowerPoint PPT Presentation

▶
mice and elephants
SMART_READER_LITE
LIVE PREVIEW

Mice and Elephants Ioannis Giannoualtos Master in System and - - PowerPoint PPT Presentation

Dec 01, 2023 291 likes •546 views

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions Mice and Elephants Ioannis Giannoualtos Master in System and Network Engineering July 3, 2013 Description Approach Packet Loss Effect Traffic Control

slide-1
SLIDE 1

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Mice and Elephants

Ioannis Giannoualtos

Master in System and Network Engineering

July 3, 2013

slide-2
SLIDE 2

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Why?

  • Google showed high and stable utilisation of the links in their

G-network. However :

  • Google has full control over the network
  • In order to achieve that kind of utilisation the ability to create

stable,limited bandwidth flows is needed.

slide-3
SLIDE 3

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Goals

  • Configure the parameters of the Linux Kernel to achieve

highest throughput.

  • Create a constant flow of limited bandwidth using traffic

control mechanisms

  • Evaluate possible advantages to using traffic control in order

to limit the throughput of flows

slide-4
SLIDE 4

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Definition

Definition

  • Elephant flow is an extremely large (in total bytes) continuous

flow set up by a TCP (or other protocol)flow over a network link.

  • Mice flow is a flow that is short(in total bytes).

These flows took their name back in 2001 after noticing that a small amount of flows carried the majority of Internet traffic. Even though, the rest of the traffic consisted of large amount of flows,these carried very little Internet traffic

slide-5
SLIDE 5

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Research Questions

How can we achieve constant throughput and high utilisation

  • f the link, while intermixing small and large TCP flows?
  • What changes should be made in the configuration of the

Linux TCP network stack to achieve the highest throughput?

  • What effect does packet loss have on throughput?
  • How can already existing traffic shaping techniques be used in
  • rder to provide a better throughput on the link with less

packet loss?

slide-6
SLIDE 6

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Restrictions

  • Knowledge of the kind of flows that go through the network.
  • Traffic Control tools that already exist in the Linux kernel
  • Focusing on Long Fat Networks (LFN)
slide-7
SLIDE 7

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Testbed

slide-8
SLIDE 8

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Tools Used

  • Iperf
  • Wireshark
  • Traffic Control(TC)
  • Tcp probe
slide-9
SLIDE 9

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Linux Traffic Control(TC)

slide-10
SLIDE 10

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Linux Traffic Control(TC)

  • Already enabled in the kernel by default
  • Queueing disciplines, Classful-Classless
  • Classes in order to simulate sublinks
  • Filters to distinguish traffic and assign it to classes

Why HTB?

  • Best documented among the classfull disciplines
  • More understandable and intuitive
slide-11
SLIDE 11

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

TCP probe

  • Kernel module that records the state of a TCP connection
  • One line for each packet captured
  • Captures Congestion window, Slow start threshold, Sequence

numbers and many more

slide-12
SLIDE 12

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Theoretical background

Mathis et. al. formula1: Rate <= (MSS/RTT) ∗ (1/√p) (1)

  • MSS: Maximum Segment Size
  • RTT: Round Trip Time
  • p: packet loss

1The Macroscopic Behavior of the TCP Congestion Avoidance Algorithm

(1997)

slide-13
SLIDE 13

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Packet Loss effect measured

slide-14
SLIDE 14

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Packet Loss effect measured cont.

slide-15
SLIDE 15

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Packet Loss effect measured cont.

slide-16
SLIDE 16

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Creating a constant TCP Stream cont.

slide-17
SLIDE 17

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Creating a constant TCP Stream cont.

slide-18
SLIDE 18

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

2 Flow Experiments

  • Full link,no traffic control, 2 Flows competing for the

bandwidth

  • Full link,divided in half,with priorities borrowing
  • Link limited to 400Mbps,no further traffic control,2 flows

competing.

  • Link limited to 400Mbps,divided in half,with priorities

borrowing Many more experiments were conducted with different bandwidth allocations and can be reviewed in the report.

slide-19
SLIDE 19

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Full link,no traffic control, 2 Flows competing for the bandwidth-Throughput(Bits) vs Time(sec)

slide-20
SLIDE 20

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Full link,divided in half,with priorities borrowing- Throughput(Bits) vs Time(sec)

slide-21
SLIDE 21

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Link limited to 400Mbps,no further traffic control,2 flows competing- Throughput(Bits) vs Time(sec)

slide-22
SLIDE 22

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Link limited to 400Mbps,divided in half,with priorities borrowing- Throughput(Bits) vs Time(sec)

slide-23
SLIDE 23

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Conclusions

  • Better utilisation of the link when full link is used
  • There is a small deviation on the bandwidth allocation when

using tc.

  • The throughput is more stable using traffic control
  • Less throughput reduction due to packet loss in contrast to

theory

slide-24
SLIDE 24

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Future Research

  • Create an Openflow monitored testbed and create the

forwarding rules needed in order utilise the links fully.

  • Changing the TCP implementation instead of only altering

parameters in order for it to cooperate better with the Traffic control policies or even avoid them altogether.

slide-25
SLIDE 25

Description Approach Packet Loss Effect Traffic Control Experimentation Conclusions

Questions?