iSCSIについて

Introduction to OSI lower
Layer
Kentaro Hayashi
Graduate school of Information Science and
Electrical Engineering
Department of Advanced Information Technology
Kyushu University
Contents

OSI Reference Model

Physical Layer

Date Link Layer

Network Layer
2
OSI Reference Model
3
Example of Layer Model
・Postal Mail Service
receiver
sender
Contents
Simple, Plain
Representa Language, Meaningful
tion
Sentence
Postal
format
Post Code, Address,
Name, Postcard
Some post offices
Transportat Motor bike, Truck, Train
ion method
4
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]
5
OSI reference model
Layer 7
Application
Layer 6 Presentation
Layer 5
Session
Layer 4
Transport
Layer 3
Network
Network process to application
Data representation and encryption
offer service
Signaling for session
End-to-end connections and reliability
Path determination and logical addressing
offer communication
Layer 2
Data Link
Layer 1
Physical
Physical addressing
Media, signal and binary transmission
6
OSI Upper Layer
Layer 7
Application
Application
Layer 6 Presentation
DATA
DATA
Format
When to start
Layer 5
Session
Signaling
7
OSI Lower Layer
Layer 4
Transport
Layer 3
Network
Layer 2
Data Link
Layer 1
Physical
Reliability
Routing
0101
Data transmission
at the node interval
0101
Physical connection
8
Layer 4
Transport
Layer 3
Network
Layer 2
Data Link
Layer 1
Physical
Physical Layer
9
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]
10
Cable
Coaxial Cable
 Twisted Pear Cable
 Optical Fiber
 Wireless

11
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.
12
Twisted
pair
cable
UTP (Unshielded twisted pair)
STP (Shielded twisted pair)
TX＋
TX－
Characteristic
RX＋
RX－
TX : Transmit pair
RX : Receive pair
・ Cheap and Easy to treat.
・ Wire freely.
・ Affected by the powerful electricity
and electromagnetic .
13
Optical fiber
Core : Light advances.
Cladding : Light is reflected.
Buffer : Relax shock, absorbent
Jacket : Protect.
14
Multi mode
Single mode
・ Strong to bend.
・ Little transmission loss.
・ Easy to connect.
・ Made of quartz glass.
( Core:Ge,P , Cladding:B,F)
・ Cheap.
・ Made of plastic.
(Cladding:fluorine-based polymer)
15
Wireless Communication
・ The wiring space is unnecessary.
・ Mobile communication is possible.
・ Able to build LAN immediately.
・ Able to communicate outdoors.
【Radio】
【FSO】 Free Space Optics
・ Electric wave
・ Infrared ray (IR)
or Visible spectrum
・line of sight is required
・ license is unnecessary
・ PC, remote controller
・ IrDA ⇒ UFIR
・ Unnecessary line of sight
(・ license is necessary)
・ mobile phone, PHS
・ Bluetooth (IEEE 802.15.1)
16
Encoding
・ NRZ
(Non-Return to Zero)
0 → Low Level
1 → Hi Level
・ Manchester
0 → Hi ⇒Low
1 → Low⇒Hi
※ 1000BASE-X
※ 10BASE5、2、-T
・ NRZI
・MLT-3
0 → No Change Level
1 → Change Level
(Non-Return to Zero Inversion)
0 → No Change Level
1 → Change Level
※ FDDI, 100BASE-FX
(Middle⇒Hi⇒Middle⇒Low⇒)
※ 100BASE-TX、CDDI
17
Encoding
18
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
19
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～
20
SONET/SDH
⇒ The international standard
of the high speed digital
communication method
with optical fiber
SONET
SDH
OC-1
‐
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
Transmission speed
51.84Mbps
21
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
4DPAM5(8BIQ4)
Optical fiber
4B/5B + NRZI
Optical fiber
8B/10B + NRZ
Optical fiber
8B/10B + NRZ
Optical fiber
8B/10B +22
NRZ
Multi mode:412m(half duplex)
100BASE-FX
100Mbps
2km(full duplex)
Single mode:20km(full duplex)
1000BASE-SX
1Gbps
1000BASE-LX
1Gbps
Multi mode:550m
Multi mode:550m
Single mode:5km
1000BASE-ZX
1Gbps
100km
Layer 4
Transport
Layer 3
Network
Layer 2
Data Link
Layer 1
Physical
Data Link Layer
23
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.
24
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)

25
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
26
Frame Format
Ethernet
Preamble
8octets
Destination
MAC address
6
Source
MAC address
6
Type
2
Source
MAC address
6
Leng
th
2
Data
46~1500
FCS
4
IEEE802.3 Ethernet
Preamble
8
Destination
MAC address
6
LLC
3
SNAP
5
Data
38~1492
FCS
4
MTU(Maximum Transmission Unit)1518bytes
8 bits = 1 bytes = 1 octets
27
MAC address



Media Access Control address
Standardized by IEEE802.3
The unique address that was allotted to the NIC(Network
Interface Card)
1
bits
1
bits
22
bits
24bits
48bits
28
MAC address

NIC receives the Frame which destination
MAC address is same as own one.
A
B
C
D
data
×
○
×
The destination MAC address is C
29
Collision


Each terminal controls it autonomously to avoid a
collision of the communication
In order to avoid collision, Ethernet use CSMA/CD.
A
B
data
data
To C
C
D
To D
Collision
30
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.

31
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
data
C
D
data
Collision
32
Switch (Switching Hub)
Filtering by the MAC address
 Iｔ decides the port which It should send

A
B
data
data
C
D
○
To D
○
To C
switch
33
Layer 4
Transport
Layer 3
Network
Layer 2
Data Link
Layer 1
Physical
Network Layer
34
Network Layer

Network Layer is
35
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
36
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.
37
IP packet format
Version
(4)
Header
Length
(4)
Service
Type
(8)
Packet Length
(16)
ID
(16)
TTL
(8)
Flag
(3)
Protocol
(8)
Fragment Offset
(13)
Header Check-Sum
(16)
Transmission former IP address
(32)
Destination IP address
(32)
Option
(32 * n)
Data
38
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
39
40

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