Computer Networks and
Communications
[Δίκτυα Υπολογιστών και Επικοινωνίες]
Lectures 8&9: Internet Protocols in Detail –
TCP/IP
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
<pkavassalis@atlantis-group.gr>
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
<pkavassalis@atlantis-group.gr>
3
Communication tools


e-mail: pkavassalis [at] atlantis-group.gr
Course web site: see fme website
<pkavassalis@atlantis-group.gr>
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]
<pkavassalis@atlantis-group.gr>
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
<pkavassalis@atlantis-group.gr>
6
Students evaluation

Class Participation (20%)
+

Assignments (20%)
+

Final Exam (60%)
<pkavassalis@atlantis-group.gr>
7
Reminder: Overview of the Internet
The structure of the Internet is roughly hierarchical
Petros KAVASSALIS <petros@cfp.mit.edu>
8
Reminder: A network architecture
Petros KAVASSALIS <petros@cfp.mit.edu>
9
Reminder: TCP/IP in practice
Petros KAVASSALIS <petros@cfp.mit.edu>
10
Operation of TCP/IP
Petros KAVASSALIS <petros@cfp.mit.edu>
11
Internet Transport Layer

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Common layer shared by all applications
Provides reliable delivery of data
In same order as sent
Commonly uses TCP


Example: Web browsing
Uses also UDP (for real-time traffic)
Petros KAVASSALIS <petros@cfp.mit.edu>
12
Internet Transport Layer key role



Provide logical communication
between app processes running
on different hosts
Transport protocols run in end
systems
 Send side: breaks app
messages into segments,
passes to network layer
 Receive side: reassembles
segments into messages,
passes to app layer
Two mail transport protocol
available to apps
 Internet: TCP and UDP
Petros KAVASSALIS <petros@cfp.mit.edu>
application
transport
network
data link
physical
application
transport
network
data link
physical
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Internet Transport Layer Protocols

Reliable, in-order delivery
(TCP)
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

Unreliable, unordered
delivery: UDP


Congestion control
Flow control
Connection setup
No-frills extension of “besteffort” IP
Services not available:


application
transport
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physicalnetwork
data link
physical
network
data link
physical
network
data link
physical
application
transport
network
data link
physical
Delay guarantees
Bandwidth guarantees
Petros KAVASSALIS <petros@cfp.mit.edu>
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TCP header
socket
door
application
writes data
application
reads data
TCP
send buffer
TCP
receive buffer
socket
door
segment
Petros KAVASSALIS <petros@cfp.mit.edu>
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UDP header
Petros KAVASSALIS <petros@cfp.mit.edu>
16
Internet Network Layer


Exchange of data between an end system and attached
network
Concerned with issues like :




Destination address provision
Invoking specific services like priority
Access to & routing data across a network link between two attached
systems
Allows layers above to ignore link specifics
Petros KAVASSALIS <petros@cfp.mit.edu>
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Internet Network Layer key role

Transport segment
from sending to
receiving host


On sending side
encapsulates segments
into datagrams
On receiving side,
delivers segments to
transport layer
Petros KAVASSALIS <petros@cfp.mit.edu>

Network layer protocols
in every host, router


Host: Creates datagrams
/ headers
Router examines header
fields in all IP datagrams
passing through it
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Internet Network Layer in a nutshell


No call setup at network layer
Routers: no state about end-to-end connections

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no network-level concept of “connection”
Packets forwarded using destination host address

packets between same source-dest pair may take different paths
application
transport
network
data link
physical
1. Send data
Petros KAVASSALIS <petros@cfp.mit.edu>
2. Receive data
application
transport
network
data link
physical
19
Internet Network Layer functionality

Forwarding


Move packets from
router’s input to
appropriate router output
application
transport
network
data link
physical
network
data link
physical
Routing

Determine route taken
by packets from source
to destination
Petros KAVASSALIS <petros@cfp.mit.edu>
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
network
data link
physical
application
transport
network
data link
physical
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Addressing requirements

Two levels of addressing required

Each host on a subnet needs a unique global network
address


IP address
Each application on a (multi-tasking) host needs a unique
address within the host

Port
Petros KAVASSALIS <petros@cfp.mit.edu>
21
IP header
Petros KAVASSALIS <petros@cfp.mit.edu>
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IPv6 header
Petros KAVASSALIS <petros@cfp.mit.edu>
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