Intro Short

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TCOM 500

Introduction to Networks

and Protocols


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A Few Words About Logistics Meeting times: Mon. & Wed. 12:00pm-1:30pm, Towne 100 (Heilmeier Hall)

Course wiki: http://alliance.seas.upenn.edu/tcom500-wiki

Announcements, documents, Q&A forums, homeworks, exams

Use https instead to access Private Content (Assignments & Solutions, pastexams, etc.) and edit the Discussion Forums to post and view questions

Grades posted on Sakai: https://learning.upenn.edu/xsl-portal

Instructor: R. Guerin ([email protected]) Office Hours: Mon. & Wed. 2:30pm-3:30pm (367 GRW )

TAs/Graders: Answer class related questions on wiki and grade homeworks

Hadi Afrasiabi ([email protected]) Office Hours: Tuesday 2:00pm-4:00pm (Moore 306)

Sangeetha Abdu Jyothi ([email protected])

Office Hours: Thursday 5:30pm-7:30pm (Moore 306)

Recitation: Towne 307, Friday 5pm-6pm

Project presentations: Towne 309, Thursday 5pm-6pm (after 11/03/11)
http://alliance.seas.upenn.edu/tcom500-wikihttps://learning.upenn.edu/xsl-portalmailto:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]:[email protected]://learning.upenn.edu/xsl-portalhttps://learning.upenn.edu/xsl-portalhttps://learning.upenn.edu/xsl-portalhttp://alliance.seas.upenn.edu/tcom500-wikihttp://alliance.seas.upenn.edu/tcom500-wikihttp://alliance.seas.upenn.edu/tcom500-wiki


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Course Structure and Material

Course material

Textbook: Peterson & Davie Computers Networks: A System Approach, 5th Ed.

Course slides, handouts, links to lots of useful material on wiki

Course grading

Homeworks (5%)Low weight, but dont do them at your own risk

On average one new homework every week

Due at beginning of class (no late homework unless agreed upon in advance)

Gradually increasing penalty (-0pts, -5pts, -10pts, -10pts, )

OPTIONAL Project - In-class Presentation + Report (20%)

Teams of 1 or 2 students

Short two-page report on selected topic (see wiki for a listSelect by 9/30/11)

15 mins (10+5 mins) presentations in 2ndhalf of semester (Thursdays 5pm)

Exams With/Without Projects: 30%/40% (Midterm); 45%/55% (Final)

Midterm in class on Monday 10/24/11 (after Fall break)

Final exam on Monday 12/19/11 9:00am-11:00am (Room TBA)

Oralmake-up exams only for reasons approved under University policy

Schedule: Full syllabus and tentative class schedule on wiki


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More on Policies

Please review Penns Code of Academic Integrityathttp://www.vpul.upenn.edu/osl/acadint.html

Collaboration

Permitted on homeworks, but what you turn in must be yours

No verbatim copies!

Grade of zero for first homework violation; course grade of F for repeat offense Projects are collaborative in nature

Both students get the samegrade

You MUST explicitly cite/acknowledge any material used in your project

Exams

Obviously, no collaboration is allowed during exams!

They are open-book and brand new every year

Access to soft copies during exams is allowed, but Internet access is prohibited

Violations of the courses collaboration policy will be punished by an

F in the class and immediate referral to the Office of StudentsConduct for further action

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http://www.vpul.upenn.edu/osl/acadint.htmlhttp://www.vpul.upenn.edu/osl/acadint.html


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Courses Goals

To give you an understanding of the variouscomponents involved in realizing moderncommunication systems and the trade-offthey embody

Generating and receiving bits, and protectingthem from errors or malicious users

Connecting devices and allowing them to deliver

bits to an increasingly large number of systems Quantifying the performance of different system

and technologies, and the associated trade-offs

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Courses Formal Objectives

Develop your Ability to assess the different components of network protocols

and packet switches in terms of their functionality andperformance and their applicability in different environments

Awareness of key performance metrics for data communication

systems and how to interpret them Ability to identify suitable networking technologies and systems

based on given performance and functionality targets

This being said, this is only an introduction to Networks andProtocols, so we will only be able to scratch the surface

Important: In order to maximize the odds that theseobjectives can be successfully met, please ASK QUESTIONS

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Reading Assignment

Textbook: Chapter 1 Sections 1.1-1.3

Section 1.5

Section 1.4 (optional)

Marsic online book: Section 1.1 (optional) Bonaventure online book: Chapter 2

(optional)


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Our Scope Broadly Speaking

What are the core technologies behind

the Internets content delivery abilities?


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Internet Content DeliveryJane watches a YouTube video

How does her computer find thelocal YouTube server?

How does data get delivered backand forth to ensure smooth video

delivery?

