Data Transmission Networks

1

References:

2

باماندرو تنن:هاي كامپيوتري تاليفشبكهفهرست مطالب

• Chap. 1 introduction

• Chapter 2

• a brief introduction to the principles of data communication

• three major sections on transmission (guided media, wireless, and satellite)

• examples (the public switched telephone system, the mobile telephone system, and cable television

• ADSL, broadband wireless, wireless MANs, and Internet access over cable and DOCSIS.

3

• Chapter 3

• fundamental principles of point-to-point protocols.

• Chapter 4

• the MAC sublayer

• wireless LANs, broadband wireless, Bluetooth, and

data link layer switching, including MPLS.

• Chapter 5

• Quality of service is now also a major topic, including

discussions of integrated services and differentiated

services.

• Wireless networks are also

• present here, with a discussion of routing in ad hoc

networks

• NAT and peer-to-peer networks.4

• Chap. 6

• transport layer

• an example of socket programming. A one-page

client and a one-page server are

• given in C and discussed.

• remote procedure call, RTP, and transaction/TCP.

• Chap. 7

• the application layer

• a short introduction to DNS

• e-mail, the Web, and multimedia

• The discussion of how the Web works(including static

and dynamic Web pages, HTTP, CGI

• scripts, content delivery networks, cookies, and Web

caching)

5

• how modern Web pages are written, including brief

introductions to XML, XSL, XHTML, PHP,...

• The wireless Web (focusing on i-mode and WAP).

• …..

• Chapter 8

• Security(covering the principles of security symmetric-

and public-key algorithms, digital signatures, and

X.509 certificates)

• the applications of these principles (authentication, e-

mail security, and Web security).

• …..

6

• Chapter 9

• all-new list of suggested readings and a

comprehensive bibliography of over 350 citations to

the current literature. Over 200 of these are to papers

and books written in 2000 or later.

7

فصل اول

introduction

8

• 1.1 Uses of Computer Networks TCP/IP• 1.2 Network Hardware• 1.3 Network Software• 1.4 Reference Models• 1.5 Example Networks• 1.6 Network Standardization

:1فصل رئوس مطالب

9

هاي كامپيوتريكاربردهاي شبكه

كاربردهاي تجاري•كاربردهاي خانگي•كاربران در حركت•مالحظات اجتماعي•

10

1. Business Applications

Figure 1-1. A network with two clients and one server.

For example, a company may have separate computers to monitor production,

keep track of inventories, do the payroll and....

resource sharing

to make all programs, equipment, and especially data available to anyone

without regard to the physical location of the resource and the user.

It is cheaper, faster, and easier

This whole arrangement is called the client-server model11

If we look at the client-server model in detail, we see that

two processes are involved:

1- one on the client machine (request)

2-one on the server machine (reply)

12

13

كاربردهاي خانگي-2

دسترسي به اطالعات از راه دور•ارتباط فرد با فرد•سرگرميهاي تعاملي•تجارت الكترونيكي•

Examples:

• Personalizing newspapers on-line!

– politic

– big fires

– Epidemics

– no football, thank you!

• on-line digital libraries like ACM (www.acm.org) and the

IEEE Computer Society

All of the above applications involve interactions between

a person and a remote database full of information.

كاربردهاي خانگي-2

14

• The second broad category of network use is person-to-

person communication.

• Another type of person-to-person communication

often goes by the name of peer-to-peer

communication.

to distinguish peer-to-peer communication from the

client-server model

• In peer-to-peer communication Every person can, in

principle, communicate with one or more other people;

there is no fixed division into clients and servers.

كاربردهاي خانگي-2

15

16

كاربردهاي خانگي-2

17

برخي انواع تجارت الكترونيكي

كاربردهاي خانگي-2

18

هاي متحرككاربران شبكه-3

Figure 1-5. Combinations of wireless networks and mobile computing

19

هاكهبندي شبتقسيم

هااز نقطه نظر تكنولوژي انتقال شبكه

بر اساس اندازه شبكه

20

(broadcast)هاي پخشي شبكه•

(Point-to-point)هاي شبكه•

وژي انتقالها از نقطه نظر تكنولتفكيک شبكه

21

Broadcastپخشي يا هاي شبكه-1

Broadcast networks have a single communication

channel that is shared by all the machines on the

network.

i. Short messages, called packets in certain contexts,

sent by any machine are received by all the others.

ii. An address field within the packet specifies the

intended recipient.

iii. Upon receiving a packet, a machine checks the

address field.

iv. If the packet is intended for the receiving machine, that

machine processes the packet; if the packet is intended

for some other machine, it is just ignored.

