Lecture 1

Internet Overview: roadmap

1.1 What is the Internet?1.2 Network edge

end systems, access networks, links

1.3 Network core network structure, circuit switching, packet switching

1.4 Delay, loss and throughput in Internet1.5 Protocol layers, service models1.6 Networks under attack: security

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Lecture 1

How is the Internet Organized

A hierarchical structure. hosts combine to form a Local Area

Network (LAN). LANs combine to form an Autonomous

System (AS) Autonomous Systems combine to form

the Internet.

Internetworked networks – Internet !

1-2

Lecture 1

What’s the Internet: “nuts and bolts” view

millions of connected computing devices: hosts = end systems running network

apps Home network

Institutional network

Mobile network

Global ISP

Regional ISP

router

PC

server

wirelesslaptop

cellular handheld

wiredlinks

access points

communication links fiber, copper,

radio, satellite transmission

rate = bandwidth

routers: forward packets (chunks of data)

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Lecture 1

What’s the Internet: “operational” view

Internet: “network of networks” Requires sending,

receiving of messages

protocols control sending, receiving of messages e.g., TCP, IP, HTTP, Skype,

Ethernet etc.

Design of protocols is the key for Internet

Home network

Institutional network

Mobile network

Global ISP

Regional ISP

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Lecture 1

What’s the Internet: an operational view

a human protocol and a computer network protocol:

human protocol

Hi

Hi

Got thetime?

2:00

time

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Lecture 1

human protocols:

… specific msgs sent… specific actions

taken when msgs received, or other events

network protocols: machines rather than

humans all communication

activity in Internet governed by protocols

What’s the Internet: an operational view

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Lecture 1

What’s a protocol?a human protocol and a computer network protocol:

Internet protocol example

Hi

Hi

Got thetime?

2:00

Connection req.

connectionreply

Get http://jjcweb.jjay.cuny.edu/ssengupta/slide.ppt

<file>time

human protocol

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Lecture 1

Thus protocols define• format, order of messages sent

and received among network entities,

• actions taken on message transmission and receipt

• address conflicts among network entities

What’s the Internet: an operational view

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Lecture 1

We have studied a high-level overview of the Internet!

Now, A closer look at the Internet structure!

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Lecture 1

Components of Internet:

Hosts (end-users) e.g. computers

access networks, physical media: wired, wireless communication links network core: interconnected

routers network of

networks1-10

Lecture 1

The network edge: End-users (hosts):

run application programs e.g. Web, email

client/server

peer-peer

client/server model client host requests,

receives service from always-on server

e.g. Web browser/server; email client/server peer-peer model:

minimal (or no) use of dedicated servers

e.g. Skype, BitTorrent

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Lecture 1

Access networks and physical media

Q: How to connect end systems to edge router?

residential access nets

institutional access networks (school, company)

mobile access networks

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Lecture 1

Residential access: point to point access

Dialup via modem up to 56Kbps direct access

to router (conceptually)

ADSL: asymmetric digital subscriber line up to 1 Mbps home-to-router up to 8 Mbps router-to-home ADSL deployment:

happening

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Lecture 1

Residential access: cable modems

HFC: hybrid fiber coax asymmetric: up to 10Mbps upstream, 1

Mbps downstream network of cable and fiber attaches homes to

ISP router shared access to router among home issues: congestion

deployment: available via cable companies, e.g., MediaOne, CableVision

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Lecture 1

Institutional access: local area networks

company/univ local area network (LAN) connects end system to edge router

Ethernet: shared or dedicated

cable connects end system and router

10 Mbps, 100Mbps, Gigabit Ethernet

deployment: institutions, home LANs happening now

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Lecture 1

Wireless access networks

shared wireless access network connects end system to router

wireless LANs: radio spectrum replaces

wire e.g., 802.11b/g (WiFi):

11 or 54 Mbps

wider-area wireless access next up (?): WiMAX

(10’s Mbps) over wide area

basestation

mobilehosts

router

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Lecture 1

The Client/Server Model Client/server model is a basic design for

Internet applications server - is the information provider client - is the information consumer

example web server and a client running web browser a CNN web server simultaneously serves

thousands of clients.

In this class, we will also learn how to construct Web pages at the client end!

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What is Internet? Components… Operational view… System (structure) view… Client-server and peer to peer model…

Access Networks…

Lecture 1

Summary: What have we learnt?

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Lecture 1

Next Up…

1.1 What is the Internet?1.2 Network edge

end systems, access networks, links

1.3 Network core network structure, circuit switching, packet switching

1.4 Delay, loss and throughput in Internet1.5 Protocol layers, service models1.6 Networks under attack: security

1-19