R1

R2

Jane

The Internet


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A Day in the Life of a (basic) Packet

1. Name to IP address (DNS)

2. IP address to IP address (defaultgateway local routing)

3. IP address to MAC address (ARP)

We have just identified three of the

core layers involved in theInternets operation

R1

R2

Jane

The Internet


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Local Delivery From Jane to R1

MAC layer forwarding(IP packet in MAClayer frame)

R1

R2

Jane

The Internet


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Crossing the Internet(A network of networks)

From R1 to R2

IP routing

(based on CNNs

destination address)

R1

R2

Jane

The Internet


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Local Delivery From R2 to CNN server

MAC layer forwarding(IP packet in MAClayer frame)

R1

R2

Jane

The Internet


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Our Scope

Well look at both the protocols involved inrealizing content delivery, and the factorsthat influence the performance of this

delivery As a preview: Two examples of issues

associated with the latter

Downloading large files Streaming real-time data, e.g., audio/video

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Living in a Packet World

Download

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Download time calculation1st packet: Starts at t=0 and arrives at R3 att1=12,000/10

9+1s+12,000/1010+3ms+12,000/1010+3ms=6.0154ms laterFrom this point onward R3 transmits non-stop until the whole file has beensent (subsequent packets arrive faster than they are transmitted at 5Mbps)Last (85,000th) packet:

- Departs R3 at tL=6.0154ms+85,000x12,000/5x106

1.026sec- Arrives at destination 1s laterNote:- No lost or erroneous packets- Bottleneck link (5Mbps) dominates the delay- Assumes R3 can store most of 1GBfile- No TCP like congestion/flow control (non-stop transmissions by sender)

File 1Gbps10Gbps 10Gbps 5Mbps

1GB 85,000 pkts

1s 3ms 3ms1s

1 pkt

12,000 bits

R1 R2 R3


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Living in a Packet World

Streaming

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100Mbps

10Gbps 10Gbps 5Mbps

8kbps and

120Bytes pkts(100B payload

+20B header)

1s 3ms 3ms 1s

Delay time calculationPacketization delay (time to generate one packet worth of bits)- 800bits/8kbps = 100ms

Transmission delay-t= 960/108+1s+960/1010+3ms+960/1010+3ms+960/5x106+1s6.2ms

Playback delay (data not played immediately when received to avoid gapsin case the next packet is late, e.g., because of network congestion)- (k-1)x100ms, where kis number of packets at received before playbackNote:- Delay dominated by packetization/playback delay- And (possibly) bottleneck link (5Mbps)

R1 R2 R3


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Identifying Internet ComponentsThe Role of Layers

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Network

Data Link

Physical

Network

Data Link

Physical

Network

End-System End-System

Why Layers? Avoid duplication of functionality

Facilitate evolution (modular)

Shield upper layers from details

and differences of lower layers


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Our Focus

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

Network

Data Link

Physical

Network

Data Link

Physical

Network

End-System End-System

Two players and their interactions


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How does a packetgets created in thefirst place?

The role or layers

Jane

R1

R2

The Internet

What happens in there?

Illustrating Layers: The User/Host Side


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Host Interfaces

Host 1 Host 2

Service

interface

Peer-to-peerinterface

High-lev elobject High-lev elobject

Protocol Protocol


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Protocol Machinery

Applications select services based on their needs

Services are invoked through well-defined interfaces

Services provide specific functionality, e.g., reliability, timing, etc.

Services can invoke other services (a nested set of interactions)

Protocols specify the semantics of service invocation and functions

Host 1 Host 2

Fileapplication

Digitallibrary

application

Videoapplication

Fileapplication

Digitallibrary

application

Videoapplication

Internet


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Illustrating Layers: The Network Side

R1

R2

Jane

The Internet

Mapping an application/service to anaddress: Naming service (DNS)

Mapping an (IP) address to a packetforwarding decision: Routing service

Mapping IP routing decisions to local

physical resources: IP address to MACaddress (ARP)


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The Internet View of Layers

Application

Network

IP

TCP UDP

Data Link &Physical

Network

Transport

ApplicationPresentationSession


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Revisiting Course Syllabus (1)

Information Generation & Transmission

Issues: Volume, speed, correctness ofinformation transmission (what is information?)

Accessing transmission resources

Controlling (or not) access to transmissionresources across users

Bits &low-levelpacketissues(PHY)

Primarilylink layer

?


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Revisiting Course Syllabus (2)

Locating and delivering information

Managing end-to-end informationdelivery

??

Where is Nikkei.com? How do I get there?

IP layer issues,i.e., name

resolution, routing

Transport layerissues, i.e.,congestion, QoS,security

What bandwidth sharefor which flow?

What security, where?


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Course Coverage

The local view Dealing with bits (phy. layer)

Generating and receiving bits

Detecting and correcting errors

Framing bits into packets

Arbitrating transmissions (link layer)

Wired and wireless links A detour into modeling

Queueing systems

Markov chains

The small network view

Connecting wires together

Switches

Connecting switches together

Locating where things are

Forwarding packets

The large network view Knowing where things are anddeciding how to get there

Naming services

Routing protocols

Forwarding packets at

increasingly high speeds The end-to-end view

End-user resource management

TCP (the end-to-end principle)

Managind network resources

Service differentiation and

resources allocation

Securing information

Encryption and authentication

Protecting access toinformation (firewalls)

Intro Short

Documents

Transcript of Intro Short