22

داراي يک کانال مشترک بين همه کامپيوترها •

مقصدآدرس کامپيوتر +پيامحاوي بسته •

ی شودبر حسب آدرس کامپيوتر مقصد به دو دسته زير تقسيم م:

broadcastingپخش يا

ي ارسال پيام برااهمه كامپيوتره

ارسال پيام برايگروهي از كامپيوترها

multicastingپخش گروهي يا

Broadcastپخشي يا هاي شبكه-1

23

Point-to-pointهاي شبكه-2

: هامسائل مطرح در اين نوع از شبكه

مسير جداگانه بين هر دو كامپيوتر•

كشف كوتاهترين مسير بين هر دو سيستم•

As a general rule (although there are many exceptions), smaller, geographically localized networks tend to use

broadcasting, whereas larger networks usually are point-to-point.

Point-to-point transmission with one sender and one

receiver is sometimes called unicasting.

24

25

ها بر اساس اندازه آنهابندي شبكهتقسيم

LAN(Local Area Networks)هاي شبكه1.

MAN(Metropolitan Area Networks)هاي شبكه2.

WAN(Wide Area Networks)هاي شبكه3.

(Wireless Networks)سيمهاي بيشبكه4.

(internetwork)ها شبكه شبكه5.

Distance is important as a classification metric because different

techniques are used at different scales.

26

27

(Local Area Networks)هاي محليشبكه

ياتمانساخيككامپيوترهايكردنمتصلبرايخصوصيايشبكهومنابعگذاشتناشتراكبهبرايكيلومتر،چندفاصلهباشركتاطالعاتتبادل

:هاي محليسه پارامتر مهم در شبكهاندازه•

انتقال اطالعاتتكنولوژي •

يا توپولوژي همبندي •

شبکه هایLANسرعت کاری چندان باالیی ندارند

28

: محليهاي شبكهيا همبنديتوپولوژيمثالهايي از

29

Token ring

Bus

LAN

Ring

: ليهاي شبكه محيا همبنديتوپولوژيمثالهايي از

Bus (وجود يک خط ارتباطی بين ايستگاه ها: گذرگاه)

(کانال ارتباطي حلقويوجود ): حلقه

Tokenring سيستم در اختيار دارنده )(به ارسال پيام مي باشدمجاز

static and dynamic networks

Broadcast networks can be further divided into static

and dynamic, depending on how the channel is

allocated.

A typical static allocation would be to divide time into

discrete intervals and use a round-robin algorithm,

allowing each machine to broadcast only when its time

slot comes up.

× Static allocation wastes channel capacity when a

machine has nothing to say during its allocated slot, so

most systems attempt to allocate the channel

dynamically.

t1 t230

31

MAN(Metropolitan Area Networks)هايشبكه

اي است در محدودهشبكهونهيك شهر كه بهترين نمون براي آن شبكه تلويزي

باشد كابلي مي

32

(MAN)اي ناحيههايشبكه

In this figure we see both television signals and Internet

being fed into the centralized head end for subsequent

distribution to people's homes. (providing two-way Internet

service in unused parts of the spectrum)

33

(Wide Area Networks)گستردههايشبكه

A wide area network, or WAN, spans a large

geographical area, often a country or continent.

WAN contains a collection of machines intended for

running user (i.e., application) programs (hosts)

The hosts are connected by a communication

subnet. Subnet means the collection of routers and

communication lines that moved packets from the

source host to the destination host.

34

Figure 1-9. Relation between hosts on LANs and the subnet

The hosts are owned by the customers

subnet is owned and operated by a telephone

company or Internet service provider. The job of the

subnet is to carry messages from host to host

WAN Network

packet-switched WAN:

When 2 hosts wants to communicate

1. Transmitter host first cuts the message into packets, each one

bearing its number in the sequence.

2. packets are then injected into the network one at a time in

quick succession.

3. The packets are transported individually over the network

and deposited at the receiving host

4. They will be reassembled into the original message and

delivered to the receiving process.

