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Sem1 - Module 7
Ethernet Technologies
10-Mbps and 100-Mbps Ethernet
All versions of Ethernet have the same:
1. MAC addressing
2. CSMA/CD
3. Frame format
However, other aspects of the MAC sub layer, physical layer, and
medium have changed.
802.2
Legacy Ethernet
Legacy Ethernet (10BASE2, 10BASE5, 10BASET)
Legacy Ethernet has common architectural features:
1.
2.
3.
4.
5.
Networks usually contain multiple types of media.
The standard ensures that interoperability is maintained.
The overall architectural design is of the utmost importance when
implementing a mixed-media network.
It becomes easier to violate maximum delay limits as the network
grows.
The timing limits are based on parameters such as:
•
Cable length and its propagation delay
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Delay of repeaters
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Delay of transceivers
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Interframe gap shrinkage
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Delays within the station
Legacy Ethernet (10BASE2, 10BASE5, 10BASET)
10BASE2:
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Coax cable (called Thinnet) flexible, 185meters max, Small
flexible cable
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Half Duplex only
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10BASE2, introduced in 1985.
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Installation was easier because of its smaller size, lighter weight,
and greater flexibility. It still exists in legacy networks.
10BASE5
•
Coax cable (called Thicknet) flexible, 500 meters max, larger,
heavier cable
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Half Duplex only
•
10BASE5 is important because it was the first medium used for
Ethernet (10BASE5 was part of the original 802.3 standard).
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The primary benefits of 10BASE5:
•
•
was length, today it may be found in legacy installations, but would
not be recommended for new installations.
10BASE5 systems are inexpensive and require no configuration
10BASET
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UTP (Cat5e, Cat5, Cat3) flexible, RJ45, Hubs and witches, 100
meters max, small, light
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most inexpensive cable, easy to install
•
Half or Full Duplex
10-Mbps Ethernet:
Common Frame Format
100-Mbps Ethernet
802.2
FastEthernet
Fast Ethernet:
• At the time copper-based Fast Ethernet was introduced, a fiber
version was also desired.
• A fiber version could be used for backbone applications,
connections between floors and buildings where copper is less
desirable in high noise environments.
• 100BASE-FX was introduced to satisfy this desire.
• However, 100BASE-FX was never adopted successfully. This
was due to the timely introduction of Gigabit Ethernet copper
and fiber standards.
• Gigabit Ethernet standards are now the dominant technology
for backbone installations, high-speed cross-connects, and
general infrastructure needs.
100BASE-FX:
• Limitations of Fiber Technology:
– The following has limited the bandwidth of Fiber:
• Emitter technology
• Detector technology
• The Fiber manufacturing Process
Fast Ethernet Architecture:
• A Class I repeater may introduce up to 140 bit-times of latency.
• Any repeater that changes between one Ethernet implementation and
another is a Class I repeater.
• A Class II repeater may only introduce a maximum of 92 bit-times latency.
• Because of the reduced latency it is possible to have two Class II
repeaters in series, but only if the cable between them is very short.
Gigabit and 10-Gigabit Ethernet:
Access:
– Point to point
– Full Duplex only:
• Half duplex is only used in 100Base and lower speeds
• Half duplex reduces distance and adds increased overhead
Introduced for fast data transfer:
–
–
–
–
Backbone connections (inter building)
Interswitch connections (Trunk lines)
Backup applications
Video and other high applications
1000 – Mbps (1 Gbps) Ethernet
802.2
1 Gb Ethernet
10000 – Mbps (10 Gbps) Ethernet
802.2
10 Gb Ethernet
Half Duplex and Full Duplex
Half Duplex:
– Capability for simultaneous data transmission between a sending
station and a receiving station.
Full Duplex:
– Capability for data transmission in only one direction at a time between
a sending station and a receiving station.
– No collisions in a switched network
10BASE2, 10BASE5:
– Half Duplex only
10Base-T, 100Base-TX, 100BASE-FX :
– Operates in Half or Full Duplex.
GigaBit Ethernet:
– Operates at Full Duplex only
1000BASE-SX and LX
• The NRZ signals are then pulsed into the fiber using
either short-wavelength or long-wavelength light
sources.
• The short-wavelength uses an 850 nm laser or LED
source in multimode optical fiber (1000BASE-SX).
• It is the lower-cost of the options but has shorter
distances.
• The long-wavelength 1310 nm laser source uses either
single-mode or multimode optical fiber (1000BASE-LX).
• Laser sources used with single-mode fiber can achieve
distances of up to 5000 meters.
• Because of the length of time to completely turn the LED
or laser on and off each time, the light is pulsed using
low and high power.
• A logic zero is represented by low power, and a logic one
by high power.
1000 - Mbps Ethernet:
1000Base-T, 1000Base-SX, 1000Base-LX
All versions of Ethernet have the same:
1. MAC addressing
2. CSMA/CD
3. Frame format
However, other aspects of the MAC sublayer, physical layer, and
medium have changed.
The differences between standard Ethernet, Fast Ethernet and Gigabit Ethernet
occur at the physical layer:
• Timing:
• Due to the increased speeds of these newer standards, the shorter
duration bit times require special considerations.
• Since the bits are introduced on the medium for a shorter duration
and more often, timing is critical.
• Transmission:
• This high-speed transmission requires frequencies closer to copper
medium bandwidth limitations.
10-Gigabit Ethernet
As is typical for new technologies, a variety of implementations are being
considered, including:
• 10GBASE-SR – Intended for short distances over already-installed
multimode fiber, supports a range between 26 m to 82 m
• 10GBASE-LX4 – Uses wavelength division multiplexing (WDM),
supports 240 m to 300 m over already-installed multimode fiber and 10
km over single-mode fiber
• 10GBASE-LR and 10GBASE-ER – Support 10 km and 40 km over
single-mode fiber
• 10GBASE-SW, 10GBASE-LW, and 10GBASE-EW – Known
collectively as 10GBASE-W are intended to work with OC-192
synchronous transport module (STM) SONET/SDH WAN equipment.
Encoding:
Manchester encoding is used by:
– 10BASE2.
– 10BASE5
– 10BASE-T
4B/5B encoding, which is then scrambled and converted to multi-level
transmit-3 levels or MLT-3:
– 100BASE-TX
8B/10B encoding which is similar to the 4B/5B concept. This is
followed by the simple Non-Return to Zero (NRZ) line encoding of
light on optical fiber:
– Fiber-based Gigabit Ethernet (1000BASE-X) uses
encoding with 4D-PAM5 line encoding is used on Cat 5e or better UTP:
– 1000BASE-T
• The 8B/ 10B scheme is used for optical fiber and shielded copper
media, and the pulse amplitude modulation 5 (PAM5) is used for
UTP.
10BASE#:
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•
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Not more than five
segments.
No more than four
repeaters may be
connected in series
between any two distant
stations.
No more than three
populated segments
between any two distant
stations.
The 5-4-3 rule.
There may be up to 30 stations on any
individual 10BASE2 segment.
Out of the five consecutive segments in series
between any two distant stations, only three
may have stations attached.
Interconnection of different versions of
Ethernet
• To interconnect
Ethernet:
– 10BaseT
– 100BaseTX
– 1000BaseT
Use an asymmetric
Bridge or Switch
End