Transcript Design and Documentation

Design and Documentation
Honolulu Community College
Cisco Academy Training Center
Semester 1
Version 2.1.1
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Overview
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Design of physical and logical topologies.
Documentation.
Wiring closet specifications.
Wiring and electrical techniques.
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General Design Process
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1. Select the technology (Ethernet).
2. Develop Layer 1 LAN topology.
 type
of cable.
 physical (wiring) topology (extended star).
 Type of Ethernet.
 Logical topology.
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3. Develop Layer 2 LAN topology.
 Segmentation
- reduce congestion & collision
domain size.
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General Design Process
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4. Develop Layer 3 topology.
 Implement
routing to build scalable internetworks.
 logical structure.
 segmentation - minimize broadcast domain.
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Other concerns:
 Placement
of servers.
 LANs link to WANs and to the Internet.
 document your physical and logical topologies.
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Network Design Issues
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First step: gather information about the
organization.
 1.organization's
history and current status
 2.projected growth
 3.operating policies and management procedures
 4.office systems and procedures
 5.viewpoints of people who will be using LAN
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Purpose is to identify and define any issues or
problems that need to be addressed.
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Network Design Issues (cont.)
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Second step: make a detailed assessment of
current and projected requirements.
Third step: identify resources and constraints of
the organization.
 document
existing computer hardware and
software.
 identify and define projected hardware and
software needs.
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Purpose: determine how much training will be
required, and how many people will be needed to
support the LAN.
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Network Design Issues (cont.)
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These steps will allow you to estimate costs and
develop a budget for the implementation of a
LAN.
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Wiring Closet Selection
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Most important decision is selection of MDF.
 Secure
location, close to POP.
 POP is where telecommunications services
connect to the building's communication facilities.
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TIA/EIA-568-A specifies that in an Ethernet star
topology, every device must be connected to the
hub (in wiring closet) by horizontal cabling.
To find location(s) of wiring closet(s), begin with a
floor plan of the building, indicating all devices
that will be connected to the network.
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Wiring Closet Selection (cont.)
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Next identify potential locations for wiring closets.
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Determing Number of Wiring Closets
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Draw circles of radius 50 m from each potential
wiring closet locations.
Number of wiring closets is determined by what
is needed to cover the building.
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Extended Star Topology
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MDF of an extended
star topology Ethernet
LAN is usually
centrally located.
In high rise building,
MDF usually located
on a middle floor, even
if POP is on the first
floor.
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MDF - multi-building campus
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MDF: a central location, close to the POP,.
IDFs are located in each building.
Note: main building also requires an IDF.
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Backbone Cabling
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Cabling between wiring closets is backbone or
vertical cabling.
Backbone cabling include:
 MCC
(main cross-connects),
 ICC (intermediate cross-connects),
 mechanical terminations
 backbone cable runs.
 Cabling between MDF and POP
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Recommended backbone is 62.5/125 µm fiberoptic cable.
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Backbone Cabling (cont.)
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TIA/EIA 568A specifies four types of networking
media for backbone cabling:
 100W
UTP, 150W STP, 62.5/125 µm fiber optic,
and single-mode fiber optic cable.
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TIA/EIA 568A recognizes 50 W coaxial cable, but
it is not recommended for new installations.
Recommended backbone is 62.5/125 µm fiberoptic cable (multi-mode fiber).
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MDF to IDF Cabling
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MCC (main cross connect) is in MDF.
 connects
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backbone cabling to the Internet.
HCC (horizontal cross connect) is in IDF.
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MDF to IDF - another method
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ICC (intermediate cross connect) in an IDF.
No work areas or horizontal wiring connects to ICC.
HCC (horizontal cross connect) in another IDF.
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No more than one ICC between MCC and HCC.
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Backbone Cabling Lengths
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TIA/EIA 568A also specifies max lengths when ICC
is used.
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Specs for Backbone Cabling
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TIA/EIA 568A specifies max lengths for backbone
cabling.
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Electrical Concern - Noise
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AC line noise, can create errors:
 adding
unwanted voltages to signals.
 preventing detection of leading and trailing edges
of square wave signals.
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Problems can be compounded with poor ground
connections.
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Electrical Concern - ESD
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Charges can be separated by friction, e.g. by
shuffling you feet across a carpet.
Very high voltages (thousands of volts) can be
generated , referred to as static electricity.
When you reach for a metal object, a spark
occurs - this is current flow, as the high voltage
pushes the free electrons to the metal object.
This is ESD or electro-static discharge.
 can
randomly damage computer chips and/or
data.
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Grounding Network Equipment
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AC power is supplied though a 3 prong plug.
Top 2 connectors are
the power.
Other connector is safety
ground (earth ground).
Any exposed metal is
connected to safety ground.
Computer motherboard’s
ground plane is connected to the chassis and
safety ground.
Ground helps dissipate static electricity.
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Safety Ground
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Purpose - to prevent exposed metal parts
from becoming energized with high voltage
should a wiring fault occur.
A wiring fault will cause current through the
ground connection, and activate protective
devices such as circuit breakers to disconnect
the power.
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Safety Ground Connection Problems
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Using copper media, such as UTP to connect
