Data Communication and Internet Technology

Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Data Communication
and Internet Technology
Lehrstuhl für Informatik 4
RWTH Aachen
Dr. rer. nat. Dirk Thißen
Prof. Dr. Otto Spaniol
Chapter 1: Introduction
Page 1
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Organization
Exercises to the lecture
•
•
•
•
More or less fortnightly
Thursday 16:30 – 18:00 h
Lecture hall AH 5
Presence exercise
Note: exercise dates are oriented at lecture
content! No fixed dates, only
announcements in the lecture.
First exercise date: November, 2nd, 6th, or
9th – to be announced. ☺
Material (Slide copies, exercise sheets, video recordings)
http://www-i4.informatik.rwth-aachen.de/content/teaching/lectures/sub/datkom/WS06-07/index.html
Written exam
At the end of winter term
Contact information
Dirk Thißen
Lehrstuhl für Informatik 4, Room 4226 (Building part E1)
Phone: 0241 / 80 - 21450
E-Mail: [email protected]
Chapter 1: Introduction
Page 2
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Content
1. Introduction
• Networks and Network Topologies
• Communication Protocols
2. Computer Networks
• Network principles
• Network Components (Cables, Repeaters, Hubs, Bridges, Switches, Routers)
• Local Area Networks (Ethernet, Token Ring, Token Bus, FDDI, DQDB)
• Wide Area Networks (Frame Relay, ATM, SDH, Resilient Packet Ring)
3. Internet Protocols
• Internet/Intranet: the TCP/IP Reference Model
• Network protocols (the Internet Protocol IP, Routing protocols)
• Next Generation Internet
• Transport protocols (TCP and UDP)
4. Application Protocols in the Internet
• Higher protocols (FTP, HTTP, E-Mail, ...)
Chapter 1: Introduction
Page 3
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Literature and Related Courses
• A.S. Tanenbaum: Computer Networks. 4th Edition, Prentice Hall, 2002.
• J.F. Kurose, K.W. Ross: Computer Networking: A Top-Down Approach
Featuring the Internet. Addison-Wesley, 2002.
• Cisco Systems: Internetworking Technologies Handbook. 3rd Edition, Cisco
Press, 2001.
Related courses:
• Mobile Communications (starting Wednesday, 25th)
Chapter 1: Introduction
Page 4
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Data Communication
Data communication is the processing and the transport of digital
data over connections between computers and/or other devices
(generally over large distances)
Data communication comprises two topical areas:
Computer Networks
→ How to connect several computers?
→ Which media can be used for data transport?
→ How to represent digital data on the medium?
→ How to coordinate the access of several computers to the medium?
Communication Protocols (Internet Technology)
→ Design of uniform data units for transfer
→ How to achieve a reliable and efficient transfer?
Chapter 1: Introduction
Page 5
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Evolution of Data Communication
Sharing resources saves costs:
• By communication, one can access resources of other parties – this reduces
the costs (compared to buying own resources)
• Several institutions can share expensive resources which cannot by completely
utilized by a single institution
• Needed:
Efficient mechanisms for data exchange between components of a
distributed systems
Mechanisms for efficient interaction
The “driving power” for the enormous increasing significance of data
communication:
• Decreasing costs for hardware...
• … while the computing power increases.
Interaction of several communication partners: usually Client/Server principle
Chapter 1: Introduction
Page 6
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The Client/Server Principle
Client
Server
Client
Process
Server
Process
Request
Network
Network
Reply
Advantages
Chapter 1: Introduction
→ Cost reduction
→ Better usage of resources
→ Modular extensions
→ Reliability by redundancy
Page 7
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Client/Server Systems
Server
Program (process) which offers a service over a network.
Servers receive requests and return a result to the inquiring party. The services
offered include simple operations (e.g. name server) or a complex set of operations
(e.g. web server).
Client
Program (process) which uses a service offered by a server.
