شرح Network Topologyمكونات الشبكة وانواع الكابلات

مكونات الشبكة وانواع الكابلاتشرح Network Topologyمكونات الشبكة وانواع الكابلات

1. Wired LANs: Ethernet
ةيكلسلا ةيلحملا لاصتلاا تاكبش(ثيلاا تنر)
ةسدنهملا :يدومحم ميركلا دبع نانب
CHAPTER 13
1

2. introduction
•local area network (LAN) is a computer network that is designed
for a limited geographic area such as a building or a campus.
Although a LAN can be used as an isolated network to connect
computers in an organization for the sole purpose of sharing
resources, most LANs today are also linked to a wide area
network (WAN) or the Internet.
•ا ءانبك ةدودحم ةيفارغج ةقطنمل ممصت رتويبمك ةكبش يه ةيلحملا ةكبشلا مرح و
يعماج . ةكبش مادختسا نكمي اضيأLANتارتويبمكلا طبرل لصف وا لزع ةكبشك
تاكبش مظعمم ، رداصملا ةكراشم وه ديحو ضرغل ةمظنم يفLAN طبرت مويلا
قاطنلا ةعساو تاكبش ىلإWAN تنرتنا وأ .
2

3. introduction
•The LAN market has seen several technologies such as Ethernet,
Token Ring, Token Bus, FDDI, and ATM LAN. Some of these
technologies survived for a while, but Ethernet is by far the
dominant technology.
• تينرثيلاا لثم تاينقت ةدع كانهEthernet, Token Ring, Token Bus, FDDI,
and ATM LAN. . نكلو ةرتفل يقب تاينقتلا هذه ضعبEthernet ةينقتلا يقب
ةنميهملا
3

4. introduction
•Although Ethernet has gone through a four-generation evolution
during the last few decades, the main concept has remained.
Ethernet has changed to meet the market needs and to make use
of the new technologies
• يقب يساسلأا موهفملا نأ لاإ روطت لايجأ عبرأب ترم تينرثيلاا نأ مغر .غت تري
ةديدجلا تاينقتلا لامعتسلاو قوسلا تاجاح ةيبلتل تينرثيلاا .
4

5. IEEE STANDARDS
•In 1985, the Computer Society of the IEEE(Institute of Electrical
and Electronics Engineers).started a project, called Project 802,
to set standards to enable intercommunication among equipment
from a variety of manufacturers.
• ماع يف1985 رتويبمك ةيعمجIEEE(تاينورتكللااو ءابرهكلا يسدنهم ةسسؤم )تأدب
هتمسأ عورشمProject 802جلأا نيب يلخادلا تلااصتلاا نيكمتل ريياعم عضول ةزه
ةفلتخم عناصم نم .
•Project 802 does not seek to replace any part of the OSI or the
Internet model. Instead, it is a way of specifying functions of the
physical layer and the data link layer of major LAN protocols.
•Project 802 نم ءزج يأ لادبتسا ديريلاOSI تنرتنلاا جذومن وا . كلذ نم لادب
وتربل تانايبلا طبر ةقبطو ةيئايزيفلا ةقبطلا ةفيظو ديدحتل ةقيرط وه ةكبش تلاوك
LAN ةيسيئرلا .
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6. IEEE STANDARDS
•The standard was adopted by the American National Standards
Institute (ANSI). In 1987, the International Organization for
Standardization (ISO) also approved it as an international standard
under the designation ISO 8802.
• يكيرملأا يموقلا ريياعملا دهعم لبق نم رقأ رايعملا(ANSI) . ماع يف1987 ةمظنملا
سيياقملل ةيملاعلاISO مسا تحت ةيملاع ريياعمك اهيلع تقفاو اضيأISO 8802
•The relationship of the 802 Standard to the traditional OSI model is
shown in Figure 13.1. The IEEE has subdivided the data link layer
into two sublayers: logical link control (LLC) and media access
control (MAC). IEEE has also created several physical layer standards
for different LAN protocols.
• سايقم ةقلاع802 جذومنبOSI يلاتلا لكشلاب ةحضوم .IEEE ةلصو ةقبط تمسق
نيتيعرف نيتقبط ىلإ تانايبلاlogical link control (LLC) وmedia access
control (MAC) .IEEE تلاوكوتربل ةيئايزيف ةقبط ريياعم ةدع تأشنأ اضيأLAN
ةفلتخملا .
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7. 7

8. Data Link Layer
•As we mentioned before, the data link layer in the IEEE standard
is divided into two sublayers: LLC and MAC.
• رايعم يف تانايبلا طبر ةقبط ، اقباس انركذ امكIEEE نيتيعرف نيتقبط ىلا مسقت:
logical link control (LLC) وmedia access control (MAC)
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9. Logical Link Control (LLC)
•Data link control handles framing, flow control, and error control.
In IEEE Project 802, flow control, error control, and part of the
framing duties are collected into one sublayer called the logical
link control. Framing is handled in both the LLC sublayer and the
MAC sublayer.
•خلاب مكحتلاو قفدتلاب مكحتلا ، ريطأتلا جلاعت تانايبلا ةلصوب مكحتلا أط . يفIEEE
Project 802 تابجاو نم ءزجو ، أطخلاب مكحتلا ، قفدتلاب مكحتلا ،framing
ىمست ةدحاو ةيعرف ةقبط يف عمجتlogical link control ( ةلصولاب مكحتلا
ةيقطنملا . ) اتلك يف جلاعي ريطأتلاLLC ةيعرفلا ةقبطلاوMAC .
9

10. Logical Link Control (LLC)
•The LLC provides one single data link control protocol for all IEEE
LANs. In this way, the LLC is different from the media access
control sublayer, which provides different protocols for different
LANs. A single LLC protocol can provide interconnectivity between
different LANs because it makes the MAC sublayer transparent.
Figure 13.1 shows one single LLC protocol serving several MAC
protocols.
• ةيعرفلا ةقبطلاLLC لكل ديحو تانايبلا ةلصوب مكحت لوكوتربب دوزتIEEE LANs .
• ةقيرطلا هذهبLLC ةيعرفلا ةقبطلا نع فلتختmedia access control دوزت يتلا ،
ةفلتخم ةيلحم تاكبشل ةفلتخم تلاوكوتوربب .
• لوكوتربLLC تاكبش فلتخم نيب يلخاد طبرب دوزي نأ نكمي ديحولاLANs ببسب
ةيعرفلا ةقبطلا لعجي هناMAC ةفافش .
• لوكوترب نيبي قباسلا لكشلاLLC تلاوكوترب ةدع مدخي ديحوMAC .
10

11. Logical Link Control (LLC)
•FramingLLC defines a protocol data unit (PDU) that is somewhat similar
to that of HDLC. The header contains a control field like the one in HDLC;
this field is used for flow and error control. The two other header fields
define the upper-layer protocol at the source and destination that uses
LLC. These fields are called the destination service access point (DSAP) and
the source service access point (SSAP). The other fields defined in a typical
data link control protocol such as HDLC are moved to the MAC sublayer. In
other words, a frame defined in HDLC is divided into a PDU at the LLC
sublayer and a frame at the MAC sublayer, as shown in Figure 13.2.
•LLC تانايب ةدحو لوكوترب فرعت(PDU) يف ةدوجوملل ةهباشمHDLC . ىلع يوتحي سأرلا
يف دوجوملا لثم مكحت لقحHDLC قفدتلاو أطخلاب مكحتلل مدختسي لقحلا اذه ، .سأرلا يلقح
اومدختسي نيذلا فدهلاو ردصملا دنع ايلعلا ةقبطلا لوكوترب نافرعي نيرخلآاLLC . لوقحلا هذه
ىمستdestination service access point (DSAP)( فدهلا ةمدخ لوصو ةطقن )و
source service access point (SSAP) ( ردصملا ةمدخ لوصو ةطقن . ) ىرخلأا لوقحلا
لثم يلاثملا تانايبلا ةلصوب مكحتلا لوكوترب فرعتHDLC ةيعرفلا ةقبطلا ىلإ كرحتتMAC .
يف فرعملا راطلإا ىرخأ تاملكبHDLC ىلإ مسقيPDU ةقبط دنعLLC دنع راطإو ةيعرفلا
ةيعرفلا ةقبطلاMAC لكشلاب نيبم وه امك :
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12. Logical Link Control (LLC)
•Need for LLC The purpose of the LLC is to provide flow and error
control for the upper-layer protocols that actually demand these
services. For example, if a LAN or several LANs are used in an
isolated system, LLC may be needed to provide flow and error
control for the application layer protocols. However, most upper-
layer protocols such as IP do not use the services of LLC. For this
reason, we end our discussion of LLC.
•Need for LLC : نم فدهلاLLCوكوتربل أطخلاو قفدتلاب مكحتلاب ديوزتلا وه تلا
تامدخلا هذه بلطت يتلا ايلعلا ةقبطلا . ةكبش ناك اذا لاثمكLAN تاكبش ةدع وا
LAN ، لوزعم ماظن يف مدختستLLCتلاو أطخلاب مكحتلاب ديوزتلل اهل جاتحي امبر قفد
قيبطتلا ةقبط تلاوكوتربل .يلعلا ةقبطلا تلاوكوترب مظعم لاوحلأا لكب لثم اIP
تامدخ مدختستلاLLC . ةقبطل انحرش يهننس ببسلا اذهلLLC .
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13. 13

