<span dir="rtl">خدمة مرحل الإطار (Frame Relay)</span>

kindlyminnowΔίκτυα και Επικοινωνίες

26 Οκτ 2013 (πριν από 3 χρόνια και 5 μήνες)

202 εμφανίσεις

( راطلإا لحرم ةمدخ
Frame Relay
)


ةمدخ رفوت

(Frame Relay)



-

مزحلاب تانايبلا لاسرإ لوكوتورب ىلع دمتعت يتلا


-


تاكبشلا نيب
ً
اطبر
قاطنلا ةعساو ةكبش نيوكتل ةددعتملا ةيلحملا

(WAN)


ىلإ ةجاحلا نع ءانغتسلاا تاكرشلل حيتتو .
ةصاخ تاكبش ليغشتو ةنايصو ءاشنإ

يف طبرلل
اهنيب ام

.


ةيلحملا تاكبشلا ربتعت

(LAN)

تانوكملا دحأ
اميف تانايبلا لدابت ةماقلإ تاكبشلا هذـه نيب طبرلا مهملا نم حبصأف ، تاكرشلا تازيهجتل ةيسيئرلا
. اهنيب



ةطقن( بولسأب ةرشابم طبترت ةيضارتفا رئاود مادختساب كتكرش راقم نيب دتمت لاصتا ةلصو ةمدخلا رفوت
طقن ىلإ
ةكبش ربع اهتارادإ متي ثيح )ة

(Frame Relay)

هذه مادختسا نكمي "تلااصتا" ـل ةعباتلا ةماعلا
. تارامإ ةدع يف ةدعابتم عقاوم طبرل وأ ةراملإا سفن نمض
ً
ايلحم تاكرشلا طبرل ةمدخلا






ايازملا

:اـــيازملاو دـئاوفلا



م ة
ّ
ينفو ةينقت تافصاوم تاذ ،ةد
ّ
حوم ةليسو ةمدخلا رفوت
كتكرش تاجايتحا عيمج ةيبلتل ،ةددح
تلااصتلاا لاجم يف




فقسل قبسملا صيصختلا نم
ً
لادب ،تانايبلا ق
ّ
فدت ةبسن عم فيكتلا يف ةنورملاب زيمتت
يباعيتسا


ةيفاضإ ةميق تاذ تامدخ

موسرلا

راطلإا لحرم ةمدخ موـسر
«

Frame Relay

»



ةمدخ موسر

ةـلودلا لخادراطلإا لحرم

سرلا بستحت
ـ
و
ةكبـش ىلإ كتكرـش راقم نم ةدـتمملا ةلصولا قاطن ضرع ىلع
ً
ادانتـسا ةيرهشلا م
راطلإا لحرم



. ةفاسملاب ةنوهرم تسيل موسرلا نأ ىنعمب ، "تلااصتا" ـل ةعباتلا



ةـمئادلا ةيضارتفلاا رئاودلا موـسر

(PVC)

ةمئادلا ةيضارتفلاا رئاودلا نم ناعون كانه

(
PVC
)
برلا نع أشنت يتلا
راطلإا لحرم ةكبش عم ام عقوم نيب ط


امهو
ةصصخملا ةمدخلاو ةيداعلا ةمدخلا


:ردصملا
ةدحتملا ةيبرعلا تاراملاا تلااصتا عقوم





ةرجؤملا ةيمقرلا طوطخلا ةمدخ
-

تنرتنلااب يرقفلا طرلا ةمدخ
-

يمقرلا كرتشملا طخ ةمدخ
ADSL

-

( كارتشا نود تنرتنلاا ةمدخ
SFI
)