Examples for Client/Server systems
Chapter 1: Introduction
Client
Server
WWW Browser
WWW Server
eMail Program
Domain Name System
(DNS)
FTP Client
FTP Server
Page 8
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Another principle: Peer-to-Peer
• Equal partners, no fixed client and server roles
• Connections between any pair of computers
• Establishment of a whole network of connections
• Best example: File Sharing, e.g. Napster, Gnutella
Chapter 1: Introduction
Page 9
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Non-technical Aspects
Communication networks enable a faster and cheaper exchange/distribution
of information. There is however a large number of social, ethnical, cultural,
juridical, ... side effects.
• Eventually dubious or forbidden contents
• Responsibility
• Juridical aspects (legislation)
• Potential censorship?
• Control over the productivity of employees,
of the whereabouts of people
• Annoyance through anonymous or unwanted messages (SPAM)
• ......
Chapter 1: Introduction
Page 10
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Data Communication
=
Protocols
Chapter 1: Introduction
Page 11
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Why Protocols?
To enable understanding in communication, all communication partners have to
speak the same „language“.
→
→
→
→
→
→
→
Data formats and their semantics
Control over media access
Priorities
Handling of transmission errors
Sequence control
Flow control mechanisms
Segmentation and composition of long
messages
→ Multiplexing
→ Routing
A protocol is defined as the whole set of agreements between
application processes with the purpose of a common communication
Chapter 1: Introduction
Page 12
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Implementation of Protocols
Solution 1:
Write one large „Communication Program“ which fulfills all requirements needed
to establish a communication process.
• Advantage: efficient data exchange for a given application.
• Disadvantage: No flexibility! Adoptions require large efforts.
Solution 2:
Write a set of small programs specialized to special tasks of the communication
process. For each application, the needed programs can be combined.
• Advantage: Very flexible, since single components can be exchanged.
• Disadvantage: Fixed structures of program interworking; adds more complexity
and overhead.
Accepted today: solution 2.
The implementation takes place in layer models.
Chapter 1: Introduction
Page 13
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Example: Exchange of Ideas between
Philosophers
Philosopher A
Thoughts about world politics
Language: Chinese
Language: Spanish
Interpreter B
Interpreter A
Language: Chinese
Philosopher B
Uninterpreted sentences,
Language: Spanish
i.e. no knowledge about politics
additionally: English
additionally: English
Technical Expert A
Technical Expert B
Recognizes single
characters and sends
them in Morse
Uninterpreted characters
in correct order
Electrical signals
Recognizes single
characters and sends
them in Morse
Network
Chapter 1: Introduction
Page 14
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Standardization
Indispensable for the area-wide practical use of communication systems:
Standardization
• On the national as well as the international level!
• Successful standardization is quite difficult due to:
Complex technical problems have to be solved
The involved parties, e.g. companies are often working against each other
Confidentially restrictions hinder the information flow
• Consequence:
Standardization processes are very slow (due to many, often non-technical
reasons).
Chapter 1: Introduction
Page 15
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Standards Organizations - ISO
International Standards Organization - ISO
• Organisation, which is working on a volunteer basis (since 1946).
• Members: standards organizations in approx. 90 countries
www.iso.ch
• Deals with a very broad range of standards
• 200 Technical Committees (TC) for specific tasks (e.g. TC97 for
computer and information processing)
• TCs consist of subcommittees comprising in turn several working
groups
• Interworking with ITU-T regarding telecommunication standards,
(ISO is a member of ITU-T).
• Pioneering work of ISO regarding data communication: the
ISO/OSI reference model
• Notice: only the concept is pioneering – not the products
developed from those concepts!
(OSI: Open Systems Interconnection)
Chapter 1: Introduction
Page 16
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The ISO/OSI Reference Model
Reduce the complexity of a communication process
(all details to be considered) through layers.
