Osi tcp ip1 models

Understanding the
Host-to-Host
Communications Model

Building a Simple Network

© 2007 Cisco Systems, Inc. All rights reserved. ICND1 v1.0—1-1

Understanding Host-to-Host
Communications

 Older model
– Proprietary
– Application and combinations software controlled by one
vendor
 Standards-based model
– Multivendor software
– Layered approach


Why a Layered Network Model?

 Standardizes interfaces
 Facilitates modular engineering
 Ensures interoperable
technology
 Accelerates evolution
 Reduces complexity
 Simplifies teaching and learning


The Seven Layers of the OSI Model (Cont.)


The Application Layer
• Example of the Application layer:
 File transfer
 Electronic mail
 Terminal access
 Web Browser
 Network management
– Simple Network Management
Protocol
 Name management
– Domain Name System


The Presentation Layer

• Let’s look at what is happening:

I have a good
file now.

I want that file too but in
3DES encryption format



The Presentation ensures that the information that
the application layer of one system sends out is
readable by the application layer of another system.


Actions of the Presentation layer:
 Format of data ( binary, BCD, ASCII…)
 Data structure ( .doc, .JPEG…)
 Data encryption ( DES, 3DES…)


The Session Layer


The Session Layer

• The Session layer establishes, manages, and terminates
sessions between two communicating hosts.


The Transport Layer
• The Transport layer can guarantee that packets are received.


The Transport Layer

• The Transport layers segments and reassembles ( lặp ráp ) data into a data
stream


The Transport Layer

• Connectionless transmission
• Connection-oriented transmission
• The three-way handshake
• Flow control
• Acknowledgement
• Windowing


The Transport Layer
Connectionless transmissions

• Let’s look at what happens:

Post Office
system
Local Destination
Post Office Post Office


The Transport Layer
(cont)

Post Office
system
Local Destination

Internet

Local Destination
Host A
Router Router


The Transport Layer
(cont)

• User Datagram Protocol (UDP) is an example of connectionless
protocol

• Applications that use UDP to send their data information is DNS,
TFTP, SNMP….


The Transport Layer
Connection-oriented transmissions

• Let’s look at what happens:

Post Office
system
Local Destination


The Transport Layer
(cont)

Post Office
system
Local Destination

Internet

Local Destination
Host A
Router Router


The Transport Layer
(cont)

• Transmission Control Protocol (TCP) is an example of connection-
oriented protocol

• Applications that use TCP to send their data information is DNS,
FTP, HTTP, HTTPs, SMTP, POP3, TELNET, SSH, …


The Transport Layer
the three-way handshake

• In connection-oriented transmission, both the sender and receiver
have to establish the session.

• It is called three-way handshake


The Transport Layer
the three-way handshake (cont)

• • InLet’safter receives the synchronize segment from Host B, itHost A,
Host B (receiver)what examine the synchronize packet from will
the look at after happens:
• Host Athree-way handshake process, when Host A (sender) want to
send an acknowledgement segment to synchronize segment receiver
establishit will send with Host B (receiver), it first send to the to to
if agree, a session acknowledgement Host B to acknowledge Host
a synchronize segment.
A.
connection.

Synchronize (Can I talk to you ?)
Connection Established

Ack (Yes), Synchronize ( Can I talk to you ?)
Data Transfer
(send(Yes)
Ack segments)


The Transport layer
Flow Control

• Once data transfer is in progress, congestion can occur for two
reasons.


The Transport layer
Flow Control (cont)

• First, the sending device might be able to generate traffic faster
than the network can transfer it.


The Transport layer
Flow Control (cont)

• The second reason is that multiple devices need to send data to
the same destination.


The Transport layer
Flow Control (cont)

• When datagram arrive too quickly for a device to process, it
temporarily stores them in memory.
ta
da
ta
da


The Transport layer
Flow Control (cont)

• If the datagrams are part of a small burst, this buffering solves the
problem.
ta
da
ta
da


The Transport layer
Flow Control (cont)

• However, if the traffic continues at this rate, the device eventually
exhausts its memory and must discard additional datagrams that
arrive.
ta
da

ta
da
ta
da

ta
da


The Transport layer
Flow Control (cont)

• Instead of losing the data, the transport function can issue a “not
ready” indicator to the sender.
ta
da

ta
da
ta
da

ta
da


The Transport layer
Flow Control (cont)
ta
da

ta
da
ta
da

ta
da


The Transport layer
Flow Control (cont)

• After the receiving device has processed sufficient segments to free
space in its buffer, the receiver sends a “ready transport “ indicator –
which is like a go signal.
ta
da

ta
da

go
ta
da

ta
da

t
or
sp
an
Tr


The Transport layer
Flow Control (cont)

go

t
or
sp
an
Tr


The Transport Layer
Acknowledgement

• The transport layer provide a reliable service regardless of the quality of
the underlying network


The Transport Layer
Acknowledgement (cont)

ta
da
ta
da


The Transport Layer
Windowing
• Acknowledging every data segment, however, has its drawback
(điều trở ngại).

• If the sender has to wait for an acknowledgement of each data
segment, the throughput will be very low.

ta
da
ta
da


The Transport Layer
Windowing (cont)

TCP TCP

You and I will use window size of 1 ?
I agree
Sender Receiver
Send 1
Ack 2
Send 2
Ack 3


The Transport Layer
Windowing (cont)

• Now let’s examine an example with windows size of 3.

TCP TCP

You and I will use window size of 3 ?
I agree
Sender Receiver
Send 1
Send 2
Send 3
Ack 4

Send 4
Send 5
Send 6
Ack 5

Send 5
Ack 7

Ethernet Frame Structure


MAC Address Components


MAC Addresses


The Seven Layers of the OSI Model


Data Stream Data Stream
Application Application

Data Stream Data Stream Data Stream
Presentation Presentation

Session Session

Data Data Data Data
Transport Data Data Data
Transport

1 IP Header 1
IP Header Data 1 Data
IP Header
Network IP Header 1
Network

Frame Header IP Header
Frame Header IP Header 1
1 II IP Header 1
Data Link Frame Header IP Header 1 I Data Link

Physical Physical


TCP/IP Stack

 Defines four layers
 Uses different names for Layers 1
through 3
 Combines Layers 5 through 7 into
single application layer


TCP/IP Stack vs. the OSI Model


Data Encapsulation


Summary

 The OSI reference model defines the network functions that occur
at each layer.
 The information sent on a network is referred to as data or data
packets. If one computer wants to send data to another computer,
the data must first be packaged by a process called
encapsulation.
 When the remote device receives a sequence of bits, the physical
layer at the remote device passes the bits to the data link layer for
manipulation. This process is referred to as de-encapsulation.


Summary (Cont.)

 TCP/IP is now the most widely used protocol for a number of
reasons, including its flexible addressing scheme, its usability by
most operating systems and platforms, its many tools and utilities,
and the need to use it to connect to the Internet.
 The components of the TCP/IP stack are the network access,
Internet, transport, and application layers.
 The OSI model and the TCP/IP stack are similar in structure and
function, with correlation at the physical, data link, network, and
transport layers. The OSI model divides the application layer of
the TCP/IP stack into three separate layers.


Osi tcp ip1 models

Recommended

Recommended

More Related Content

What's hot

What's hot (20)

Viewers also liked

Viewers also liked (20)

Similar to Osi tcp ip1 models

Similar to Osi tcp ip1 models (20)

Recently uploaded

Recently uploaded (20)

Osi tcp ip1 models