Lesson 27:
IEEE - Institute of Electrical and Electronics Engineers. Professional
organization whose activities include the development of communications
and network standards. IEEE LAN standards are the predominant LAN
standards today.
EIA - Electronic Industries Association. Group that specifies electrical
transmission standards. The EIA and TIA have developed numerous
well-known communications standards, including EIA/TIA-232 and
EIA/TIA-449. See also TIA.
TIA - Telecommunications Industry Association. Organization that
develops standards relating to telecommunications technologies. Together,
the TIA and the EIA have formalized standards, such as EIA/TIA-232, for
the electrical characteristics of data transmission. See also EIA.
IEEE 802.3 - IEEE LAN standard that specifies an implementation of
the physical layer and the MAC sublayer of the data link layer. IEEE
802.3 uses CSMA/CD access at a variety of speeds over a variety of
physical media. Extensions to the IEEE 802.3 standard specify
implementations for Fast Ethernet. Physical variations of the original IEEE
802.3 specification include 10Base2, 10Base5, 10BaseF, 10BaseT, and
10Broad36. Physical variations for Fast Ethernet include 100BaseT,
100BaseT4, and 100BaseX.
IEEE 802.5 - IEEE LAN standard that specifies an implementation of
the physical layer and MAC sublayer of the data link layer. IEEE 802.5
uses token passing access at 4 or 16 Mbps over STP cabling and is similar
to IBM Token Ring. See also Token Ring.
EIA/TIA-568 - Standard that describes the characteristics and
applications for various grades of UTP cabling. Since it originated,
additions have been made to this standard that include information on fiber
optic cable and link performance. The revised standard has been released
as EIA/TIA-568B. See EIA/TIA-568A. See also Category 1 cabling,
Category 2 cabling,Category 3 cabling, Category 4 cabling, Category
5 cabling, and UTP.
EIA/TIA-569 - Standard that defines and describes horizontal
pathways, telecommunications closets, backbone pathways, equipment
rooms, work stations, and entrance facilities for local area network
systems and, where applicable, the minimum requirements for them.
Five grades of UTP cabling described in the EIA/TIA-568B standard.
Category: Use:
1 used for telephone communications and is not suitable for
transmitting data.
2 cabling is capable of transmitting data at speeds up to 4
Mbps.
3 used in 10BaseT networks and can transmit data at speeds
up to 10 Mbps.
4 used in Token Ring networks and can transmit data at
speeds up to 16 Mbps.
5 used for running CDDI and can transmit data at speeds up
to 100 Mbps.
Of these, only category 3, category 4, and category 5 are recognized for
use in local area networks. Of these three categories, category 5 is the
one most frequently recommended and implemented in installations today.
Jumper - 1.)Term used for patchcords found in a wiring closet.
2.)Electrical switch consisting of a number of pins and a connector that can
be attached to the pins in a variety of different ways. Different circuits are
created by attaching the connector to different pins.
For STP cable, the standard for horizontal cabling is two pair of 150 ohm
cable. For UTP, the standard is four pair of 100 ohm cable. For
fiber-optic, the standard is two fibers of 62.5/125 um multimode cable.
Although 50 ohm coaxial cable is a recognized type of networking media in
EIA/TIA-568B, it is not recommended for new installations.
According to EIA/TIA-568B, the maximum distance for cable runs in
horizontal cabling is 90 meters or 295 feet. This is true for all types of
category 5 UTP recognized networking media. With patch cords that do not
exceed 6m or 20 feet. With a max. of 3m between the connector and the
workstation. All grounding must conform with EIA/TIA-607 specifications.
Lesson 29:
Topology - Physical arrangement of network nodes and media within
an enterprise networking structure.
Bus topology - Linear LAN architecture in which transmissions from
network stations propagate the length of the medium and are received by
all other stations. Compare with ring topology, star topology, and tree
topology.
Star topology - LAN topology in which end points on a network are
connected to a common central switch by point-to-point links. A ring
topology that is organized as a star implements a unidirectional
closed-loop star, instead of point-to-point links.
Extended star topology - Star topology where a central hub is
connected by vertical cabling to other hubs that are dependent on it. See
hierarchical star topology.
Bus - Common physical signal path composed of wires or other media
across which signals can be sent from one part of a computer to another.
Sometimes called highway.