7 layers:
7
Application
6
Presentation
5
Session
4
Transport
3
Network
2
Data Link
1
Physical
Common services for the
end user
Criticism of the model:
Network-independent
end-to-end data transfer
Layer 5 and 6 are rarely
being implemented
Addressing and
routing of “packets”
Generally to much
overhead – some details
are unnecessary, some
are overloaded
Securing of “frames”;
Flow Control
Signal representation,
character transmission
Transmission medium („Layer 0”)
Chapter 1: Introduction
Page 17
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Layer Tasks
1. Physical layer
This layer is responsible for transmitting single bits over the medium. Signal
representation is defined here to ensure that a sent „1“ is understood by the
receiver as „1“. For this, e.g. on a copper cable it is defined, which voltage is used
to represent a „1“ resp. a „0“ and how long this voltage has to be for one bit.
Moreover details are being defined like the type of cables, meaning of pins of
network connectors, transmission direction on the cable (uni-/bidirectional), …
2. Data Link Layer
Ensures an error-free data transmission between two neighbored hosts (e.g. in a
sub-network). Therefore the incoming data are segmented into so-called frames
which are being transmitted separately. The receiver, which identifies the start and
the end of a frame e.g. with a bit pattern, checks if the transmission has been
correct (e.g. with the help of a checksum). Additionally, flow control is used to
control the re-transmission of corrupt frames and protect the receiver from
overload.
An additional task in broadcast networks is the control of medium access, i.e. the
stations are coordinated in some way to prevent from access conflicts.
Chapter 1: Introduction
Page 18
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Layer Tasks
3. Network Layer
This layer is responsible for the data transmission over larger distances and between
heterogeneous sub-networks. The main task is (worldwide) uniform addressing of
hosts and choosing a path through the whole network (routing). A necessary prerequisite for doing so is among other things a common address range and an
agreement about a maximum size of the transferred data units. Intermediate stations
(the routers) manage tables with routing information and use the uniform addresses
to make a decision about the best path to the receiver.
4. Transport Layer (ISO/OSI)
Layer 4 manages end-to-end communication between two processes. It is
responsible for ensuring that the received data are complete and in correct order.
For this, again flow control is used (sequence numbers, acknowledgements) to
detect missing or wrong ordered data units. Beneath this, the current network state
is considered to not only adapt to the receiver, but to the network capacities as well.
Addressing is a topic here as well. On the transport layer, a single communication
process on receiver side is addressed.
Chapter 1: Introduction
Page 19
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Layer Tasks
5. Session Layer
This layer (like the transport layer) manages reliable data transport between the
computers. However also additional services are being offered, like e.g. the
possibility for dialogue control. I.e. it can be defined in which direction the
transmission can take place.
Closely related with this topic is the token management which also belongs to level
5. During the transmission so called tokens can be exchanged. With certain
operations only the communication partner which owns the token is allowed to
conduct the operation.
Token management is also used here for other purposes, i.e. a set of tokens exist
to coordinate several operations. One important operation is to set synchronization
points in the communication process, to restart the transmission at the point it has
ended in case of a connection loss.
Chapter 1: Introduction
Page 20
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Layer Tasks
6. Presentation Layer
The task of this layer is to display the data to transmitted that way, that they can be
handled from a lot of different systems. So computers code a string with ASCII
characters, others use Unicode, some for integers the 1-, other the 2-complement.
Instead of defining a new transmission syntax and –semantics for every
application, it is tried to provide a universally valid solution. Specific data are
encoded in an abstract (and commonly recognized) data format before the
transmission and are being translated back by the receiver into its own personal
data format.
7. Application Layer (ISO/OSI)
In this layer (standard-) protocols are being provided which can be used from a
whole set of applications/systems. One example is file transfer. On the application
layer a universally valid protocol including an interface of file transfer is being
provided. For systems from different manufacturers only the link-up into the local
file system has to be realized. Other examples are file transfer, e-mail, remote
operations etc.
Chapter 1: Introduction
Page 21
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Interplay between the Layers
• Layer (n-1) offers its functionality to the above lying layer n as a communication
service.
