Transcript Introduction to TCP/IP

Introduction to TCP/IP
What is TCP/IP?
• It is a protocol suite
• Enables computers within a network to
communicate with each other
• Network can be made up of different
computers running different operating
systems
• Is used by the Internet
• Is used in many private computer networks
History of TCP/IP
• Developed in late 1960s by U.S. Department of
Defense’s Advanced Research and Projects
Administration (ARPA) to be able to link DoD
computers together.
• During the 1970s, the number of computers
connected grew and the network became known as
ARPANET
• During the late 1970s/early 1980s, the protocols
used were refined and formed the basis of TCP/IP
History of TCP/IP Continued
• BSD 4.2 version of UNIX was released in 1983
• Contained a TCP/IP protocol suite
• Bell licensed the operating system to universities
for $150.00
• Corporate version was $20,000
• This made minicomputers more affordable for
universities
• Resulted in an explosive growth in the use of
ARPANET
Open System Interconnection
(OSI) Model
• Developed during the 1970s by International
Organization for Standards(ISO)
• This is a model for allowing communication
between different types of computers within a
network
• Specific protocols can be developed using this
general model
• Was intended to promote the development of
protocols that could cause different types of
computer systems to communicate with each other
Layers of the OSI Model
• Communication between two computers is
sufficiently complex that it should be broken down
into separate units (layers)
• Each layer is built on top of a lower layer
• One layer only communicates with layers adjacent
to that layer
• Each layer has speified what is to take place at that
layer, but does not specify how that operation is to
take place
• Seven layers are in the OSI model
Names of the OSI Layers
•
•
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Layer 7 - Application
Layer 6 - Presentation
Layer 5 - Session
Layer 4 - Transport
Layer 3 - Network
Layer 2 - Data Link
Layer 1 – Physical
Physical Layer
• Responsible for sending bits of data
• Deals with the physical connection and
transmission/reception of of signals
• You would define physical and electrical
details at this layer
Data Link Layer
• Provides for the flow of data over a single link
from one device to another
• It accepts data units from the Network Layer and
packages the information into data units called
frames to be presented to the Physical Layer
• CRC error-detection bits are added at this layer
• This layer can detect when frames are lost and
request that those frames be sent again
Network Layer
• Routing decisions are made here
• Packets are forwarded for devices that are farther
away than one single link
• Logical network addresses are translated into
physical machine addresses
• Large packets are broken into smaller chunks if
the packet is larger than the largest data frame the
Data Link Layer will accept
Transport Layer
• Ensures that packets are delivered error
free, in sequence, and with no losses or
duplications
• Breaks large messages from the Session
Layer into packets to be sent to the
destination computer and reassembles
packets into messages to be presented to the
Session Layer
Session Layer
• Allows Applications on separate computers to
share a connection called a session
• Provides services such as name lookup and
security to allow two programs to find each other
and establish the communication link
• Provides for data synchronization and
checkpointing so that in the event of a network
failure, only the data sent after the point of failure
need be re-sent
• Controls who can transmit and who can receive at
what point during the communication
Presentation Layer
• Translates data between the format used by
the computer and the format used by the
network
• Character set conversion
Application Layer
• Provides network services to the user
• Examples of such services:
– Database access
– E-mail
– File transfers
Back to TCP/IP
• The designers of TCP/IP chose a simpler model
with fewer layers
• There are only four layers
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–
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–
Application
Transport
Internet
Network Interface
• See p. xxvii to compare OSI model with DARPA
model