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Data Transmission Networks
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References:
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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.
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• 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)
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• 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).
• …..
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• 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.
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فصل اول
introduction
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• 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
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هاي كامپيوتريكاربردهاي شبكه
كاربردهاي تجاري•كاربردهاي خانگي•كاربران در حركت•مالحظات اجتماعي•
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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)
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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
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• 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
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كاربردهاي خانگي-2
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برخي انواع تجارت الكترونيكي
كاربردهاي خانگي-2
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هاي متحرككاربران شبكه-3
Figure 1-5. Combinations of wireless networks and mobile computing
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هاكهبندي شبتقسيم
هااز نقطه نظر تكنولوژي انتقال شبكه
بر اساس اندازه شبكه
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(broadcast)هاي پخشي شبكه•
(Point-to-point)هاي شبكه•
وژي انتقالها از نقطه نظر تكنولتفكيک شبكه
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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.
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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
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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.
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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.
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(Local Area Networks)هاي محليشبكه
ياتمانساخيككامپيوترهايكردنمتصلبرايخصوصيايشبكهومنابعگذاشتناشتراكبهبرايكيلومتر،چندفاصلهباشركتاطالعاتتبادل
:هاي محليسه پارامتر مهم در شبكهاندازه•
انتقال اطالعاتتكنولوژي •
يا توپولوژي همبندي •
شبکه هایLANسرعت کاری چندان باالیی ندارند
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: محليهاي شبكهيا همبنديتوپولوژيمثالهايي از
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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
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MAN(Metropolitan Area Networks)هايشبكه
اي است در محدودهشبكهونهيك شهر كه بهترين نمون براي آن شبكه تلويزي
باشد كابلي مي
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(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)
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(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.
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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.
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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
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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.
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• 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.
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• 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.
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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
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(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
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Second session
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افزار شبكهنرم
پروتكل با ساختار سلسله مراتبي•هااصول طراحي اليه•اتصالگرا و خدمات بيخدمات اتصال•ارتباط سرويسها به پروتكلها•
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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
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network architectureمعماري شبكه
هاها و واسطها، پروتكلاليه
51The philosopher-translator-secretary architecture.
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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
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Firmware is software that's installed on a
small memory chip on a hardware device
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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
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Layers can offer two different types of service to the layers above them:
connection-oriented
connectionless
Connection-Oriented and Connectionless Services
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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.
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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.
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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.
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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.
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• 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.
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• 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.
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هاانواع خدمات اليه
اداعتمغيرقابلداعتماقابل داعتماقابلاداعتمغيرقابل
اتصالبي گرااتصال
مهاي پيادنباله يهاي بايترشته
Figure 1-16. Six different types of service.
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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)
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Packets sent in a simple client-server interaction on a connection-oriented
network.
Service Primitives (operations)
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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.
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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.
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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
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The Data Link Layer (OSI model):
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بررابكهشاليهديدازخطابدونارتباطيكانالبهخطتبديلوظيفهاليهاينMACشبكهدستيابياليهزيرنامبهخاصياليهزيرحاويوداردعهده
dataبهوروديدادهشكستنباكاراين.باشدمي frameترتيبيارسالوودشميارسالگيرندهطرفازكهوصولياعالمقابهايپردازشسپسوآن
شودمي،انجام
(كندگيرندهوسريعفرستنده)ترافيكتنظيم
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اليه شبكهNetwork layerتهدايچگونگيهمچنينوشبكهزيركنترلوظيفهاليهاين
.داردعهدهبرمقصدبهمبدأازرااطالعاتيهايبسته
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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
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جلسهاليهSession layerراتيجلساكهدهدمياجازهمختلفماشينهايدركاربرانبهاليهاينوفتگوگكنترلمانندگوناگونيخدماتوكنندبرقرارخودشانبين
.دهدميارائهنيزراسازيهمگامونشانهمديريت
آندراربحرانيعمليكطرفدوكهمعناستاينبه:نشانهمديريت.ندهندانجامواحد
ايلفيكارسالهنگامدركهكندميكمكسازيهمگام:سازيهمگامنقطهآخرينازدوبارهانتقالمشكل،بروزوافتادنازكارازپسبزرگ،
.گرددتكراركنترلي،
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اليه نمايشPresentation layer.ودشاين اليه به قواعد و معناي اطالعات فرستاده شده مربوط مي
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اليه كاربردApplication layerانكاربرعمومينيازموردكهگوناگونيقراردادهايشاملاليهاين
ادهاستفموردگستردهبطوركهقراردادهاييجملهاز.باشدمياست.شدبامياينترنتجهانيشبكهاساسكهباشدميhttpگيردميقرار
پستازتوانميفايل،انتقالبراياليه،اينقراردادهايديگراز.بردنام...وشبكهاخباروالكترونيكي
Reference Models (2)
• The TCP/IP reference model.
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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.
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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.
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اليه ميزبان به شبكه(Network Interface)
متصلكهشببهقراردادهاازبعضيازاستفادهباميزبانكهكندميبيانفقطازقرارداداين.كندارسالآنطريقازراIPهايبستهتواندميبنابراين.شود
.استنشدهتعريفشبكهبهشبكهازوميزبانبهميزبان
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TCP/IPها در مدل اوليهپروتكلها و شبكه
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TCP/IPو OSIمقايسه مدلهاي مرجع
اندشدهگذاريپايهمستقلقراردادهايازايپشتهمفهوماساسبردوهر.
باشدميهمبهمشابهآنهادرهااليهعملكرد.
مدلOSIفقطوشبكهاليهدررااتصالبيواتصالگراارتباطدوهر.كندميپشتيبانيانتقالاليهدررااتصالگرا
مدلوTCP/IPباطارتهردوازوشبكهاليهدراتصالبيارتباطازفقط.كندميپشتيبانيانتقالاليهدر
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OSIسه مفهوم اساسي در مدل مرجع
خدماترابطهاقراردادها
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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
90
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
91
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
93
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
98
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.