Terminator - Device that provides electrical resistance at the end of a
transmission line to absorb signals on the line, thereby keeping them from
bouncing back and being received again by network stations.
Lesson 31:
Star topology - LAN topology in which end points on a network are
connected to a common central switch by point-to-point links. A ring
topology that is organized as a star implements a unidirectional closed-loop
star, instead of point-to-point links. Compare with bus topology.
Passive hubs do not regenerate the signals, Active hubs do.
Lesson 32:
Max length of cord is 100m. Star toplogy can give 200m because of hub.
Extended star topology - Star topology where a central hub is
connected by vertical cabling to other hubs that are dependent on it. See
hierarchical star topology.
Lesson 33:
CSMA/CD - Carrier sense multiple access collision detect.
Media-access mechanism wherein devices ready to transmit data first
check the channel for a carrier. If no carrier is sensed for a specific
period of time, a device can transmit. If two devices transmit at once, a
collision occurs and is detected by all colliding devices. This collision
subsequently delays retransmissions from those devices for some random
length of time. CSMA/CD access is used by Ethernet and IEEE 802.3.
Connectionless - Term used to describe data transfer without the
existence of a virtual circuit. Compare with connection-oriented. See also
virtual circuit.
Best-effort delivery - Describes a network system that does not
use a sophisticated acknowledgment system to guarantee reliable delivery
of information.
Token passing - Access method by which network devices access
the physical medium in an orderly fashion based on possession of a small
frame called a token.
IEEE 802.3i - Physical variation of the original IEEE 802.3
specification that calls for using Ethernet type signaling over twisted
pair networking media. The standard sets the signaling speed at 10
megabits per second using a baseband signaling scheme transmitted over
twisted pair cable employing a star or extended star topology.
10 Description
-----------------------------------------------------------------
base2 10mbs, 50ohm thin coaxial cable, 185m/segment
base5 10mbs, 50ohm thick coaxial cable, 500m/segment
baseF Fiber optical ethernet.
baseT 10mbs, 2pair twisted pair, cat. 3-5, 100m/segment
broad36 10mbs, broadband coaxial cable, 3600m/segment
Baseband - Characteristic of a network technology where only one
carrier frequency is used. Ethernet is an example of a baseband network.
Also called narrowband.
An access method is, formally stated, an access method is a set of
predefined rules or protocols that determine how a device gains access or
entry to the networking media.
If it detects any errors, the data packet is discarded. When it discards
the data, the destination device does not notify the source that it
discarded the data. Nor does the destination device notify the source if
the data was received in good condition. For this reason Ethernet is
considered to be a connectionless network architecture. It is also why
Ethernet is known as a best-effort delivery system.
Lesson 34:
Skit:
1. Why couldn't a linear bus topology be used in a Token Ring network
architecture?
2. Can collisions occur in a Token Ring Network architecture? Why or Why
not?
3. Which of the two network architectures listed above could be
considered to be deterministic?
4. Which of the two network architectures listed above could be
considered to be opportunistic?
5. In which of the two network architectures listed above is delivery of
the data assured?
6. In which of the two network architectures listed above is a broadcast
access method used?
7. What is a token?
8. What is token passing?
9. What are some advantages of using the token passing access method?
10. What are some advantages of using the CSMA/DA access method?
11. Why and how can network architecture determine the type of topology
used?
Lesson 36:
Surface mounted jacks can be mounted to the wall by means of an
adhesive-backed box, or screw mounted box. They cannot be moved once they
are mounted.
## Surface mounting:
Advantages: A) No Cutting.
B) Less time (lower cost)
## Flush mounting:
A) Plaster Crumbles
B) If there is a wide, wooden baseboard. Avoid using first 2",
the walls bottom plate will block your box.
C) Use box or low-voltage mounting bracket?
Preparation:
Notes: A) Plaster:
I) Use hammer and chizel to remove plaster.
II) Put template over holes (equally overlapping 3 pieces of
lath at top and bottom).
III) Use utility knife to trim plaster.
IV) Using an electric saw, cut away the full lath strip that is
exposed in the center of the opening (alternating between
sides). Be careful when you do this. If you attempt to cut all
the way through one side before cutting into the other side
the saw will cause the lath to vibrate when you make the second
cut. This can cause the plaster around the opening to crack and
come loose.
B) Drywall:
I) Mount 12" - 18" above floor.
