Advanced Network Technologies Introduction
Dr. | Lecturer School of Computer Science
› Title: Advanced Network Technologies › UOS code: COMP5416
› Credit point: 6
– Wednesday 18:00-20:00, weeks 1-13 – Online
› Lab/Tutorial:
– Wednesday 20:00-21:00, weeks 1-13, starting from today
– Thursday 17:00-18:00, weeks 1-13
– Sydney time by default
– Note your time zone, especially ADST/AEST change in October. – Online
› , Coordinator and Lecturer – Weeks 1-13
– Office: J12-4W-425
– Phone: (02) 8627 4865
– https://www.sydney.edu.au/engineering/about/our-people/academic-staff/wei-bao.html
– Officehour:Byappointment,throughZoom
– Clearly note COMP5416 in the email title when you contact me
› Background
– Research: Networking, Mobile Computing, Internet of Things, Distributed Systems.
– Research Group: Centre for Distributed and High Performance Computing (http://sydney.edu.au/distributed_computing/)
– University of Toronto
› Zhengjie Yang, Tutor
– Weeks 1-13
– Office: J12-West Wing
– Office hour: by appointment, through Zoom › Background
– Research: Networking, mobile computing, distributed machine learning.
– 4-year experience in tutoring this UoS › , Tutor
Weeks 1-13
Office: J12-West Wing
Office hour: by appointment, through Zoom
Emergency procedures (on campus)
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– In some circumstances, we might be asked to remain inside the building for our own safety. We call this a lockdown or shelter- in-place.
– Furtherinformationisavailableat www.sydney.edu.au/emergency
Keeping our community safe
We can all help reduce the spread of COVID-19 through following good hygiene practices:
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Keeping our community safe
– Allstudentsandstaffwhohavecoldorflusymptomsshould isolate themselves from others.
– Ifyouareunwellwithcoldorflusymptomspleaseexcuse yourself from this class and we will support you to continue the work remotely.
– Makesureyoureadtheinformationonspecialconsideration in the unit outline.
Keeping our community safe
– TheUniversityisfollowingadvicefromthegovernmentand related public health authorities.
– Forthelatestinformation,seetheadviceontheUniversity website.
– Insomeclasses,especiallythoseinvolvinguseofshared equipment, please follow additional advice from your coordinators.
– Pleasetakecareofeachotherandyourselvesandifyouneed support reach out to your unit coordinator or the health and wellbeing area of the Current Students website.
Tips for students joining online
– Remember that you are still in a space with other students.
– Mute your microphone when not speaking.
– Use earphones or headphones – the mic is better and you’ll disturb others less.
– Ifyouhaveawebcam,pleaseswitchitonsowecanseeyou!
– Ifyouarespeakingtothecamera,makeeyecontactwiththe
camera (and therefore your classmates and teacher).
– Try not to talk over someone else.
– Usethechatfunctiontosendmessagestotheteacheror classmates during class.
Tips for students learning online
– For tips and guides on learning online and the tools you will use, refer to Learning while off campus resources in Canvas.
Canvas: https://canvas.sydney.edu.au/
Login using Unikey and password
Link to Units website: https://sydney.edu.au/units/
Official schedule, list of learning outcomes, etc Copies of slides
Lab instructions Assignment instructions Lecture videos
We intend to record the lectures, but the technology is not reliable Submit official assignment work here;
see your grades; etc
Textbook and material
Computer Networking: A TopDown Approach 6th or 7th edition, and ,
Some of the information on the slides of this course is taken from the companion material of this textbook that is subject to copyright 1996-2012, J.F Kurose and K.W. Ross, All Rights Reserved.
Expectations
Ø Students attend scheduled classes, and devote an extra 6-9 hrs per week Ø doing assessments
Ø preparing and reviewing for classes
Ø revising and integrating the ideas
Ø practice and self-assess
Ø Students are responsible learners
Ø Participate in classes, constructively
Ø Respect for one another (criticize ideas, not people)
Ø Humility: none of us knows it all; each of us knows valuable things
Ø Check canvas site at least once a week!