35

36

Figure 1-10. A stream of packets from sender to receiver.

In this Fig route ACE is better than ABDE or ACDE or ….

In some networks all packets from a given message must follow the

same route; in others each packet is routed separately.

Wireless Networks

(Bluetooth)ارتباطات داخل سيستمي •

•LANسيمبي(IEEE802.11 )

•WANسيم بي

37

38

System interconnection is all about interconnecting the

components of a computer using short-range radio.

No cables, no driver installation, just put them down, turn

them on, and they work. For many people, this ease of

operation is a big plus.

This relation is just like a master(system) & slave(mouse,

keyboard, etc.)

The master tells the slaves what addresses to use, when

they can broadcast, how long they can transmit, what

frequencies they can use, and so on.

39

• wireless LANs :every computer has a radio modem and

antenna with which it can communicate with other

systems.

• if the systems are close enough, they can communicate

directly with one another in a peer-to-peer configuration.

• There is a standard for wireless LANs, called IEEE

802.11, which most systems implement and which is

becoming very widespread.

40

41

• wireless WANs:

• Example: The radio network used for cellular telephones is an

example of a low-bandwidth wireless system.

i. The first generation was analog and for voice only.

ii. The second generation was digital and for voice only.

iii. The third generation is digital and is for both voice and data.

42

The difference of wireless LAN &

WAN:

In a certain sense, cellular wireless networks

are like wireless LANs

× except that the distances involved are much

greater

× the bit rates much lower

43

44

(internetwork)ها شبكه شبكه

A collection of interconnected networks is

called an internetwork or internet

A common form of internet is a collection of

LANs connected by a WAN.

If the system within the gray area contains only routers, it is a subnet

if it contains both routers and hosts, it is a WAN.

WAN networkWAN internetwork

Subnets, networks, and internetworks are often confused.

• Subnet is the collection of routers and communication lines

owned by the network operator.

Tel. Tel.

Tel. Tel.

Tel. Office

Tel. Office

High speed

line

Low speed

line

Low speed

line

Subnet

network45

network network

An internetwork is formed when distinct networks are interconnected.

if different organizations paid to construct different parts of the network

and each maintains its part, we have an internetwork rather than a single

network

if the underlying technology is different in different parts (e.g., broadcast

versus point-to-point), we probably have two networks.

Internetwork/ two networks

46

Second session

47

48

افزار شبكهنرم

پروتكل با ساختار سلسله مراتبي•هااصول طراحي اليه•اتصالگرا و خدمات بيخدمات اتصال•ارتباط سرويسها به پروتكلها•

49

کاهش پيچيدگيهاي طراحیلزوم طراحی اليه اي

:مفاهيم کلي

اجزاء تشکيل دهنده شبکه ها با ارائه سرويسهاي خاص به اليه باالتر: اليه

قواعد برقراري ارتباط يک اليه با اليه ديگر: پروتكل

در اليه هاي متناظردر ماشين هاي مختلفموجود اجزاء : (peer)همتا

االتر سرويسها و عملکردهايی که هر اليه در اختيار اليه بتعيين: (interface)واسط قرار می دهد

پروتکلهامجموعه اليه ها و : (network architecture)معماري شبكه

پروتكل با ساختار سلسله مراتبي

50

network architectureمعماري شبكه

هاها و واسطها، پروتكلاليه

51The philosopher-translator-secretary architecture.

52

سلسله مراتب در پروتكل

Example information flow supporting virtual communication in

layer 5.

لی اگرچه اين بخش تحت نام نرم افزار شبکه ارايه گرديده وفزار بايد توجه کرد که سلسله مراتب قرارداد به صورت سخت ا

پياده سازي می شودfirmwareيا

53

Firmware is software that's installed on a

small memory chip on a hardware device

54

هااصول طراحي اليه• Addressing :for identifying senders and receivers

Since a network normally has many computers

• rules for data transfer: data only travel in one

direction / data can go both ways

• Error Control: physical communication circuits are not

perfect.

• error-detecting and error-correcting codes are

needed, but both ends of the connection must agree

on which one is being used.

