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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.
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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.
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Basics of circuit switching
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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
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Client/Server paradigm
Basically all early applications were based on the
client/server paradigm.
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Request
Reply
Telnet
Telnet was invented in 1969, and provided access to a
remote terminal.
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TELNET,
klient
Terminal
driver
Network
TELNET,
server
Local computer
Applications
Pseudoterminal
driver
• 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
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.
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Basic idea of Kahn and Cerf’s
internetworking
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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.
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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.
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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
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Peer-to-peer paradigm
Several of the modern Internet applications are based
on the Peer-to-peer (P2P) paradigm.
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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
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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.
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Course content?
10 lectures
6 problem solving classes
2 mandatory laboratory sessions
One volontary midterm exam
Final exam: 23/10
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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.
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Lectures
Mondays 10-12, Aulan
Wednesday 8-10, E:A
10 lectures, please look at the schedule for exact dates!
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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.
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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!
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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
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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.
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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,
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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.