• Layer n enhances the data to be sent with control information (Header) and
sends the data together with the header as Protocol Data Units (PDU).
• Two communication partners on layer n exchange PDUs by using the
communication service of the nearest lower lying layer (n-1).
• For layer (n-1), these PDUs are the data to be transmitted.
Layer n
Layer (n-1)
H
n-PDU
Layer n
Data
Layer (n-1)
(n-1)-PDU
Chapter 1: Introduction
H: Header, e.g. control
information of the layer
Page 22
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The whole Communication Process
Application
process
Application Layer
H
Presentation
Layer
H
Session Layer
H
Transport Layer
H
Network Layer
Data Link Layer
H
H
Application
process
Data
Application Layer
Presentation
Layer
A-PDU
Session Layer
P-PDU
Transport Layer
S-PDU
Network Layer
T-PDU
N-PDU
Physical Layer
T
Data Link Layer
Physical Layer
Bit stream
Chapter 1: Introduction
Data
Transmission medium
Page 23
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The Communication Process
• Not necessarily a one-to-one mapping between layers
• Depending on the protocol, n-PDUs can be segmented into several (n-1)-PDUs
before transmission:
Chapter 1: Introduction
Page 24
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The OSI Reference Model in the Network
Application
process
Application
process
Application Protocol
Application Layer
Presentation
Layer
Application Layer
Presentation Protocol
Session Protocol
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Host A
Chapter 1: Introduction
Transport Protocol
Presentation
Layer
Session Layer
Transport Layer
Network
Layer
Data Link
Layer
Physical
Layer
Network
Layer
Data Link
Layer
Physical
Layer
Data Link Layer
Router A
Router B
Host B
Internal Protocols
Network Layer
Physical Layer
Page 25
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Computer Networks
Chapter 1: Introduction
Page 26
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
First Generation Computer Networks
Computing Center
Operator
Rest of
the world
Mainframe
Telephone lines
Demultiplexer
Multiplexer
Terminals
Terminals
Chapter 1: Introduction
Peripherals
Page 27
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Introduction of Local Area Networks
Building A
Rest of
the world
Fixed lines
Building B
Computing Center
Operator
Mainframe
Router
Building C
Terminals
Chapter 1: Introduction
Peripherals
Page 28
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Global Networking
Building A
Rest of the
world
(Internet)
Clients
Local
Server
Fixed lines,
ISDN, Provider ...
Switch
Computing Center
Router
Router
Server
Network and system
administrator
Router
Backbone
Building B
Clients
Local
Server
Switch
Peripherals
Switch
Mainframe
Router
Chapter 1: Introduction
Page 29
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Important Terms
Switch
A switch has several connectors, from each connector a cable can be
drawn to a computer. These computers then are linked to a small
network. The switch knows which computer is plugged in at which
connector (address of the network interface card) and forwards data to a
destination computer.
Router
A switch only knows which computers are connected to it directly; if
someone wants to send data to a computer far away, some instance is
needed which knows the way to the destination over several other
computers or switches. Routers are used to manage global address
information and forward data through complex networks.
Backbone A backbone is a set of computers (usually routers) which are connected
by point-to-point links over large distances. A backbone serves for
covering a large region with a communication network which can
interconnect small, local networks of single institutions.
Chapter 1: Introduction
Page 30
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Classification of Networks
Point-to-Point Network
• A pair of computers is directly connected by one cable
Broadcast Network
• One-to-all (e.g.: radio, television)
• All connected stations are sharing one transmission channel
• For ensuring that the data are sent the correct receiver, they have to
marked with the destination address of the receiving computer
• Data are being packed into packets with the Unicast Address of the
receiver
• Every computer connected controls each received packet for its destination
address. Only the addressed computer processes the data, all others are
simply deleting them.
