Transcript document

Networks
Physical Structure
ISO Model
• Seven layers
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Application Layer
Presentation Layer
Session Layer
Transport Layer
Network Layer
Data Link Layer
Physical Layer
Cabling
• Types
– Copper
– Glass
– Plastic
What is Network Cabling?
• Cable - medium through which information
usually moves from one network device to
another.
• Several types of cable are commonly used
with LANs.
What is Network Cabling?
• In some cases, a network will utilize only one type
of cable; other networks will use a variety of cable
types.
• The type of cable chosen for a network is related
to the network's topology, protocol, and size.
• Understanding the characteristics of different
types of cable and how they relate to other aspects
of a network is necessary for the development of a
successful network.
Cables
• Baseband (Copper)
– Signals are sent over the entire cable
– One digital frequency
– One device transmits at a time
• Broadband
– Cable is divided into channels
– Several analog signals
– Requires special equipment
Baseband
• Speeds from 10 to 80 Mbs
• Easy to add / remove clients
• Bidirectional
• Distances 1.8 mile (3km)
– 1500 ft, 500 meters more
realistic
• Cannot send integrated signals
– Audio, digital, video
Broadband
• Carry multiple signals
• Commercial cable companies use 6mhz / channel
• Signals are sent to a “Head End” for amplification
• Unidirectional
• Dual Broadband Cable
• One cable for inbound traffic
• One cable for outbound traffic
– 50 channels (6Mhz) on each
• Lines need balancing and Amplifiers
Multiplexing - mixing different frequencies
Over the same wire.
Broadband Components
– Cable
• Trunk cables, feeder cables, drop cables
– 10’s of kilometers, 800 meters, 10-50 feet
– Terminators 75 ohms
– Amplifiers
• Used on trunks to overcome attenuation (signal loss)
– Directional Couplers (splitters)
– Modems – analog to digital conversion
Data Quality Impacts
• Bandwidth of a cable
• How much of a signal can be carried (Mbps)
• Attenuation
• The loss of a signal due mostly to resistance
• Interference
• Bleeding of one signal over into another
– Electromagnetic, Radio Freq Interference, CrossTalk
– Motors / Broadcast station / Strong signal negates weaker
Coaxial Cable
• Coaxial cabling has a single copper
conductor at its center. A plastic layer
provides insulation between the center
conductor and a braided metal shield.The
metal shield helps to block any outside
interference from fluorescent lights, motors,
and other computers.
Coaxial Cable
• Although coaxial cabling is difficult to
install, it is highly resistant to signal
interference. In addition, it can support
greater cable lengths between network
devices than twisted pair cable. The two
types of coaxial cabling are thick coaxial
and thin coaxial.
Coaxial Cable
• Thin coaxial cable is also referred to as thin
net. 10Base2 refers to the specifications for
thin coaxial cable carrying Ethernet signals.
The 2 refers to the approximate maximum
segment length being 200 meters. In actual
fact the maximum segment length is 185
meters. Thin coaxial cable is popular in
school networks, especially linear bus
networks.
Coaxial Cable
• Coaxial cabling has a single copper
conductor at its center. A plastic layer
provides insulation between the center
conductor and a braided metal shield.The
metal shield helps to block any outside
interference from fluorescent lights, motors,
and other computers.
Coaxial Cable
• Although coaxial cabling is difficult to
install, it is highly resistant to signal
interference. In addition, it can support
greater cable lengths between network
devices than twisted pair cable. The two
types of coaxial cabling are thick coaxial
and thin coaxial.
Coaxial Cable
• Thin coaxial cable is also referred to as thin
net. 10Base2 refers to the specifications for
thin coaxial cable carrying Ethernet signals.
The 2 refers to the approximate maximum
segment length being 200 meters. In actual
fact the maximum segment length is 185
meters. Thin coaxial cable is popular in
school networks, especially linear bus
networks.
Coaxial Cable
• Thick coaxial cable is also referred to as thick net.
10Base5 refers to the specifications for thick
coaxial cable carrying Ethernet signals. The 5
refers to the maximum segment length being 500
meters. Thick coaxial cable has an extra protective
plastic cover that helps keep moisture away from
the center conductor. Thick coaxial a great choice
for longer lengths in a linear bus network. A
disadvantage of thick coaxial is that it does not
bend easily and is difficult to install.
Coaxial Cable Connectors
• The most common type of connector used with
coaxial cables is the Bayone-Neill-Concelman
(BNC) connector. Different types of adapters are
available for BNC connectors, including a Tconnector, barrel connector, and terminator.
Connectors on the cable are the weakest points in
any network. To avoid problems with a network,
always use the BNC connectors that crimp, rather
than screw onto the cable.
Copper Cables
Copper Cables
Twisted Pair (STP) Cable
• Twisted pair cabling comes in two varieties:
shielded and unshielded.
• Unshielded twisted pair (UTP) is the most
popular and is generally the best option for
school networks.
– A disadvantage of UTP is that it is susceptible
to radio and electrical frequency interference.