14. Media Access Control (MAC)
•Multiple access methods including random access, controlled
access, and channelization. IEEE Project 802 has created a
sublayer called media access control that defines the specific
access method for each LAN. For example, it defines CSMA/CD as
the media access method for Ethernet LANs and the token passing
method for Token Ring and Token Bus LANs. As we discussed in
the previous section, part of the framing function is also handled
by the MAC layer.
• يئاوشعلا لوصولا نمضتت ددعتملا لوصولا قرطrandom access لوصولاو
مكحتملاcontrolled access وchannelization .IEEE Project 802 أشني
طسولل لوصولاب مكحتلا ىمست ةيعرف ةقبطmedia access control فرعت يتلا
لكل ةددحم لوصو قرطLAN . لاثمك : فرعت اهناCSMA/CD لوصو ةقيرطك
تنريثيا لجا نم طسوللLAN ةقيرطوtoken passing لجا نمToken Ring
and Token Bus LANs .بط لبق نم جلاعي ريطأتلا نم ءزج نأ اقباس انحرش امكو ةق
MAC .
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15. Media Access Control (MAC)
•In contrast to the LLC sublayer, the MAC sublayer contains a
number of distinct modules; each defines the access method and
the framing format specific to the corresponding LAN protocol.
• ةيعرفلا ةقبطلا عم ةنراقملابLLC ةيعرفلا ةقبطلا ،MAC تادحولا نم ددع يوحت
وكوترب لكل نيعملا ريطأتلا لكشو لوصو ةقيرط فرعي اهنم لك ، ةزيمتملا لLAN
قباطملا .
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16. Physical Layer
•The physical layer is dependent on the implementation and type
of physical media used. IEEE defines detailed specifications for
each LAN implementation. For example, although there is only
one MAC sublayer for Standard Ethernet, there is a different
physical layer specifications for each Ethernet implementations.
•دختسملا يئايزيفلا طسولا عونو قيبطت ىلع دمتعت ةيئايزيفلا ةقبطلا م .IEEE فرعي
ةيلحم ةكبش قيبطت لكل ةلصفم تافصاومLAN . طقف كانه هنا نم مغرلاب لاثمك
لجا نم ةدحاو ةيعرف ةقبطStandard Ethernet ةيئايزيف ةقبط تافصاوم كانه ،
تنرثيلاا تاقيبطت لكل ةفلتخم.
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17. STANDARD ETHERNET
•The original Ethernet was created in 1976 at Xerox's Palo Alto
Research Center (PARC). Since then, it has gone through four
generations: Standard Ethernet (l0 Mbps), Fast Ethernet (100
Mbps), Gigabit Ethernet (l Gbps), and Ten-Gigabit Ethernet (l0
Gbps), as shown in Figure 13.3 .
• ماع أشنا يلصلاا تينرثيلاا1976 وتلا ثوحب زكرم يف(PARC) . تقولا كلذ نم
لايجا عبرا ربع روطت :
•Standard Ethernet (l0 Mbps), Fast Ethernet (100 Mbps), Gigabit
Ethernet (l Gbps), and Ten-Gigabit Ethernet (l0 Gbps)
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18. لايجأ عبرأ ربع تينرثيلاا روطت
18

19. MAC Sublayer
•In Standard Ethernet, the MAC sublayer governs the operation of
the access method. It also frames data received from the upper
layer and passes them to the physical layer.
• ةقبط يسايقلا تينرثيلاا يفMAC لوصولا ةقيرط ةيلمع مكحت ةيعرفلا .راطإ عنصتو
ةيئايزيفلا ةقبطلا ىلإ اهررمتو ايلعلا ةقبطلا نم ةلبقتسملا تانايبلل .
19

20. Frame Format
•The Ethernet frame contains seven fields: preamble, SFD, DA, SA,
length or type of protocol data unit (PDU), upper-layer data, and
the CRC. Ethernet does not provide any mechanism for
acknowledging received frames. Acknowledgments must be
implemented at the higher layers. The format of the MAC frame
is shown in Figure 13.4.
• لوقح عبس يوحي تنرثيلاا راطإ :
•preamble, SFD, DA, SA, length or type of protocol data unit
(PDU), upper-layer data, and the CRC.
• ةلبقتسملا تاراطلإا رارقلإ ةينقت يأب دوزيلا تنرثيلاا .أ بجي تارارقلإا يف قبطت ن
ايلعلا تاقبطلا . راطإ لكشMAC يلاتلا لكشلاب نيبم :
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21. 21

22. Frame Format
•Preamble. The first field of the 802.3 frame contains 7 bytes (56
bits) of alternating 0s and Is that alerts the receiving system to
the coming frame and enables it to synchronize its input timing.
The pattern provides only an alert and a timing pulse. The 56-bit
pattern allows the stations to miss some bits at the beginning of
the frame. The preamble is actually added at the physical layer
and is not (formally) part of the frame.
•Preamble : راطإ يف لولأا لقحلا802.3 ىلع يوتحي7 تياب(56 تب ) بوانتب
نيب0s و1s قوت ةنمازمل هنكميو مداقلا راطلإا ىلإ لابقتسلاا ماظن هبني يذلا تي
هلخد . تيقوت تاضبنو هبنمب طقف دوزي طمنلا .56-bit ضعب دقفتل ةطحملل حمست
راطلإا ةيادب يف تاتبلا .
•Preambleم ءزج سيل ايمسر هنكلو ةيئايزيفلا ةقبطلا دنع فاضي ايلعف راطلإا ن
22

23. Frame Format
•Start frame delimiter (SFD).The second field (l byte: 10101011)
signals the beginning of the frame. The SFD warns the station or
stations that this is the last chance for synchronization. The last 2
bits is 11 and alerts the receiver that the next field is the
destination address.
•Start frame delimiter (SFD) : يناثلا لقحلا(l byte: 10101011) ريشي
راطلإا ةيادب ىلإ . رذحيSFD ةصرف رخآ يه هذه نا نأب تاطحملا وا ةطحملا
نمازتلل . امه نيتب رخآ11 فدهلا ناونع وه يلاتلا لقحلا نا لبقتسملا هبنتو .
23

24. Frame Format
•Destination address (DA). The DA field is 6 bytes and contains
the physical address of the destination station or stations to
receive the packet.
• فدهلا ناونع : فدهلا ناونع لقحDA وه6طحمل يئايزيفلا ناونعلا يوحيو تياب ة
مزرلا لبقتستل تاطحملا وا فدهلا .
•Source address (SA). The SA field is also 6 bytes and contains the
physical address of the sender of the packet.
•ردصملا ناونع : ردصملا ناونع لقحSA اضيأ6 يئايزيفلا ناونعلا يوحيو تياب
مزرلا لسرمل .
24

25. Frame Format
•Length or type. This field is defined as a type field or length field.
The original Ethernet used this field as the type field to define
the upper-layer protocol using the MAC frame. The IEEE standard
used it as the length field to define the number of bytes in the
data field. Both uses are common today.
• عونلا وا لوطلا : لوطلا لقحو عونلا لقحك فرعي لقحلا اذه .لصلأا تنرثيلاا ي
إ مادختساب ايلعلا قبطلا لوكوترب فيرعتل عون لقحك لقحلا اذه مدختسي راطMAC.
•IEEE standardنايبلا لقح يف تاتيابلا ددع فيرعتل لوط لقحك همدختست تا . لاك
مويلا عئاش مادختسلاا .
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26. Frame Format
•Data. This field carries data encapsulated from the upper-layer
protocols. It is a minimum of 46 and a maximum of 1500 bytes,
as we will see later.
• تانايبلا : ايلعلا ةقبطلا تلاوكوترب نم ةفلغملا تانايبلا لمحي لقحلا .ا ىندلأا دحل46
يمظعلااو1500 تياب .
•CRC. The last field contains error detection information, in this
case a CRC-32.
• نوكي ةلاحلا هذه يفو أطخلا فشك تامولعم يوحي لقح رخآCRC32
26

27. Frame Length
•Ethernet has imposed restrictions on both the minimum and
maximum lengths of a frame, as shown in Figure 13.5.
•اب نيبم وه امك راطلإل يمظعلااو ىندلأا لوطلا ىلع دويقلا تضرف تنرثيلاا لكشل :
27

28. Frame Length
•The minimum length restriction is required for the correct
operation of CSMAlCD as we will see shortly. An Ethernet frame
needs to have a minimum length of 512 bits or 64 bytes. Part of this
length is the header and the trailer. If we count 18 bytes of header
and trailer (6 bytes of source address, 6 bytes of destination
address, 2 bytes of length or type, and 4 bytes of CRC), then the
minimum length of data from the upper layer is 64 -18 = 46 bytes.
If the upper-layer packet is less than 46 bytes, padding is added to
make up the difference.
• ـلل ةحيحصلا ةيلمعلل بولطم ىندلأا لوطلا دييقت نإCSMAlCD اقحلا ىرنس امك .
نم ىندا لوط هل نوكي نلا جاتحي تنرثيلاا راطإ512 وا تب64 تياب . اذه نم ءزج
لييذتلاو سأرلا وه لوطلا .
• انبسح اذا18 لييذتو سأر تياب(6 ، ردصملا ناونعل تاتياب6، فدهلا ناونعل تاتياب2
، عونلا وا لوطلل تياب4 لقحل تيابCRC ) نم تانايبلل يرغصلاا لوطلا اهدعب
نوكي ايلعلا ةقبطلا64-18=46 تياب . نم لقا ايلعلا ةقبطلا ةمزر تناك اذا46 تياب
قرفلا عنصتل ةوشح فاضت .
28

29. Frame Length
•The standard defines the maximum length of a frame (without
preamble and SFD field) as 1518 bytes. If we subtract the 18 bytes
of header and trailer, the maximum length of the payload is 1500
bytes. The maximum length restriction has two historical reasons.
First, memory was very expensive when Ethernet was designed: a
maximum length restriction helped to reduce the size of the
buffer. Second, the maximum length restriction prevents one
station from monopolizing the shared medium, blocking other
stations that have data to send.
• راطلإل يمظعلاا لوطلا فرعي سايقملا( لقح نودبpreamble لقحوSFD ) امك
1518 bytes . انحرط اذإ18 يمظعلاا لوطلا نوكي ، لييذتلاو سأرلا نم تياب
ةلومحلل1500 تياب . ناببس هل يمظعلاا لوطلا دييقت :لاواج ةيلاغ ةركاذلا نا اد
تنرثيلاا ممص امدنع :فابلا مجح ضيفخت يف دعاسي يمظعلاا لوطلا دييقت ر .
•ايناث :يو ، كراشملا طسولا راكتحا نم ةدحاو ةطحم عنمي يمظعلاا لوطلا دييقت عنم
لاسرلال تانايب كلمت ىرخأ تاطحم .
29

