Models (kỹ THUẬT TRUYỀN số LIỆU SLIDE)

Packet Switching,
Layer Models and
Protocol Suites


Outline





Circuit vs. packet switching
Layered tasks
Internet protocol suites
ISO's OSI model

2


End-to-End Communication


Direct communication


Most basic form of communication
TX
RX
GND



TX
RX
GND

Serial Port

Internet communication


Communication is performed over the Internet

Internet

3


Internet Comm. - App's
Viewpoint



Two network applications should
interact as if they were directly
connected
write
read
App

App

A



Internet

B

But what's going on underneath?


What is inside the "cloud"?
4


Circuit vs. Packet Switching



Dedicated circuits
Circuit switching




Telephone switches
establish circuits
for communication

Packet switching







Data are put into
packets
Each stamped with
source and destination
addresses
Routers know where to
forward packets

telephone
switch

Packet

Router

6


Layered Tasks


Computer networks are complex
systems




Tasks involve varieties of hardware and
software components, and protocols

Networking task is divided into
several subtasks, or layers

7


Real World Example


Communication between managers
of two companies

Communicate

8


What Actually Happens


Communication takes place thru many
layers
Logical communication

Secretary:
types a letter

Delivery boy:
drops the letter

Secretary:
reads and reports
the message

Delivery boy:
takes the letter

Postal truck
Post office:
Processes and routes the letter
9


Internet Layer Model


The Internet Protocol Stack
User
Application Layer

Software

Transport Layer
Network Layer

Data Link Layer
Physical Layer

Hardware

Transmission
Medium
12


Application Layer
Responsible
Responsible for
for providing
providing services
services to
to the
the user
user


The only layer to interact with user
Data

Application
Layer

SMTP

HTTP

Data

Data

Logical communication

FTP
H5

to Transport

SMTP

HTTP
Data

FTP
H5

from Transport

13


Transport Layer
Responsible
Responsible for
for delivery
delivery of
of aa message

message
from
from one
one process
process to
to another
another


Duties/services






Port addressing
Segmentation and reassembly
Connection control
Flow control (end-to-end)
Error control (end-to-end)

14


Transport Layer
Process

Process

…

Process

Process

PORT #

PORT #

Data
Transport
Layer

…

Data1 H4 Data2 H4 Data3 H4

Data
Data1 H4 Data2 H4 Data3 H4

(segments)

to Network

from Network

15

Network Layer
Responsible
Responsible for
for the
the delivery
delivery of
of packets
packets
from
from the
the original
original source
source to
to the
the destination
destination


Duties/services



Logical addressing
Routing

16


Network Layer
from Transport

Network
Layer

to Transport

Data

Data

Data
H3
(packet)

Data

to Data Link

H3

from Data Link

17


Network Layer
Data 1.1 5.7

1.1

1.1,
1.1,1.2,
1.2,6.1,
6.1,5.7,
5.7, ...
...are
arelogical
logical addresses
addresses

1.2

Network 1
R1

6.1

6.6

Network 6
6.3
R3

R2
Router

5.2

3.3
5.7

3.8

Network 5

Network 3

18


Data Link Layer
Responsible
Responsible for
for transmitting
transmitting frames
frames
from
from one
one node
node to
to the
the next
next


Duties/services







Framing
Physical addressing
Flow control (hop-to-hop)
Error control (hop-to-hop)
Access control

19


Data Link Layer
from Network

to Network

Data
Data Link
Layer

T2

Data
(frame)

to Physical

Data
H2

T2

Data

H2

from Physical

20


Data Link Layer
A3,
A3,3B,
3B,82,
82,9F,
9F,...
...are
arephysical
physicaladdresses
addresses

Data
9F

T2

Data

3B

9F

82

A3

A3
H2

21


Data Link Layer
Data 1.15.7

1.1
97

1.2
32

Data 1.15.7 97 25

Network 1

25

R1

6.1

79

12

Network 6

Data 1.15.7 79 62

6.6

6.3

62
R3

R2

5.2

54

88

3.3

3.8

Network 3

Data 1.15.7 54 74

5.7
74

Network 5

22


Physical Layer
Responsible
Responsible for
for transmitting
transmitting individual
individual bits
bits
from
from one
one node
node to
to the
the next
next


Duties/services






Physical characteristics of
interfaces and media
Representation of bits
Data rate (transmission rate)
Synchronization of bits

23


Physical Layer
from Data Link

Physical
Layer

to Data Link

Data

Data

01001011
(bits)

01001011

Transmission medium

24


The Big Picture

L5 data

H5

L4 data
L3 data
T2

L2 data

H4
H3
H2

5

5

4

4

3

3

2

2

0111011010101001010101001 1

L5 data

H5

L4 data
L3 data
T2

L2 data

H4
H3
H2

1 0111010101010010101010101

Transmission medium
25


Internet Model

sender

Applicati
on
Transport
Network
Data Link
Physical

router
router

Network
D.L D.L
.
.
P.L. P.L.

Transmission medium

receiver

Network
D.L D.L
.
.
P.L. P.L.

Applicati
on

Transport
Network
Data Link
Physical
26


Internet Model

27


Protocol Suites


A set of protocols must be
constructed






to ensure that the resulting
communication system is complete and
efficient

Each protocol should handle a part of
communication not handled by other
protocols

How can we guarantee that protocols
work well together?


Instead of creating each protocol in

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