Twisted Pair (STP) Cable
• Shielded twisted pair (STP) is suitable for
environments with electrical interference;
however, the extra shielding can make the
cables quite bulky.
• Shielded twisted pair is often used on
networks using Token Ring topology.
Wiring pinouts
TWISTED PAIR ETHERNET HORIZONTAL
WIRING (Solid 24Awg)
Pin Color
Signal
1
White/orange
Tx data +
2
Orange/white
Tx data 3
White/green
Rx data +
4
Blue/white
-5
White/Blue
-6
Green/white
Rx data 7
White/brown
-8
Brown/white
-Each run < 80m from nearest hub
Twisted Pair (STP and UTP)
• 10BaseT (Ethernet 10MB/s)
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Cheap
easy to terminate
UTP prone to interference
low to medium capacity
medium to high loss
category 3 = 10MB/s, category 5 = 100MB/s
Category 5 cable uses 8 wires. The length of exposed
wires is very critical, the standard limits this to less than
1/2" an inch.
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8
6
4
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8 12 16
20
40 60 80 100
Freq Mhz
200 300 400
Cables-Twisted Pair
Shielded
Specifications
Cable Type — Twisted pair, gray PVC jacket
Capacitance — 30 pF/ft.
Conductor Gauge — 22 AWG (7 x 24 AWG), stranded
Resistance — 16 ohms/1000 ft. (max.)
Shield — Foil around each pair, each with a drain wire
Cables-Twisted Pair
Unshielded UTP
UL® listed/CSA approved.
ETL verified to TIA 568 TSB 40A specifications.
Constructed of solid or stranded wire. All are 24 AWG, except
the EVMSL06A which is 26 AWG.
Low attenuation and near-end cross talk (NEXT) for 100-MHz
applications.
Capacitance is 14 pF/ft
Impedance is 100 ±15 ohms.
UTP Categories
• Established Standards of the EIA/TIA
– EIA/TIA 568A & EIA/TIA 568B
Fiber Optic
Fiber Optic Cable
• Fiber optic cabling consists of a center glass core
surrounded by several layers of protective
materials. It transmits light rather than electronic
signals eliminating the problem of electrical
interference. This makes it ideal for certain
environments that contain a large amount of
electrical interference. It has also made it the
standard for connecting networks between
buildings, due to its immunity to the effects of
moisture and lighting.
Network Interface Card
• The NIC serves as the connection between
the personal computer and the network
media.
• It connects to the computer on its base by
plugging into an expansion slot of the
computer.
• Another connection is accessible from the
outside of the computer and has connections
for the cables to plug into the network.
Fiber optic cable
• Can transmit signals over much longer distances
than coaxial and twisted pair. Carrys information
at vastly greater speeds. This capacity broadens
communication possibilities to include services
such as video conferencing and interactive
services. Fiber optic cabling cost is comparable to
copper cabling; it is more difficult to install and
modify. 10BaseF refers to the specifications for
fiber optic cable carrying Ethernet signals.
Fiber Optic Cable
• Facts about fiber optic cables:
Outer insulating jacket is made of Teflon or
PVC.
Kevlar fiber helps to strengthen the cable
and prevent breakage.
A plastic coating is used to cushion the fiber
center.
Center (core) is made of glass or plastic
fibers.
Fiber Optic Connector
• The most common connector used with
fiber optic cable is an ST connector. It is
barrel shaped, similar to a BNC connector.
A newer connector, the SC, is becoming
more popular. It has a squared face and is
easier to connect in a confined space.
Fiber Optic cable
• The features of fiber-optic cable systems are:
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Expensive
used for backbones or FDDI rings (100MB/s)
long distance
high capacity
immune to electro magnetic interference
low loss
difficult to join
connectors are expensive
Fiber Optic cable
• Fiber optic is often used to overcome
distance limitations. It can be used to join
two hubs together, which normally could
not be connected due to distance limitations.
In this instance, a UTP to Fiber converter is
necessary.
Coaxial cable
Unshielded twisted pair
BNC connector
RJ-45 connector
Fiber optic cable
Protocol Summary
Protocol
Cable
Ethernet
Star, Tree
Speed
Twisted Pair,
Topology
10 Mbps
Linear Bus,
Coaxial, Fiber
Fast Ethernet Twisted Pair,
Fiber
100 Mbps
Star
Local Talk
Twisted Pair
.23 Mbps
Linear Bus or Star
Token Ring
Twisted Pair
4 - 16 Mbps
Star-Wired Ring
FDDI
Fiber
100 Mbps
Dual ring
ATM
Twisted Pair
Fiber
155-2488 Mbps Linear Bus, Star, Tree
Specification Cable Type
Maximum length
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10BaseT Unshielded Twisted Pair 100 meters
10Base2 Thin Coaxial 185 meters
10Base5 Thick Coaxial 500 meters
10BaseF Fiber Optic 2000 meters
100BaseT Unshielded Twisted Pair 100 meters
100BaseTX Unshielded Twisted Pair 220 meters
Wireless LANs
• Not all networks are connected with cabling; some
networks are wireless. Wireless LANs use high
frequency radio signals, infrared light beams, or
lasers to communicate between the workstations
and the file server or hubs. Each workstation and
file server on a wireless network has some sort of
transceiver/antenna to send and receive the data.
