OSI Reference Model &

warmersafternoonNetworking and Communications

Oct 23, 2013 (3 years and 9 months ago)

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OSI Reference Model &
Layered Communication

S. Sukaridhoto, ST

OSI Layer


Open Systems Interconnection

for
Communications


There are 7 Layers


Layers 7,6,5 are oriented more
toward services to the applications


Layer 4,3,2,1 are oriented more
toward the flows data from end
-
to
-
end through network


7 Layer OSI

How to Remember (CISCO)


Please




Physical


Do




Data Link


Not




Network


Throw




Transport


Sousces



Session


Pizza




Presentation


Away




Application

Application

Layer 7

Function & Description


An application that communicates
with other computers is
implementing OSI application layer
concepts. Application layer refer to
communications service to
application.

Example


Telnet


HTTP


FTP


WWW Browser


NFS


SMTP Gateway


SNMP

Presentation


Layer 6

Function & Description


This layer main purpose is defining
data format such as ASCII text,
EBCDIC text, binary, BCD, JPEG.


Encryption is also defined by OSI as
presentation layer service.

Example


JPEG


ASCII


TIFF


GIF


PICT


MPEG


MIDI


Encryption


Session

Layer 5

Function & Description


This session layer defines how to
start, control, and end conversation
(called session).


This includes the control and
management of multi bidirectional
messages so that application can be
notified if only some of a series of
messages are completed.

Example


RPC


SQL


NFS


Netbios Names


AppleTalk


ASP


SCP


DECnet


Transport

Layer 4

Function & Description


Layer 4 includes the choice of
protocols that either do or do not
provide error recovery. Multiplexing
of incoming data for different flows
to applications on the same host.

Example


TCP


UDP


SPX

Network

Layer 3

Function & Description


This layer defines end
-
to
-
end delivery
packets. To accomplish this, the network
layer defines logical addressing so that
any endpoint can be identified. It also
defines how routing works and how routes
are learned so that the packets can be
delivered


Network layer also defines how to
fragment a packet into smaller packets to
accommodate media with smaller
maximum transmission unit size

Example


IP


IPX


AppleTalk DDP

Data Link

Layer 2

Function & Description


The data link specifications are
concerned with getting data across
one particular link or medium. The
data link protocols define delivery
across an individual link. These
protocols are necessary concerned
with the type of media in question.

Example


IEEE 802.3/802.2


HDLC


Frame Relay


PPP


FDDI


ATM


Physical

Layer 1

Function & Description


Deal with the physical characteristics
of the transmission medium,
Connection pins, use of pins,
electrical currents, encoding and
light modulation.

Example


Ethernet


RJ
-
45


V.35


FDDI


EIA/TIA
-
232



Some protocol define details of
multiple layers.


Example: NFS

Summary


Application (Layer 7)


User Interface


Telnet, HTTP


Application (Layer 6)


How data is presented


JPEG,
ASCII


Session (Layer 5)


Keeping data separate from different
application


OS, application access scheduling


Transport (Layer 4)


Reliable or unreliable delivery,
Multiplexing


TCP, UDP, SPX


Network (Layer 3)


Logical addressing, Routing


IP, IPX


Data Link (Layer 2)


MAC, error detection


802.3/802.2,
HDLC


Physical (Layer 1)


Devices


Ethernet, V.35