Ø Notify academics whenever there are difficulties
Evaluation
› W6: Assignment 1, 20% Covers W1—W6
› W12: Assignment 2, 20% Covers W6—W12
› Exam period: Final exam, 60% Covers everything
› School of CS policy: you must get at least 40% of the marks available on the exam, in order to pass the unit. (40% barrier on exam, less than 40% in the exam is automatically a FAIL.)
Special Consideration (University policy)
Ø If your performance on assessments is affected by illness or misadventure
Ø Follow proper bureaucratic procedures
Ø Have professional practitioner sign special USyd form
Ø Submit application for special consideration online, upload scans Ø Note you have only a quite short deadline for applying
Ø http://sydney.edu.au/current_students/special_consideration/
Ø Also, notify coordinator by email as soon as anything begins to go wrong
Ø There is a similar process if you need special arrangements eg for religious observance, military service, representative sports
Late assessments
Ø Suppose you hand in work after the deadline:
Ø Penalty of 5% per day late, e.g.:
Ø A good assignment that would normally get 9/10 and is 2 days late loses 10% of the full 10 marks, i.e. new mark = 8/10
Ø An average assignment that would normally get 5/10 and is 5 days late loses 25% of the full 10 marks, i.e. new mark = 2.5/10
Ø Assignments more than 10 days late get 0.
Ø Warning: submission sites get very slow near deadlines.
Ø You can resubmit if there is time before the deadline. Only the latest version will be marked.
Academic Integrity (University policy)
Ø “The University of Sydney is unequivocally opposed to, and intolerant of, plagiarism and academic dishonesty.
Ø Academic dishonesty means seeking to obtain or obtaining academic advantage for oneself or for others (including in the assessment or publication of work) by dishonest or unfair means.
Ø Plagiarism means presenting another person’s work as one’s own work by presenting, copying or reproducing it without appropriate acknowledgement of the source.” [from site below]
Ø http://sydney.edu.au/elearning/student/EI/index.shtml
Ø Submitted work is compared against other work (from students, the internet etc)
Ø Turnitin
Ø Penalties for academic dishonesty or plagiarism can be severe
Ø Complete self-education AHEM1001
DISABILITY SERVICES
Do you have a disability?
You may not think of yourself as having a ‘disability’ but the definition under the Disability Discrimination Act is broad and includes temporary or chronic medical conditions, physical or sensory disabilities, psychological conditions and learning disabilities.
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Students needing assistance must register with Disability Services – it is advisable to do this as early as possible.
http://sydney.edu.au/study/academic-support/disability-support.html
Other support
Learning support
http://sydney.edu.au/study/academic-support/learning-support.html
International students
http://sydney.edu.au/study/academic-support/support-for-international-students.html
Aboriginal and Islanders
http://sydney.edu.au/study/academic-support/aboriginal-and-torres-strait-islander- support.html
Student organization (can represent you in academic appeals etc) http://srcusyd.net.au/ or http://www.supra.net.au/
Please make contact, and get help
You are not required to tell anyone else about this
If you are willing to inform the unit coordinator, they may be able to work with other support to reduce the impact on this unit
eg provide advice on which tasks are most significant
Metacognition
Pay attention to the learning outcomes Self-check that you are achieving each one Think how each assessment task relates to these
Time management
Watch the due dates
Start work early, submit early
Networking and community-formation
Make friends and discuss ideas with them
Know your tutor, lecturer, coordinator
Keep them informed, especially if you fall behind
Don’t wait to get help Enjoy the learning!
https://www.sydney.edu.au/units/COMP5416
1.Introduction, Network overview 2.Network performance, Application layer 1 3.Application 2
4.Transport 1
5.Transport 2
6.Network science: queues
7.Multimedia network 1
8.Multimedia network 2
9.Wireless and Mobile 1
10.Wireless and Mobile 2
11.Advance Network Protocols
12.Network science: Network optimization* 13.Recent advances in Network*, Review
1.Basic network performance analysis 2.Wireshark, HTTP packet sniffing 3.Python socket programming
4.Math foundations for network analysis 5.Transport layer and TCP
6.Network and queue simulator 7.Multimedia network 8.Real-time protocol 9.Scheduling and Queues 10.Network programming 11.Wireless and noise 12.Internet of Things Experiment 13.T: Review and Q&A
Facts/Knowledge
› How is information transported?