30. 30

31. Addressing
•Each station on an Ethernet network (such as a PC, workstation,
or printer) has its own network interface card (NIC). The NIC fits
inside the station and provides the station with a 6-byte physical
address. As shown in Figure 13.6, the Ethernet address is 6 bytes
(48 bits), normally written in hexadecimal notation, with a colon
between the bytes.
• تنرثيلاا ةكبش ىلع ةطحم لك( ةعباطلا وا لمعلا ةطحم وا رتويبمكلاك )لا اهل ترك
اهب صاخلاnetwork interface card (NIC) . دوزيو ةطحملا لخاد نوكي تركلا
نم فلؤملا يئايزيفلا ناونعلاب ةطحملا6 تياب .نرثيلاا ناونع لكشلاب نيبم وه امك ت
6 تياب(48 bits) امهنيب طيقنت عم يرشع ةتسلا ميقرتلاب بتكي ةداع ، .
31

32. 32

33. Addressing
•Unicast, Multicast, and Broadcast Addresses A source address is
always a unicast address-the frame comes from only one station. The
destination address, however, can be unicast, multicast, or broadcast.
Figure 13.7 shows how to distinguish a unicast address from a
multicast address. If the least significant bit of the first byte in a
destination address is 0, the address is unicast; otherwise, it is
multicast.
•Unicast, Multicast, and Broadcast Addresses : امئاد ردصملا نيوانع
نيوانعunicast طقف ةدحاو ةطحم نم يتأي راطلإا ، .
• نوكي نأ نكمي فدهلا ناونعunicast, multicast وا ،broadcast .
• ناونع نيب قرفنو زيمن فيك نيبي يلاتلا لكشلاunicast ناونعوmulticast .
• فدهلا ناونعب لولأا تيابلا يف ةبتر لقلأا تبلا ناك اذإ0 ناونعلا نوكيunicast لاإو
نوكيmulticast
•The least significant bit of the first byte defines the type of address. If
the bit is 0, the address is unicast; otherwise, it is multicast.
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34. 34

35. Addressing
•A unicast destination address defines only one recipient; the
relationship between the sender and the receiver is one-to-one. A
multicast destination address defines a group of addresses; the
relationship between the sender and the receivers is one-to-many.
• فدهلا ناونعunicast نوكت لبقتسملاو لسرملا نيب ةقلاعلاو ، ملتسملا طقف فرعيone-
to-one.
• فدهلا ناونعmulticast لبقتسملاو لسرملا نيب ةقلاعلا ، نيوانعلا نم ةعومجم فرعي
نوكتone-to-many .
•The broadcast address is a special case of the multicast address; the
recipients are all the stations on the LAN. A broadcast destination
address is forty-eight Is.
• ناونعbroadcast ناونع نم ةصاخ ةلاح وهmulticast تاطحملا لك مه نيملتسملا ،
ةكبش ىلعLAN . فدهلا ناونعbroadcast وه48 نم1
The broadcast destination address is a special case of the multicast
address in which all bits are 1 s.
فدهلا ناونعbroadcast ناونعلا نم ةصاخ ةلاح وهmulticast تاتبلا لك ثيح
نوكت1
35

36. Example 13.1
•Define the type of the following destination addresses:
• ةيلاتلا نيوانعلا نم لك عون يدجوأ:
a. 4A:30:10:21:1O:1A
b. 47:20:1B:2E:08:EE
c. FF:FF:FF:FF:FF:FF
•Solution
•To find the type of the address, we need to look at the second
hexadecimal digit from the left. If it is even, the address is unicast. If it is
odd, the address is multicast. If all digits are F's, the address is
broadcast. Therefore, we have the following:
• راسيلا نم ةيرشع ةتس ةناخ يناث ىلإ رظنن نلا جاتحن ناونعلا عون داجيلإ .تناك اذإ ةيجوز
نوكي ناونعلاunicast. ناونعلا نوكي ةيدرف تناك اذإ امأmulticast . تاناخلا لك تناك اذإ
F نوكي ناونعلاbroadcast .
a. This is a unicast address because A in binary is 1010 (even).
b. This is a multicast address because 7 in binary is 0111 (odd).
c. This is a broadcast address because all digits are F's.36

37. Example 13.1
•The way the addresses are sent out on line is different from the
way they are written in hexadecimal notation. The transmission is
left-to-right, byte by byte; however, for each byte, the least
significant bit is sent first and the most significant bit is sent last.
This means that the bit that defines an address as unicast or
multicast arrives first at the receiver.
•تكي يتلا ةقيرطلا نع فلتخت طخلا ىلع ناونعلا اهيف لسري يتلا ةقيرطلا يف اهب ب
يرشع ةتسلا ميقرتلا .، تياب تياب ، نيميلا ىلإ راسيلا نم نوكي لاسرلإا لكل كلذل
ةياهنلاب لسرت ةبتر رثكلاو لاوا لسري ةبتر لقلاا تبلا تياب .ا ينعي اذه يذلا تبل
ناونعلا عون فرعيunicast واmulticast لبقتسملل لاوأ لصي
37

38. Example 13.2
•Show how the address 47:20:1B:2E:08:EE is sent out on line.
•Solution
•The address is sent left-to-right, byte by byte; for each byte, it is
sent right-to-Left , bit by bit, as shown below:
38

39. Access Method: CSMA/CD
•Standard Ethernet uses I-persistent CSMA/CD
•Slot Time In an Ethernet network, the round-trip time required for a
frame to travel from one end of a maximum-length network to the
other plus the time needed to send the jam sequence is called the
slot time.
•Slot Time :قتنيل راطلإل بولطملا بايلإاو باهذلا ةلحر نمز تنرثيلاا ةكبش يف نم ل
س لاسرلإ جاتحملا تقولا ىلإ ةفاضإ ىرخلأا ىلإ ةكبشلل يمظعلاا لوطلاب ةياهن لوأ ةلسل
ىمسي لطعلاslot time
•The slot time in Ethernet is defined in bits. It is the time required for a
station to send 512 bits. This means that the actual slot time depends
on the data rate; for traditional 10-Mbps Ethernet it is 51.2 μs.
• تبلاب تقولا اذه فرعي . لسرتل ةطحملل بولطملا تقولا وه512 تب . نمز نأ ينعي اذه
slot time نوكي ةيديلقتلا تنرثيلاا لجا نم، تانايبلا لدعم ىلع دمتعي يلعفلا51.2μs
39

40. Access Method: CSMA/CD
•Slot Time and Collision The choice of a 512-bit slot time was not
accidental. It was chosen to allow the proper functioning of
CSMA/CD. To understand the situation, let us consider two cases.
•Slot Time and Collision : نمز رايتخاslot time 512-bit ةفداصم سيل . مت
ـل بسانملاو حيحصلا لمعلاب حامسلل هرايتخاCSMA/CD . دوجو ربتعنس ةلاحلا مهفل
نيتلاح.
40

41. Access Method: CSMA/CD
•Slot Time and Collision
•In the first case, we assume that the sender sends a minimum-size packet of
512 bits. Before the sender can send the entire packet out, the signal travels
through the network and reaches the end of the network. If there is
another signal at the end of the network (worst case), a collision occurs.
The sender has the opportunity to abort the sending of the frame and to
send a jam sequence to inform other stations of the collision. The round-
trip time plus the time required to send the jam sequence should be less
than the time needed for the sender to send the minimum frame, 512 bits.
The sender needs to be aware of the collision before it is too late, that is,
before it has sent the entire frame.
• ىلولأا ةلاحلا يف : نم ىندا دح مجحب مزر لسري لسرملا نأ ضرتفن512 تب . حبصي نأ لبق
لا ةياهن ىلا لصتو ةكبشلا ربع لقتنت ةراشلاا ، اجراخ ةمزرلا لماك لاسرإ لسرملا ناكمإب ةكبش .
ةكبشلا ةياهن يف ىرخأ ةراشإ كانه ناك اذإ( ةلاح أوسا ) ثدحي مادطصلاا ، .فلا هيدل لسرملا ةصر
مادطصلاا نع تاطحملا يقاب ملاعلإ لطع ةلسلس لاسرلاو راطلإا لاسرا فاقيلإ . نمزround-
trip لطعلا ةلسلس لاسرلا بولطملا نمزلا دئازjam sequence نمزلا نم لقأ نوكي نأ بجي
ىندلأا مجحلا وذ راطلإا لاسرلا لسرملا هجاتحي يذلا512 تب . كردم نوكي نلا جاتحي لسرملا
راطلاا لماك لسري نا لبق يأ ، ناولأا تاوف لبق مادطصلال.41

42. Access Method: CSMAICD
•Slot Time and Collision
•In the second case, the sender sends a frame larger than the
minimum size (between 512 and 1518 bits). In this case, if the station
has sent out the first 512 bits and has not heard a collision, it is
guaranteed that collision will never occur during the transmission of
this frame. The reason is that the signal will reach the end of the
network in less than one-half the slot time. If all stations follow the
CSMA/CD protocol, they have already sensed the existence of the
signal (carrier) on the line and have refrained from sending.
• ةيناثلا ةلاحلا يف : ىندلاا دحلا نم ربكا راطا لسري لسرملا( نيب512 و تب1518 تب )
. لوأ اجراخ تلسرأ ةطحملا اذإ ةلاحلا هذه يف512 هناب نمضت ، مادطصا عمست ملو تب
راطلاا لاسرا ءانثا مادطصا ثدحي نل.ةكبشلا ةياهن لصت فوس ةراشلاا نا ببسلا لقا يف
نمز فصن نمslot time . لوكوترب عبتت تاطحملا لك اذإCSMA/CD ، اورعشيس
ةراشلإا دوجوب( لماحلا ) لاسرلاا نع عنتمتو طخلا ىلع .
42

