osi means open system interconnect model. osi means open system interconnect model. developed by the...
TRANSCRIPT
OSI means Open System Interconnect model.OSI means Open System Interconnect model.
Developed by the International Organization for Developed by the International Organization for Standardization in 1974.Standardization in 1974.
It consists of seven layers.It consists of seven layers.
Each layer has a different but specific processing Each layer has a different but specific processing function.function.
OSI Model
Advice
Person
Sales
Take
Not
Do
Please
OSI Model Layers
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Layer - 7
Layer - 6
Layer - 5
Layer - 4
Layer - 3
Layer - 2
Layer - 1
Upper Layer or
Software Layer
Lower Layer or
Hardware Layer
Heart of OSI
Application LayerApplication Layer is responsible for providing Networking Services to user. It also known as Desktop Layer. Identification of Services is done using Port Numbers.
Ports are nothing but Socket i.e. Entry and Exit Point to the Layer
Total No. Ports 0 – 65535 Reserved Ports 0 – 1023 Open Ports 1024 – 65535
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Application Application
Example of HTTP request
Client Web Server
http://www.zoomgroup.com
Example of HTTP request
Client Web Server
HTTP Request http:// www.zoomgroup.com
Webpage
HTTP Request Listen on
Port 80Sending HTTP Reply
Webpage
Received HTTP Reply http://www.zoomgroup.com
Webpage
Example of FTP request
Client FTP Server
ftp://ftp.microsoft.com
Example of FTP request
FTP Request ftp://ftp.microsoft.com
FTP Request Listen on
Port 21Sending FTP Reply
Received FTP Reply ftp://ftp.microsoft.com
Client FTP Server
Examples of Networking Services
Service Port No.
HTTP 80
FTP 21
SMTP 25
TELNET 23
TFTP 69
Application Application
2180 25 6753 69
How data flows from Application Layer
Data
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Presentation Layer
Presentation Layer is responsible for converting data into standard format.
Examples : ASCII, EBCDIC, JPEG, MPEG, BMP, MIDI, WAV, MP3
Following tasks are perform at Presentation layer :
Encoding – DecodingEncryption – DecryptionCompression – Decompression
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
PresentationPresentation
How data flows from Presentation Layer
Data
DataApplication Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Session Layer
Session Layer is responsible establishing, maintaining and terminating session. Session ID also works at Session Layer.
Examples :
RPC Remote Procedure Call SQL Structured Query languageNFS Network File System
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
SessionSession
How data flows from Session Layer
Data
Data
Data
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Transport Layer
Transport Layer is responsible for end-to-end connectivity. It is also known as heart of OSI Layers. Following task are performed at Transport Layer : -
• Identifying Service
• Multiplexing & De-multiplexing
• Segmentation
• Sequencing & Reassembling
• Flow Control
• Error Correction
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Transport Transport
Identifying Service
• Transmission Control
Protocol
• Connection Oriented
• Acknowledgement
• Reliable
• Slower
• Port No. 6
• e.g. HTTP, FTP, SMTP
• User Datagram
Protocol
• Connection Less
• No Acknowledgement
• Unreliable
• Faster
• Port No. 17
• e.g. DNS, DHCP, TFTP
TCP UDP
Application Application
PresentationPresentation
SessionSession
Multiplexing & De-multiplexing
2180 25 6753 69
Transport Transport
TCP - 6 UDP - 17
Network Network
Data LinkData Link
PhysicalPhysical
Segmentation
Hello! How are you ?
Hello! How Are You ?
Hello!
How are you ?
A B
Sequencing & Reassembling
Hello! How are you ?
Hello! How Are You ?
Hello!
How are you ?
A B
You Hello! How ? Are
Hello! How AreYou ?
you
Hello! How ?
are
Sequencing & Reassembling
Hello! How are you ?
Hello!1/5
How2/5
Are3/5
You4/5
?5/5
Hello!
How are you ?
A B
Hello! How are you ?
Hello!1/5
How2/5
Are3/5
You4/5
?5/5
Hello!1/5
How2/5
Are3/5
You4/5
?5/5
Hello!
How are you ?
Error Correction
Hello! How are you ?
Hello!1/5
How2/5
Are3/5
You4/5
?5/5
Hello!
How are you ? Hello!