II) Put 2 holes in location.
III) Check for obstructions (insert wire and rotate).
IV) Determine size of hole (use template).
V) Test box fit.
VI) Use box or low-voltage mounting bracket?
C) Wood:
I) Trace outline.
II) Make starter holes at each corner.
III) Use saw to cut from corner to corner.
Mounting:
Box: A) Feed cable through opening.
B) Push box into wall opening.
C) Tighten screws.
Low-voltage mounting bracket:
A) Put bracket against opening (smooth side out).
B) Push top and bottom flanges toward back.
C) Push first one up and other down.
Lesson 42:
MDF - Main distribution facility - Primary communications room for a
building. Central point of a star networking topology where patch panels,
hub, and router are located.
IDF Intermediate distribution facility - Secondary communications room
for a building using a star networking topology. The IDF is dependent on
the MDF.
Horizontal cabling is a term used to describe the networking media that is
used in the area extending from the wiring closet to a work area.
Pin location - A color-coded slot on a patch panel. Cable wires are
punched down using a punch tool to make an electrical connection that
allows the network to function. Located on back of patch panel.
In any local area network system, connectors are the weakest links. To
avoid exposing too much wire, be sure to keep the jacket within 1/4" of
the pin locations you are working on. When you use the punch tool, be
sure to position it so that its blade is on the side away from where the
wire enters each pin location.
Lesson 43:
TDR - Time domain relfectometer. Device capable of sending signals
through a network medium to check cable continuity, length, and other
attributes. TDRs are used to find physical layer network problems.
Time-domain reflectometry Technique of sending an electrical
signal down a cable and then timing the signal's reflection back from the
end of the cable.
Wire map - Feature provided by most cable testers. Used to test
twisted pair cable installations, it shows which wire pairs connect to what
pins on the plugs and sockets.
Signal injector - Device used to measure attenuation of a signal on a
network.
When testing your network you should follow these steps:
A) Break the system into logically conceived functional elements.
B) Note any symptoms.
C) Based on the symptoms you observe, determine what the most likely
dysfunctional element is.
D) Use substitution or additional testing to discover if the likely element
is in fact dysfunctional.
E) If the element suspected of being dysfunctional proves not to be the
problem, proceed to the next most likely element you suspect.
F) When the dysfunctional element is found, repair it if possible.
G) If it is not possible to repair the dysfunctional element, replace
it.
When it(The TDR) measures distance on a cable, the TDR sends an electrical
signal that is reflected when it encounters the most distant open
connection.
You should test the network periodically.
A Cable tester sends a seignal the cable and then measures the time it
takes for the singal to return.
A wire map is used to determine if wires were connected to a plug or jack
in reverse order, but will not detect split pairs.
An example of cross-pair is 1=2, 2=1, they're an indication that the
connection is not good.
(paren. 1 is the wire, paren. 2 is the connection owner)
An example of split pari is 1(A)=1(A), 2(B)=2(A), 3(A)=3(B)
Near-end crosstalk can be caused by TP that have become untwisted.
Flourecent lights are one source of outside interference.
Lesson 46:
A wiring closet's size varies on the size of the LAN, and must be large enough
to accommodate future growth.
EIA/TIA-569 specifies that there be a minimum of one wiring closet per floor
and states that additional wiring closets should be provided for each area
up to 1000 square meters when the floor area served exceeds 1000 square
meters or the horizontal cabling distance exceeds 90 meters.
Wiring closets must have suffcient power and HVAC (heating, vent., A/C) and
must adhere to the guidlines governing the types of walls, floors, and ceiling
acceptable temprature and humidty.
All interior walls on which equipment will be mount should be covered with
0.75" plywood that is raised away from the underlying wall a min of 1.75".
If the wiring closet has a PBX, it should be covered from the floor to the
ceiling with 0.75" plywood and a min of 15 feet of wall space for terminations
and equip. The ceiling should not be dropped or false for security reasons.
MDF's floors must be able to bear a min. of 250lb/ft^2. IDF's floors should
be able to bear 100lb/ft^2. Where possible rooms should have raised floors,
if they cannot have a raised floor there should be a 12" ladder rack to
support all proposed equipment and cable.
No water or steam pipes should run through or above the room (except a
sprinkler if required by fire codes). Relative humidity should remain
between 30% and 50%. The temprature should maintian aprrx. 70F when
fully operational.