• In addition, the receiver must have some way of

telling the sender which messages have been

correctly received and which have not

• Flow Control: keeping a fast sender from swamping a

slow receiver with data

• Multiplexing: for sending a data it should be

disassembled, transmitted, and then reassembled

– For small units of transmitted data the solution is to

gather several small messages into a single large

message.

• Routing: When there are multiple paths between source

and destination

55

56

Layers can offer two different types of service to the layers above them:

connection-oriented

connectionless

Connection-Oriented and Connectionless Services

57

Connection-oriented

is modeled after the telephone system. To talk to someone,

i. you pick up the phone

ii. dial the number

iii. Talk

iv. and then hang up

Similarly, to use a connection-oriented network service, the service user

i. first establishes a connection

ii. uses the connection

iii. releases the connection

The essential aspect of a connection is that it acts like a tube: the sender

pushes objects (bits) in at one end, and the receiver takes them out at the

other end. In most cases the order is preserved so that the bits arrive in

the order they were sent.

• In some cases when a connection is established, the

sender, receiver, and subnet conduct a negotiation about

parameters to be used, such as maximum message

size, quality of service required, and other issues.

• Typically, one side makes a proposal and the other side

can accept it, reject it, or make a counterproposal.

58

Connection-oriented

connectionless service

• is modeled after the postal system. Each message

(letter) carries the full destination address, and each one

is routed through the system independent of all the

others.

• when two messages are sent to the same destination, it

is possible that the first one sent can be delayed so that

the second one arrives first.

59

Quality of service

Each service can be characterized by a quality of service.

• reliable services :

– they never lose data

– receiver acknowledge( the sender is sure that

message is arrived)

– The acknowledgement process introduces overhead

and delays, which are often worth it but are

sometimes undesirable.

60

Reliable connection-oriented service has two minor

variations: message sequences and byte streams.

• message sequences the message boundaries are

preserved. When two 1024-byte messages are sent,

they arrive as two distinct 1024-byte messages, never as

one 2048-byte message.

• In byte streams, the connection is simply a stream of

bytes, with no message boundaries. When 2048 bytes

arrive at the receiver, there is no way to tell if they were

sent as one 2048-byte message, two 1024-byte

messages, or 2048 1-byte messages.

61

• Unreliable (meaning not acknowledged) connectionless

service is often called datagram service, in analogy with

telegram service, which also does not return an

acknowledgement to the sender.

62

• Still another service is the request-reply service. In this

service the sender transmits a single datagram

containing a request; the reply contains the answer.

• Request-reply is commonly used to implement

communication in the client-server model: the client

issues a request and the server responds to it.

63

64

هاانواع خدمات اليه

اداعتمغيرقابلداعتماقابل داعتماقابلاداعتمغيرقابل

اتصالبي گرااتصال

مهاي پيادنباله يهاي بايترشته

Figure 1-16. Six different types of service.

65

66

Five service primitives for implementing a simple connection-oriented

service.

A service is formally specified by a set of primitives (operations) available

to a user process to access the service.

Service Primitives (operations)

67

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

network.

Service Primitives (operations)

68

The Relationship of Services to Protocols

A service is a set of primitives (operations) that a layer

provides to the layer above it.

• it defines what operations the layer is prepared to

perform on behalf of its users, but it says nothing at all

about how these operations are implemented.

• It relates to an interface between two layers, with the

lower layer being the service provider and the upper

layer being the service user.

A protocol is a set of rules governing the format and

meaning of the packets, or messages that are

exchanged by the peer entities within a layer.

services relate to the interfaces between layer

protocols relate to the packets sent between peer

entities on different machines.

69

70

The relationship between a service and a protocol.

Reference Models

• The OSI Reference Model

• The TCP/IP Reference Model

• A Comparison of OSI and TCP/IP

• A Critique of the OSI Model and Protocols

• A Critique of the TCP/IP Reference Model

The OSI reference model

• The model is called the ISO OSI (Open Systems

Interconnection) Reference Model because it deals with

connecting open systems—that is, systems that are

open for communication with other systems. We will just

call it the OSI model for short.

72

The OSI reference model

The Physical Layer (OSI model):

transmitting raw bits over a communication

channel.

