Introduction to OSI lower Layer

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30 Οκτ 2013 (πριν από 3 χρόνια και 9 μήνες)

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Introduction to OSI lower
Layer

Kentaro Hayashi

Graduate school of Information Science and
Electrical Engineering

Department of Advanced Information Technology

Kyushu University

2

Contents


OSI Reference Model



Physical Layer



Date Link Layer



Network Layer


3

OSI Reference Model

4

Example of Layer Model


Postal Mail Service

Contents

Simple, Plain

Representa
tion

Language, Meaningful
Sentence

Postal
format

Post Code, Address,
Name, Postcard

Transportat
ion method

Motor bike, Truck, Train

sender

Some post offices

receiver

5

OSI Reference Model



Open Systems Interconnection Reference Model



In 1977, work on a layered model of network architecture,


which was to become the OSI model, started in the


American National Standards Institute
(ANSI) working


group on Distributed Systems (DISY). With the DISY

work and worldwide input,
the International Organization

for Standardization
(ISO) began to develop its OSI


networking suite.




OSI has two major components: an abstract model of


networking (the Basic Reference Model, or seven
-
layer


model) and a set of concrete protocols.


[Wikipedia]

6

OSI reference model

Application

Presentation

Session

Transport

Network

Data Link

Physical

Layer 1

Layer 2

Layer 3

Layer 4

Layer 5

Layer 6

Layer 7

Media, signal and binary transmission

Physical addressing

Path determination and logical addressing

End
-
to
-
end connections and reliability

Signaling

for session

Data representation and encryption

Network process to application

offer service

offer communication

7

OSI Upper Layer

Layer 5

Layer 6

Layer 7

Application

Presentation

Session

Application

DATA

DATA

Format

When to start

Signaling

8

OSI Lower Layer

Transport

Network

Data Link

Physical

Layer 1

Layer 2

Layer 3

Layer 4

Reliability

0101

0101

Data transmission

at the node interval

Routing

Physical connection

9

Physical Layer

Transport

Network

Data Link

Physical

Layer 1

Layer 2

Layer 3

Layer 4

10

Physical Layer


The Physical Layer defines the electrical and physical
specifications for devices. In particular, it defines the
relationship between a device and a physical medium.
This includes the layout of pins, voltages, cable
specifications, Hubs, repeaters, network adapters, and
more.



[Wikipedia]

11

Cable


Coaxial Cable


Twisted Pear Cable


Optical Fiber


Wireless

12

Coaxial cable

1. Inner conductor

2. Insulator surrounding the Inner conductor

3. Metallic shield and outer conductor

4. Outer insulating jacket

Characteristic



Few leaks of the electromagnetic wave to the outside.



Able to bend.



Able to transmit of a wide frequency range.



Structure is complicated, and price is high.

13

Twisted pair cable

STP (Shielded twisted pair)

UTP (Unshielded twisted pair)

TX


TX


RX


RX


TX : Transmit pair

RX : Receive pair

Characteristic



Cheap and Easy to treat.



Wire freely.



Affected by the powerful electricity


and electromagnetic .

14

Optical fiber

Core : Light advances.

Cladding : Light is reflected.

Buffer : Relax shock, absorbent

Jacket : Protect.

15

Multi mode

Single mode



Strong to bend.



Easy to connect.



Cheap.



Made of plastic.

(Cladding:fluorine
-
based polymer)



Little transmission loss.



Made of quartz glass.

( Core:Ge,P , Cladding:B,F)

16

Wireless Communication


Radio




Electric wave




Unnecessary line of sight

(


license is necessary)



mobile phone, PHS



Bluetooth (
IEEE 802.15.1
)


FSO


Free Space Optics



Infrared ray (IR)


or Visible spectrum


line of sight is required



license is unnecessary



PC, remote controller



IrDA


UFIR



The wiring space is unnecessary.



Mobile communication is possible.



Able to build LAN immediately.



Able to communicate outdoors.

17

Encoding



NRZ

(Non
-
Return to Zero)



0 →
Low

Level




1 →
Hi

Level



1000BASE
-
X




NRZI

(Non
-
Return to Zero Inversion)



0 → No Change Level




1 → Change Level



FDDI, 100BASE
-
FX



Manchester



0 →
Hi


Low



1


Low

Hi



10BASE5

2

-
T



MLT
-
3



0 → No Change Level




1 → Change Level


(
Middle

Hi

Middle

Low

)



100BASE
-
TX

CDDI

18

Encoding

19

Protocol



RS
-
232C (Recommended Standard 232C)



ISDN (Integrated Services Digital Network)



xDSL (x Digital Subscriber Line)


-

ADSL (Asymmetric DSL)



IEEE 802.11 (Wireless LAN)



SDH (Synchronous Digital Hierarchy)


SONET (Synchronous Optical NETworking)



Protocol for Ethernet

20

IEEE 802.11


one of the wireless LAN related standards



Release Date

Frequency band

Official speed

IEEE 802.11

1997

2.4

2.5GHz

2Mbps

IEEE 802.11b

October,

1999

2.4

2.5GHz

11Mbps / 22Mbps

IEEE 802.11a

October,

1999

5.15

5.35GHz

5.47

5.725GHz

(Max)54Mbps

IEEE 802.11g

June, 2003

2.4

2.5GHz

54Mbps

IEEE 802.11j

--

4.9

5.0GHz

5.03

5.091GHz

54Mbps

IEEE 802.11n

--

2.4GHz / 5GHz

100Mbps


21

SONET/SDH



The international standard
of the high speed digital
communication method
with optical fiber

