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Seminar on Advanced Internet applications and Systems . Hanoch Levy ( hanoch at cs.tau.ac.il ) Some slides adopted from Y. Mansour, Y. Afek. Course Information. Lectures: Tuesday 13-15 Kaplun324 .

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Seminar on Advanced Internet applications and Systems

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Seminar on advanced internet applications and systems l.jpg

Seminar on Advanced Internet applications and Systems

Hanoch Levy (hanoch at cs.tau.ac.il)

Some slides adopted from Y. Mansour, Y. Afek

H. Levy Advanced Net Seminar


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Course Information

Lectures: Tuesday 13-15 Kaplun324

Web site: http://www.cs.tau.ac.il/~hanoch/Courses/Seminar-2009/seminar-page.htm

Resources: A list of articles (web site + class)

Supporting Books:

  • An Engineering Approach to Computer Networking / Keshav

  • Computer Networks / Tanenbaum

  • Data Networks / Bertsekas and Gallager

H. Levy Advanced Net Seminar


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Course Objective

  • Get exposed to the advanced material in Computer Networks

  • Learn how to:

    • Read professional articles

    • Give Professional presentations

  • Exposition to what required of at Master Thesis.

H. Levy Advanced Net Seminar


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Structure + Grades

  • Structure:

  • Every week one lecture by a student.

    • Lecturer is encouraged to encourage students to participate.

    • Students are encouragedto participate.

  • Grade:

    • Based on material understanding + quality of presentation

    • Bonus for active participation

H. Levy Advanced Net Seminar


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Motivation

  • Last 10-15 years: communications revolution

    • Internet + Computer communications

  • Is a key factor of the Information revolution

  • Implications

    • A drastic change of some aspects of life

    • Revolution is affected by life

    • Technology drives applications

    • Applications drive technology

H. Levy Advanced Net Seminar


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Motivation (cont)

  • Applications / technology / research  rapidly change over time

  • If want to stay in frontier:

    • => Research material very dynamic

    • => Course materialvery dynamic

H. Levy Advanced Net Seminar


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Objectives

  • 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.

H. Levy Advanced Net Seminar


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Objectives (2)

  • Advanced Material – network development following technology

    • Peer to Peer (P2P): Bittorent, Skype

      • Songs /movies / video-on-demand/video online

    • Wireless  AdHoc + delay tolerant networks

    • Social networks

    • Security / DDoS

H. Levy Advanced Net Seminar


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Internet Physical Infrastructure

Residential access

Cable

Fiber

DSL

Wireless

ISP

Backbone ISP

ISP

  • The Internet is a network of networks

  • Each individually administrated network is called an Autonomous System (AS)

Campus access, e.g.,

  • Ethernet

  • Wireless

H. Levy Advanced Net Seminar

9


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Data Networks

  • 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.

H. Levy Advanced Net Seminar


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Real Network

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Layers:

Person delivery of parcel

Post office counter handling

Ground transfer: loading on trucks

Airport transfer: loading on airplane

Airplane routing from source to destination

Peer entities

each layer implements a service

  • via its own internal-layer actions

  • relying on services provided by layer below

H. Levy Advanced Net Seminar


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The seven Layers

Application

Application

Presentation

Presentation

Session

Session

Transport

Transport

Network

Network

Network

Data Link

Data Link

Data Link

Physical

Physical

Physical

There are only 5 !!

Application

Intermediate

system

End system

End system

H. Levy Advanced Net Seminar


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The seven Layers - protocol stack

data

Application

Application

AH

data

Presentation

Presentation

PH

data

Session

Session

SH

data

Transport

Transport

Network

Network

NH

data

Data Link

Data Link

Physical

Physical

TH

data

Network

Data Link

DH+data+DT

Physical

bits

  • Session and presentation layers are not so important, and are often ignored

H. Levy Advanced Net Seminar


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עיקרון השכבות

בשכבה X מתקבלת הודעה

זהה להודעה ששכבה

X מסרה בצד המקור

Destination

Source

Application

Application

Identical message

Transport

Transport

Identical message

Network

Network

Identical message

Data-Link

Data-Link

Network

H. Levy Advanced Net Seminar


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Internet protocol stack

application

transport

network

link

physical

  • application: supporting network applications

    • ftp, smtp, http

  • transport: host-host data transfer

    • tcp, udp

  • network: routing of datagrams from source to destination

    • ip, routing protocols

  • link: data transfer between neighboring network elements

    • ppp, ethernet

  • physical: bits “on the wire”

H. Levy Advanced Net Seminar


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Protocol layering and data

M

M

H

H

H

H

H

H

H

H

H

H

H

H

t

t

n

t

n

l

n

l

t

t

n

t

M

M

M

M

application

transport

network

Link

physical

M

M

source

destination

message

application

transport

network

Link

physical

segment

datagram

frame

H. Levy Advanced Net Seminar


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Physical layer L1

  • Moves bits between physically connected end-systems

  • Standard prescribes

    • coding scheme to represent a bit

    • shapes and sizes of connectors

    • bit-level synchronization

  • Internet

    • technology to move bits on a wire, wireless link, satellite channel etc.