The design issues

‘0’→’0’ and not ‘1’

how many volts =‘1’

transmission proceed in one/both directions

how the initial connection is established

how it is torn down when both sides are

finished

how many pins the network connector has and

what each pin is used for

….. 74

The Data Link Layer (OSI model):

75

بررابكهشاليهديدازخطابدونارتباطيكانالبهخطتبديلوظيفهاليهاينMACشبكهدستيابياليهزيرنامبهخاصياليهزيرحاويوداردعهده

dataبهوروديدادهشكستنباكاراين.باشدمي frameترتيبيارسالوودشميارسالگيرندهطرفازكهوصولياعالمقابهايپردازشسپسوآن

شودمي،انجام

(كندگيرندهوسريعفرستنده)ترافيكتنظيم

76

اليه شبكهNetwork layerتهدايچگونگيهمچنينوشبكهزيركنترلوظيفهاليهاين

.داردعهدهبرمقصدبهمبدأازرااطالعاتيهايبسته

77

اليه انتقالTransport layerت نياز وظيفه اصلي اين اليه دريافت داده از اليه باالتر و در صور

شبكه و هاي كوچكتر، فرستادن آنها به اليهشكستن آن به اندازهقابل ها بطور صحيح به طرف ماطمينان حاصل كردن از اينكه داده

.رسدمي

78

جلسهاليهSession layerراتيجلساكهدهدمياجازهمختلفماشينهايدركاربرانبهاليهاينوفتگوگكنترلمانندگوناگونيخدماتوكنندبرقرارخودشانبين

.دهدميارائهنيزراسازيهمگامونشانهمديريت

آندراربحرانيعمليكطرفدوكهمعناستاينبه:نشانهمديريت.ندهندانجامواحد

ايلفيكارسالهنگامدركهكندميكمكسازيهمگام:سازيهمگامنقطهآخرينازدوبارهانتقالمشكل،بروزوافتادنازكارازپسبزرگ،

.گرددتكراركنترلي،

79

اليه نمايشPresentation layer.ودشاين اليه به قواعد و معناي اطالعات فرستاده شده مربوط مي

80

اليه كاربردApplication layerانكاربرعمومينيازموردكهگوناگونيقراردادهايشاملاليهاين

ادهاستفموردگستردهبطوركهقراردادهاييجملهاز.باشدمياست.شدبامياينترنتجهانيشبكهاساسكهباشدميhttpگيردميقرار

پستازتوانميفايل،انتقالبراياليه،اينقراردادهايديگراز.بردنام...وشبكهاخباروالكترونيكي

Reference Models (2)

• The TCP/IP reference model.

82

اليه اينترنتNetwork layer

The internet layer defines an official packet format and protocol called IP (Internet Protocol).

The job of the internet layer is to deliver IP packets where

they are supposed to go. Packet routing is clearly the

major issue here, as is avoiding congestion.

For these reasons, it is reasonable to say that the TCP/IP

internet layer is similar in functionality to the OSI network layer.

83

اليه انتقالTransport layer:باشداين اليه شامل دو قرارداد به شرح زير مي

•TCP:ازايرشتهدهدمياجازهكهاستاتصالگراييواعتمادقابلقرارداددرديگريماشينبهخطابدونكنند،ميحركتبهشروعماشينيكازكهبايتهايي

.شوندتحويلاينترنتاليه

•UDP:نآدركهكاربردهاييبراياتصالبيواعتمادقابلغيرقرارداديكباشدميصحيحتحويلازمهمترسريعتحويل

84

اليه كاربردApplication layerاليه اليه كاربرد در باالي اليه انتقال قرار دارد و شامل تمام قراردادهاي

و انتقال فايل ( telnet)شامل پايانه مجازي ،مدلهاي اوليه. باشدباالتر مي(ftp ) و پست الكترونيكي(SMTP )اندبوده.

85

اليه ميزبان به شبكه(Network Interface)

متصلكهشببهقراردادهاازبعضيازاستفادهباميزبانكهكندميبيانفقطازقرارداداين.كندارسالآنطريقازراIPهايبستهتواندميبنابراين.شود

.استنشدهتعريفشبكهبهشبكهازوميزبانبهميزبان

86

TCP/IPها در مدل اوليهپروتكلها و شبكه

87

TCP/IPو OSIمقايسه مدلهاي مرجع

اندشدهگذاريپايهمستقلقراردادهايازايپشتهمفهوماساسبردوهر.