Information is relayed between transceivers as if
they were physically connected.
Wireless LANs
• For longer distance, wireless communications can
also take place through cellular telephone
technology, microwave transmission, or by
satellite.
Wireless networks are great for allowing laptop
computers or remote computers to connect to the
LAN. Wireless networks are also beneficial in
older buildings where it may be difficult or
impossible to install cables.
Wireless LANs
• Two common types of infrared communications
used in schools are line-of-sight and scattered
broadcast. Line-of-sight communication means
that there must be an unblocked direct line
between the workstation and the transceiver. If a
person walks within the line-of-sight while there is
a transmission, the information would need to be
sent again. This kind of obstruction can slow
down the wireless network.
Wireless LANs
• Scattered infrared communication is a
broadcast of infrared transmissions sent out
in multiple directions that bounces off walls
and ceilings until it eventually hits the
receiver.
Wireless LANs
• Networking communications with laser are
virtually the same as line-of-sight infrared
networks.
Wireless LANs have several disadvantages:
– very expensive, provide poor security, are
susceptible to interference from lights and
electronic devices, and are also slower than
LANs using cabling.
Installing Cable - Some Guidelines
• When running cable, follow a few simple rules:
– Always use more cable than you need. Leave plenty of
slack.
– Test every part of a network as you install it. Even if it
is brand new, it may have problems that will be difficult
to isolate later.
– Stay at least 3 feet away from fluorescent light boxes
and other sources of electrical interference.
Installing Cable - Some Guidelines
– If it is necessary to run cable across the floor,
cover the cable with cable protectors.
– Label both ends of each cable.
– Use cable ties (not tape) to keep cables in the
same location together.
Building wiring systems
• Horizontal Wiring
The horizontal wiring extends from the wall
outlet to the system center
(telecommunications closet). It includes the:
– the wall outlet
– the horizontal cable
– cross-connects or patch cables in the
telecommunications closet (TC)
Building wiring systems
• Some general features of the horizontal wiring:
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uses star topology
limit of 90 meters (295') from TC to wall outlet
limit of 3 meters (10') to connect from wall outlet to PC
patch cords and cross-connect leads are limited to 6
meters (20')
– minimum of two outlets per user (phone+data)
– standardized media
Patch Cables
• Two varieties, straight through or reversed. One
application of patch cables is for patching between
modular patch panels in system centers. These are
the straight through variety. Another application is
to connect workstation equipment to the wall jack,
and these could be either straight through or
reversed depending upon the manufacturer.
Reversed cables are normally used for voice
systems.
Patch Cables
• How to determine the type of patch cable
Align the ends of the cable side by side so
that the contacts are facing you, then
compare the colors from left to right.
If the colors are in the same order on both
plugs, the cable is straight through. If the
colors appear in the reverse order, the cable
is reversed.
Backbone Wiring
• The backbone wiring system interconnects
telecommunication closets, equipment rooms and
entrance facilities (ie, the outside world). Some
general features are:
– star topology
– maximum of two hierarchical levels
– interconnections between any two TC must not go
through more than 3 cross connects
– use of recognized media
– adherence to distance limitations
NETWORK SEGMENTS
• A network segment is a length of cable
– devices can be attached to the cable
– it has its own unique address
– it has a limit on its length and the number of
devices which can be attached to it
Ethernet Cards
• usually purchased separately from a computer
• pre-installed Ethernet card (Dell Optiplex)
• contain connections for either coaxial or twisted
pair cables (or both)
• designed for coaxial cable, the connection will be
BNC
• twisted pair design has a RJ-45 connection
– Some cards also contain an AUI connector
– used to attach coaxial, twisted pair, or fiber
optics cable
Network Interface Card
• The NIC serves as the connection between the
personal computer and the network media.
• It connects to the computer on its base by
plugging into an expansion slot of the computer.
• Another connection is accessible from the outside
of the computer and has connections for the cables
to plug into the network.
NIC
Network Interface Card
SPECIFICATIONS
3Com Fast Ether Link Server Network Interface Card
Cable Requirements — Category 5
2–pair UTP
Hardware — PCI 2.1 compatible servers
Maximum Distance — 100 m (328.1 ft.)
Management — SNMP
Operating Systems NetWare® 4.x, 5.0,
Windows NT® 4.0, SCO UnixWare® 7;
Standards — IEEE 802.3 10BASE–T, IEEE 802.3u
100BASE–TX , IEEE 802.1Q
Indicators — LEDs: Link Status, Speed, Activity
Connectors — (1) RJ–45
Network Cards
• ISA Cards
• PCI Cards
• Contain the MAC address
– 00:58:79:90:33:A3:C2:03
• First 24 bits identify the company
• Last 24 bits are assigned by the company