H. Levy Advanced Net Seminar


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Datalink layer L2

  • (Reliable) communication over a single link.

  • Introduces the notion of a frame

    • set of bits that belong together

  • Idle markers tell us that a link is not carrying a frame

  • Begin and end markers delimit a frame

  • Internet

    • a variety of datalink layer protocols

    • most common is Ethernet

    • others are FDDI, SONET, HDLC

H. Levy Advanced Net Seminar


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Datalink layer (contd.)

  • Ethernet (broadcast link)

    • end-system must receive only bits meant for it

    • need datalink-layer address

    • also need to decide who gets to speak next

    • these functions are provided by Medium ACcess sublayer (MAC)

  • Datalink layer protocols are the first layer of software

  • Very dependent on underlying physical link properties

  • Usually bundle both physical and datalink in hardware.

H. Levy Advanced Net Seminar


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Network layer L3

  • Carries data from source to destination.

  • Logically concatenates a set of links to form the abstraction of an end-to-end link

  • Allows an end-system to communicate with any other end-system by computing a route between them

  • Hides individual behavior of datalink layer

  • Provides unique network-wide addresses

  • Found both in end-systems and in intermediate systems

H. Levy Advanced Net Seminar


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Network layer (contd.)

  • Internet

    • network layer is provided by Internet Protocol (IP)

    • found in all end-systems and intermediate systems

    • provides abstraction of end-to-end link

    • segmentation and reassembly

    • packet-forwarding, routing, scheduling

    • unique IP addresses

    • can be layered over anything, but only best-effort service

H. Levy Advanced Net Seminar


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Network layer (contd.)

  • At end-systems

    • primarily hides details of datalink layer

    • segments and reassemble

    • detects errors

  • At intermediate systems

    • participates in routing protocol to create routing tables

    • responsible for forwarding packets

    • schedules the transmission order of packets

    • chooses which packets to drop

H. Levy Advanced Net Seminar


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Transport layer L4

  • Reliable end-to-end communication.

  • creates the abstraction of an error-controlled, flow-controlled and multiplexed end-to-end link

    (Network layer provides only a ‘raw’ end-to-end service)

  • Some transport layers provide fewer services

    • e.g. simple error detection, no flow control, and no retransmission

  • Internet

    • TCP provides error control, flow control, multiplexing

    • UDP provides only multiplexing

H. Levy Advanced Net Seminar


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Transport layer (contd.)

  • Error control

    • GOAL: message will reach destination despite packet loss, corruption and duplication

    • ACTIONS: retransmit lost packets; detect, discard, and retransmit corrupted packets; detect and discard duplicated packets

  • Flow control

    • match transmission rate to rate currently sustainable on the path to destination, and at the destination itself

  • Multiplexes multiple applications to the same end-to-end connection

    • adds an application-specific identifier (port number) so that receiving end-system can hand in incoming packet to the correct application

H. Levy Advanced Net Seminar


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Session layer

  • Not common

  • Provides full-duplex service, expedited data delivery, and session synchronization

  • Internet

    • doesn’t have a standard session layer

H. Levy Advanced Net Seminar


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Session layer (cont.)

  • Duplex

    • if transport layer is simplex, concatenates two transport endpoints together

  • Expedited data delivery

    • allows some messages to skip ahead in end-system queues, by using a separate low-delay transport layer endpoint

  • Synchronization

    • allows users to place marks in data stream and to roll back to a prespecified mark

H. Levy Advanced Net Seminar


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Presentation layer

  • Usually ad hoc

  • Touches the application data

    (Unlike other layers which deal with headers)

  • Hides data representation differences between applications

    • characters (ASCII, unicode, EBCDIC.)

