Communication Communication Nt k Networks

inexpensivedetailedNetworking and Communications

Oct 23, 2013 (4 years and 2 months ago)

238 views

Communication
Communication

N t k
N
e
t
wor
k
s
國立成功大學
國立成功大學
電機系及電腦與通信研究所
電機系及電腦與通信研究所
李忠憲

Textbook:A S Tanenbaum

Computer Networks

4th Ed
注意事項

Textbook:

A
.
S
.
Tanenbaum
,
Computer

Networks
,
4th

Ed
.

Reference: L. L. Peterson & B. S. Davie, “Computer
Networks: A System Approach”, 3rd Ed.

http://hsnet.ee.ncku.edu.tw

Grading: Midterm Exam.: 40%, Final Exam: 40%

Homework:10%, Report: 10% ( from Further Reading, IEEE
Network Mag., IEEE Communication Mag.)—手寫,中文,打字
零分
零分

助教:劉昆玹Tel. ~62400~1629
Ch t 1
Ch
ap
t
er
1
Introduction
Introduction
*Uses of Computer Networks

Business Applications

Home Applications

Home

Applications

Mobile Users

Social Issues
Business Applications of
Networks

A network with two clients and one server.
*Business Applications of
Networks (2)

The client-server model involves requests
and replies.
and

replies.
*Home Network Applications

Access to remote information

葉  ﹥ ﹡ﱩ贈

葉



﹥

﹡ﱩ贈

ョﵬ葉ﰠﱩ
ョ

ョ

Person
-
to
-
person

communication

Instant messaging; chat room; newsgroups
(non-real-time)

Interactive entertainment
El t i

El
ec
t
ron
i
c commerce
*Home Network Applications (2)

In peer-to-peer system there are no fixed
clients and servers.
clients

and

servers.
Home Network Applications (3)
1.
Napster (MP3 music): peak 50 million fans swapping ( already
shut down by the courts due to copyright): members register
the music the
y
had on local HD in a central DB on Na
p
ster
y p
server
2.
Next generation: eliminate the central DB, each user maintains
his own local DB and provides a list of other nearby members
his

own

local

DB

and

provides

a

list

of

other

nearby

members
.
A new user can go to any existing member to see its DB and
other members. The searching can repeat.
Internet gambling (servers in legal casino for clients in
3.
Internet

gambling

(servers

in

legal

casino

for

clients

in

countries banning gambling)
4.
Internet telephone, video phone, Internet radio, telelearning;
5.
Killer application: video on demand, on-line game playing
(virtual reality)
6
Electronic commerce:on
-
line auctions
6
.
Electronic

commerce:

on
line

auctions
Home Network Applications (3)

Some forms of e-commerce.
*Mobile Network Users

Combinations of wireless networks and
mobile computing.
mobile

computing.
Mobile Network Users
Mobile

Network

Users
1.
Notebook and PDA (personal digital assistant)
2.
Portable office
3.
WAP1.0failed due to microscopic screens, low BW
and poor service

    


イ

北





ﵡ






壟ﴠ葉
葉﹧郎沈葉
﹮ョ
﹮ョ

ﰠ deeply offensive to
some people, pornography; network operator:
ibl f lik lik
respons
ibl
e
f
or contents
lik
e a newspaper or not
lik
e a
telephone company? Censor messages? Rights to free
speech?Employer v.s.Employee rights;FBI Carnivore
speech?

Employer

v.s.

Employee

rights;

FBI

Carnivore
(食肉猛獸), now DCS1000; cookies for tracking users’
activities; anonymous messages; Spam; fast but not
sure information;identity theft (credit card)
sure

information;

identity

theft

(credit

card)
6.
Along with the good comes the bad!!!
Network Hardware

Local Area Networks
M t lit A N t k

M
e
t
ropo
lit
an
A
rea
N
e
t
wor
k
s

  ﹥イﭳ





﹥イﭳ

ﱥ ﹥イﭳ

ﱥ

﹥イﭳ

Home Networks

Internetworks
Broadcast Networks

Types of transmission
h l
tec
h
no
l
ogy
B d t li k

B
roa
d
cas
t

li
n
k
s
(Broadcast multicast
(Broadcast
,
multicast
,
unicast
)
)

Point-to-point links
Broadcast Networks (2)

Classification of interconnected processors
by scale.
by

scale.
Local Area Networks

Two broadcast networks

Two

broadcast

networks

(a) Bus: IEEE 802.3 Ethernet from 10 Mbps to
10 Gbps

(b) Ring: IEEE 802.5, FDDI
Metropolitan Area Networks

A metropolitan area network based on cable
TV.
TV.
Wide Area Networks

Relation between hosts on LANs and the
subnet.
subnet.
*Wide Area Networks (2)

A stream of packets from sender to receiver. Store and
forward; packet switching; Routing decisions are made
locally. Routing algorithm is needed.
*Wireless Networks

Categories of wireless
t k
ne
t
wor
k
s:

