Computer Communication

- an introduction

Maria Kihl

Reading directives

Forouzan 4th ed.: Chapter 1, Introductions of

Chapters 26 and 27.

Forouzan 5th ed: Chapter 1, 25.1, Introductions of

26.1-4

Kihl: Kapitel 1, 8.8

2

Internet from your perspective

Internet from my perspective

4

Data communication

After torches and smoke signals, the optical telegraph

was invented in the 18th century.

5

Data communication

Optical telegraphs evolved into electrical telegraphs, which

quickly increased the available data communication speed and

distance.

6

Telephone networks

7

The need for telephone networks became obvious in the late

19th century...

Telephone networks

The telephone networks were built on the idea of circuit switching.

8

Basics of circuit switching

9

Packet switched networks

Several people proposed the idea of packet switched

networks in the early 1960s.

10 Source: http://www.samhassan.com

Basics of packet switching

11 Source: http://www.tcpipguide.com

ARPAnet was developed in 1968

Robert Taylor at ARPA (later DARPA) had three

terminals for connecting with different sites:

“For each of these three terminals, I had three different

sets of user commands. So if I was talking online with

someone at S.D.C. and I wanted to talk to someone I

knew at Berkeley or M.I.T. about this, I had to get up

from the S.D.C. terminal, go over and log into the

other terminal and get in touch with them. I said, oh,

man, it's obvious what to do: If you have these three

terminals, there ought to be one terminal that goes

anywhere you want to go where you have interactive

computing. That idea is the ARPAnet.” 12 Source: http://partners.nytimes.com

ARPAnet

• Four Interactive Message

Processors (IMP) at four

universities connected with

leased lines of 50 kbps.

• The IMPs could store and

forward messages.

• The picture shows Leonard

Kleinrock with the first IMP at

UCLA. 13

Source: http://www.lk.cs.ucla.edu

Protocols

• To form a computer network, there must be standardized

rules for the communication and host identification, which

is called protocols.

• ARPAnet used a network protocol called the 1822 protocol.

It defined how IMPs could communicate and forward

messages. Also, each host computer had a numeric address.

• Also, the Network Control Protocol (NCP) enabled several

applications on the same host.

14

ARPAnet evolution

15

Client/Server paradigm

Basically all early applications were based on the

client/server paradigm.

16

Request

Reply

Telnet

Telnet was invented in 1969, and provided access to a

remote terminal.

17

TELNET,

klient

Terminal

driver

Network

TELNET,

server

Local computer

Applications

Pseudoterminal

driver

Email

• Ray Tomlinson sent the first email in 1971 between

two computers in the same room.

• To separate a specific user on a host computer, he

used the ”@” sign,

which was unused on

the keyboard.

18

Email

Today, email basically works the same way:

19 Source: http://www.tekguard.com

File Transfer Protocol (FTP)

Another original application was FTP, which was

devloped in 1971, and that enabled file transfer

between two host computers.

20 Source: http://opcenter.cites.uiuc.edu

Internet protocol

• In 1973, Robert E. Kahn and Vincent Cerf at DARPA

developed the ideas of an internetwork protocol that made

it possible for hosts on different networks to communicate

with each other.

• The ideas were defined as the Transmission Control

Protocol (TCP) protocol in 1974, where the term

”Internet” was introduced.

• Later, some parts of the TCP protocol were moved to the

Internet protocol (IP), creating the TCP/IP protocol suite.

21

Basic idea of Kahn and Cerf’s

internetworking

22

NetworkNetwork

Network

Host identification

(Addresses)

Forwarding of messages

between networks

(routing)

End-to-end reliability

(error and flow control)

Internet was born

• The Internet protocol suite was formalized in 1982.

• Jan 1 1983, all networks connected to the Internet had to

use the TCP/IP protocol suite.

23

1991: World Wide Web (WWW)

1984-1990: Tim Berners-Lee and his

group at CERN worked on the ideas of

information presentation and sharing.

1990: HyperText Transfer Protocol

(HTTP), HyperText Markup Language

(HTML), a web browser, and server

software were presented at CERN.

1991: WWW goes public

1993: Mosaic, the first public web

browser was presented. 24 Source: http://info.cern.ch/

First web site: http://info.cern.ch

• The first web site is

still working.

• WWW is based on a

simple client/server

protocol HTTP, where

clients send requests

for pages to the web

server.

25

1991: The Trojan Coffee room pot

• The people working at the Computer Laboratory at

the University of Cambridge implemented the first

real-time Internet video application for their coffee

pot.

• The application server sent real-time images of the

coffee pot to the clients.