• To address all connected stations at once, so-called Broadcast
Addresses are used
Chapter 1: Introduction
Page 31
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Classification of Networks
Classification by Distance
1m
Personal Area Network (PAN)
10 m
Room
100 m
Building
1 km
Campus
10 km
Town
100 km
Country
1000 km
Continent
10000 km
Planet
Chapter 1: Introduction
Local Area Network (LAN)
Metropolitan Area Network (MAN)
Wide Area Network (WAN)
Internet
Page 32
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Networks
Connection
to a WAN
Switch
Local Networks (LAN)
Router
Metropolitan
Network (MAN),
Backbone for a
town or a region
Chapter 1: Introduction
Page 33
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Networks
Chapter 1: Introduction
Page 34
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Networks
Chapter 1: Introduction
Page 35
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Networks
Router
10 GBit/s
2,4 GBit/s
2,4 GBit/s
622 MBit/s
Backbone in Germany
Rostock
Kiel
Hamburg
Global Upstream
Oldenburg
Braunschweig
Hannover
Berlin
Magdeburg
Bielefeld
Essen
Göttingen
Leipzig
St. Augustin
Dresden
Marburg
Aachen
Ilmenau
Würzburg
Frankfurt
Erlangen
Central entry
router of RWTH.
GEANT
Heidelberg
Karlsruhe
Regensburg
Kaiserslautern
Stuttgart
Augsburg
Garching
Point-to-Point connections
Chapter 1: Introduction
Page 36
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Networks
Central node Frankfurt
– connection to the
European research
network Géant.
Also in Frankfurt and
Hamburg:
intercontinental
connections.
Chapter 1: Introduction
Page 37
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Standards Organizations - IEEE
Institute of Electrical and Electronic Engineers - IEEE
• Standardization e.g. of the IEEE 802.XStandards for Local Area Networks
•
•
•
•
•
•
•
802.1
802.2
802.3
802.4
802.5
802.6
802.7
Overview and Architecture of LANs
Logical Link Control (LLC)
CSMA/CD („Ethernet“)
Token Bus
Token Ring
DQDB (Distributed Queue Dual Bus)
Broadband Technical Advisory
Group (BBTAG)
• 802.8 Fiber Optic Technical Advisory
Group (FOTAG)
• 802.9 Integrated Services LAN
(ISLAN) Interface
• 802.10 Standard for Interoperable
LAN Security (SILS)
Chapter 1: Introduction
www.ieee.org
• 802.11 Wireless LAN (WLAN)
• 802.12 Demand Priority
(HP’s AnyLAN)
• 802.14 Cable modems
• 802.15 Personal Area Networks
(Bluetooth)
• 802.16 WirelessMAN
• 802.17 Resilient Packet Ring
• 802.18 Radio Regulatory Technical
Advisory Group (RRTAG)
• 802.19 Coexistence Technical
Advisory Group
• 802.20 Mobile Broadband Wireless
Access (MBWA)
Page 38
• 802.21 Media Independent Handover
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Communication Protocols
Chapter 1: Introduction
Page 39
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
Standards Organizations - IETF
Internet Engineering Task Force - IETF
www.ietf.org
• Forum for the technical coordination of the work regarding
Arpanet, the precursor of the Internet (since 1986).
• Evolution to a large, open, and international community of
administrators, vendors and researchers.
• Works on evolution of the Internet architecture and the smooth
operation of the Internet.
• Several working groups on Internet protocols, applications,
routing, security, …
• Standard draft proposals can become a full standard only if an
implementation of the proposal is successfully tested at two
independent locations for at least four month.
• Result of such a standardization process: the resounding
success of the Internet protocols TCP/IP
Chapter 1: Introduction
Page 40
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The TCP/IP Reference Model
Application Layer
Application Layer
Presentation Layer
Don´t exist
Session Layer
Transport Layer
Transport Layer
Network Layer
Internet Layer
Data Link Layer
Host-to-Network Layer
Physical Layer
ISO/OSI
Chapter 1: Introduction
TCP/IP
Page 41
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The Tasks of the TCP/IP Layers
Host-to-Network Layer (corresponds to ISO/OSI 1-2)
Not defined exactly. The design does not matter, it is only defined that a host must
be connected to the network via a protocol in a way that it is able to send and
receive IP datagrams. The protocol design is left over to other standards to cover
heterogeneous networks of all kinds.