grounds in different buildings or from different
power panels can present an electrical shock
hazard.
Different ground voltages can also severely
damage delicate computer memory chips.
Minimize danger by using “one-hand rule”.
“One-hand Rule” - touch electrical equipment with
only one hand (current will not pass across your
body through your heart).
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Safety Ground Connection Problems (cont.)
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TIA/EIA 568A specifications permit the use of
fiber-optic cable for backbone cabling.
Fiber does not conduct electricity, eliminating the
shock hazard.
Fiber-optic cable is recommended for the
backbone cabling between buildings, and also for
linking wiring closets on different floors.
Fiber also beneficial in areas with lightning; it will
not conduct lightning strike into the building.
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Classifying Power Problems
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Three connections on AC power:
 Hot,
neutral, and safety ground.
 Power problems classified by
which wires are affected.
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Normal mode problems - between hot and neutral.
Common mode problems - between safety ground
and either hot or neutral.
Common mode problems are more serious.
Normal mode problems are intercepted by the
computer’s power supply, UPS, or AC line filter.
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Typical Power Line Problems
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Power disturbance is unwanted excess energy
that is sent to electrical equipment.
Typical power disturbances include:
 surges
 sags
 spikes
 oscillations.
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Typical Power Disturbances
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Surge - 10% voltage increase for few secs.
 Causes
most hardware damage in devices,
particularly hubs (sensitive low voltage lines).
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Spike - a momentary >100% increase in voltage
for 0.5 to 100 msecs (very short duration).
Sag - voltage drops below 80% of normal
voltage for less than 1 sec.
Brownout - voltage below 80% of normal for
greater than 1 sec.
Oscillations - AC voltage harmonics or noise,
caused by excessively long wires.
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Surges and Spikes
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Causes:
 Lightning.
 Utility
company
switching operations.
 Cycling equipment
like HVAC, elevators,
copy machines.
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Problems:
 Altered
or loss data, lockups, damage to electrical
devices or electronic chips.
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Addressed with surge suppressors.
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Sags and Brownouts
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>20% decrease in line voltage (below 80% of
normal).
 Sags
- short duration (<1sec).
 Brownouts - longer duration (>1sec).
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Can cause system crashes, and loss of data.
Solved by using an UPS (uninterruptible power
supply).
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Oscillations
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Can cause excessive noise and erroneous data.
Solved by rewiring, to ensure clean and direct
power and ground connections.
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Effectiveness of Surge Suppressors
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Individual surge suppressors - placed at wall
outlet, close to networking device.
Most use a MOV, metal oxide varistor.
 Capable
of absorbing very large currents without
damage (diverts currents to ground).
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May not be very effective!
Diverting surges to ground avoids equipment
damage, but can cause garbled data by changing
ground voltage.
MOVs have limited lifetime; are not the best
choice for network protection.
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Best Surge Suppressor
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Use large commercial
grade surge suppressor
at the power panel.
By diverting surges to
ground at the power
panel you minimize
effect of changing
ground potentials
at your networking devices.
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UPS - for problem of sags & brownouts
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What devices should be supported by UPS?
 Factors
to consider: cost, importance of service,
quality of ac line power.
 Every network file server should have power
backup.
 Any critical devices (hubs, bridges, switches,
routers) should be backed up.
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UPS - for outages of short duration.
For extended periods of time, a generator is
needed.
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UPS Components
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Batteries - storage of electrical energy (DC).
 Larger
batteries (greater storage capacity); UPS
can supply backup power longer.
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Battery Charger - keeps batteries fully charged
when ac line power is available.
Power Inverter - converts DC voltage from
batteries into AC line voltage.
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UPS Operation
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Basic UPS:
 Monitors
power line.
 When line power is interrupted, UPS switches to
inverter powered by batteries.
 Transfer time - time UPS takes to switch over to
inverter power (typically few milli-secs).
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More expensive on-line UPS:
 operates
continuously on-line, supplying AC
power from inverter. Batteries are charged from
AC line voltage.
 Transfer time is zero.
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Basic UPS Block Diagram
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S1 & S2 normally closed, S3 & S4 normally
open.
When AC voltage is lost, the inverter switches on,
S1 & S2 open, and S3 & S4 close.
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On-line UPS Block Diagram
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Operates continuously on-line.
Transfer time is zero.
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Intelligent UPS
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Has data communications capability.
Communicates with file server, informing it
when battery power is running low.
Informs workstations when a power outage has
occurred.
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Summary
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General design process.
 Select
technology (Ethernet, Token Ring, etc)
 Layer 1 topology.
 Layer 2 topology.
 Layer 3 topology.

Network Design Issues
 1.Gather
information.
 2.Analyze requirements.
 3.Identify resources and constraints.


Wiring closet specs - TIA/EIA 569.
Selecting wiring closets
 MDF
- secure, central location, close to POP.
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Summary (cont.)
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Horizontal and Backbone Cabling.
 Cat
5 UTP for horizontal cabling.
 Multi-mode fiber for backbone.
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Electrical concerns:
 AC
line noise.
 ESD.
 Ground problems.
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Power Line Problems.
 Normal
mode and common mode.
 Surges, spikes, sags, brownouts, oscillations.
 Surges & spikes addressed with surge supressors.
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Summary (cont.)
 MOV,
metal-oxide varistor, found in individual surge
suppressors.
 Commercial grade surge suppressor, installed at
the power panel, is best.
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UPS
 Basic
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and on-line.
Troubleshooting
 work
up through the OSI model.
The End
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