SONET

SDH

Transmission speed

OC
-
1



51.84Mbps

OC
-
3

STM
-
1

155.52Mbps

OC
-
9



466.56Mbps

OC
-
12

STM
-
4

622.08Mbps

OC
-
18



933.12Mbps

OC
-
24



1244.16Mbps

OC
-
36



1,866.24Mbps

OC
-
48

STM
-
16

2,488.32Mbps

OC
-
192

STM
-
64

9,953.28Mbps

OC : Optical Carrier

22

Protocol for Ethernet



Transmission speed

Maximum length

Cable

Encoding

10BASE
-
5

10Mbps

500m

Coaxial cable

Manchester

10BASE
-
2

10Mbps

185m

Coaxial cable

Manchester

10BASE
-
T

10Mbps

100m

Twisted pair
cable

Manchester

100BASE
-
TX

100Mbps

100m

Twisted pair
cable

4B/5B + MLT
-
3

1000BASE
-
T

1Gbps

100m

Twisted pair
cable

4D
-
PAM5(8BIQ4)

100BASE
-
FX

100Mbps

Multi mode:412m(half duplex)

Optical fiber

4B/5B + NRZI

2km(full duplex)

Single mode:20km(full duplex)

1000BASE
-
SX

1Gbps

Multi mode:550m

Optical fiber

8B/10B + NRZ

1000BASE
-
LX

1Gbps

Multi mode:550m

Optical fiber

8B/10B + NRZ

Single mode:5km

1000BASE
-
ZX

1Gbps

100km

Optical fiber

8B/10B + NRZ

23

Data Link Layer

Transport

Network

Data Link

Physical

Layer 1

Layer 2

Layer 3

Layer 4

24

Date Link Layer


The Date Link Layer provides the functional and
procedural means to transfer data between network
entities and to detect and possibly correct errors that
may occur in the Physical Layer.

25

Protocol


IEEE802.3 (Ethernet)


FDDI (Fiber distributed data interface)


ATM (Asynchronous Transfer Mode)


PPP (Point
-
to
-
Point Protocol)


Token Ring


ARP (Address Resolution Protocol)


IEEE802.11(wireless LAN)

26

Ethernet


The protocol that spreads in LAN most today


American Xerox company, Intel Company and old DEC
Company devised


Standardized by IEEE802.3 afterwards


As for these 2, the forms of the frame are different


CSMA/CD


27

Frame Format

Data

46~1500

Data

38~1492

Destination

MAC address

6

Destination

MAC address

6

Source

MAC address

6

Source

MAC address

6

Type

2

SNAP

5

Leng
th

2

LLC

3

FCS

4

FCS

4

Ethernet

IEEE802.3 Ethernet

Preamble

8octets

Preamble

8

MTU(Maximum Transmission Unit)1518bytes

8 bits = 1 bytes = 1 octets

28

MAC address


Media Access Control address


Standardized by IEEE802.3


The unique address that was allotted to the NIC(Network
Interface Card)

22

bits

24bits

1

bits

1

bits

48bits

29

MAC address


NIC receives the Frame which destination
MAC address is same as own one.

A

B

C

D

data

data

×

×



The destination MAC address is C

30

Collision


Each terminal controls it autonomously to avoid a
collision of the communication


In order to avoid collision, Ethernet use CSMA/CD.

A

B

C

D

data

data

data

Collision

To C

To D

31

CSMA/CD(Collision Detection)


Non
-
persistent CSMA + While itself
transmits a message, It examines that
there are only it's data in a network


If a collision happens, It waits in random
time and retransmits afterwards


When a collision occurs more than the
constant number of times, It stops the
transmission of a message.

32

CSMA(Carrier Sense Multiple
Access)


Each terminal controls it autonomously to avoid a
collision of the communication


The transmission of a data is performed unless a
signal is passed to LAN

A

B

C

D

data

data

Collision

data

data

33

Switch (Switching Hub)


Filtering by the MAC address


I


decides the port which It should send

A

B

C

D

data

data



switch

To C

data

To D



34

Network Layer

Transport

Network

Data Link

Physical

Layer 1

Layer 2

Layer 3

Layer 4

35

Network Layer


Network Layer is

36

IP


Protocol developed in U.S. Department of
Defense (DoD) to bear network layer of
TCP/IP model



IP is a protocol of a connectionless type


37

IP


IP maintains the logic address that is
called IP address in all machines on the
network


IP address is hierarchized structure and keep
unique all over the world



The relay node of IP is called a router.

38

IP packet format

Version


(4)

Header
Length

(4)

Service
Type

(8)

Packet Length

(16)

ID

(16)

Flag

(3)

Fragment Offset

(13)

TTL

(8)

Protocol

(8)

Header Check
-
Sum

(16)

Transmission former IP address

(32)

Destination IP address

(32)

Option

(32 * n)

Data

39

IP address


Logic address used by IP protocol


When you write Internet Protocol address
32 all bits are written by one byte by the
decimal number with the dot separately for
four parts (octet)


(

) 11010011 00000111 01011010 01110001 → 211.7.90.113


Network address

n bits

Host address

(32

n) bits

40