1/5Are3/5
You4/5
?5/5
Hello!1/5
Are3/5
You4/5
?5/5
Segment Missing
Hello!1/5
Are3/5
You4/5
?5/5
How2/5
How2/5
Hello! How are you ?
Hello! How are you ?
A B
Flow Control - Windowing
Sending 3-window
Received 3-window
Ack-Rec-3Sending
5-window
Received 4-window
A B
Ack. Received-4
PC-A can send 4 Segment
at a time to PC-B
PC-A can send 4 Segment
at a time to PC-B
How data flows from Transport Layer
Data
Data
Data
DataTHSegment
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Network Layer
Network Layer is responsible for providing best path to data to reach destination. Logical Addressing sits on this layer. Device working on Network Layer is Router.
It is divided into two parts
• Routed Protocols
e.g. IP, IPX, Apple Talk.
• Routing Protocols
e.g. RIP, IGRP, OSPF, EIGRP
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Network Network
Routed Protocols
Hello!
How are you ?
192.168.1.1 192.168.1.2
A B
Segment
Segment
Source IP 192.168.1.1
Destination IP192.168.1.2
Source IP 192.168.1.1
Destination IP192.168.1.2
Segment
Hello!
How are you ?
Routing Protocols
A
www.zoomgroup.com
How data flows from Network Layer
Data
Data
Data
Segment
Segment
NH
e.g. Router
Packet
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Data link Layer
Datalink Layer is divided into two Sub Layers :
• LLC – Logical Link ControlIt talks about Wan protocols e.g. PPP, HDLC, Frame-relay
• MAC – Media Access ControlIt talks about Physical Address. It is 48 bit Addressing i.e. 12 digit Hexadecimal No. It is also responsible for Error DetectionDevice working on Data Link Layer is Switch, Bridge, NIC.
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Data LinkData Link
Error Detection – CRC Check
Hello!
How are you ?
Packet
Packet
Source MAC 00-20-18-C0-07-71
Destination MAC00-20-18-C0-07-72
000003243422222896965543499323434349943446323111143333300000324342222289696554349932343434994344632311114Error Detected
192.168.1.100-20-18-C0-07-71
192.168.1.200-20-18-C0-07-72
A B
PC-A CRC No. 33333
PC-B CRC No. 11114Error Detected
For Error Correction Contact Source Transport
layer
PC-A CRC No. 33333
PC-B CRC No. 11114Error Detected
For Error Correction Contact Source Transport
layer
Error Detection – CRC Check
Packet
Packet
Source MAC 00-20-18-C0-07-71
Destination MAC00-20-18-C0-07-72
00000324342222289696554349932343434994344632311114202020000032434222228969655434993234343499434463231111420202
Source MAC 00-20-18-C0-07-71
Destination MAC00-20-18-C0-07-72
Packet
Hello!
How are you ?
192.168.1.100-20-18-C0-07-71
192.168.1.200-20-18-C0-07-72
A B
e.g. Switch
How data flows from Data Link Layer
Data
Data
Data
Segment
DH
Packet
DT
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
PacketPacketFrame
Physical Layer
Physical Layer is responsible for electrical, mechanical or procedural checks. Data will be converted in Binary that is 0’s & 1’s. Data will be in the form of electrical pulses if it is Coaxial or Twisted Pair cable and in the form of Light if it is Fiber Optic Cable.
Devices working at Physical Layer are Hubs, Repeaters, Cables, Modems etc.
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysicalPhysicalPhysical
Physical Layer Example
Frame
Frame
10101010101010101010101010101010
Frame
Hello!
How are you ?
A B01010110101010101010101011010101101010101010101010010101101010101010101010110101011010101010101010100101011010101010101010101
How data flows from Physical Layer
Data
Data
Data
Segment
Packet
Frame
Bits
e.g. Hub
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Segment
Packet
Frame
A B
Packet
Data
Data
Data
Bits
Data
Segment
Data Encapsulation & De-capsulation
Packet
Data
Data
Data
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysicalBits
DH DT
NH
THSegment
Packet
DT PacketDH DTDH
NH Segment NH
TH Data TH
Frame Packet
Application Application
Transport Transport
InternetInternet
Network Access
Network Access
Comparing OSI with TCP/IP Layers
OSI Layers TCP/IP Layers
Application Application
PresentationPresentation
SessionSession
Transport Transport
Network Network
Data LinkData Link
PhysicalPhysical