A wall switch to turn the room lighting on and off should be immediately
inside the door. Fluorescent lightng should be avoided.
MDFs must have atleast 1 duplex power outlet every 10'. IDFs must have atleast
2 per wall.
The door should be atleast 3' wide and should swing open out of the room and
lock from the outside.
All wires leaving the room should leave via 4" conduits.
Lesson 47:
Catchment area - Zone that falls within area that can be served by an
internetworking device such as a hub.
Cut sheet - A rough diagram indicating where cable runs are located
and the numbers of rooms they lead to.
To determine the location of the wiring closet determine where all the
devices on your network will be (on a floor plan), taking into consideration
the location of the POP. Next draw circles indicating 50m to depict where
the horiz. cables will travel.
1) Do any of the circles overlap?
2) Can any of the potential wiring closet locations be eliminated?
3) Do any of the circles provide coverage for all of the devices that will
be connected to the network?
4) Which of the potential wiring closet locations seems to be the best?
5) Are there any circles where only a few of the devices fall outside the
catchment area?
6) Which potential wiring closet is closest to the POP?
7) Based on your findings, list the three best possible locations for wiring
closets.
8) Based on your findings, how many wiring closets do you believe will be
required for this network?
9) What are the advantages and disadvantages of each of the potential
wiring closet locations shown on the floor plan?
Lesson 48:
Read about several wiring closets.
Lesson 49:
Backbone - The part of a network that acts as the primary path for
traffic that is most often sourced from, and destined for, other networks.
Backbone cabling - Cabling that provides interconnections
between wiring closets, wiring closets and the POP, and between buildings
that are part of the same LAN. Sometimes known as vertical cabling.
Hierarchical star topology - Extended star topology where a
central hub is connected by vertical cabling to other hubs that are
dependent on it.
Hierarchical star topology - Extended star topology where a
central hub is connected by vertical cabling to other hubs that are
dependent on it.
MCC Main cross-connect. Wiring closet that serves as the most central
point in a star topology and where LAN backbone cabling connects to the
Internet.
ICC Intermediate cross-connect. IDF that connects the horizontal
cross-connect to the main cross-connect.
micron or µ - Unit of measure equal to one millionth of a meter or one
thousandth of a millimeter. Sometimes the symbol µ is used instead of the
word micron.
EIA/TIA-568 specifies four types of networking media that can be used for
backbone cabling:
100 ohm UTP
150 ohm STP
50 ohm Coaxial Cable (not recommened)
62.5/125 micron optical fiber, single fiber.
Media: Distance:
HCC to MCC HCC to ICC ICC to MCC
---------------------------------------------------------------
62.5/125 2,000m 500m 1,500m
Fiber OC
Single- 3,000m 500m 2,500m
Mode OC
UTP 800m 500m 300m
(voice)
UTP data applications limited to 90m total
(data)
Lesson 51:
Ground - Electrically neutral contact point.
ESD - Electrostatic Discharge - A flow or spark of electricity that
originates from a static source such as a carpet and arcs across a gap to
another object.
Conductor - Any material with a low resistance to electrical current.
Any material capable of carrying an electrical current. See insulator.
Insulator - Any material with a high resistance to electrical current. See
conductor.
Safety ground wire - Circuit wire that connects to a local earth
ground and the chassis of an electrical appliance or device via an electrical
outlet and plug. It is used to ensure that no voltage potential exists between
the chassis of the electrical device and the earth ground.
Neutral wire - Circuit wire that is connected to an earth ground at the
power plant and at the transformer.
Hot wire - Ungrounded lead wire that connects the transformer and
electrical devices or appliances via an electrical outlet and power plug.
Lesson 52:
Lesson 56:
Signal reference ground - Reference point used by computing devices to
measure and compare incoming digital signals to.
Because there is a link between the signal reference ground and the power
ground, problems with the power ground can lead to interference with the data
system.
Lesson 57:
Common mode - Term used to describe problems involving either the hot or
neutral wires and the safety ground wire on a power line.
Normal mode - Term used to describe problems between the hot and neutral
wires on a power line.
UPS - Uninterruptable power supply. Backup device designed to provide an
uninterrupted power source in the event of a power failure. They are commonly
installed on al file servers and wiring hubs.