باشدميهمبهمشابهآنهادرهااليهعملكرد.

مدلOSIفقطوشبكهاليهدررااتصالبيواتصالگراارتباطدوهر.كندميپشتيبانيانتقالاليهدررااتصالگرا

مدلوTCP/IPباطارتهردوازوشبكهاليهدراتصالبيارتباطازفقط.كندميپشتيبانيانتقالاليهدر

88

OSIسه مفهوم اساسي در مدل مرجع

خدماترابطهاقراردادها

89

TCP/IPوOSIمعايب مدلهاي مرجع

زمانبندي نادرست•

تكنولوژي نادرست•

پياده سازي نادرست•

سياستهاي نادرست•

لمكاشفه دو في

دومين دليل عدم اين است OSIرشد

كه هم مدل و هم .قرارداد ناقص است

عظيم، فاقد كارايي و كند

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TCP/IPنقدي بر مدل مرجع

نيستتفكيكقابلواضحبطورقراردادوواسطخدمات،مفاهيممدلايندر.

مدلTCP/IPزجبهقراردادهاازايپشتههرتشريحبرايونيستعموميمدليكTCP/IPنيستمفيد.(توصيفمثالBluetoothاستغيرممكنمدلاينبا)

هالييكبعنوانداشت،وجوداياليهقراردادهايمورددركهشبكهميزباناليه.كندميلعم(دادهپيوندوشبكهاليهبين)رابطيكعنوانبهتنهاوشودنميمحسوب

مدلدرTCP/IPصورتيكهدر.نيستهادادهپيوندوفيزيكيهاياليهبينتمايزي..وفيبر،مسيسيمهايويژگيبافيزيكياليه).هستندمتمايزهمازكامالًاليهدواين

رجهدباآنانتقالوقابانتهايوابتداجداکردنداده پيونداليهوظيفهاماسروکاردارد(باالستاطمينان

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مدل هيبريد

مدل هيبريد كه در اين كتاب از آن استفاده خواهد شد

92

بررسي چند شبكه

اينترنت-1

ATMو x.25،Frame Relay: گرا-شبكه هاي اتصال-2

اترنت-3

شبكه هاي محلي بيسيم-4

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آرپانت

(a) Structure of the telephone system.

(b) Baran’s proposed distributed switching system.

• The original ARPANET design.

The ARPANET (3)

• Growth of the ARPANET (a) December 1969. (b) July 1970

(c) March 1971. (d) April 1972. (e) September 1972.

NSFNET( used TCP/IP)

• The NSFNET backbone in 1988.

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كاربردهاي اينترنت

ترونيکو دريافت نامه هاي پست الكارسال نوشتن، : ايميل-1

ام در يک گروه خبري يک محفل اختصاص يافته براي تبادل پي: اخبار-2زمينه خاص است

هر روز هزاران نفر در سراسر دنيا براي ورود به : ورود از راه دور-3، telnetكامپيوترهاي ديگر از طريق اينترنت از برنامه هايي مانند

rlogin ياsshاستفاده مي كنند

، كار بران اينترنتFTPبا استفاده از برنامه هاي : انتقال فايل-4.ي كنندمي توانند فايلهاي خود را از يک ماشين به ماشين ديگر گپ

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معماري اينترنت

Overview of the Internet.

(Point Of Presence)

a room full of routers

Connection-Oriented Networks:

• X.25

• Frame Relay

• ATM

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Why do the telephone companies like Connection-

Oriented Networks ?

1. Quality of service.

2. Billing.

ATM Virtual Circuits

• Since ATM networks are connection-

oriented, sending data requires first

sending a packet to set up the connection

ATM Virtual Circuits (2)

• An ATM cell.

The ATM Reference Model

• The ATM reference model.

The ATM Reference Model (2)

• The ATM layers and sublayers and their functions.

Ethernet

• Architecture of the original Ethernet.

کابل هم محور ضخیم

Wireless LANs

The proposed standard had to work in two modes:

1. In the presence of a base station.

2. In the absence of a base station(ad hoc networking).

Wireless LANs (2)

• The range of a single radio may not cover the entire

system.

• radio signal can be reflected off solid objects. This

interference results in what is called multipath fading.

Wireless LANs (3)

• A multicell 802.11 network.

Metric Units

• The principal metric prefixes.