43. Access Method: CSMA/CD
•Slot Time and Collision
•In the second case, If they sent a signal on the line before one-half of
the slot time expired, a collision has occurred and the sender has sensed
the collision. In other words, collision can only occur during the first half
of the slot time, and if it does, it can be sensed by the sender during the
slot time. This means that after the sender sends the first 512 bits, it is
guaranteed that collision will not occur during the transmission of this
frame. The medium belongs to the sender, and no other station will use
it. In other words, the sender needs to listen for a collision only during
the time the first 512 bits are sent.
• ةيناثلا ةلاحلا يف عباتن : تقو فصن ءاهتنا لبق طخلا ىلع ةراشا لاسرا مت اذاslot time ،
مادطصلااب سحي لسرملاو ثدحي مادطصلاا .قف ثدحي نأ نكمي مادطصلاا ىرخأ تاملكب ط
نم لولأا فصنلا ءانثأslot time ءانثأ لسرملا هب رعشي نأ نكمي ثدح اذإو ،slot time .
لوأ لسرملا لسري نأ دعب هنا ينعي اذه512 لاسرا ءانثا مادطصا ثدحي نل هناب نمضي ، تب
راطلاا اذه . همدختست فوس ىرخأ ةطحملاو لسرملل دوعي طسولا . لسرملا ىرخأ تاملكب
لوأ هيف لسرت يذلا تقولا ءانثأ طقف مادطصلال عامتسلال جاتحي512 تب .
43

44. Access Method: CSMA/CD
•Slot Time and Collision
•In the second case
•Of course, all these assumptions are invalid if a station does not
follow the CSMA/CD protocol. In this case, we do not have a
collision, we have a corrupted station.
• لوكوترب عبتتلا ةطحملا اذإ ةحيحص ريغ نوكت تايضرفلا هذه لك اعبط.CSMA/CD
ةلطعتم ةطحم نوكي امنإو مادطصا انيدل نوكيلا ةلاحلا هذه يف .
44

45. Access Method: CSMA/CD
•Slot Time and Maximum Network Length
•There is a relationship between the slot time and the maximum
length of the network (collision domain). It is dependent on the
propagation speed of the signal in the particular medium. In most
transmission media, the signal propagates at 2 x 10
8
mls (two-thirds
of the rate for propagation in air). For traditional Ethernet, we
calculate
•Slot Time and Maximum Network Length
• نيب ةقلاع كانهslot time ةكبشلل يمظعلاا لوطلاو( مادطصلاا لاجم . ) ىلع دمتعت
ددحملا طسولا يف ةراشلإا ديلوت ةعرس .شتنت ةراشلإا لاسرلإا طاسوأ مظعم يف ر
ةعرسب2 x 10
8
mls( ءاوهلا يف اهراشتنا لدعم يثلث يهو . )يديلقتلا تنرثيلال ة
بسحن :
45

46. Access Method: CSMA/CD
•Slot Time and Maximum Network Length
•Of course, we need to consider the delay times in repeaters and
interfaces, and the time required to send the jam sequence. These
reduce the maximum-length of a traditional Ethernet network to
2500 m, just 48 percent of the theoretical calculation.
•لا بولطملا تقولاو ، تلاصولاو رركملا يف ريخأتلا تقو رابتعلا جاتحن اعبط لاسر
لطعلا ةلسلس . ىلإ ةيديلقتلا تنرثيلاا ةكبشل يمظعلاا لوطلا للقي اذه2500 m طقف
48 يرظنلا باسحلا نم ةئاملاب .
MaxLength=2500 m
46

47. 47

48. Physical Layer
•Encoding and Decoding
•All standard implementations use digital signaling (baseband) at
10 Mbps. At the sender, data are converted to a digital signal
using the Manchester scheme; at the receiver, the received signal
is interpreted as Manchester and decoded into data.
• ةيمقر ةراشإ مدختست ةيسايقلا تاقيبطتلا لك (baseband ) دنع10 Mbps. دنع
ا دنع ، رتسيشنام ططخم مادختساب ةيمقر ةراشإ ىلإ لوحت تانايبلا لسرملا ، لبقتسمل
نايبل لوحتتو زيمرتلا كفيو رتسشنام بسح مجرتت ةلبقتسملا ةراشلاا تا .
•Manchester encoding is self-synchronous, providing a transition
at each bit interval. Figure 13.9 shows the encoding scheme for
Standard Ethernet.
• تب ةرتف لك دنع لاقتنلااب دوزي ، نمازتلا يتاذ رتسشنام زيمرت .لكشلا نيبي يلاتلا
يسايقلا تنرثيلال زيمرتلا ططخم .
48

49. 49

50. Physical Layer
•10 Base5: Thick Ethernet
•The first implementation is called 10Base5, thick Ethernet, or
Thicknet. The nickname derives from the size of the cable, which
is roughly the size of a garden hose and too stiff to bend with your
hands. 10Base5 was the first Ethernet specification to use a bus
topology with an external transceiver (transmitter/receiver)
connected via a tap to a thick coaxial cable. Figure 13.10 shows a
schematic diagram of a lOBase5 implementation.
• ىمسي قيبطت لوأ10Base5, thick Ethernet واThicknet. راعتسملا مسلاا
نكميلا ادج بلصو ةقيدح موطرخ مجح ابيرقت وه يذلا ، لباكلا مجح نم قتشي
ديلاب هؤانحنا .
•10Base5مو لبقتسمب يطخلا ليصوتلا تمدختسا تنرثيا تافصاوم لوا وه لسر
يجراخtransceiver (transmitter/receiver) لباك ىلإ بات ربع ةلوصوم
كيمس يروحم . قيبطتل يطيطخت ططخم نيبي يلاتلا لكشلا10Base5
50

51. 51

52. Physical Layer
•10Base5: Thick Ethernet
•The transceiver is responsible for transmitting, receiving, and detecting
collisions. The transceiver is connected to the station via a transceiver
cable that provides separate paths for sending and receiving. This
means that collision can only happen in the coaxial cable.
•Transceiver تامادطصلاا فشكو لابقتسلااو لاسرلإا نع لوؤسم .transceiver
لباك قيرط نع ةطحملاب لصويtransceiver لاسرلإل ةلصفنم تاراسمب دوزي يذلا
لابقتسلااو . يروحملا لباكلا يف طقف ثدحي نا نكمي مادطصلاا نا ينعي اذه .
•The maximum length of the coaxial cable must not exceed 500 m,
otherwise, there is excessive degradation of the signal. If a length of
more than 500 m is needed, up to five segments, each a maximum of
500-meter, can be connected using repeaters. Repeaters will be
discussed in Chapter 15.
• زواجتيلا نا بجي يروحملا لباكلل يمظعلاا لوطلا500 m كانه نوكي كلذ ادعام ،
ةراشلال ضيفخت . نم رثكأ لوطلا ناك اذإ500 m لك عطق سمخل اهميسقت نكمي ، بولطملا
يمظعا لوطب اهنم500 m تارركملا مادختساب لصتت نا نكمي .
52

53. Physical Layer
•10Base2: Thin Ethernet
•The second implementation is called 10Base2, thin Ethernet, or
Cheapernet. 10Base2 also uses a bus topology, but the cable is
much thinner and more flexible. The cable can be bent to pass
very close to the stations. In this case, the transceiver is normally
part of the network interface card (NIC), which is installed inside
the station. Figure 13.11 shows the schematic diagram of a
10Base2 implementation.
• ىمسي يناثلا قيبطتلا10Base2, thin Ethernet, or Cheapernet.
•10Base2ثكأو ريثكب فحنا لباكلا نكلو يطخلا ليصوتلا مدختسي اضيأ ةنورم ر .
ةطحملا نم برقلاب رميل ىنحي نا نكمي لباكلا . ةلاحلا هذه يفtransceiver وه
ةكبشلا ترك نم ءزج ةداعnetwork interface card (NIC) لخاد تبثي يذلا ،
ةطحملا . قيبطتل يطيطخت ططخم نيبي يلاتلا لكشلا10Base2
53

54. 54

55. Physical Layer
•10Base2: Thin Ethernet
•Note that the collision here occurs in the thin coaxial cable. This
implementation is more cost effective than 10Base5 because thin
coaxial cable is less expensive than thick coaxial and the tee
connections are much cheaper than taps. Installation is simpler
because the thin coaxial cable is very flexible. However, the length
of each segment cannot exceed 185 m (close to 200 m) due to the
high level of attenuation in thin coaxial cable.
• يروحملا لباكلا يف ثدحي مادطصلاا نا انه ظحلان . نم ةفلك لقا قيبطتلا اذه
10Base5 ةلصوو كيمسلا نم صخرا عيفرلا يروحملا لباكلا نا ببسبtee
نم صخراtaps .ورم رثكأ فيحنلا يروحملا لباكلا نا ببسب لهسأ بيكرتلا ةن .
زواجتي نا نكميلا عطقم لك لوط لاوحلأا لكب185 m ىوتسملا ببسب كلذو
يروحملا لباكلا اذه يف دماختلل يلاعلا .
55

56. Physical Layer
•10Base-T: Twisted-Pair Ethernet
•The third implementation is called 10Base-Tor twisted-pair
Ethernet. 10Base-T uses a physical star topology. The stations are
connected to a hub via two pairs of twisted cable, as shown in
Figure 13.12.
• ىمسي ثلاثلا قيبطتلا10Base-T وأtwisted-pair Ethernet .
•10Base-T يئايزيفلا يمجنلا ليصوتلا مدختسي .هلا ىلإ لصتت تاطحملا نع با
يلاتلا لكشلاب نيبم وه امك ، ةيئانثلا ةجودزملا كلاسلأا نم نانثا قيرط.
56

57. 57

58. Physical Layer
•10Base-T: Twisted-Pair Ethernet
•Note that two pairs of twisted cable create two paths (one for
sending and one for receiving) between the station and the hub.
Any collision here happens in the hub. Compared to 10Base5 or
10Base2, we can see that the hub actually replaces the coaxial
cable. The maximum length of the twisted cable here is defined
as 100 m, to minimize the effect of attenuation in the twisted
cable.
• نيراسم أشنت ةيئانثلا كلاسلأا يجوز نا ظحلان(قتسلال دحاوو لاسرلال دحاو لاب )
باهلاو ةطحملا نيب . عم ةنراقملاب10Base5 وا10Base2 نا دهاشن نا اننكمي ،
يروحملا لباكلا لحم لحي ةقيقحلا يف باهلا .ئانثلا لباكلل يمظعلاا لوطلا ي
وه جودزملا100 m اهيف دماختلا ريثأت ليلقتل .
58