Internet Layer (corresponds to ISO/OSI 3)
The term Internet refers here to the interworking of different networks, therefore not
on the Internet itself. The protocol enables communication between hosts over the
own network borders. In the Internet, the transmission is connectionless, meaning
that the data are segmented into packets which are addressed and sent
independently into the network. On each network border, a router takes over the
forwarding of the packets. The choice of path can be dynamic, depending on the
current network load. As a result, single packets can get lost by overload situations
or received in wrong order. Such faults are not handled (this task is left over to the
transport layer).
In contrast to ISO, only one packet format is defined, together with a connectionless
protocol, the Internet Protocol (IP).
Chapter 1: Introduction
Page 42
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
The Layers of TCP/IP
Transport Layer (corresponds to ISO/OSI 4)
This layer covers the communication between the end systems. To adapt to
different applications, two protocols are defined.
TCP (Transmission Control Protocol) is a reliable, connection-oriented protocol
to protect the transmission of a byte stream between two hosts. The byte stream is
segmented to fit into IP packets. On the receiving side the packets are reassembled in the original order with the purpose of restoring the original data
stream. It also includes flow control to adapt to the receiver‘s capabilities and to
overcome the faults caused by the connectionless IP.
UDP (User Datagram Protocol) is an unreliable and connectionless protocol („best
effort“). No error correction is integrated, thus the transmission is used when the
speed of the data transmission is more important than the reliability (speech, video).
Application Layer (corresponds to ISO/OSI 7)
This layer defines common communication services. This comprises TELNET
(remote work on another computer), FTP (file transfer), SMTP (electronic mail),
DNS („phonebook“ for the Internet), HTTP (used for World Wide Web), etc.
Chapter 1: Introduction
Page 43
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
OSI vs. TCP/IP
1. Time
The TCP/IP protocols were already widely used before OSI had finished
the standardization activities.
2. Freedom from obligation
A „reference model“ like OSI is free from obligation. It only defines what
is to be done, but not how to do it. Result: incompatibility of products.
3. Complicatedness
Very high and partly unneeded expense in the OSI specification
(thousands of pages of specification descriptions).
By the wish to consider all special cases, lots of options were included,
making the products lavish, unhandy, and for too expensive - “The
option is the enemy of the standard”!
Chapter 1: Introduction
Page 44
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
OSI vs. TCP/IP
4. Political reasons
OSI was dominated too much by Europe – especially from the national
telecommunication companies which had lucrative monopolies. The real
market power was in the USA – nobody was interested in OSI over there.
5. Hurriedly product implementation
The first OSI products were implemented too fast (driven by the
success of TCP/IP protocols), were covered with faults, and had an
overall low performance.
In contrast, the “theoretically far more unmodern“ TCP/IP protocols
were continuously modified and improved. They were of a high quality
level and successfully tested before deployment and cheap to buy due
to high production numbers.
Chapter 1: Introduction
Page 45
Lehrstuhl für Informatik 4
Kommunikation und verteilte Systeme
And now…
1. Introduction
• Networks and Network Topologies
• Communication Protocols
2. Computer Networks
• Network principles
• Network Components (Cables, Repeaters, Hubs, Bridges, Switches, Routers)
• Local Area Networks (Ethernet, Token Ring, Token Bus, FDDI, DQDB)
• Wide Area Networks (Frame Relay, ATM, SDH, Resilient Packet Ring)
3. Internet Protocols
• Internet/Intranet: the TCP/IP Reference Model
• Network protocols (the Internet Protocol IP, Routing protocols)
• Next Generation Internet
• Transport protocols (TCP and UDP)
4. Application Protocols in the Internet
• Higher protocols (FTP, HTTP, E-Mail, ...)
Chapter 1: Introduction
Page 46