Transcript 3 장 OSI 기본 참조 모델

3 장 OSI 기본 참조 모델
OSI : Open System Interconnection
Basic Reference Model : ISO-7498
Purpose of OSI Model
~ is to open communication between different
systems without requiring changes to the logic of
the underlying hardware and software.
1
목차
3.1 모델
3.2 각 계층의 기능
3.3 요약
2
3.1 Model
OSI Model
~ is layered framework for the design of network
systems that allows for communication across all
types of computer systems
Layered Architecture
~ shows the layers involved when a message is sent
from device A to device B
3
Model(cont’d)
OSI Model
4
Model(cont’d)
7
Peer-to-peer protocol(7th layer)
Application
7-6 interface
6
Presentation
6-5 interface
5
Session
5-4 interface
4
Transport
4-3 interface
3
Network
3rd
Application
Peer-to-peer protocol(6th layer)
7-6 interface
Peer-to-peer protocol(5th layer)
6-5 interface
Peer-to-peer protocol(4th layer)
5-4 interface
Network
3rd
Network
Presentation
Session
Transport
3rd
3-2 interface
2
Data Link
2-1 interface
1
Physical
4-3 interface
Network
3-2 interface
2nd
Data Link
2nd
Data Link
2nd
Data Link
7
6
5
4
3
2
2-1 interface
1st
Physical
1st
Physical
1st
Physical
1
5
Model(cont’d)
Peer-to-peer process
~ process on each machine that communicate at a
given layer
Interfaces between Layers
~ defines what information and services a layer
much provide for the layer above it
6
Model(cont’d)
Organization of the Layers
Layer 1, 2, 3(network support layers)
~ deal with the physical aspects of moving data
from one device to another
Layer 5, 6, 7(user support layers)
~ allow interoperability among unrelated software
systems
Layer 4(transport layer)
~ links the two subgroups and ensures that what the
lower layers have transmitted is in a form that the
upper layers can use
7
Model(cont’d)
OSI 모델을 이용한 교환
H6
H6
H5
H5
H4
H4
H3
T2
H3
H2
T2
H2
8
3.2 각 계층의 기능
물리 층(Physical Layer)
데이터 링크 층(Data Link Layer)
네트워크 층(Network Layer)
전송 층(Transport Layer)
세션 층(Session Layer)
표현 층(Presentation Layer)
응용 층(Application Layer)
9
물리 층(Physical Layer)
~ coordinates the functions required to transmit
a bit stream over a physical medium.
(deal with the mechanical and electrical
specification of the primary connections: cable,
connector)
10
물리 층(cont’d)
Physical Layer
11
물리 층(cont’d)
고려사항
회성 구성(Line configuration)
데이터 전송 모드(Data transmission mode)
토폴로지(Topology)
신호방식(Signals): 신호유형
부호화(Encoding)
인터페이스(Interface)
전송매체(Medium)
12
데이터 링크 층(Data Link Layer)
~ is responsible for delivering data units(group
of bits) from one station to the next without
errors.
~ It accepts a data unit from the third layer and
adds meaningful bits to the beginning(header)
and end(trailer) that contain addresses and
other control information: Frame
13
데이터 링크 층(cont’d)
Data Link Layer
14
데이터 링크 층(cont’d)
Specific responsibilities
node-to-node 전달(delivery): station-to-station
주소지정(Addressing)
액세스 제어(Access control)
흐름 제어(Flow control)
에러 처리(Error handling)
동기화(Synchronization)
15
데이터 링크 층(cont’d)
Data Link Layer(예 3.1)
16
네트워크 층(Network Layer)
~ is responsible for the source-to-destination
delivery of a packet across multiple network
link.
cf: the data link oversees station-to-station(nodeto-node) delivery.
~ provides two related services.
Switching
17
네트워크 층(cont’d)
Switching
~ refer to temporary connections between physical
links, resulting in longer links for network
transmission.(ex: telephone conversation)
routing
~ means selecting the best path for sending a packet
from one point another when more than one path
is available
18
네트워크 층(cont’d)
Network Layer
19
네트워크 층(cont’d)
Specific responsibilities
Source-to-destination delivery(packet)
Logical addressing
Routing
Address transformation
Multiplexing
20
네트워크 층(cont’d)
예 3.2
21
네트워크 층(cont’d)
예 3.2(cont’d)
22
전송 층(Transport layer)
~ is responsible for source-to destination (endto-end) delivery of the entire message.
cf: the network layer oversees end-to-end
delivery of individual packet.
23
전송 층(cont’d)
Transport Layer
24
전송 층(cont’d)
Specific responsibility
End-to-end message delivery
Service-point(port) addressing
Segmentation and reassembly
Connection control
25
전송 층(cont’d)
예 3.3
T2
T2
H2
T2
H2
T2
H2
H2
Physical link
26
세션 층(Session Layer)
~ is the network dialog controller
27
세션 층(cont’d)
Specific responsibility
Session management
Synchronization
Dialog control
Graceful close
28
표현 층(Presentation Layer)
~ ensures interoperability among communicating
devices.
~ is responsible for the encryption and
decryption of data for security purpose and for
the compression and expansion of data when
necessary for transmission efficiency.
29
표현 층(cont’d)
Presentation Layer
30
표현 층(cont’d)
Specific responsibility
Translation
Encryption
Compression
Security
31
응용 층(Application Layer)
~ enables the user, whether human or software,
to access the network.
~ provides user interfaces and support for
services.
32
응용 층(cont’d)
Application Layer
33
응용 층(cont’d)
Specific services
Network virtual terminal
File access, transfer, and management
Mail services
Directory services
34
각 계층의 기능 요약
35