59. Physical Layer
•10Base-F: Fiber Ethernet
•Although there are several types of optical fiber 10-Mbps
Ethernet, the most common is called 10Base-F. 10Base-F uses a
star topology to connect stations to a hub. The stations are
connected to the hub using two fiber-optic cables, as shown in
Figure 13.13.
• ةيئوضلا فايللأا نم عاونأ ةدع كانه نا نم مغرلاب10-Mbps Ethernet رثكلأا ،
وه اعويش10Base-F.
•10Base-F باهلا ىلإ تاطحملا لصول يمجنلا ليصوتلا مدختسي .تت تاطحملا لص
لكشلاب نيبم وه امك ، ةيئوض فايلأ نيلباك مادختساب باهلا ىلإ .
59

60. 60

61. Summary
61

62. CHANGES IN THE STANDARD
•The 10-Mbps Standard Ethernet has gone through several
changes before moving to the higher data rates. These
changes actually opened the road to the evolution of the
Ethernet to become compatible with other high-data-rate
LANs. We discuss some of these changes in this section.
• يسايقلا تنرثيلاا10-Mbps لدعم ىلإ كرحتي نا لبق تاريغت ةدع ربع بهذي
ىلعأ تانايب .رثيلاا روطتل قيرطلا حتفت ةقيقحلا يف تاريغتلا هذه حبصيل تن
تاكبش عم قفاوتمLANs يلاع تانايب لدعمب .ريغتلا هذه نم ضعب حرشنس تا
مسقلا اذه يف .
62

63. Bridged Ethernet
•The first step in the Ethernet evolution was the division of a LAN
by bridges. Bridges have two effects on an Ethernet LAN: They
raise the bandwidth and they separate collision domains. We
discuss bridges in Chapter 15.
•روسجلاب ةيلحملا تاكبشلا مسق تناك تنرثيلاا ريوطت يف ىلولأا ةوطخلا . روسجلا
ةيلحملا تنرثيلاا ةكبش ىلع ناريثأت اهل :لصفيو ةمزحلا ضرع نوعفري تلااجم او
مادطصلاا .
63

64. Bridged Ethernet
•Raising the Bandwidth
•In an unbridged Ethernet network, the total capacity (10 Mbps) is
shared among all stations with a frame to send; the stations share the
bandwidth of the network. If only one station has frames to send, it
benefits from the total capacity (10 Mbps). But if more than one station
needs to use the network, the capacity is shared. For example, if two
stations have a lot of frames to send, they probably alternate in usage.
When one station is sending, the other one refrains from sending. We
can say that, in this case, each station on average, sends at a rate of 5
Mbps. Figure 13.14 shows the situation.
• ةكبش يفunbridged Ethernet يه ةلماكلا ةعسلا(10 Mbps) لك نيب كراشت
ةكبشلل ةمزحلا ضرع عم كرتشت تاطحملا ، لاسرلإل راطإ عم تاطحملا . ةطحم طقف اذا
ةلماكلا ةعسلا نم ديفتستس ، لاسرلإل راطإ كلمت ةدحاو(10 Mbps) . نم رثكأ اذا نكلو
كراشتتس ةعسلا ، ةكبشلا مادختسلا جاتحت ةطحم .
• لاثمك :سلااب اوبوانتي نا لمتحملا نم لاسرلال تاراطلاا نم ديدعلا نيتطحمل ناك اذا مادخت .
لاسرلإا نع عنتمتس ىرخلأا ةدحاو ةطحم لسرت امدنع . لك ةلاحلا هذه يف لوقلا نكمي
لسرت لدعملا يف ةطحم5 ةيناثلا يف تياباغيم . ةلاحلا نيبي يلاتلا لكشلا .64

65. 65

66. Bridged Ethernet
•Raising the Bandwidth
•The bridge, can help here. A bridge divides the network into two or
more networks. Bandwidth-wise, each network is independent. For
example, in Figure 13.15, a network with 12 stations is divided into
two networks, each with 6 stations. Now each network has a capacity
of 10 Mbps. The 10-Mbps capacity in each segment is now shared
between 6 stations (actually 7 because the bridge acts as a station in
each segment), not 12 stations. In a network with a heavy load, each
station theoretically is offered 10/6 Mbps instead of 10/12 Mbps,
assuming that the traffic is not going through the bridge.
• انه ةدعاسملا هنكمي رسجلا . رثكأ وأ نيتكبش ىلا ةكبشلا مسقي رسجلا .ا ضرعو لكل ةمزحل
لقتسم ةكبش . يوحت ةكبش دجوت يلاتلا لكشلا يف لاثمك12 اهنم لك نيتكبشل مسقت ةطحم
اهيف6 تاطحم . ةعس كلمت ةكبش لك نلآا10 تياباغيم . لك يف كراشتتس ةعسلا هذهو
نيب عطقم6 تاطحم( مامتلاب7 عطقم لك يف ةطحمك فرصتي رسجلا نلا )تاكبشلا يف
حنمت ايرظن ةطحم لك ليقث لمحب10/6 Mbps نم لادب10/12 Mbps نأ ضارتفاب
رسجلاب رميلا رورملا .
66

67. 67

68. Bridged Ethernet
•Raising the Bandwidth
•It is obvious that if we further divide the network, we can gain
more bandwidth for each segment. For example, if we use a four-
port bridge, each station is now offered 10/3 Mbps, which is 4
times more than an unbridged network.
•طقم لكل رثكأ ةمزح ضرع بسكن فوس رثكا ةكبشلا انمسق اذا هنا حضاولا نم ع .
لاثمك : حنمت ةطحم لك ، ذفانم عبرا هل رسج انمدختسا اذا10/3 Mbps عبرأ وهو
ةكبشلا نم رثكا تارمunbridged
68

69. Bridged Ethernet
•Separating Collision Domains
•Another advantage of a bridge is the separation of the collision
domain. Figure 13.16 shows the collision domains for an
unbridged and a bridged network. You can see that the collision
domain becomes much smaller and the probability of collision is
reduced tremendously. Without bridging, 12 stations contend for
access to the medium; with bridging only 3 stations contend for
access to the medium.
• مادطصلاا لاجم لصف وه رسجلل ىرخأ ةدئاف .صلاا لاجم نيبي يلاتلا لكشلا مادط
ةكبشلunbridged ةكبشوbridged . حبصي مادطصلاا لاجم نأ ةيؤر اننكمي
ريبك لكشب ضفخني مادطصلاا لامتحاو رثكا رغصا . ريسجتلا نودب12 ةطحم
طقف ريسجتلا دوجوب ، طسولل لوصولل سفانت3 طسولل لوصولل سفانت تاطحم .
69

70. 70

71. Switched Ethernet
•The idea of a bridged LAN can be extended to a switched LAN.
Instead of having two to four networks, why not have N networks,
where N is the number of stations on the LAN? In other words, if we
can have a multiple-port bridge, why not have an N-port switch? In
this way, the bandwidth is shared only between the station and the
switch (5 Mbps each). In addition, the collision domain is divided into
N domains.
• ةكبش ةركفLAN ىلا عسوت نأ نكمي ةرسجملاswitched LAN . نيتكبش دوجو نم لادب
كانه نوكي لا امل ، تاكبش عبرا ىلاN ثيح ةكبشN ةكبش تاطحم ددعLAN ؟
• ذفنمب لدبم انيدل نوكيلا امل ذفانملا ددعتم رسج انيدل ناك اذا ىرخأ تاملكبN . هذه يف
لدبملاو ةطحملا نيب طقف كراشتيس ةمزحلا ضرع ةقيرطلا(5 Mbps each) . ةفاضلإاب
ىلا مسقي مادطصلاا لاجم نأN لاجم .
71

72. Switched Ethernet
•A layer 2 switch is an N-port bridge with additional
sophistication that allows faster handling of the packets.
Evolution from a bridged Ethernet to a switched Ethernet was
a big step that opened the way to an even faster Ethernet, as
we will see. Figure 13.17 shows a switched LAN.
• ةقبطلا2 ذفنمب رسجلا لدبتN مزرلل عرسأ ةجلاعمب حمسي يفاضإ روطتب .
نم روطتلاbridged Ethernet ىلاswitched Ethernet ةريبك ةوطخ وه
ىرنس امك عرسأ تنرثيلا قيرطلا تحنف . ةكبش نيبي يلاتلا لكشلاswitched
LAN
72

73. 73

74. Full-Duplex Ethernet
•One of the limitations of 10Base5 and 10Base2 is that communication is
half-duplex (10Base-T is always full-duplex); a station can either send or
receive, but may not do both at the same time. The next step in the
evolution was to move from switched Ethernet to full-duplex switched
Ethernet. The full-duplex mode increases the capacity of each domain
from 10 to 20 Mbps. Figure 13.18 shows a switched Ethernet in full-
duplex mode. Note that instead of using one link between the station
and the switch, the configuration uses two links: one to transmit and
one to receive.
• نيعونلل تادييقتلا ىدحإ10Base5 and 10Base2 لاصتلاا نأ وهhalf-duplex
(10Base-T is always full-duplex) نكلو ، لابقتسلاا وأ لاسرلإا اهنكمي ةطحملا ،
تقولا سفن يف نينثلاا لعفت نا اهنكميلا .نلال تناك روطتلا يف ةيناثلا ةوطخلا نم لاقت
switched Ethernet ىلاfull-duplex switched Ethernet .
• طمنfull-duplex نم لاجم لكل ةعسلا ديزي10 ىلا20 ةيناثلا يف تب اغيم .يلاتلا لكشلا
نيبيswitched Ethernet in full-duplex mode.
•لال ةدحاو نلاتلصو كانه ، لدبملاو ةطحملا نيب ةدحاو ةلصو مادختسا نم لادب هنا ظحلان لاسر
لابقتسلال ةدحاوو .
74