مقرلا طوطخلا
ةرجؤملا ةي

?”?ô?ä?ô?à?Ì?˜?ß?•??ì?”?ô?ã?î?Ü?¤?ß?•??ì?”?ô?Ó?®?¼?ä?ß?•??•?Ž?Ë?Ž?Ä?Ø?à?ß??•?Ž?ã?î?à?Ì?ä?ß?•??Þ?Ø?è?ß??Ž?ë?®?ô?Ó?î?—??â?—??”?ã?ª?§??ò?ë??“?®?Ÿ?†?ä?ß?•??”?ô?ä?×?®?ß?•??Á?î?Ä?¨?ß?•
?
?
??”?ó?-?Ž? ?˜?ß?•?í
??æ?ã??¡?í?•?®?˜?—??•?Ž?Ë?®?´?‘??í??”?ô?ß?Ž?Ë??”?×?ª?‘??®?ô?’?Ü?ß?•??Ž?ì?ä? ?¤?‘??•?Ž?ç?Ž?ô?’?ß?•??é?¬?ë??Þ?Ø?ç??â?˜?ó???”?ã?Ž?ì?ß?•??”?ó?î?ô?¤?ß?•??•?Ž?Ë?Ž?Ä?Ø?ß?•??æ?ã??Ú?ß?«??®?ô?Ï?í
64Kbps
?
??”?ó?Ž?Ð?ß?í
2Mbps
?
??-?•?ª?ã??ð?à?Ë?í
??
?
?
?
?
??“?®?Ÿ?†?ä?ß?•??”?ô?ä?×?®?ß?•??Á?î?Ä?¨?ß?•??”?ã?ª?§??â?ó?ª?Ø?—??”?ô?ç?Ž?Ü?ã?‡??®?Ó?î?—??ð?ß?‡??”?Ó?Ž?¿?ù?Ž?‘??•?¬?ë
??æ?ô?Ä?´?à?Ó??•?-?Ž?§??ï?®?§?•??Ê?×?•?î?ã??Ê?ã??æ?ô?Ä?´?à?Ó??ò?Ó??Ê?×?î?ã??ñ?ƒ??Â?‘?-??æ?Ü?ä?—??ò?˜?ß?•?í??”?ô?ä?ß?Ž?Ì?ß?•
?
?
?
??“?®?Ÿ?†?ä?ß?•??”?ô?ä?×?®?ß?•??Á?î?Ä?¨?ß?•??æ?ã??æ?ô?Ë?î?ç??®?ô?Ó?î?˜?‘??”?ô?è?ô?Ä?´?à?Ô?ß?•??•?û?Ž?¼?—?û?•??á?î?Ø?—
?
?
?
?
?
?
?
??”?»?Ž?¨?ß?•??Á?î?Ä?¨?ß?•
Private Leased Lines
-
TDM
?

ايازم
:ةمدخلا



ةطقن ىلإ ةطقن يأ نيعقوم نيب طبرلا متي
Point
-
to
-

Point




ً
امئاد حوتفم طخ نيمأت

نيتباث نيعقوم نيب تانايبلا لقنل
dedicated line




طوطخلا نم هريغ نع امامت لصفنم طخلا نوكي



تانايبلا لقن يف ةيلاع ةقد



عم ةعرسلاب كرتشي لا

رخآ طخ يأ

راسفتسلااو كارتشلال


ةمدخلا رعس


4
.

رم طوطخ
راطلإا لح



Frame Relay



:ةمدخلا ايازم



ةطقن نيب طبرلا متي

طاقن ةدع عم
Point
-
to
-
Multi Points



عقاوملا عيمج نيب لاصتلال
ً
امئاد حوتفم طخ نيمأت



مادختساب ددحت ةيسيئرلا ةعرسلا نم ةبسن طخلا ذخأيو ردصملا ةعرس يف ةيعرفلا طوطخلا كرتشت
قفدتلا حومج ةبسن
Burst Excess
Rate.




.يسيئرلا لخدملا ةعرسب درفني طخلا اذه ناف دحاو طخ ادع ام طوطخلا عيمج ىلع ةكرحلا تمدعنإ اذإ



ةكراشملا أدبم ىلع ادامتعا لخدملا ةعرس فاعضأ يواست طوطخلا عيمجل ةيلامجإ ةعرس ءاطعإ نكمي
.



راسفتسلااو كارتشلال


ةمدخلا رعس






تنرتنلااب يرقفلا طرلا

ةينيطسلفلا تلااصتلاا دوزت

ىلإ ةنومضم ةيرارمتساو ةيلاع ةعرسب تنرتنلإا ةكبش ىلإ يرقفلا طبرلا ةمدخ
(تنرتنلاا تامدخل ةدوزملا ةيلحملا تاكرشلا
ISPs
ةيملاع تافصاومبو ةقئاف ةدوجو ةءافكب كلذو اهريغو تاسسؤملاو )
نع ديزت يتلا ةمدخلا ةيرارمتسا ةبسنو ليئضلا ريخأتلا نمز ثيح نم
99.9
ا ضورع حيتتو .%
ةيبلت ةعونتملا ةمدخل
( ةمدخلا ةدوج ثيح نم ةفلتخملا تاجايتحلاا
burst and dedicated
نيب حوارتت يتلا تاعرسلاو )
42

