Computer Networks and
Communications
[Δίκτυα Υπολογιστών και Επικοινωνίες]
Lecture 1: Introduction
Univ. of the Aegean
Financial and Management Engineering Dpt
Petros KAVASSALIS
1
What you will learn in this course

A set of fundamental concepts for understanding Data
Networks and the Internet






What is the Internet?
Internet architecture and layers
Internet applications and services
New concepts in the evolution of the Internet
The Internet goes Wireless…
Familiarization with the structure and organization of Digital
Networks


Business and Social Networks
Electronic Markets and Online Feedback Mechanisms
<[email protected]>
2
Who am I?

PhD in Economics and Management (Univ. Paris Dauphine
& Ecole polytechnique)

Research experience



Ecole polytechnique, Paris
MIT Center of Technology Policy and Industrial Development, MIT
CTPID (MIT Internet Telecommunications Convergence Consortium)
Current positions


Univ. of the Aegean (FME): Assoc. Professor
RACTI: Director of ATLANTIS Group
<[email protected]>
3
Communication tools


e-mail: pkavassalis [at] atlantis-group.gr
Course web site: see fme website
<[email protected]>
4
Course Textbook
[http://books.google.gr/books?id=Pdz64SJRBAC&dq=tanenbaum+networks&printsec=frontcover&source=bn&hl=el&ei=mldSfH9L4S2jAeJ5L3ZBQ&sa=X&oi=book_result&resnum=4&ct=result]
<[email protected]>
5
Supplementary Texts & References


William Stallings, Computer Networking with Internet
Protocols, Prentice Hall, 2004
James F. Kurose and Keith W. Ross, Computer Networking:
A Top-Down Approach, Addison-Wesley, 2008
<[email protected]>
6
Students evaluation

Class Participation (20%)
+

Assignments (20%)
+

Final Exam (60%)
<[email protected]>
7
What is a network?

A hardware and software communications system formed by
the interconnection of three or more devices

Devices may include:




Telephones
PCs
Routers
Other communications devices (please give examples)
<[email protected]>
8
Why use a network?

Allow multiple devices to
communicate concurrently

Allow communications to
proceed at the highest
achievable speed

Reduce cost associated
with the interconnections!


Look at that    
k = n (n-1) / 2
<[email protected]>
9
Network: The organization of a
communication network…

Assumes the use of some
interconnection equipment
in the middle

That was, in the early days of
communications, a Central
Office (CO)

That is, today, a Router
(please find a router picture
from the Web: what is the
functionality it provides?)
<[email protected]>
10
Like that!
Trunk Lines Connect
Switches to Switches and
Switches to Routers
Client Application
Access Lines
Connect Computers
to Switches
Server Application
Message (Frame)
Access
Line
Switch
2
Client
Computer
Server
Computer
Switch
1
Switch
3
Trunk
Line
Mobile
Client
Switch
4
Router
Wireless
Access Point
<[email protected]>
11
Outside
World
(The Internet)
11
Note 1: the Ethernet
C3- is out Port 15
D4-47-55-C4-B6-F9
Switch
Switching Table
Port
Host
10
A1-44-D5-1F-AA-4C
2
13
B2-CD-13-5B-E4-65
15
C3-2D-55-3B-A9-4F
15
C3-2D-55-3B-A9-4F
16
D4-47-55-C4-B6-F9
Port 15
3
1
A1-44-D5-1F-AA-4C
<[email protected]>
B2-CD-13-5B-E4-65
C3-2D-55-3B-A9-4F
12
12
Note 2: … and Internet
Host A
R1
Network X
Network Y
Route A-B
Network Z
R2
Host B
<[email protected]>
13
Network+: Functions grouped in layers
<[email protected]>
14
The geography of the Internet
<[email protected]>
15
Internet in a nutshell

Protocols control sending, receiving
of msgs




loosely hierarchical
public Internet versus private
intranet
Standards


Global ISP
e.g., TCP, IP, HTTP, IM, Ethernet
Composition: “network of networks”

Mobile network
Home network
Regional ISP
Institutional network
RFC: Request for comments
IETF: Internet Engineering Task
Force
<[email protected]>
16
Infrastructures and applications…

Communication infrastructure
enables various distributed
applications


E-mail, Web browsing,
Skypying, file sharing, online
games
Communication applications
are supported by


reliable data delivery from
source to destination
“best effort” (unreliable) data
delivery
<[email protected]>
Mobile network
Global ISP
Home network
Regional ISP
Institutional network
17
… “separated” in two blocks

IP (spanning-layer)
separates information
bitways from applications

Applications may work over
multiple substrates
(network techs) and these
substrates do not prespecify the development of
new applications
[I will come back!]

<[email protected]>
18