75. 75

76. Full-Duplex Ethernet
•No Need for CSMA/CD
•In full-duplex switched Ethernet, there is no need for the CSMA/CD
method. In a full duplex switched Ethernet, each station is connected
to the switch via two separate links.
• يفfull-duplex switched Ethernet ةقيرطل ةجاح دجويلاCSMA/CD . يفfull
duplex switched Ethernetتلصفنم نيتلصو ربع شتيوسلاب لصتت ةطحم لك ني
•Each station or switch can send and receive independently without
worrying about collision. Each link is a point-to-point dedicated path
between the station and the switch. There is no longer a need for
carrier sensing; there is no longer a need for collision detection. The
job of the MAC layer becomes much easier.
•ا لوح قلقلا نودب لقتسم لكشب لابقتسلااو لاسرلاا اهنكمي شتيوس وآ ةطحم لك مادطصلا .
ةلصو لكpoint-to-point شتيوسلاو ةطحملا نيب راسم صصخت . ةجاح دجويلا
مادطصلاا فشكل ةجاح دجويلاو لقانلا ساسحلا . ةقبط ةمهمMAC ةلوهس رثكا حبصت .
76

77. Full-Duplex Ethernet
•MAC Control Layer
•Standard Ethernet was designed as a connectionless protocol at the
MAC sublayer. There is no explicit flow control or error control to
inform the sender that the frame has arrived at the destination
without error. When the receiver receives the frame, it does not
send any positive or negative acknowledgment.
• ةيعرفلا ةقبطلا دنع لقا لاصتا لوكوتربك ممص يسايقلا تنرثيلااMAC . كانه سيل
فدهلا ىلإ لصاولا راطلإا نأ لسرملا ملاعلإ حضاو أطخلاب مكحت وأ قفدتلاب مكحت نودب
أطخ . يبلس وا يباجيا رارقإ يأ لسريلا راطلإا لبقتسملا ملتسي امدنع .
•To provide for flow and error control in full-duplex switched
Ethernet, a new sublayer, called the MAC control, is added between
the LLC sublayer and the MAC sublayer.
• يف أطخلا وا قفدتلاب مكحتلاب ديوزتللfull-duplex switched Ethernet ةيعرف ةقبط ،
ىمست ةديدجMAC control نيب فاضتLLC sublayer نيبوMAC sublayer
77

78. FAST ETHERNET
•Fast Ethernet was designed to compete with LAN protocols such as
FDDI or Fiber Channel. IEEE created Fast Ethernet under the name
802.3u. Fast Ethernet is backward-compatible with Standard
Ethernet, but it can transmit data 10 times faster at a rate of 100
Mbps.
• تلاوكوترب عم سفانتلل ممص عيرسلا تنرثيلااLAN لثمFDDIةيئوضلا ةانقلا وا .
IEEE مسا تحت عيرس تنرثيا أشنت802.3u .تنرثيلاا عم ةقفاوتم عيرسلا تنرثيلاا
عرسا تانايب لسري نا نكمي هنكلو ، ةيسايقلا10 تانايب لدعمب تارم100 Mbps .
78

79. FAST ETHERNET
•The goals of Fast Ethernet can be summarized as follows:
1. Upgrade the data rate to 100 Mbps.
2. Make it compatible with Standard Ethernet.
3. Keep the same 48-bit address.
4. Keep the same frame format.
5. Keep the same minimum and maximum frame lengths.
يلي امك صخلتي نأ نكمي عيرسلا تنرثيلاا نم فدهلا :
.1 ىلا تانايبلا لدعم ةيقرت100 Mbps.
.2 ةيسايقلا تنرثيلاا عم قفاوتم هلعج.
.3 ناونعلا سفنب ظفتحي48-bit
.4 راطلإا لكش سفنب ظفتحي
.5 راطلإل يمظعلااو يرغصلاا لوطلاب ظفتحي .
79

80. MAC Sublayer
•A main consideration in the evolution of Ethernet from 10 to 100
Mbps was to keep the MAC sublayer untouched. However, a
decision was made to drop the bus topologies and keep only the
star topology. For the star topology, there are two choices, as we
saw before: half duplex and full duplex. In the half-duplex
approach, the stations are connected via a hub; in the full-duplex
approach, the connection is made via a switch with buffers at
each port.
• نم تنرثيلاا مييقت يف يساسلأا رابتعلاا10 ىلا100Mbps مدعب ظافتحلاا وه
ةيعرفلا ةقبطلاب ريثأتلاMAC . طقف ظافتحلااو يطخلا ليصوتلا طاقسلإ رارقلا
يمجنلا ليصوتلاب .قباس انيأر امك ، نيرايخ كانه يمجنلا ليصوتلا لجا نم ا :half
duplex and full duplex .
• يفhalf-duplex يف ، باهلاربع لصتت تاطحملاfull-duplex نوكي لاصتلاا
ذفنم لك دنع رفاب دوجوب شتيوسلا ربع .
80

81. MAC Sublayer
•The access method is the same (CSMA/CD) for the half-duplex
approach; for full duplex Fast Ethernet, there is no need for
CSMA/CD. However, the implementations keep CSMA/CD for
backward compatibility with Standard Ethernet.
• اهسفن يه لوصولا ةقيرط(CSMA/CD) ـللhalf-duplex لجا نم ،full
duplex Fast Ethernet ـلل ةجاح دجويلاCSMA/CD . ظفحت تاقيبطتلا
CSMA/CD يسايقلا تنرثيلاا عم يفلخلا قفاوتلل .
81

82. Autonegotiation
•A new feature added to Fast Ethernet is called autonegotiation. It
allows a station or a hub a range of capabilities. Autonegotiation
allows two devices to negotiate the modeor data rate of operation. It
was designed particularly for the following purposes:
• ىمست عيرسلا تنرثيلاا ىلا فاضت ةديدج ةزيمautonegotiation . وا ةطحملل حمست
تايلباقلا نم لاجمب باهلا .Autonegotiation لدعم ىلع ضوافتلل نيزاهجل حمست
ةيلمعلل طمنلاو تانايبلا . ةيلاتلا ضارغلأل اصوصخ ممص وه :
•To allow incompatible devices to connect to one another. For example,
a device with a maximum capacity of 10 Mbps can communicate with
a device with a 100 Mbps capacity (but can work at a lower rate).
• اهضعب عم لاصتلال ةقفاوتم ريغلا ةزهجلأل حامسلل . ىمظع ةعسب زاهجلا لاثمك10 Mbps
ةعسب زاهجب لاصتلاا هنكمي100 Mbps( لقأ لدعمب لمعي نأ هنكمي نكلو )
•To allow one device to have multiple capabilities.
•ةددعتم تايلباق هل نوكي نأ دحاو زاهجل حامسلل .
•To allow a station to check a hub's capabilities.
• باهلا تايلباق قيقدتل ةطحملل حامسلل .
82

83. Physical Layer
•The physical layer in Fast Ethernet is more complicated than the
one in Standard Ethernet.
•زيفلا ةقبطلا نم رثكا ةدقعم عيرسلا تنرثيلاا يف ةيئايزيفلا ةقبطلا تنرثيلاا يف ةيئاي
يسايقلا .
•Topology
•Fast Ethernet is designed to connect two or more stations
together. If there are only two stations, they can be connected
point-to-point. Three or more stations need to be connected in
a star topology with a hub or a switch at the center, as shown in
Figure 13.19.
• ضعب عم رثكا وا نيتطحم لاصتلا ممص عيرسلا تنرثيلاا .ف كانه ناك اذا طق
اولصتي نأ مهنكمي نيتطحمpoint-to-point. اوجاتحي رثكا وا تاطحم ثلاث
نيبم وه امك ، زكرملا يف لدبملا وا باهلاب يمجنلا ليصوتلا يف لاصتلال لكشلاب
يلاتلا.
83

84. 84

85. Physical Layer
•Implementation
•Fast Ethernet implementation at the physical layer can be
categorized as either two-wire or four-wire. The two-wire
implementation can be either category 5 UTP (100Base-TX) or
fiber-optic cable (100Base-FX). The four-wire implementation
is designed only for category 3 UTP (100Base-T4). See Figure
13.20.
•فنصت نأ نكمي ةيئايزيفلا ةقبطلا دنع عيرسلا تنرثيلاا تاقيبطت عبرا وا نيكلسك
كلاسا . نوكت نأ نكمي نيكلسلا تاقيبطت5 UTP (100Base-TX) واfiber-
optic cable (100Base-FX) .فنصلل طقف ممصي كلاسا عبرلأا تاقيبطت3
UTP (100Base-T4) . يلاتلا لكشلا يرظنا .
85

86. 86

87. Physical Layer
•Encoding
•Manchester encoding needs a 200-Mbaud bandwidth for a data
rate of 100 Mbps, which makes it unsuitable for a medium such
as twisted-pair cable. For this reason, the Fast Ethernet
designers sought some alternative encoding/decoding scheme.
However, it was found that one scheme would not perform
equally well for all three implementations. Therefore, three
different encoding schemes were chosen (see Figure 13.21).
• ةمزح ضرع ىلا جاتحي رتسشنام ريفشت200-Mbaud تانايب لدعمل100
Mbps لثم طاسولأل بسانم هلعجي امم ،twisted-pair cable . ببسلا اذهل
ليدب ريفشت كفو ريفشت ططخم اودارأ عيرسلا تنرثيلاا وممصم .لكب مه لاوحلأا
ت ريفشت تاططخم ثلاث كلذل تاقيبطتلا لك زجنيلا دحاو ططخم نأ اودجو م
اهرايتخا .
87

88. 88

89. Physical Layer
•Encoding
•100Base-TX uses two pairs of twisted-pair cable (either category
5 UTP or STP). For this implementation, the MLT-3 scheme was
selected since it has good bandwidth performance. However,
since MLT-3 is not a self-synchronous line coding scheme, 4B/5B
block coding is used to provide bit synchronization by preventing
the occurrence of a long sequence of 0s 1(see Chapter 4). This
creates a data rate of 125 Mbps, which is fed into MLT-3 for
encoding.
•100Base-TX نم نيجوز مدختسيtwisted-pair cable ( امإ5 UTP or STP . )
ططخم رايتخا مت قيبطتلا اذه لجا نمMLT-3 ديج ةمزح ضرع ءادأ هل نلا . لكب
نأ امب لاوحلأاMLT-3 ريفشت مدختسي ، نمازتلا يتاذ ريفشت ططخم سيل4B/5B
block coding وا رافصلاا نم ةليوط ةلسلس ثودح عنمب نمازت تبب دوزيل
تادحاولا . تانايب لدعم أشني اذه125 Mbps يذغت يتلاMLT-3 ريفشتلل
89