يف تيب وليك
ىلإ ةيناثلا
111

.ةيناثلا يف تيب اغيم


ةسسؤم ىدل نيطسلف يف تنرتنلإل لولأا يلحملا لجسملا اهتفصبو
RIPE NCC

تلااصتلاا نإف ،ةيملاعلا
طسلفلا
ماقرأ لجست نأ اهنكميو امك ،اهنوجاتحي يتلا تنرتنلإا نيوانع تاحاسم ةفاك اهنئابزل رفوت نأ ىلع ةرداق ةيني
Autonomous System Numbers (ASNs
لوكوتورب ليغشتل ةمزلالا )
Border Gateway Protocol

(
BGP
نئابزلل .)
.لوكوتوربلا اذهل اقفو لمعلاب نوبغري نيذلا


ا ةينبلا للاخ نم
تنرتنلإا تامدخ يدوزم ةدعاسم تعاطتسا ،ةينيطسلفلا تلااصتلااب ةصاخلا ةروطتملا ةيتحتل
تاونق تحتف ثيح ،تنرتنلإا ةكبش ىلإ يرقفلا طبرلا ىلع نيطسلف يف ةلماعلا ةيراجتلا تاكرشلا نم مهريغو
.نييئاهنلا مهيمدختسمل ةقوثومو ةعيرس تنرتنإ تامدخ ميدقت اهللاخ نم مهتنكم



راسفتسلااو كارتشلال


ةمدخلا رعس






يمقرلا كرتشملا طخ
ADSL


Asymmetric

Digital Subscriber Line
:


ةمدخ
ADSL

قيرط يه
ةينقت مدختست ،تنرتنلإا ةكبشب رمتسملاو عيرسلا لاصتلال ة
ADSL

طوطخ سفن ىلع
ةريغصلا بتاكملا يف نيمدختسملا ةصاخ ( لامعلأا عاطق و نييداعلا نيمدختسملا عاطق فدهتست و ةيداعلا فتاهلا
مئادلا لاصتلاا رفوت ثيح .)ةيلزنملا بتاكملا و ةطسوتملاو

بقتسا ةيناكمإ عم تنرتنلإاب
تاملاكملا لاسرإ و لا
.دحاو نآ يف ةيفتاهلا



:ةمدخلا دئاوفو ايازم


-

.طخلا عاطقنا وأ لاغشنا نود تنرتنلإاب طبرلا يف ةيلاع ةعرس

-

ةيداعلا فتاهلا طوطخ ةعرس قوفت ةعرس
Dial
-
up

.رثكأ وأ تارم ةرشع

-

كرتل ةجاح لاو دوجوملا يداعلا فتاهلا طخ ىلع لمعت ثيح بيكرتلا ةعرس
.صاخ فتاه طخ بي

-

.دحاو نآ يف سكاف لاسرإ وأ ةيفتاه ةملاكم ءارجإ و تنرتنلإا مادختسا نم كنكمت

-

.مادختسلاا ةدم و مجح و لاصتلاا تقوب ديقتت لا ةددحم و ةتباث ةيرهش موسر

-

،ةيعامجلا باعللأا لثم ( ةلوهسب قاطنلا ةعساو ةيعمسلا و ةيئرملا جماربلل لوصولا ةيناكمإ

يزنتو
. .).....روصلا تاموبلأ لوادتو ،ةينورتكلا ةيميلعت تارودب قاحتللااو ،ويديفلا ملافأ ل




ةمدخ ةفرعت
ADSL









ارتشا نود تنرتنلاا
ك
-

SFI


كارتشا ىلإ ةجاحلا نود ةرشابم تنرتنلإا ةكبشب لاصتلاا نم نيكرتشملا كارتشا نود تنرتنلإا ةمدخ نكمت
تنرتنلإا ةمدخ يدوزم عم قبسم
ISP
رورم مسا ىلإ اضيأ ةجاحلا نودبو ،
Login Name

رورم ةملكو
Password

ثيحب
لا تباث فتاه طخو بوساح زاهج هيدل رفوتي كرتشم يأ عيطتسي
صاخ لاصتا زمر ةطساوب تنرتنلإا ةكبش ىلإ لوخد
تنرتنإ دوزم لكل صاخ مقر(
010 XXXXXX
تنرتنلإا ةمدخ دوزم رايتخا يف ةيرحلا كرتشمللو .)
ISP


.ةرم لك


: ةمدخلا هذهل ماعلا فدهلا


1
يف ةتباثلا ةكبشلا طوطخ عيمج ىلع ةمدخلا رفوت للاخ نم تنرتنلإا مادختسا ةدعاق عيسوت .



