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2004.3.18.

Chapter 1.5. ~ 1.6.

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KNSS

Students’ feedbackHad difficulties due to:

•Lack of knowledge in networking•English•No microphone for audience

Picked up new terms/ideas•ad-hoc networking•incentives, coupons•QoS

Overall, it was a good experience

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Chapter 1. Foundation

Requirements of applications and people

Network architecture Key elements of computer networks Key performance metrics

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What do we do with the Internet?

Run ApplicationsWWW, email, soribada, bugsmusic, daum cafes, MP3 file sharing, MSN messengers, etc.

Type of data vs Application text/video/audio vs emailvideo/audio vs eDonkey/KaZaa

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How do these applications differ?

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Requirements in Network Design

Different from one’s perspectiveApplication programmer

•e.g. needs reliable delivery guaranteeNetwork designer

•cost-effective in that resources are efficiently utilized and fairly allocated

Network provider•easy to administer, manage, isolate faults, and account for usage

Ordinary user?

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Basic Requirements

Connectivity Cost-effective resource sharing Support for common services

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Basic Requirements: Connectivity

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Basic Requirements: Connectivity

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Basic Requirements: Connectivity

source

destination

Address?

Routing?

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Basic Requirements:Cost-effective resource sharing

Full Mesh

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Resource sharingSynchronous time division multiplexing

•each user takes a turn in transmission•user idles when one has nothing to send

Frequency division multiplexing•e.g. different TV stations on a physical TV cable link

Statistical multiplexing•physical link is shared over time•transmission on demand

Basic Requirements:Cost-effective resource sharing

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STDM vs Statistical Multiplexing

user1

user2

STDM

Statistical Multiplexing

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How to share?Whose packet to serve first?

•First-In First-Out (FIFO)•Round Robin

Whose packet to drop?•in congestion

How to guarantee or allow special treatment?•Quality of service (QoS) guarantee

Basic Requirements:Cost-effective resource sharing

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Basic Requirements:Support for common services

Identify common communication patterns request/replymessage stream

Reliability againstbit/burst errorpacket lossnode/link failure

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Network Architecture

What is it? Blueprint that guides design and implementation of networks

Core ideas: layering and protocols Layering

Abstraction of functions It provides manageability and modularity

Protocols abstract objects that make up layers service interface vs peer interface protocol specification vs protocol implementation

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OSI Architecture

Application

Presentation

Session

Transport

Network

Data link

Physical

Application

Presentation

Session

Transport

Network

Data link

Physical

Network

Data link

Physical

Network

Data link

Physical

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Internet Architecture

UDPTCP

IP

Network

Application

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The Internet Hourglass (Deering@IETF)

IP

TCP, UDP, ...

SMTP, HTTP, RTP, ...

email, WWW, phone, ...

ethernet, PPP, ...

CSMA, Sonet, ...

Copper, fiber, radio, ...