90. Physical Layer
•Encoding
•100Base-FX uses two pairs of fiber-optic cables. Optical fiber can
easily handle high bandwidth requirements by using simple encoding
schemes. The designers of 100Base-FX selected the NRZ-I encoding
scheme (see Chapter 4) for this implementation. However, NRZ-I has
a bit synchronization problem for long sequences of 0s (or 1s, based
on the encoding), as we saw in Chapter 4. To overcome this problem,
the designers used 4B/5B block encoding as we described for
100Base-TX. The block encoding increases the bit rate from 100 to
125 Mbps, which can easily be handled by fiber-optic cable.
•100Base-FX نم نيجوز مدختسيfiber-optic cables . ةلوهسب هنكمي يئوضلا فيللا
ةطيسب ريفشت تاططخم مادختساب يلاعلا ةمزحلا ضرع تابلطتم ةجلاعم .وممصم
100Base-FX ريفشت ططخم اومدختسيNRZ-I قيبطتلا اذهل . لاوحلأا لكبNRZ-I هل
رافصلاا نم ةليوطلا لسلاسلل تبلا نمازت ةلكشم(شتلا ىلع ادامتعا تادحاولا وا ريف . )
اومدختسي نوممصملا ، ةلكشملا هذه ىلع بلغتلل4B/5B block encoding لجا نم
100Base-TX . ريفشتblock نم تبلا لدعم ديزت100 to 125 Mbps نكمي يذلا ،
يئوضلا فيللا لباك مادختساب هتجلاعم ةلوهسب .90

91. Physical Layer
•Encoding
•A 100Base-TX network can provide a data rate of 100 Mbps, but it
requires the use of category 5 UTP or STP cable. A new standard,
called 100Base-T4, wasdesigned to use category 3 or higher UTP.
The implementation uses four pairs of UTP for transmitting 100
Mbps. Encoding/decoding in 100Base-T4 is more complicated. As
this implementation uses category 3 UTP, each twisted-pair cannot
easily handle more than 25 Mbaud.
• ةكبش100Base-TX تانايب لدعمب دوزت نأ اهنكمي100 Mbps بلطتت اهنكلو ،
مادختساcategory 5 UTP or STP cable . ىمسي ديدج رايعم100Base-T4 ممص
مدختسيلcategory 3 واhigher UTP . نم جاوزأ عبرا مدختسي قيبطتلاUTP
لاسرلإ100 Mbps . يف زيمرتلا كفو ريفشتلا100Base-T4 اديقعت رثكا . اذه لثم
مدختسي قيبطتلاcategory 3 UTP نم رثكا ةجلاعم ةلوهسب هنكميلا يئانث جوز لك ،
25 Mbaud.
91

92. Physical Layer
•Encoding
•In this design, one pair switches between sending and receiving.
Three pairs of UTP category 3, however, can handle only 75
Mbaud (25 Mbaud) each. We need to use an encoding scheme
that converts 100 Mbps to a 75 Mbaud signal. As we saw in
Chapter 4, 8B/6T satisfies this requirement. In 8B/6T, eight data
elements are encoded as six signal elements. This means that 100
Mbps uses only (6/8) x 100 Mbps, or 75 Mbaud.
• لابقتسلااو لاسرلاا نيب دحاو جوز لدبي ، ميمصتلا اذه يف .نم جاوزأ ةثلاثUTP
category 3 طقف ةجلاعم هنكمي لاوحلأا لكب،75 Mbaud اهنم لك(25
Mbaud) لوحي يذلا ريفشت ططخم مادختسلا جاتحن100 Mbps ةراشإ ىلإ75
Mbaud . اقباس انيأر امك8B/6T بلطتملا اذه زجني . يف8B/6T رصانع ةينامث
ةراشإ رصانع تسك رفشت تانايب . نأ ينعي اذه100 Mbps طقف مدختست(6/8) x
100 Mbps وا75 Mbaud
92

93. Summary
93

94. GIGABIT ETHERNET
•The need for an even higher data rate resulted in the design of the Gigabit
Ethernet protocol (1000 Mbps). The IEEE committee calls the Standard 802.3z.
The goals of the Gigabit Ethernet design can be summarized as follows:
• لوكوترب ميمصتل ىدأ ىلعأ تانايب لدعمل ةجاحلاGigabit Ethernet(1000 Mbps) . ةنجلIEEE
رايعملا تعد802.3z . ميمصت نم فدهلاGigabit Ethernet يلاتلاب هصيخلت نكمي :
1.Upgrade the data rate to 1 Gbps.
• ىلا تانايبلا لدعم ةيقرت1Gbps .
2. Make it compatible with Standard or Fast Ethernet.
• عيرسلاو يسايقلا تنرثيلاا عم قفاوتم هلعج .
3. Use the same 48-bit address.
• ناونع سفن مدختسي48 تب .
4. Use the same frame format.
• راطلإا لكش سفن مدختسي
5. Keep the same minimum and maximum frame lengths.
• يرغصلااو يمظعلاا راطلإا لوط سفنب ظفتحي .
6. To support autonegotiation as defined in Fast Ethernet.
• عيرسلا تنرثيلاا يف فرعم وه امك يللآا ضوافتلا معدل .
94

95. •A main consideration in the evolution of Ethernet was to keep the
MAC sublayer untouched. However, to achieve a data rate 1 Gbps,
this was no longer possible. Gigabit Ethernet has two distinctive
approaches for medium access: half-duplex and full-duplex.
•ا ةقبطلا رثأت مدع ىلع ءاقبلإا وه تنرثيلاا مييقت يف يسيئرلا رابتعلاا ةيعرفلMAC .
تانايبلا لدعم زاجنلا لاوحلأا لكب1 Gbps نكمم دعي مل اذه ، .Gigabit
Ethernet طسولل لوصولل ناتزيمتم ناترظن اهل :half-duplex وfull-duplex
•Almost all implementations of Gigabit Ethernet follow the full-
duplex approach.
• تاقيبطت لك ابيرقتGigabit Ethernet عبتتfull-duplex .
MAC Sublayer
95

96. •Full-Duplex Mode
•In full-duplex mode, there is a central switch connected to all
computers or other switches. In this mode, each switch has buffers
for each input port in which data are stored until they are
transmitted. There is no collision in this mode. This means that
CSMA/CD is not used. Lack of collision implies that the maximum
length of the cable is determined by the signal attenuation in the
cable, not by the collision detection process.
• طمن يفfull-duplexشتيوسلا وا تارتويبمكلا لكب لصتي يزكرم شتيوس كانه تا
ىرخلأا .ت تانايبلا ثيح لخد ذفنم لكل زجاوح كلمي شتيوس لك طمنلا اذه يف نزخ
مهلاسرإ متي ىتح . طمنلا اذه يف مادطصا دجويلا. نا ينعي اذهCSMA/CD مدختسيلا .
كلا يف ةراشلإا دماختب ددحي لباكلل يمظعلاا لوطلا نأ ىلا ريشي مادطصلاا ةلق ، لبا
مادطصلاا فشك ةيلمعب سيلو .
MAC Sublayer
96

97. •Full-Duplex Mode
•In the full-duplex mode of Gigabit Ethernet, there is no collision;
the maximum length of the cable is determined by the signal
attenuation in the cable.
• طمن يفfull-duplex ـللGigabit Ethernet يمظعلاا لوطلا ، مادطصا دجويلا
لباكلا يف ةراشلاا دماختب ددحي لباكلل .
MAC Sublayer
97

98. •Half-Duplex Mode
•Gigabit Ethernet can also be used in half-duplex mode, although
it is rare. In this case, a switch can be replaced by a hub, which
acts as the common cable in which a collision might occur. The
half-duplex approach uses CSMA/CD. However, as we saw before,
the maximum length of the network in this approach is totally
dependent on the minimum frame size. Three methods have
been defined: traditional, carrier extension, and frame bursting.
•Gigabit Ethernet طمن يف مدختسي نا اضيأ هنكميhalf-duplex mode مغرلاب ،
ردان كلذ نا نم .تي يذلا ، باهلاب لدبتسي نا نكمي شتيوسلا ةلاحلا هذه يف فرص
ثدحي امبر مادطصلاا ثيح ماع لباكك .half-duplex مدختسيCSMA/CD . امك
يرغصلاا راطلإا مجح ىلع دمتعي ةكبشلل يمظعلاا لوطلا اقباس انيأر .ثلاث قرط
فرعت :traditional, carrier extension, and frame bursting
MAC Sublayer
98

99. •Half-Duplex Mode
•TraditionalIn the traditional approach, we keep the minimum length of
the frame as in traditional Ethernet (512 bits). However, because the
length of a bit is 11100 shorter in Gigabit Ethernet than in 10-Mbps
Ethernet, the slot time for Gigabit Ethernet is 512 bits x 111000 μS, which
is equal to 0.512 μS. The reduced slot time means that collision is detected
100 times earlier. This means that the maximum length of the network is
25 m. This length may be suitable if all the stations are in one room, but it
may not even be long enough to connect the computers in one single
office.
•Traditionalيلقتلا تنرثيلااك راطلإل يرغصلاا لوطلا ظفحن ةيديلقتلا ةرظنلا يف يد(512
bits) . تبلا لوط نلا11100 يف رغصاGigabit Ethernet نم10-Mbps Ethernet
نمزslot ـللGigabit Ethernet نوكي512 bits x 111000 μS يواسي يذلاو0.512 μS
. نمز ضافخناslot time ركبأ فشكي مادطصلاا نا ينعي100 ةرم . لوطلا نأ ينعي اذه
وه ةكبشلل يمظعلاا25m . ةفرغ يف تناك تاطحملا لك اذا ابسانم نوكي امبر لوطلا اذه
دحاو بتكم يف تارتويبمكلا لصول يفاك اكشب ليوط نوكيلا دق هنكل ، ةدحاو .
MAC Sublayer
99