  • Can also encrypt data

  • Internet

    • no standard presentation layer

    • only defines network byte order for 2- and 4-byte integers

H. Levy Advanced Net Seminar


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Application layer

  • The set of applications that use the network

  • Doesn’t provide services to any other layer

H. Levy Advanced Net Seminar


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עיקרון השכבות

Destination

Source

אפליק 3

אפליק 2

אפליק 1

Application

UDP

TCP

Transport

Network (IPv4)

Network

Modem

Ethernet

WiFi

Data-Link

Network

H. Levy Advanced Net Seminar


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עיקרון השכבות

אפליק 3

אפליק 2

אפליק 1

UDP

TCP

Network (IPv4)

Modem

Ethernet

WiFi

Destination

Source

אפליק 3

אפליק 2

אפליק 1

UDP

TCP

Network (IPv4)

Modem

Ethernet

WiFi

Network

H. Levy Advanced Net Seminar


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Advanced Topics – this course

  • Denial of service (network security) – network maliciousness

  • Peer to Peer systems (files, video on demand, streaming)

  • Wireless Networks

  • Mobility

  • Delay tolerant networks

  • Social network

H. Levy Advanced Net Seminar


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Network Maliciousness – Denial of service

  • Network fundamental design principle:

    • User is polite/obey rules

    • User aims at maximizing his/her own performance

  • Today: Some users’ aim:

    • DEGRADE NETWORK PERFORMANCE

  • Many aspects of network design may collapse

  • Research subject:

    • How much damage: malicious user to innocent users

    • How vulnerable network mechanisms to malicious behavior

H. Levy Advanced Net Seminar


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Network Maliciousness – Cont

  • Anything studied in: Data structures /algorithms / Computer networks

    • If one user becomes malicious

    • How much damage can she pose

    • How should we pick our algorithms/design

  • Examples: Hash Table (open / closed)

  • Data structure course: Equivalent = O(1) avg per insert/delete/member

  • Malicious analysis (our master student)

    • Closed much more vulnerable

    • Attacker can hurt performance of innocent much more

    •  if you design a net  pick open

closed

open

H. Levy Advanced Net Seminar


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Peer to Peer

  • “Historical” Internet : send data from A to K.

  • Client-server model:

    • A = server = data source

    • K = client data consumer

  • If C wants too – get from A (unicast or broadcast)

H. Levy Advanced Net Seminar


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Peer to Peer

  • A (source) sends to K.

  • K (client) may become now a server.

  • K sends to C (another client).

H. Levy Advanced Net Seminar


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Peer to Peer – WHY??

  • Legal (this is how it started…)

  • Broadcast is not really implemented

  • A is bottleneck

  • Resource Utilization: K is idle X% (95?)of the day

    • Communications (costs!!)

    • CPU

  • Issues:

    • BW cost? Free ride?

    • Files? Video on demand? Stream (video Broadcast)

H. Levy Advanced Net Seminar


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Wireless Networks

  • Cellular net: base stations tx to mobiles

H. Levy Advanced Net Seminar


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Wireless Networks

  • Multihop wireless – use wireless devices as forwarding mechanisms

  • Difficulty: when node x transmits the whole area must be quiet (avoid colision).

  • How much spatial capacity the network has?

H. Levy Advanced Net Seminar


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Wireless Networks

1

  • Questions:

  • Difficulty (1) : when node x transmits the whole area must be quiet (avoid collision).

  • How much spatial capacity the network has?

    • Paper 2.1

  • Difficulty (2): How connected is the network

    • Paper 2.2

  • X

    2

    H. Levy Advanced Net Seminar


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    Wireless Networks

    1

    • Questions:

    • How do you allocate resources fairly + efficiently among users?

    • Difficulty (3) : x can be noisy on purpose, or can request many resources  denial of service to others.

      • Paper 2.3

    X

    2

    H. Levy Advanced Net Seminar


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    Wireless – Mobility

    • Wireless devices move around.

    • Movement can determine:

      • Density/ Load on network

      • Connectivity

      • Ability to transfer data from place to place

    • Need to understand the mobility patterns

    • Papers (3)

    H. Levy Advanced Net Seminar


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    Delay tolerant networks

    • Network of wireless mobiles

    • Not necessarily connected all the time

    • Application can afford DELAY (not real time). E.g:

      • Non urgent email

      • Copy of a song

      • General news

    • handheld mobility assist in transfering the info over the net.

    • Delay Tolerant Net

    • E.g: use the buss system over a campus

    • Papers (4)

    H. Levy Advanced Net Seminar


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    Social networks

    • The new (old?) hot thing on the net.

    • Data generated by users – for users == YouTube.

    • Understanding its properties = 5.1

    • Social contacts can be used to transfer data

      • E.g – spread info in campus.

    • Understanding the social interaction is needed.

    • Paper (5.2)

    Spreading info in university? In conference?

    H. Levy Advanced Net Seminar


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