26 Source: http://www.cl.cam.ac.uk/coffee/coffee.html

The rest is almost not history

• 1994: Pizza Hut started first online webshop

• 1997: AOL instant messanger

• 1997: Sixdegrees.com (first modern social network)

• 1997: Google.com

• 1999: Napster

• 2001: BitTorrent

• 2003: Skype

• 2005: YouTube

• 2005: Facebook.com

• 2008: Spotify

27

Peer-to-peer paradigm

Several of the modern Internet applications are based

on the Peer-to-peer (P2P) paradigm.

28

Example: Skype

29 Source: http://www.technology-training.co.uk

Me: Maria Kihl, Associate Professor at Dept. of Electrical and Information technology

• MSc in Computer Science and Engineering (D88)

• PhD in Communication Systems, 1999

• Research leader for several projects with focus on

Performance of Content-based Internet

applications and architectures.

• Strong academic collaboration with Dept. of

Automatic Control and Acreo AB

• Industry collaborations with Ericsson, TeliaSonera,

TV4, SVT, Spotify, Procera Networks, etc. 30

Evolution of Internet usage (traffic

volumes) seen from the users

31

2007: 2011:

J. Li, A. Aurelius, V. Nordell, M. Du, Å. Arvidsson, M. Kihl:

A five year perspective of traffic pattern evolution in a residential broadband access network

Future Network & Mobile Summit 2012

Content distribution architectures

Media content is stored in back-end server clusters

(cloud) and then distributed to clients when requested.

32

Internet

ContentClients

Example:Live sport channel at TV4

33

National ISPAccess network

Modem

Speakers

Cache servers

(http)

ProductionTransmissi

on control

IP multicast

networkEncoding

Encryption Ingest serversOrigin servers

(http)

PC / CE

device (TV /

bluray)

Content

Distribution

Network

(CDN)Ingest servers

(http)

Performance challenges

• Client/server archictures are usually deployed:

• Standardized protocols as HTTP are used.

• Control of the material.

• Client/server archtectures cause performance

problems:

• Heavy traffic loads on network infrastructure (unicast

transmission).

• Delays due to centralized data centers and overloaded

access networks. 34

One solution: P2P and caches

(Spotify)

35 Source: http://www.csc.kth.se/~gkreitz/

Impact of using caches and P2P

(Spotify)

36 Source: http://www.csc.kth.se/~gkreitz/

Internet from your perspective

Internet from my perspective

38

Course objectives

• Introduction to computer communication and

networking, with focus on the Internet.

• Digital communication

• Network access

• Internet protocols

• Routing

• Mobile networks

• ”Hands-on” experience in two laboratory sessions.

39

40

Course content?

10 lectures

6 problem solving classes

2 mandatory laboratory sessions

One volontary midterm exam

Final exam: 23/10

41

Course material

Main textbook: ”Data Communications and Networking”

4th ed. by B.A. Forouzan.

Alternative textbook (in Swedish) ”Datakommunikation – en

inledande översikt” by M. Kihl. This book is used together

with the extra matreial by J.A. Andersson sold at KFS.

Material for the problem solving classes and laboratory

sessions sold at KFS.

42

Lectures

Mondays 10-12, Aulan

Wednesday 8-10, E:A

10 lectures, please look at the schedule for exact dates!

43

Problem solving classes

6 groups:

Monday 15-17, E:1409

Tuesday 10-12, E:1409

Tuesday 15-17, E:3319

Thursday 8-10, E:1409

Thursday 13-15, E:1409

Thursday 15-17, E:3318

The problem solving classes start next week.

44

Laboratory sessions

Two mandatory laboratory sessions:

Week 4-5: Point to Point Protocol (PPP)

Week 6-7: Networking

You need to sign up for each laboratory session on the

web. Before the lab you need to do the preparations.

You need to pass a written test!

45

Midterm exam

There is one voluntary midterm exam Monday 1/10 in

Aulan. The midterm exam is worth max 20 credits that

can be used for the final exam.

Content:

Lectures 1-6

Problem solving classes 1-3

46

Final exam

The final exam is given 23/10 at 14-19 in Victoria stadium.

The final exam is worth 100 credits, 50 credits are

needed to pass the exam.

47

International student?

The lectures will be given in Swedish. All material is in

English.

Also, Q&A sessions may be organized if needed.

If you need any help, please email Maria Kihl,

maria.kihl@eit.lth.se

48

Previous knowledge?

Read through the old exam

Classify yourself as between 1-5 where

1 = knows very little

5 = knows a lot

Write down your classification on the piece of paper

and hand in.