_mod3_ ethernet.html#toc10BASE5
Content
7.1 10-Mbps and 100-Mbps Ethernet 7.1.3
10BASE2 10BASE2 was introduced in 1985. Installation was
easier because of its smaller size, lighter weight, and greater
flexibility. It still exists in legacy networks. Like 10BASE5,
it is not recommended for installations in networks today. It
has a low cost and a lack of need for hubs. Again, NICs are
also difficult to obtain for this medium. 10BASE2 also uses
Manchester encoding. Computers on the LAN were linked together
by an unbroken series of coaxial cable lengths. These lengths
were attached by BNC connectors to a T-shaped connector on the
NIC. 10BASE2 has a stranded central conductor. Each of the
maximum five segments of thin coax may be up to 185 meters long
and each station is connected directly to the BNC “T” connector
on the coax. Only one station can transmit at a time or else a
collision will occur. 10BASE2 also uses half-duplex. The
maximum transmission rate of 10BASE2 is 10 Mbps. 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.
Interactive Media Activity Matching: 10BASE2 After
completing this activity, the student will learn the
characteristics of 10BASE2 technology. Web Links
10BASE2 http://www.usyd.edu.au/is/comms/ networkcourse/
USydNet_mod3_ethernet. html#toc10BASE2
Content 7.1
10-Mbps and 100-Mbps Ethernet 7.1.4
10BASE-T 10BASE-T was introduced in 1990. 10BASE-T used
cheaper and easier to install Category 3 unshielded twisted
pair (UTP) copper cable rather than coax cable. The cable
plugged into a central connection device that contained the
shared bus. This device was a hub. It was at the center of a
set of cables that radiated out to the PCs like the spokes on a
wheel. This is referred to as a star topology. The distances
the cables could extend from the hub and the way in which the
UTP was installed increasingly used stars made up of stars,
referred to as an extended star topology. Originally 10BASE-T
was a half-duplex protocol, but full-duplex features were added
later. The explosion in the popularity of Ethernet in the
mid-to-late 1990s was when Ethernet came to dominate LAN
technology. 10BASE-T also uses Manchester encoding. A 10BASE-T
UTP cable has a solid conductor for each wire in the maximum 90
meter horizontal cable. UTP cable uses eight-pin RJ-45
connectors. Though Category 3 cable is adequate for use on
10BASE-T networks, it is strongly recommended that any new
cable installations be made with Category 5e or better. All
four pairs of wires should be used either with the T568-A or
T568-B cable pinout arrangement. With this type of cable
installation, supports the use of multiple protocols without
rewiring. Figure shows the pinout arrangement for a 10BASE-T
connection. The transmitting pair on the receiving side are
connected to the receiving pair on the attached device. Half
duplex or full duplex is a configuration choice. 10BASE-T
carries 10 Mbps of traffic in half-duplex mode and 20 Mbps in
full-duplex mode. Interactive Media Activity Matching:
10BASE-T After completing this activity, the student will learn
the characteristics of 10BASE-T technology. Web Links
10BASE-T http://www.usyd.edu.au/is/comms/
networkcourse/USydNet_mod3_ ethernet.html#toc10baseTtoc10baseT
Content 7.1 10-Mbps and 100-Mbps Ethernet
7.1.5 10BASE-T wiring and architecture 10BASE-T
links generally consist of a connection between the station and
a hub or switch. Hubs are multi-port repeaters and count toward
the limit on repeaters between distant stations. Hubs do not
divide network segments into separate collision domains.
Because hubs or repeaters merely extend the length of a network
segment within a single collision domain, there is a limit on
how many hubs may be used in that segment. Bridges and switches
divide a segment into separate collision domains, only leaving
the media limitations to determine the distance between the
switches. 10BASE-T limits the distance between switches to 100
m (328 ft).Although hubs may be linked, it is best to avoid
this arrangement. This is to prevent exceeding the limit for
maximum delay between distant stations. When multiple hubs are
required, it is best to arrange them in hierarchical order as
to create a tree structure. Performance will be improved if
fewer repeaters separate stations. An architectural example is
shown in Figure . All distances between stations are
acceptable. However, the total distance from one end of the
network to the other, places the architecture at its limit. The
most important aspect to consider is how to keep the delay
between distant stations to a minimum, regardless of the
architecture and media types involved. A shorter maximum delay
will provide better overall performance. 10BASE-T links can
have unrepeated distances up to 100 m. While this may seem like
a long distance, it is typically “used up” when wiring an
actual building. Hubs can solve the distance issue but will
allow collisions to propagate. The widespread introduction of
switches has made the distance limitation less important. As
long as workstations are located within 100 m of a switch, the
100 m distance starts over at the switch. Web Links
Ethernet Design Rules http://www.bostontech.net/assets/files/
articles/ TechBrief1_P1.pdf
Content 7.1 10-Mbps
and 100-Mbps Ethernet 7.1.6 100-Mbps
Ethernet 100-Mbps Ethernet is also known as Fast Ethernet.
The two technologies that have become important are 100BASE-TX,
which is a copper UTP medium and 100BASE-FX, which is a
multimode optical fiber medium.Three characteristics common to
100BASE-TX and 100BASE-FX are the timing parameters, the frame
format, and parts of the transmission process. 100BASE-TX and
100-BASE-FX both share timing parameters. Note that one bit
time in 100-Mbps Ethernet is 10nsec = .01 microseconds = 1
100-millionth of a second. The 100-Mbps frame format is the
same as the 10-Mbps frame. Fast Ethernet represents a 10-fold
increase in speed over 10BASE-T. Because of the increase in
speed, extra care must be taken because the bits being sent are
getting shorter in duration and occurring more frequently.
These higher frequency signals are more susceptible to noise.
In response to these issues, two separate encoding steps are
used by 100-Mbps Ethernet. The first part of the encoding uses
a technique called 4B/5B, the second part of the encoding is
the actual line encoding specific to copper or fiber. Web
Links Fast Ethernet Training and Resources
http://www.iol.unh.edu/training/fe.html
Content
7.1 10-Mbps and 100-Mbps Ethernet 7.1.7
100BASE-TX In 1995, 100BASE-TX was the standard, using
Cat 5 UTP cable, which became commercially successful. The
original coaxial Ethernet used half-duplex transmission so only
one device could transmit at a time. However, in 1997, Ethernet
was expanded to include a full duplex capability that allowed
more than one PC on a network to transmit at the same time.
Switches increasingly replaced hubs. These switches had the
capability of full duplex and rapid handling of Ethernet
frames. 100BASE-TX uses 4B/5B encoding, which is then scrambled
and converted to multi-level transmit-3 levels or MLT-3. In the
example, the highlighted window shows four waveform examples.
The top waveform has no transition in the center of the timing
window. No transition indicates that a binary 0 is present. The
second waveform shows a transition in the center of the timing
window. A binary 1 is represented by a transition. The third
waveform shows an alternating binary sequence. The absence of
binary transition indicates a binary 0, and the presence of a
transition indicates a binary 1. Rising or falling edges
indicate 1s. Very steep signal changes indicate 1s. Any
noticeable horizontal line in the signal indicates a 0. Figure
shows the pinout for a 100BASE-TX connection. Notice that the
two separate transmit-receive paths exist. This is identical to