introduction to osi lower layer kentaro hayashi graduate school of information science and...

Introduction to OSI lower Layer

Kentaro HayashiGraduate school of Information Science and Electric

al EngineeringDepartment of Advanced Information Technology

Kyushu University

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Contents

OSI Reference Model

Physical Layer

Date Link Layer

Network Layer

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OSI Reference Model

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Example of Layer Model・ Postal Mail Service

Contents Simple, Plain

Representation

Language, Meaningful Sentence

Postal format

Post Code, Address, Name, Postcard

Transportation method

Motor bike, Truck, Train

sender

Some post offices

receiver

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OSI Reference Model・ Open Systems Interconnection Reference Model・ In 1977, work on a layered model of network architectur

e, 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]

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OSI reference model

Application

Presentation

Session

Transport

Network

Data Link

PhysicalLayer 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

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OSI Upper Layer

Layer 5

Layer 6

Layer 7 Application

Presentation

Session

Application

DATADATA

Format

When to start

Signaling

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OSI Lower Layer

Transport

Network

Data Link

PhysicalLayer 1

Layer 2

Layer 3

Layer 4 Reliability

0101

0101Data transmissionat the node interval

Routing

Physical connection

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Physical Layer

Transport

Network

Data Link

PhysicalLayer 1

Layer 2

Layer 3

Layer 4

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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]

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Cable

Coaxial Cable Twisted Pear Cable Optical Fiber Wireless

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Coaxial cable

1. Inner conductor2. Insulator surrounding the Inner conductor3. Metallic shield and outer conductor4. 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.

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Twisted pair cableSTP (Shielded twisted pair)UTP (Unshielded twisted pair)

TX ＋TX －RX ＋RX －

TX : Transmit pairRX : Receive pair

Characteristic

・ Cheap and Easy to treat.・ Wire freely.・ Affected by the powerful electricity and electromagnetic .

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Optical fiber

Core : Light advances.

Cladding : Light is reflected.

Buffer : Relax shock, absorbent

Jacket : Protect.

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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)

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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.

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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

・ Manchester0 → Hi ⇒Low1 　→ Low⇒Hi

※ 10BASE5 、 2 、 -T

・ MLT-3 0 → No Change Level

1 → Change Level (Middle⇒Hi⇒Middle⇒Low )⇒

※ 100BASE-TX 、 CDDI

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Encoding

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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

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IEEE 802.11

⇒one of the wireless LAN related standards

　 Release DateFrequency

bandOfficial speed

IEEE 802.11 1997 2.4 ～ 2.5GHz 2Mbps

IEEE 802.11b

October, 　1999

2.4 ～ 2.5GHz11Mbps /

22Mbps

IEEE 802.11a

October, 　1999

5.15 ～ 5.35GHz5.47 ～

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 ～

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SONET/SDH⇒ The international standard

of the high speed digital communication method with optical fiber

SONET SDHTransmission

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-48STM-

162,488.32Mbps

OC-192STM-

649,953.28Mbps

OC : Optical Carrier

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Protocol for Ethernet　 Transmission

speedMaximum length Cable Encoding

10BASE-5 10Mbps 500m Coaxial cable Manchester

10BASE-2 10Mbps 185m Coaxial cable Manchester

10BASE-T 10Mbps 100mTwisted pair

cableManchester

100BASE-TX 100Mbps 100mTwisted pair

cable4B/5B + MLT-

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1000BASE-T 1Gbps 100mTwisted pair

cable4D-

PAM5(8BIQ4)

100BASE-FX 100Mbps

Multi mode:412m(half duplex)

Optical fiber 4B/5B + NRZI2km(full duplex)

Single mode:20km(full duplex)

1000BASE-SX 1Gbps Multi mode:550m Optical fiber 8B/10B + NRZ

1000BASE-LX 1GbpsMulti mode:550m

Optical fiber 8B/10B + NRZSingle mode:5km

1000BASE-ZX 1Gbps 100km Optical fiber 8B/10B + NRZ

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Data Link Layer

Transport

Network

Data Link

PhysicalLayer 1

Layer 2

Layer 3

Layer 4

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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.

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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)

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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

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Frame Format

Data46~1500

Data38~1492

Destination MAC address

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Destination MAC address

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SourceMAC address

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Source MAC address

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Type2

SNAP5

Length2

LLC3

FCS4

FCS4

Ethernet

IEEE802.3 Ethernet

Preamble8octets

Preamble8

MTU(Maximum Transmission Unit)1518bytes

8 bits = 1 bytes = 1 octets

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MAC address Media Access Control address Standardized by IEEE802.3 The unique address that was allotted to the NIC(Network Interfa

ce Card)

22bits 24bits1

bits1

bits

48bits

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MAC address

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

A B C Ddatadata

× ×○

The destination MAC address is C

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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 Ddatadata data

Collision

To C To D

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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.

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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 Ddata data

Collision

data data

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Switch (Switching Hub) Filtering by the MAC address I ｔ decides the port which It should send

A B C Ddatadata

○

switch

To C

data

To D ○

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Network Layer

Transport

Network

Data Link

PhysicalLayer 1

Layer 2

Layer 3

Layer 4

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Network Layer

Network Layer is

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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

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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.

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IP packet formatVersion

(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

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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) ( 例 ) 11010011 00000111 01011010 01110001 → 211.7.90.113

Network address

n bits

Host address

(32 –n) bits

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