› How to make communications efficient?
› Why does it work in this way? (Differentiate this unit from basic-level units.)
› Tutorials: Use math to solve problems
› Why is math important? Practice
› Labs: will require programming
› All programming will be done in Python (version 3.X)
You should be fine if you know Java/C › Wireshark experiment
Layered Network
ISO/OSI model
application
presentation
› ISO: International Organization for Standardization › OSI:OpenSystemsInterconnection
Network Layers
internetwork /Internet
network interface
application
presentation
application
application
ISO/OSI model textbook Other textbooks Other names
Network Layers
How to provide network applications satisfies users?
How to provide end-to-end connections for programs running at different devices in the network?
How to send message to non-adjacent nodes?
How to organize data transfer among adjacent network nodes?
How to transfer bits from one device to another?
Application
Physical Layer
Role: Transmitting raw bits over a physical link connecting network nodes.
http://www.eetimes.com/document.asp?doc_id=1276305
Link Layer
Role: data transfer between neighboring network elements.
Bit error detection:
Sender 010101, receiver 010100 Medium access control:
Two devices talking at the same time? Link-layer addressing:
This information is for you.
Network Layer
Role: routing and forwarding packets from (every) source to (every) destination
Transport Layer
Role: manage program-program (process-process) data transfer
Application Layer
Role: support network applications
Preview: Practice
application
HTTP, FTP, SMTP, DNS, P2P…
TCP, UDP, Transport Protocol
Video/Audio Over TCP/UDP
network support for multimedia
Wireless network
Preview: Theory
application
Network Optimization
Max min fairness
Queueing Theory
Principles of CDMA
Example: Game Theory
Preview: Programming/Experiment
application
Socket programming
Queue simulator
Network analysis example
Two users competing for one channel
Two users competing for one channel
A collision happens! No one is successful!
Two users competing for one channel
Situations
User 1’s benefit
User 2’s benefit
1 off, 2 off
1 on, 2 off
1 off, 2 on
1 on, 2 on
Two users competing for one channel
Situations
User 1’s benefit
User 2’s benefit
1 off, 2 off
1 on, 2 off
1 off, 2 on
1 on, 2 on
In cellular network, for example, we can schedule 1 and 2 in a fair way. In many other situations? Selfish users.
Two users competing for one channel
Situations
User 1’s benefit
User 2’s benefit
1 off, 2 off
1 on, 2 off
1 off, 2 on
1 on, 2 on
Solution: Game Theory!
Mathematical models of conflict and cooperation between intelligent rational decision-makers!
Useful to solve many economical problems!
Also useful to analyse computer networks and the Internet!
Prisoner’s dilemma
Two members of a criminal gang are arrested
Each prisoner has no means of communicating with the other
Each prisoner can: 1 confess
2 keep silent
Prisoner’s dilemma
Both confess: both serve 5 years in prison Both keep silent: both serve 1 year in prison
A confesses, B keeps silent (vice versa): A is set free
B serves 10 years in prison
Prisoner’s dilemma
A’s decision (A, B) utility
B’s decision
Keep silent
Keep silent
A’s decision (A, B) utility
B’s decision
Keep silent
Keep silent
The tuple satisfies: no player has anything to gain by changing only his own strategy
A’s decision (A, B) utility
B’s decision
Keep silent
(-5,-5) (-10,0)
A changes his/decision, loss
Keep silent
The tuple satisfies: no player has anything to gain by changing only his own strategy
A’s decision (A, B) utility
B’s decision
Keep silent
Confess (-5,-5)
B changes his/decision, loss
Keep silent
The tuple satisfies: no player has anything to gain by changing only his own strategy
A’s decision (A, B) utility
B’s decision
Keep silent
Keep silent
Not a Nash (-1,-1) Equilibrium !
