Wednesday, 16 January 2019
OSI Model
WHAT IS OSI LAYER?
OSI
means OPEN SYSTEM INTERCONNECT model or layer.it means every System is open to
connect with other.
# Developed
by ISO (INTERNATIONAL ORGANIZATION FOR STANDARDIZATION)
IN 1974.
#It consist of seven layer.
#Each layer has a different but specific processing function.
Layer 7>>APPLICATION
|
Layer 6>>PRESENTATION
|
Layer 5>>SESSION
|
Layer 4>>TRANSPORT
|
Layer 3>>NETWORK
|
Layer
2>>DATA LINK
|
Layer 1>>PHYSICAL
7.)APPLICATION LAYER
it provides
networking services to user.
It also
known as desktop layer.
protocols
like dhcp,http,webbroweretc are used in this layer.
6.) PRESENTATION LAYER
It converts
data into standard formats for to receive or transmit.
(American
standard code for information interchange)
e.g.>>ASCII,JPEG,BMP,MP3
etc.
following
tasks are done in this layer
ENCODING – DECODING
ENCRYPTION -
DECRYPTION
5.) SESSION LAYER
It is
responsible for establishing,maintenance,and terminating session.
SESSION ID
WORKS IN THIS LAYER.
E.G.-
RPCàREMOTE PROCEDURE CALL
SQLàSTRUCTURED QUERY LANGUAGE
NFSàNETWORK FILE SYSTEM
4.)TRANSPORT LAYER
IT maintains
END TO END connectivity.
It is the
heart of OSI LAYERS.
Two
protocols works in this layer they are-
1. TCP
(TRANSMISION CONTROL PROTOCOL)
2. UDP
(USER DATAGRAM PROTOCOL)
FOLLOWING
TASKS ARE DONE HERE
#
IDENTIFYING SERVICES.
#
MULTIPLEXING & DE-MUX.
#
SEGMENTATION.
# SEQUENSING
& REASSEMBLING.
# FLOW
CONTROL.
# ERROR
CORRECTION.
3.)NETWORK LAYER
IT provides
best path for data to reach destination.
Logical
addressing is done on this layer.
Device works
on this layer is router.
It is
divided into two parts
1. routed
protocols
e.g.
ip,ipx,apple talk etc.
2. routing
protocols
e.g. rip
>routing information protocol
ospf>open
shortest path first
igrp>integrated
gateway routing protocol
eigrp>enhance
igrp
2.) DATA LINK LAYER
It is divided
into two sub layers.
1. LLC –LOGICAL LINK CONTROL
WAN
protocols works here.provides error-free data from one node to other node.
e.g. ppp(point
to point protocol),hdlc(high level data link control).
2. MAC – MEDIA
ACCESS CONTROLLER.
It talks
about physical address.
1.)PHYSICAL LAYER
It talks
about electrical,mechanical or procedural checks.
Co-axial or
twisted pair cable> data will be in electrical pulse or e- form.
Fiber optic
cable>>data will be in light form.
Devices works
in this are>>
ethernet
Hubs (active
& passive)
Cables
repeaters
connectors
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