100. •Half-Duplex Mode
•Carrier Extension To allow for a longer network, we increase the
minimum frame length. The carrier extension approach defines
the minimum length of a frame as 512 bytes (4096 bits). This
means that the minimum length is 8 times longer. This method
forces a station to add extension bits (padding) to any frame that
is less than 4096 bits. In this way, the maximum length of the
network can be increased 8 times to a length of 200 m. This
allows a length of 100 m from the hub to the station.
•Carrier Extension يرغصلاا راطلإا لوط ديزن لوطأ ةكبشل حامسلل .carrier
extension approach راطلإل يرغصا لوط فرعت512 bytes (4096 bits) .
لوطأ يرغصلاا لوطلا نا ينعي اذه8 تارم . ةفاضلإ ةطحملاربجت ةقيرطلا هذه
عيسوت تاتب( وشح ) نم لقا راطا يأ ىلا4096 bits . لوطلا ةقيرطلا هذه يف
دادزي نا نكمي ةكبشلل يمظعلاا8 لوطلا ىلا تارم200 m . لوطب حمسي اذه
100 m ةطحملا ىلا باهلا نم .
MAC Sublayer
100

101. •Half-Duplex Mode
•Frame Bursting : Carrier extension is very inefficient if we have a
series of short frames to send; each frame carries redundant
data. To improve efficiency, frame bursting was proposed. Instead
of adding an extension to each frame, multiple frames are sent.
However, to make these multiple frames look like one frame,
padding is added between the frames (the same as that used for
the carrier extension method) so that the channel is not idle. In
other words, the method deceives other stations into thinking
that a very large frame has been transmitted.
•Carrier extension ةريصقلا تاراطلإا نم ةلسلس انيدل ناك اذا ةءافك وذ سيل
ةيفاضإ تانايب لمحي راطإ لك ، لاسرلإل . حارتقا مت ةءافكلا نيسحتلframe
bursting . لسرت تاراطا ةدع ، راطا لكل دادتما ةفاضإ نم لادب . هذه لعجلو
تاراطلاا نيب ةوشحلا فاضت ، دحاو راطإك ودبت ةددعتملا تاراطلإا(شحلا سفن ةو
ىرخأ ةقيرط لجا نم مدختست ) ةلطاعريغ ةانقلا كلذل .ةقيرطلا ىرخأ تاملكب عدخت
لسرأ دق ادجريبك راطا كانه نا ريكفتلاب ىرخأ تاطحم
MAC Sublayer
101

102. •The physical layer in Gigabit Ethernet is more complicated than that
in Standard or Fast Ethernet. We briefly discuss some features of this
layer.
• يف ةيئايزيفلا ةقبطلاGigabit Ethernet عيرسلا وا يسايقلا تنرثيلاا نم رثكأ ةدقعم.
ةقبطلا هذه تازيمم ضعب حرشنس.
•Topology
•Gigabit Ethernet is designed to connect two or more stations. If
there are only two stations, they can be connected point-to-point.
Three or more stations need to be connected in a star topology with
a hub or a switch at the center. Another possible configuration is to
connect several star topologies or let a star topology be part of
another as shown in Figure 13.22.
•Gigabit Ethernet رثكا وا نيتطحم لصول ممص .نكمي طقف نيتطحم كانه ناك اذا
اولصوي ناpoint-to-point .يصوت يف اولصوي نلا اوجاتحي رثكا وا تاطحم ثلاث ل
زكرملا يف شتيوسلا وا باهلا ثيح يمجن .يصوت ةدع لصو وه نكمم رخآ بيترت تلا
رخلآا نم ءزجك يمجنلا ليصوتلا كرت وا ةيمجن
Physical Layer
102

103. 103

104. •Implementation
•Gigabit Ethernet can be categorized as either a two-wire or a four-wire
implementation. The two-wire implementations use fiber-optic cable
(1000Base-SX, short-wave, or 1000Base-LX, long-wave), or STP
(1000Base-CX). The four-wire version uses category 5 twisted-pair cable
(1000Base-T). In other words, we have four implementations, as shown in
Figure 13.23. 1000Base-T was designed in response to those users who
had already installed this wiring for other purposes such as Fast Ethernet
or telephone services.
•Gigabit Ethernet قيبطت امإ فنصي نا نكميtwo-wire قيبطت واfour-wire . تاقيبطت
two-wire يئوضلا فيللا لباك مدختست(1000Base-SX, short-wave, or 1000Base-
LX, long-wave), واSTP (1000Base-CX)
• ةخسنfour-wire مدختستcategory 5 twisted-pair cable (1000Base-T)
• يلاتلا لكشلاب نيبم وه امك تاقيبطت عبرا انيدل ىرخأ تاملكب.
•1000Base-Tم ىرخأ ضارغلأ كلاسلأا هذه اوبكر نيذلا نيمدختسملل ةباجتسا يف ممصي لث
فتاهلا تامدخ وا عيرسلا تنرثيلاا .
Physical Layer
104

105. 105

106. •Encoding
•Figure 13.24 shows the encoding/decoding schemes for the four
implementations.
Physical Layer
106

107. •Encoding
•Gigabit Ethernet cannot use the Manchester encoding scheme because
it involves a very high bandwidth (2 GBaud). The two-wire
implementations use an NRZ scheme, but NRZ does not self-
synchronize properly. To synchronize bits, particularly at this high data
rate, 8BI10B block encoding, discussed in Chapter 4, is used.
•Gigabit Ethernet ح ضرع نمضتي هنلأ رتسيشنام ريفشت ططخم مادختسا هنكميلا ةمز
ادج يلاع(2 Gbaud) . ططخم مدختست نيكلسلا تاقيبطتNRZ نكلو ،NRZ نمازيلا
حيحص لكشب . مدختسن يلاعلا تانايبلا لدعم دنع تاتبلا ةنمازمل8BI10B block
encoding
•This block encoding prevents long sequences of 0s or 1s in the stream,
but the resulting stream is 1.25 Gbps. Note that in this implementation,
one wire (fiber or STP) is used for sending and one for receiving.
• زيمرتblock لا نكلو ، ةقفدلا يف تادحاولا وا رافصلاا نم ةليوطلا لسلاسلا عنمي اذه ةقفد
نوكت ةجتانلا1.25 Gbps . دحاو كلس قيبطتلا اذه يف هنا ظحلان(fiber or STP ) مدختسي
لابقتسلال ةدحاوو لاسرلإل .
Physical Layer
107

108. •Encoding
•In the four-wire implementation it is not possible to have 2 wires
for input and 2 for output, because each wire would need to carry
500 Mbps, which exceeds the capacity for category 5 UTP. As a
solution, 4D-PAM5 encoding, as discussed in Chapter 4, is used to
reduce the bandwidth. Thus, all four wires are involved in both
input and output; each wire carries 250 Mbps, which is in the
range for category 5 UTP cable
• انيدل نوكي نا نكميلا ةعبرلأا كلاسلأا قيبطت يف2 wires for input and 2 for
output لمحل جاتحي كلس لك نلا ،500 Mbps ةعس زواجتي يذلاcategory 5
UTP . ريفشت كلذل لحك4D-PAM5ضرع ضيفختل مدختسي اقباس هحرش مت يذلا
ةمزحلا . لمحي كلس لك ، جرخلاو لخدلا لاك يف نمضت كلاسا ةعبرأ لك اذكهو
250 Mbps لباك لاجم نمض وه يذلا ،category 5 UTP
Physical Layer
108

109. Summary
109

110. •The IEEE committee created Ten-Gigabit Ethernet and called it
Standard 802.3ae. The goals of the Ten-Gigabit Ethernet design
can be summarized as follows:
• ةنجلIEEE تأشنأTen-Gigabit Ethernet هتمساوStandard 802.3ae .
ميمصت فادهأTen-Gigabit Ethernet يلي امك صخلت نا نكمي :
1.Upgrade the data rate to 10 Gbps.
• ىلا تانايبلا لدعم ةيقرت10Gbps .
2. Make it compatible with Standard, Fast, and Gigabit Ethernet.
• يسايقلاو عيرسلا تنرثيلاا عم قفاوتم هلعجوGigabit Ethernet .
3. Use the same 48-bit address.
• ناونع سفن مدختسي48 تب
Ten-Gigabit Ethernet
110

111. 4. Use the same frame format.
• راطلإا لكش سفن مدختسي.
5. Keep the same minimum and maximum frame lengths.
• راطلإل يمظعلااو يرغصلاا لوطلا سفنب ظفتحي
6. Allow the interconnection of existing LANs into a metropolitan
area network (MAN) or a wide area network (WAN).
• تاكبشل يلخادلا لاصتلال حمسيLANs ةكبش يف ةدوجوملاmetropolitan area
network (MAN) قاطنلا ةعساو ةكبش واwide area network (WAN).
7. Make Ethernet compatible with technologies such as Frame Relay
and ATM .
• و رطلأا ليحرتك تاينقتلا عم قفاوتم تنرثيلاا لعجيATM .
Ten-Gigabit Ethernet
111

112. •Ten-Gigabit Ethernet operates only in full duplex mode which
means there is no need for contention; CSMA/CD is not used in
Ten-Gigabit Ethernet.
•Ten-Gigabit Ethernet طمن يف لمعتfull duplex ةجاح دجويلا هنا ينعي امم
،ةسفانمللCSMA/CD يف مدختسيلاTen-Gigabit Ethernet.
MAC Sublayer
112

113. •The physical layer in Ten-Gigabit Ethernet is designed for using
fiber-optic cable over long distances. Three implementations are
the most common: 10GBase-S, l10GBase-L, and 10GBase-E. Table
13.4 shows a summary of the Ten-Gigabit Ethernet
implementations.
• يف ةيئايزيفلا ةقبطلاTen-Gigabit Ethernet يئوضلا فيللا لباك مدختستل ممصت
ةليوط تافاسمل . مه اعويش رثكلأا مه تاقيبطت ثلاث :10GBase-S, l10GBase-L,
and 10GBase-E . تاقيبطتل صخلم نيبي يلاتلا لودجلاTen-Gigabit Ethernet
Physical Layer
113

114. Summary
114