.ةءافكلاو رعسلا سفنبو نيطسلف

4
امبو كارتشا موسر نودب اهضرع للاخ نم تنرتنلإا مادختسا ةرئاد عيسوتو بوساحلا ةفاقث رشن .



.عمتجملل يجولونكتلاو يفاقثلا يعولا ةدايز ىلإ ةفاضلإاب يلحملا عمتجملا ريوطت يف مهاسي

3
ملا تائف عيمجل تنرتنلإا ةكبشل لوخدلا ةيلمع ليهست .
.عمتج




: ردصملا
عقوم
:

ةينيطسلفلا تلااصتلاا

frame relay







-

Frame relay is a telecommunication service designed for cost
-
efficient data
transmission for intermittent traffic between local area networks (
LAN
s) and between
end
-
points in a wide area network (
WAN
). Frame relay puts data in a variable
-
size
unit called
a
frame

and leaves any necessary error correction (retransmission of data)
up to the end
-
points, which speeds up overall data transmission. For most services, the
network provides a permanent virtual circuit (
PVC
), which means that the customer
sees a continous, dedicated connection without having to pay for a full
-
time leas
ed
line, while the service provider figures out the route each frame travels to its
destination and can charge based on usage. An enterprise can select a level of service
quality
-

prioritizing some frames and making others less important. Frame relay is
o
ffered by a number of service providers, including AT&T. Frame relay is provided
on
fractional T
-
1

or full
T
-
carrier system

carriers. Frame relay complements and
provides a mid
-
range service between
ISDN
, which offers
bandwidth

at 128 Kbps,
and Asynchronous Transfer Mode (
ATM
), which operates in somewh
at similar
fashion to frame relay but at speeds from 155.520 Mbps or 622.080 Mbps.

Frame relay is based on the older
X.25

packet
-
switching technology which was
de
signed for transmitting
analog

data such as voice conversations. Unlike X.25 which
was designed for analog signals, frame relay is a
fast packet technology
, which means
that the protocol does not attempt to correct errors. When an error is detected in a
frame, it is simply "dropped." (thrown away). The end points are responsible for
detectin
g and retransmitting dropped frames. (However, the incidence of error in
digital networks is extraordinarily small relative to analog networks.)

Frame relay is often used to connect local area networks with major backbones as
well as on public wide area n
etworks and also in private network environments with
leased lines over T
-
1 lines. It requires a dedicated connection during the transmission
period. It's not ideally suited for voice or video transmission, which requires a steady
flow of transmissions. Ho
wever, under certain circumstances, it is used for voice and
video transmission.

Frame relay relays packets at the
data link layer

of the Open Systems Interconnec
tion
(
OSI
) model rather than at the
Network layer
. A frame can incorpo
rate packets from
different protocols such as
Ethernet

and
X.25
. It is

variable in size and can be as large
as a thousand bytes or more.


Frame Relay

Frame Relay is a packet
-
switched technology that uses bridges, routers, or
FRADs (Frame
-
Relay access devices). These devices aggregate and convert
data into Frame
-
Relay pack
ets at
-

56kbps, FT1, T1

speeds.



Frame Relay Technology


By
Black Box

T
oday's LANs and computing equipment have the potential to run at much higher
speeds and transfer very large quantities of data. With the diversity and complexity of
today's networks,

management can be a mammoth task if you don't have the proper
tools. Each environment is a unique combination of equipment from different vendors.
Frame Relay, which is a relatively new wide area networking method, is gaining in
popularity. It uses a pack
et
-
switching technology, similar to X.25, but is more efficient.
As a result, it can make your networking quicker, simpler, and less costly.


Frame Relay was developed to solve communication problems that other protocols
could not: the increased need for h
igher speeds, an increased need for large
bandwidth efficiency, particularly for clumping ("bursty" traffic), an increase in
intelligent network devices that lower protocol processing, and the need to connect
LANs and WANs.

