Lecture 1

staff.fisika.ui.ac.id

Lecture 1

Introduction to

Computer Networks

Adhi Harmoko S, M.Komp

1


What is Network

• Telephone network

• Dialup

• Local area network

• Internet

• Mobile phone

• …

Nodes -- Interconnected

2


Why Internet

• The most successful network

• Open

• Heterogeneous

• Simple network, complex end-terminals

• End-to-end argument

• How about other networks

• Telephone

• Mobile phone

• Wireless LAN

• Cable TV

• IP convergence…

• And, about the authors of the text book

3


Motivation: Communication

• Need some common interface to communicate

network protocol

• A->B: Hi

• B->A: Hi

• A->B: What time is it

• B->A: 1:00pm

• What if no protocol…

• Woi kx ioa nio

• #@!> …

• …

4


An Example: Simple Mail

Transfer Protocol (SMTP)

• Scenario

• Email client: Outlook, TheBat, NetscapeMail …

• Email server: in Unix, Windows …

• Messages from a client to a mail server

• HELO

• MAIL FROM:

• RCPT TO:

• DATA


• QUIT

• Messages from a mail server to a client

• status code

• 1xx - Informative message

• 2xx - Command ok

• 3xx - Command ok so far, send the rest of it.

• 4xx - Command was correct, but couldn't be performed for

some reason.

• 5xx - Command unimplemented, or incorrect, or a serious

program error occurred.

• mail body

5


An Example: Simple Mail

Transfer Protocol (SMTP)

Outgoing message queue

user mailbox

mail

server

user

agent

SMTP

user

agent

SMTP

mail

server

user

agent

mail

server

SMTP

user

agent

user

agent

POP3,

IMAP

SMTP

user

agent

6


Internet Standardization Process

• All standards of the Internet are published as RFC (Request for

Comments)

• but not all RFCs are Internet Standards !

• available: http://www.ietf.org

• Till this morning: RFC3099

• A typical (but not the only) way of standardization:

• Internet draft

• RFC

• Proposed standard

• Draft standard (requires 2 working implementations)

• Internet standard (declared by Internet Architecture Board)

7


Internet Standardization Process

• All standards of the Internet are published as RFC (Request for

Comments)

• but not all RFCs are Internet Standards !

• available: http://www.ietf.org

• Till now: RFC3866

• A typical (but not the only) way of standardization:

• Internet draft

• RFC

• Proposed standard

• Draft standard (requires 2 working implementations)

• Internet standard (declared by Internet Architecture Board)

8


A Brief History of the Internet

• 1957

• USSR launches Sputnik, US formed Advanced Research

Projects Agency (ARPA) as a response

• 1968

• Bolt Beranek and Newman, Inc. (BBN) was awarded

Packet Switch contract to build Interface Message

Processors (IMPs) for ARPANET

9


A Brief History of the Internet

• 1969

• ARPANET (The Advanced Research Projects Agency

Network) commissioned: 4 nodes, 50kbps

10


Multiple Networks

• 1974: Initial design of TCP to connect multiple networks

• 1986: NSF builds NSFNET as backbone, links 6

supercomputer centers, 56 kbps; this allows an explosion

of connections, especially from universities

• 1987: 10,000 hosts

• 1989: 100,000 hosts

WELCOME by Leonard Kleinrock …

11


Web and Commercialization of the Internet

• 1991: NSF lifts restrictions on the commercial use of the

Net; World Wide Web released

• 1992: 1 million hosts

• Today: backbones run at 10Gbps, 100s millions

computers in 150 countries

• Internet history and Timeline

• http://www.zakon.org/robert/internet/timeline/

12


Growth of the Internet

in Terms of Number of Hosts

Number of Hosts on the

Internet:

Aug. 1981 213

Oct. 1984 1,024

Dec. 1987 28,174

Oct. 1990 313,000

Jul. 1993 1,776,000

Jul. 1996 19,540,000

Jul. 2000 93,047,000

Jul. 2002 162,128,493

1.000.000.000

100.000.000

10.000.000

1.000.000

100.000

10.000

1.000

100

10

1

1981 1984 1987 1990 1993 1996 1999 2002

13


Internet Physical Infrastructure

Local/Regional

ISP

Backbone:

National ISP

Local/Regional

ISP

• Residential Access

• Modem

• DSL

• Cable modem

• Internet Service Providers

• Local/Regional/National

• They exchange packets at

Point of Presence (POP)

• Campus network access

• Ethernet

• FDDI

• Wireless

• Access to ISP, Backbone

transmission

• T1/T3, OC-3, OC-12

• ATM, SONET, WDM

14


Local Access: ADSL

• Asymmetrical Digital Subscriber Line (ADSL)

• Telephone company’s solution to “last mile problem”

15


Local Access: Cable Modems

• Fiber node: 500 - 1K homes

• Distribution hub: 20K - 40 K homes

• Regional headend: 200 K - 400 K homes

16

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