The tuple satisfies: no player has anything to gain by changing only his own strategy
Back to our problem
Back to our problem
1’s decision (1, 2) utility
2’s decision
Keep silent
Keep silent
Back to our problem
1’s decision (1, 2) utility
2’s decision
Keep silent
Keep silent
Two Nash Equilibria
Back to our problem
1’s decision (1, 2) utility
2’s decision
Keep silent
Keep silent
Two Nash Equilibria
Pure and mix strategy
This is still not ideal.
Solution: mixed strategy.
Each player can make probabilistic decision! User 1: transmit with probability p1
keep silent with probability (1-p1) User 2: transmit with probability p2
keep silent with probability (1-p2)
Back to our problem
1’s decision (1, 2) utility
2’s decision
Keep silent
Keep silent
(1-p1)*(1-p2)
-5*p1*p2+10*p1*(1-p2)+0*(1-p1)*p2+0*(1-p1)*(1-p2) = -5*p1*p2+10*p1*(1-p2)
Let’s try p2=2/3
User 1’s average utility
-5*p1*p2+10*p1*(1-p2) =-5*p1*2/3+10*p1*1/3
No matter how to change p1, user 1’s utility is 0
No matter how to change p2, user 1’s utility is 0
p1=p2=2/3 is a Why?
User 1’s average utility
No matter how to change p1, user 1’s utility is 0 If p1=2/3
No matter how to change p2, user 1’s utility is 0
What happens if users are cooperative?
If the users are not selfish,
p1=p2=1/3 is the optimal solution User 1’s average utility is 5/3
User 2’s average utility is 5/3
Network performance in summery
Situations
Selfish users
p1=2/3, p2=2/3
Cooperative users
p1=1/3 p2=1/3
Four sources of packet delay
transmission
dnodal = dproc + dqueue + dtrans + dprop
propagation
dproc: nodal processing §check bit errors §determine output link §typically < msec
dqueue: queueing delay § time waiting at output link for
transmission
nodal processing
§ depends on congestion level of router
Four sources of packet delay
transmission
dnodal = dproc + dqueue + dtrans + dprop
propagation
nodal processing
dtrans: transmission delay:
§ L: packet length (bits) § R: link bandwidth (bps) § dtrans = L/R
dtrans and dprop very different
dprop: propagation delay:
§ d: length of physical link
§ s: propagation speed in medium (~2x108 m/sec)
§ dprop = d/s
Transmission Delay and Propagation Delay
bit 1 trans
bit 2 trans
Transmission delay
...... t bit N trans
Overall delay
Propagation delay
t bit1 arrives bit2 arrives Bit N arrives
Store and Forward
Store-and-forward
per packet
›one-hopnumericalexample: - L = 7.5 Mbits
- R=1.5Mbps
- delay = 5 sec
destination
› takesL/Rsecondstotransmit(pushout)
L-bit packet into link at R bps
› storeandforward:entirepacketmust arrive at router before it can be transmitted on next link
› end-enddelay:2L/R(assumingzero propagation delay)
Queueing delay
› R: link bandwidth (bps)
› L: packet length (bits)
› a: average packet arrival rate
v La/R ~ 0: avg. queueing delay small
v La/R <~ 1: avg. queueing delay large v La/R > 1: more “work” arriving
than can be serviced, average delay infinite!
traffic intensity = La/R
A Brief Discussion on Queueing Theory
Properties of a Queue
› Job arrival
› Job service time
› Number of servers › Queue size
› Service disciplines
Properties of a Queue
› Job arrival
– Poisson process
– Number of arrivals in [0, t): N(t) – Distribution of N(t)
– Mean:E(N(t))=λt – Arrival rate λ
Properties of a Queue
› Job service time
– Exponential distribution, with mean of 1/μ
– PDF: probability density function μ e−μx
– CDF: Cumulative distribution function 1 − e−μx – Mean: 1/μ
– Can serve μ jobs per unit time.
– Service rate: μ
Properties of a Queue
› Number of servers -1
› Queue size – Infinity
› Service disciplines – First in first served
Properties of a Queue
› Conclusions
› Mean waiting time › 1/(μ- λ)
› Derivation will be shown later.