 葉ョ﹥說




葉ョ﹥說


イ﹧@ﵰョヲ
ﵰ   ﭥ異。 ョ若イ
ﵰ





ﭥ異。

ﵯ﹩

ﵯﹴﰠ Bluetooth

Wireless LANs
Wireless WANs

Wireless

WANs
*Wi
re
l
ess
N
e
t
wor
k
s
(2)

IEEE

802.11 Wireless LAN v.s. cellular tele
p
hones
(
3G
)
;
p ( )
short (meters) v.s. long (kilometers); 50 Mbps v.s. 1
Mbps;

(a) Bluetooth configuration

(b) Wireless LAN
*Wireless Networks (3)

(a) Individual mobile computers


 ﱹ葉 ﱁ




數﹧

ﱁ
Home Network Categories

Computers (desktop PC PDA shared

Computers

(desktop

PC
,
PDA
,
shared

peripherals)
E i (TV DVD VCR

E
nterta
i
nment
(TV
,
DVD
,
VCR
, camera, stereo,
MP3)

Telecomm (telephone, cell phone, intercom, fax)

率﹣ 北  」 ﹡

率﹣

北

磻

」



I
    ﱩ    
盜竊


T
e
l
eme
t
ry
(
u
tilit
y me
t
er,
b
urg
l
ar
(
盜竊
)

l
慲洬a
扡批捡洩b
Network Software

Protocol Hierarchies

Protocol

Hierarchies

Desi
g
n Issues for the La
y
ers
g y

Connection-Oriented and Connectionless
S i
S
erv
i
ces

Service Primitives
Service

Primitives

The Relationship of Services to Protocols
*
Network Software
Network

Software
Protocol Hierarchies

Layers, protocols, and interfaces.
protocols, and interfaces

Protocol = an agreement betw comm. Parties
on how comm.is to proceed.
=>
data
on

how

comm.

is

to

proceed.

data

structure + algorithm

    ﵰ﹧ 









ﵰ﹧



﹤葉ﱡ便︠ﵡ葉

Interface= betw. Each pair of adjacent layers
Protocol Hierarchies (2):
The
Protocol

Hierarchies

(2)

:

The

philosopher-translator-secretary architecture

.
I like
rabbits
Location A Location B
Message Philosopher
J'aime
bien les
rabbits
3
3
Message Philosopher
bien les
lapins
2
2
Translator
Information
for the remote
translator
L: Dutch
Ik vind
konijnen
leuk
L: Dutch
Ik vind
konijnen
leuk
Information
leuk
Fax #---
leuk
Fax #---
1
1
Secretary
for the remote
secretary
Fax #---
L: Dutch
Ik vind
konijnen
leuk
Fax #---
L: Dutch
Ik vind
konijnen
leuk
Protocol Hierarchies (3)
Example
information flow supporting virtual communication in
information

flow

supporting

virtual

communication

in

layer 5.
Design Issues for the Layers

Addressing
E C t l
d t ti d

E
rror
C
on
t
ro
l
: erro
r
-
d
e
t
ec
ti
ng an
d
erro
r
-
correcting

Flow Control: fast sender to a slow receiver

ﵵﱴ殺ﱥ﹧ ﹯  ョ﹥說  イ

ﵵﱴ殺ﱥ﹧





﹮ョ





沈ﵭ︠」
ﵵﱴ殺ﱥ﹧


R
ou
ti
ng
Connection-Oriented and Connectionless
Services

Six different types of service.
Service Primitives(operations)

Five service primitives for
implementing a simple connection
-
implementing

a

simple

connection
oriented service.
Service Primitives (2)

Packets sent in a simple client-
server interaction on a connection
-
server

interaction

on

a

connection
oriented network.
Services to Protocols
Relationship

The relationship between a service and a
protocol.
protocol.
Reference Models

The OSI Reference Model
Th TCP/IP R f M d l

Th
e
TCP/IP

R
e
f
erence
M
o
d
e
l

 ュ    i



ﵰ拾ョ



s



縷


A
C
ri
t
i
que

o
f
t
h
e

OS
I M
ode
l
a
n
d

A

Critique

of

the

OSI

Model

and

Protocols

A Critique of the TCP/IP Reference
Model
Model
*Reference Models
The OSI
reference
model.
Reference Models (2)

The TCP/IP reference model.
Reference Models (3)

Protocols and networks in the TCP/IP model
initially.
initially.
Comparing OSI and TCP/IP
Models