Like X.25, Frame Relay is a pack
et
-
switched protocol. But the Frame
-
Relay process is
streamlined. There are significant differences that make Frame Relay a faster, more
efficient form of networking. A Frame
-
Relay network doesn't perform error detection,
which results in a considerably sm
aller amount of overhead and faster processing than
X.25. Frame Relay is also protocol independent
-
it accepts data from many different
protocols. This data is encapsulated by the Frame
-
Relay equipment, not the network.

The intelligent network devices conne
cted to a Frame
-
Relay network are responsible
for the error correction and frame formatting. Processing time is minimized, so the
transmission of data is much faster and more efficient.

In addition, Frame Relay is entirely digital, which reduces the chance

of error and
offers excellent transmission rates. Frame Relay typically operates at 56 kbps to 1.544
mbps.

What does Frame Relay do?

Frame Relay sends information in packets called frames through a shared Frame
-
Relay
network. Each frame contains all the i
nformation necessary to route it to the correct
destination. So in effect, each endpoint can communicate with many destinations over
one access link to the network. And instead of being allocated a fixed amount of
bandwidth, Frame
-
Relay services offer a CI
R (committed information rate) at which
data is transmitted. But if traffic and your service agreement allow, data can burst
above your committed rate.

Why choose Frame Relay?

Since Frame Relay has a low overhead, it's a perfect fit for today's complex net
works.
You get several clear benefits: First, multiple logical connections can be sent over a
single physical connection, reducing your internetworking costs. By reducing the
amount of processing required, you get improved performance and response time.
An
d because Frame Relay uses a simple link layer protocol, your equipment usually
requires only software changes or simple hardware modifications, so you don't have to
invest a lot of money to
upgrade

your system.

Since Frame Relay is protocol independent, i
t can process traffic from different
networking protocols like IP, IPX, and SNA.

Frame Relay is an idea
l choice for connecting Wide Area Networks
(WANs) that have unpredictable, high
-
volume, and bursty traffic
.


Typically, these applications include data t
ransfer, CAD/CAM, and client
-
server
applications.

Frame Relay also offers advantages for interconnecting WANs. In the past, setting up
WANs required the use of private lines or circuit switching over a leased line. Single,
dedicated lines are not needed to

make each WAN
-
to
-
WAN connection with Frame
Relay, reducing costs.

Permanent Virtual Circuits.

Essentially, a permanent virtual circuit (PVC) is your dedicated connection through the
shared Frame
-
Relay network replacing a dedicated end to
-
end line. A PVC i
s needed
for each site in the network, just as a private line is. But in a Frame Relay network, the
bandwidth is shared among multiple users. So any single site can communicate with
any other single site without the need for multiple dedicated lines.

PVCs
function via a Local Management Interface (LMI), which provides control
procedures. The control procedures function in three ways: link integrity verification
initiated by the user device, network status report giving details of all PVCs, and
network notif
ication of whether a PVC's status changes from active to inactive or vice
versa. Data
-
Link Connections (DLCs) are PVCs pre
-
configured by both sides of the
connection. The DLC identifier (DLCI) is used as the logical address for frame
-
layer
multiplexing.

Wh
at do I need to get started?

First, you need a Frame
-
Relay Bearer Service (FRBS), which is offered by the local
telephone company. You'll sign up for a committed information rate (CIR), which might
be 64 kbps. That means you're guaranteed the data will go
through your PVC at this
rate. But, depending on network traffic and what type of line you have, such as a
fractional T1 line capable of 128 kbps, you may actually get higher transmission rates
thanks to 2
-
second bursts of speed across the network. At peak

times when there is a
lot of congestion, you may only transmit at 64 kbps.

Next, you need Frame
-
Relay equipment. Since Frame Relay doesn't provide protocol
conversion and error detection/correction, the end
-
user devices need to be intelligent.
Typically y
ou can access the Frame
-
Relay service through Frame
-
Relay devices, such
as Frame
-
Relay Assembler/Disassemblers (FRADs), frame routers, bridges, or
switches.

Frame Routers.

Frame routers translate existing data communications protocols for transmission ove
r
a Frame
-
Relay network, then route the data across the network to another frame router
or other Frame
-
Relay compatible device. Frame routers can handle many types of
protocols, including LAN protocols. They're u
sed in environments that require T1 or
slower network access speeds. Each router supports one of many physical data
interfaces and can provide several user ports.

Bridges, Routers, and FRAIDs.

