Peer to Peer networks and
Performance
Hanoch Levy
(hanoch at cs.tau.ac.il)
Office: Kaplun 511
Office hours: by appointment
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Course Information
Lectures:
Wed
9-12 Shreiber 8
Web site: http://www.cs.tau.ac.il/~hanoch/
And follow the link: Advanced topics in Computer-Networks –
Peer-to-Peer Networks
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Course Objective
1. Study P2P networks
2. Open the door for research in this area
(Master/ Ph.D)
3. Cover both: Theoretical background
and advanced material
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Course Approach
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Prerequisites: Course in computer Networks/
Equivalent / teacher approval
Requirements:
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Most material is New (articles)
Requires some analytic models
Approach:
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Theoretical background (performance: elementary
queueing theory) – frontal lectures by teacher.
Recent material: (articles) – lectures by students
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Course Structure and requirements
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First half of semester: Teacher lectures
2nd half of semester – student lectures.
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Each student gets one paper – and covers
one paper in 45 minutes.
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Course requirements
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First half (theoretical): In Class Exam (5060% of grade)
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2nd Half: Give a good lecture. (40-50% of
grade)
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exam time: see Mazkirut
HW assignments
Active participation will benefit a bonus
Overflow students (if any): lecture can be
replaced by special assignment by lecturer.
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Course Information
Supporting Books (theoretical part)
1. Queueing Theory, L. Kleinrock, Vol I, Wiley
(hard copy)
2. Online books:
1. Web site: http://web2.uwindsor.ca/math/hlynka/qonline.html
(search “queueing hlynka)
2. Introduction to Queueing Theory (2nd edition).
Robert B. Cooper. 1981. 347 pp. This classic book is available
on line through Robert Cooper's home page. The link to the book is:
http://www.cse.fau.edu/~bob/publications/IntroToQueueingTheory_
Cooper.pdf
The solution manual (by Borge Tolt, 182 pages, 1981)
is available online at
http://www.cse.fau.edu/%7Ebob/publications/QueueingTheory_soln
s.pdf
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Course Information
Supporting Books (theoretical part – cont )
3. Queueing Theory. Ivo Adan and Jacques
Resing. 2001. 180 pp.
4. Queues: –A Course in Queueing Theor. Moshe Haviv.
October 1, 2009. New and complete.
5. more…
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Motivation
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Last 10-15 years: communications revolution
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Internet + Computer communications
Is a key factor of the Information revolution
Implications
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A drastic change of some aspects of life
Revolution is affected by life
Technology drives applications
Applications drive technology
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Motivation (cont)
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Applications / technology / research 
rapidly change over time
If want to stay in frontier:
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=> Research material
=> Course material
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very dynamic
very dynamic
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Objectives
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Computer Networking course: Internet infra-structure
1 Introduction and Layering
2 Physical Layer, Data Link Layer, MAC Protocols
3 Hubs, Bridges, SwitchesData Link Layer
4 Switching UnitsSTP, Switching Fabric
5 Scheduling: Buffer Management Scheduling, WFQ example
6 Network Layer: RoutingRouting
7 Reliable Data TransferIP
8 End to End ProtocolsARQ
10 Flow Control, Congestion ControlTCP flow & congestion control
11 Network SecurityNetwork Sniffing (no slides)
12 DNS, HTTPTCP (state chart)
13 DDoS
ALL – operations of network of networks.
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Objectives (2)
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Advanced Material – network development
following technology
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Peer to Peer (P2P): Bittorent, Skype
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Songs /movies / video-on-demand/video online
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Internet Physical Infrastructure
Residential access
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Cable
Fiber
DSL
Wireless
ISP
Backbone ISP
ISP
 The Internet is a network
Campus access,
e.g.,
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Ethernet
Wireless
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of networks
 Each individually
administrated network is
called an Autonomous
System
(AS)
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Data Networks
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Set of interconnected nodes exchange information
sharing of the transmission circuits= "switching".
many links allow more than one path between every
2 nodes.
network must select an appropriate path for each
required connection.
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Real Network
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Peer to Peer – what is it?
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“Historical” Internet : send
data from A to K.
Client-server model:
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A = server = data source
K = client data consumer
If C wants too – get from
A (unicast or broadcast)
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Peer to Peer – what is it
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A (source) sends to K.
K (client) may
become now a
server.
K sends to C (another
client).
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Peer to Peer – what the diff?
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A
K
Server
Client (user)
Commercial
Costs
Private
“Cost free”
Charges
“contributes”
Legal
obligations
Legal??
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Peer to Peer – what the diff?
A
K
Small number
Huge number
Reliable
Non reliable
planned
unplanned
Huge traffic
80%!!!!
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Peer to Peer – How important
• 0% of costs
• O(0)% of revenues
• 0% of planning
•  “Nothing”
• BUT: 80% of traffic
•  cannot disregard…
•  If you can’t beat them, join them…
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Peer to Peer – Historical View
• Networks developed for 40+ years
• Internet – started developing late 70’s early 80’s
• Distributed, Semi Organized
• ATM – developed throughout the 90’s
• huge amount of money!!!
• Very well organized network
• “failed”
• P2P – started in the 00’s
• VERY unorganized
• 80% of traffic (though SMALL % of money)
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Peer to Peer – WHY??
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Legal (this is how it started…)
Broadcast is not really
implemented
A is bottleneck
Resource Utilization: K is idle
X% (95?)of the day
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Scalability
Issues:
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Communications (costs!!)
CPU
BW cost? Free ride?
Files? Video on demand? Stream
(video Broadcast)
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Questions for this course
Is it viable? Does it have life of itself?
 Can it survive without economy?
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Can you carry 80% of traffic without make
charges?
 Are users (clients) going to let it go?
 Are ISP’s going to be happy?
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Can 80% go unnoticeable without
economic bodies “join the party”
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E.g – will ISP take advantage of it?
Is it the right way to plan a net?
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Theory
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Many network models – based on
stochastic modeling
Queueing systems
 Stochastic processes
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P2P models – included
 Objective: study basic stochastic /
queueing models
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Elementary Queueing theory
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