Ethernet at the Concrete Layer
Written on 04:00 by Ahmet Emir
Ethernet was aboriginal implemented by a accumulation alleged DIX (Digital, Intel, and Xerox). They created
and implemented the aboriginal Ethernet LAN specification, which the IEEE acclimated to actualize the IEEE
802.3 Committee. This was a 10Mbps arrangement that ran on allure and again eventually twistedpair
and cilia concrete media.
The IEEE continued the 802.3 Committee to two new committees accepted as 802.3u (Fast
Ethernet) and 802.3ab (Gigabit Ethernet on class 5) and again assuredly 802.3ae (10Gbps
over cilia and coax).
Figure 1.21 shows the IEEE 802.3 and aboriginal Ethernet Concrete band specifications.
When designing your LAN, it’s absolutely important to accept the altered types of Ethernet
media accessible to you. Sure, it would be abundant to run Gigabit Ethernet to anniversary desktop and
10Gbps amid switches, and although this ability appear one day, answer the amount of that
network today would be appealing difficult. But if you mix and bout the altered types of Ethernet
media methods currently available, you can appear up with a cost-effective arrangement solution
that works great.
FIGURE 1 . 2 1 Ethernet Concrete band specifications
The EIA/TIA (Electronic Industries Association and the newer Telecommunications Industry
Alliance) is the standards anatomy that creates the Concrete band blueprint for Ethernet.
The EIA/TIA specifies that Ethernet use a registered jack (RJ) adapter with a 4 5 wiring
sequence on defenseless twisted-pair (UTP) cabling (RJ45). However, the industry is moving
toward calling this aloof an 8-pin modular connector.
Each Ethernet cable blazon that is authentic by the EIA/TIA has inherent attenuation, which is
defined as the accident of arresting backbone as it campaign the breadth of a cable and is abstinent in decibels
Data Link
(MAC layer)
Physical
Ethernet
802.3
10Base2
10Base5
10BaseT
10BaseF
100BaseTX
100BaseFX
100BaseT4
38 Chapter 1 Internetworking
(dB). The cabling acclimated in accumulated and home markets is abstinent in categories. A higherquality
cable will accept a higher-rated class and lower attenuation. For example, category
5 is bigger than class 3 because class 5 cables accept added wire twists per bottom and therefore
less crosstalk. Crosstalk is the exceptionable arresting arrest from adjoining pairs in the cable.
Here are the aboriginal IEEE 802.3 standards:
10Base2 10Mbps, baseband technology, up to 185 meters in length. Accepted as thinnet and
can abutment up to 30 workstations on a distinct segment. Uses a concrete and analytic bus with
AUI connectors. The 10 agency 10Mbps, Base agency baseband technology (which is a signaling
method for advice on the network), and the 2 agency about 200 meters. 10Base2
Ethernet cards use BNC (British Naval Connector, Bayonet Neill Concelman, or Bayonet Nut
Connector) and T-connectors to affix to a network.
10Base5 10Mbps, baseband technology, up to 500 meters in length. Accepted as thicknet.
Uses a concrete and analytic bus with AUI connectors. Up to 2,500 meters with repeaters and
1,024 users for all segments.
10BaseT 10Mbps application class 3 UTP wiring. Unlike with the 10Base2 and 10Base5 networks,
each accessory charge affix into a hub or switch, and you can accept alone one host per segment
or wire. Uses an RJ45 adapter (8-pin modular connector) with a concrete brilliant topology
and a analytic bus.
Each of the 802.3 standards defines an Attachment Assemblage Interface (AUI), which allows a
one-bit-at-a-time alteration to the Concrete band from the Data Link media admission method. This
allows the MAC to abide connected but agency the Concrete band can abutment any absolute and
new technologies. The aboriginal AUI interface was a 15-pin connector, which accustomed a transceiver
(transmitter/receiver) that provided a 15-pin-to-twisted-pair conversion.
The affair is, the AUI interface cannot abutment 100Mbps Ethernet because of the aerial frequencies
involved. So 100BaseT bare a new interface, and the 802.3u blueprint created
one alleged the Media Independent Interface (MII), which provides 100Mbps throughput. The
MII uses a nibble, authentic as 4 bits. Gigabit Ethernet uses a Gigabit Media Independent Interface
(GMII) and transmits 8 $.25 at a time.
802.3u (Fast Ethernet) is accordant with 802.3 Ethernet because they allotment the aforementioned physical
characteristics. Fast Ethernet and Ethernet use the aforementioned best manual assemblage (MTU), use
the aforementioned MAC mechanisms, and bottle the anatomy architecture that is acclimated by 10BaseT Ethernet. Basically,
Fast Ethernet is aloof based on an addendum to the IEEE 802.3 specification, except that it
offers a acceleration access of 10 times that of 10BaseT.
Here are the broadcast IEEE Ethernet 802.3 standards:
100BaseTX (IEEE 802.3u) EIA/TIA class 5, 6, or 7 UTP two-pair wiring. One user per
segment; up to 100 meters long. It uses an RJ45 adapter with a concrete brilliant cartography and
a analytic bus.
100BaseFX (IEEE 802.3u) Uses cilia cabling 62.5/125-micron multimode fiber. Pointto-
point topology; up to 412 meters long. It uses an ST or SC connector, which are mediainterface
connectors.
1000BaseCX (IEEE 802.3z) Copper twisted-pair alleged twinax (a counterbalanced coaxial pair)
that can alone run up to 25 meters.
Ethernet Cabling 39
1000BaseT (IEEE 802.3ab) Class 5, four-pair UTP base up to 100 meters long.
1000BaseSX (IEEE 802.3z) MMF application 62.5- and 50-micron core; uses an 850 nano-meter
laser and can go up to 220 meters with 62.5-micron, 550 meters with 50-micron.
1000BaseLX (IEEE 802.3z) Single-mode cilia that uses a 9-micron amount and 1300 nanometer
laser and can go from 3 kilometers up to 10 kilometers.
If you appetite to apparatus a arrangement average that is not affected to electromagnetic
interference (EMI), fiber-optic cable provides a added secure,
long-distance cable that is not affected to EMI at aerial speeds.
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