You can also use bridges, routers, or FRADs (Frame
-
Relay access

devices). These
devices aggregate and convert data into Frame
-
Relay packets.

Bridges are easy to configure and maintain, and they usually connect a branch off ice
to a hub location.

Routers can handle traffic from other WAN protocols, re
-
route a connectio
n if a line
fails, or provide support for flow control and congestion control.

FRADs format outgoing data into the format required by a Frame
-
Relay network, and
some even function as routers. They work well in applications where a site already has
bridges
and routers or when sending mainframe traffic over a Frame
-
Relay network.

What's next for Frame Relay?

While Frame Relay offers many benefits, a host of problems have to be overcome
before it can be used effectively as a carrier for voice, fax, or video tr
affic. Until
recently, the advancements were vendor
-
specific solutions that offered no
interoperability. Recently ratified industry standards have addressed such issues as
compression, packetization, and prioritization. This move towards standardization ha
s
been led by the Frame
-
Relay Forum (FRF) and the International Telegraphic Union
(ITU).

Compression
-

in February 1998, the ITU ratified an umbrella standard for simultaneous transmission
of voice, data, and video traffic over I P. Known as H.323, this sta
ndard incorporates
other newly adopted criteria, such as G.729 and G.723. These standards specify
algorithms for compressing voice traffic (which usually travels over a full 64
-
kbps telco
circuit) down to 8 kbps for (Voice Over Frame Relay) VOFR.

Packetiza
tion
-

The FRF recently agreed to ratify two new procedures for VOFR. FRFA 1 specifies a
process for connecting PBXs over Frame Relay to carry voice, data, and fax traffic over
one PVC. FRF. 12 addresses packetization and (consequently) prioritization. It
s
tandardizes a procedure for Frame Relay to break down larger frames into a series of
smaller ones.

This technique helps alleviate network congestion problems that occur during peak
usage periods when larger data blocks queue up ahead of time
-
sensitive voic
e traffic.
In lieu of a formal (Quality of Service) QoS protocol, such as that implemented by
asynchronous transfer mode (ATM), FRFA 2 relies on smaller
-
sized packets to ensure
predictable delay patterns and therefore maintain the quality and integrity of
voice
transmissions. Instead of traffic
-
snarling data packets clogging up the circuitry,
smaller, fragmented data frames are interleaved with delay
-
sensitive traffic, reducing
jitter and delay and clearing the path for voice calls.

Prioritization
-

Currentl
y, (resource reservation protocol) RSVP is the only industry standard
specifically designed to support traffic prioritization. While RSVP is rather limited
compared to ATM's QoS capabilities, it is a dynamic mechanism that helps keep traffic
flowing by act
ivating automatically whenever voice packets are present on the line.


The future.

As new standards continue to emerge, we predict you'll see more VOFR in data centers
that rely heavily on international communications, where the potential for savings
looms

largest


Try this
Tutorial site

on Frame Relay

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Other Frame Relay

pages



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Paradyne 9620 56/64 kbps


pages

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Paradyne 9120 T1/FT1/E1


pages



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-
0226



bandwidth







-

1) In electronic communication, bandwidth is the width of the range (or
band
) of frequencies that an electronic
signal

uses on a given transmission medium. In

this usage, bandwidth is expressed in terms of the difference between the highest
-
frequency signal component and the lowest
-
frequency signal component. Since the
frequen
cy

of a signal is measured in
hertz

(the number of cycles of change per
second), a given bandwidth is the difference in hertz between the highest frequency
the signal uses and the lowest frequency it uses. A typical voice signal has a
bandwidth of approximately three kilohertz (3
kHz
); an analog television (TV)
broadc
ast video signal has a bandwidth of six megahertz (6 MHz)
--

some 2,000 times
as wide as the voice signal.

2) In computer networks, bandwidth is often used as a synonym for
data transfer rate

-

the amount of data that can be carried from one point to another in a given time period
(usually a second). This kind of bandwidth is usually expressed in bits (of data) per
second (
bps
). Occasionally, it's expressed as bytes per second (Bps). A
modem

that
works at 57,600 bps has twice the ba
ndwidth of a modem that works at 28,800 bps. In
general, a link with a high bandwidth is one that may be able to carry enough
information to sustain the succession of images in a video presentation.

It should be remembered that a real communications path
usually consists of a
succession of links, each with its own bandwidth. If one of these is much slower than
the rest, it is said to be a bandwidth bottleneck