Concepts central to the
OSI model

Services

Interfaces

Protocols
A Critique of the OSI Model
and Protocols

Why OSI did not take over the world

Why

OSI

did

not

take

over

the

world

Bad timing: next slide

 ﹯ﱯ



﹯ﱯ


session, presentationnearly empty

Data link,network
Æ
overfull
Data

link,

network


カﱬ

Addressing, flow control, error control reappear
again and again
B d i l t ti

B
a
d

i
mp
l
emen
t
a
ti
ons

Poor quality

 ﱩ



ﱩ

EU and US government

Like PL/I for IBM and Ada for DoD
Like

PL/I

for

IBM

and

Ada

for

DoD
*Bad Timing

The apocalypse (啟示) of the two elephants. If the standards
are written too early

 ﹤ 復  




若














ﱡ




略鸞不﹯葉@イ 
standard guys crushed.
standard

guys

crushed.
A Critique of the TCP/IP
Reference Model

Problems:

Service, interface, and protocol not distinguished

Not a general model: unable to be used to describe
Bluetooth

Host-to-network “layer” not really a layer (an
interface)

No mention of physical and data link layers

Minor protocols deeply entrenched, hard to replace,
e.g. Telnet
Hybrid Model

The hybrid reference model to be used in this
book.
book.
Example Networks

The Internet

The

Internet

Connection-Oriented Networks:
X.25, Frame Relay, and ATM





Wireless LANs: 802:11
The ARPANET
The

ARPANET

(a) Structure of the telephone system.

(b) Baran’s proposed distributed
switchin
g
s
y
stem.
g y
The ARPANET (2)

The original ARPANET design.
The ARPANET
(
3
)
( )

Growth of the ARPANET (a) December 1969. (b)
July 1970
(c)
March 1971
(d)
April 1972
(e)
July

1970
.
(c)
March

1971
.
(d)
April

1972
.
(e)
September 1972.
NSFNET

The NSFNET backbone in 1988.
Internet Usage

Traditional applications (1970

1990)
1990)



ﵡ塞



ﵡ塞

﹥

﹥

ﵯ ァ葉

ﵯ

ﱯ

File transfer
Architecture of the Internet

Overview of the Internet.
ATM Virtual Circuits

A virtual circuit.
ATM Virtual Circuits (2)

An ATM cell.
The ATM Reference Model

The ATM reference model.
The ATM Reference Model (2)
Th ATM l d bl d th i f ti

Th
e
ATM

l
ayers an
d
su
bl
ayers an
d

th
e
i
r
f
unc
ti
ons.
Ethernet

Architecture of the original Ethernet.
Wireless LANs

(a) Wireless networking with a base station.
( )

(
b
)
A
d hoc networking.
Wireless LANs (2)

The range of a single radio may not cover the
entire system.
entire

system.
Wireless LANs (3)

A multicell 802.11 network.
Network Standardization

Who’s Who in the Telecommunications
World
World

Who’s Who in the International
Standards World
Who

s Who in the Internet Standards

Who

s

Who

in

the

Internet

Standards

World
ITU

Main sectors

Main

sectors

Radiocommunications
T l i ti St d di ti

T
e
l
ecommun
i
ca
ti
ons
St
an
d
ar
di
za
ti
on

Development

Classes of Members
National governments

National

governments

Sector members

A
ssociate members

Regulatory agencies
IEEE 802 Standards
The 802 working groups. The important ones are

ﵡ若郞ョﭥ


葉ョﵡ若
*Metric Units

The principal metric prefixes.
What Goes Wrong in the
Network?

Bit-level errors (electrical interference)



ﱥ  ョ說︩


ﱥ



ョ說︩

Link and node failures

Messages are delayed

Messages are deliver out-of-orde
r

Third
p
arties eavesdro
p
p p
Internet Architecture

Defined by Internet Engineering Task Force
(
IETF
)
( )

Hourglass Design

北說  北說  

北說



北說

エ」ャ




  ﹖






﹅

﹅

﹅
﹅

﹅

﹅

Performance Metrics
B d idth (th h t)

B
an
d
w
idth

(th
roug
h
pu
t)

data transmitted per time unit

ﱩ﹫  



ﱩ﹫









notation

KB = 2
10
bytes

Mbps = 10
6
bits per second

Latency (delay)

time to send message from point A to point B

one-way versus round-trip time (RTT)

ﵰョ

ﵰョ
ﱡ﹣鸞ﴠー說︠ﬠ若ﬠ
ー說︠ﴠ@
     

ﹳ



贈






磻
Bandwidth versus Latency

Relative importance



 ﵳ   ﵩ﹡  











ﵩ﹡







﵂    ﵩ﹡  

﵂







ﵩ﹡







葉﹩ ﹤

葉﹩

﹤

RTT dominates
Th h t T f Si/T f Ti

Th
roug
h
pu
t
=
T
rans
f
er
Si
ze
/

T
rans
f
er
Ti
me

TransferTime = RTT + 1/Bandwidth x TransferSize



file
to1
Gbpslink as1
KB
packet
to1
Mbps





file
to

1
-
Gbps

link

as

1
-
KB

packet

to

1
-
Mbps

link
Delay x Bandwidth Product

Amount of data “in flight” or “in the pipe”

Example:100ms
x
45Mbps = 560KB

Example:

100ms

x
45Mbps

=

560KB
Delay
Bandwidth