Common mode problems can do more damage (no filters) and are harder to detect.
Surge - Any voltage increase above 110 % of the normal voltage carried by a
power line.
Sag - Any decrease of below 80% in the normal voltage carried by a power line.
A sag is sometimes referred to as a brownout.
Spike - Any power impulse lasting between .5 and 100 microseconds and
possessing an amplitude over 100 % of peak power line voltage.
Oscillation - Secondary signal on top of the 60-Hz waveform. It has a
magnitude that ranges from 15 % to 100 % of the normal voltage carried on
the power line.
Ground loop - Arrangement that exists when a multi-path connection exists
between computers. Usually this occurs when computers are connected to each
other through a ground wire and when computers are attached to the same
network using twisted pair cable.
The best way to address the problem of oscillation is to rewire.
Lesson 58:
MOV - Metal oxide varistor. Voltage clamping surge suppressor capable of
absorbing large currents without damage.
Typically, a MOV can hold voltage surges on a 120 volt circuit to a
level of approximately 330 volts.
MOV's prevent damage but may cause interference.
To avoid the problems of surge protoectors in close proximity to the
networking device, use a commercial class surge supressor at the power
distribution panel.
Every network fileserver, bridge, and router should be protected with a UPS
(power backup), and power wiring hubs must also be protected if they exist.
A generator should be present if the LAN requires power during long power
outages.
UPS consist of batteris, a charger, and a power inverter. The inverter
converts voltage DC to voltage AC.
The time it takes for the UPS to switch from AC to batteries is known as the
transfer time (a few ms) and does not pose a problem to most computers.
Some UPSs take AC in and send all power threw the inverter reducing transfer
time to 0 and elimating spikes.
Lesson 61:
SNMP - Simple Network Management Protocol. Network management
protocol used almost exclusively in TCP/IP networks. SNMP provides a
means to monitor and control network devices, and to manage
configurations, statistics collection, performance, and security.
CMIP - Common Management Information Protocol. OSI network
management protocol created and standardized by ISO for the monitoring
and control of heterogeneous networks.
MIB collection - Polling technique used by the SNMP protocol to
gather information needed to monitor the network.
MIB reporting - Technique used by the CMIP protocol to obtain
information needed to monitor the network. It is dependent upon network
devices to initiate reports regarding their status to a central monitoring
station on the network.
When the LAN has been implemented do inventory audit, a facility audit, an
operational audit, an efficiency audit, and a security audit.
Inventory Audit should include the device's serial number, the type of device,
and the name of the individual using the device.
A facility audit allows you to note where everything is, including cabling,
workstations, printers, and other devices (hubs, etc...)
Use the Inv. and Facility audit to create a network map, including MAC and IP
addresses, and Distances.
Information for the operational, efficiency, and security audits can and
should be obtained after the network has begun to function.
An operational audit detect the effiency of the network.
Lesson 62:
Network analyzer - Network monitoring device that maintains
statistical information regarding the status of the network and each device
attached to it. More sophisticated versions using artificial intelligence can
detect, define, and fix problems on the network.
Information provided by the day-to-day network view tells you when the peak
hours are, what the avg. amount of load in the network is, popularity of
some applications, etc.
An effciency audit determines how well the network is peforming against
its potentional preformance using IEEE &&/|| EIA/TIA standards as baseline.
Other factors that should be included in an Effciency audit:
Cost Analysis
Analysis of the ease with which data is retrieved
Analysis of integrety of network packets
Security Audits determine what hardware and software combination provide the
best network security. Use information based on which segments require
encrpytion, workstations require passwords, and how often to backup in a
security audit.
If you are convinced that you need a network analyzer to help you monitor and
troubleshoot your network, but your budget does not permit you to purchase
one, you can hire someone to check the network for you.
As a general rule, the more information you have the easier it is to solve
problems.
Record problems in a detailed log.
Some network problems will be detected using analysis tools, others will
be brought to the attention of the administrator by the users.
Requests for help should be documented in five parts:
1) Assign an ID # to the request
2) Prelim. information (who, time, method of report)
3) On-site information (power on site, temp, humidity)
4) Information regarding how it was fixed, on-site or taken to shop.
5) Summary of all work done, type of problem (hw/sw/user)
Trouble shoot the problem by switching components starting with what you
suspect is the most likely cause.
Lesson 63:
Evaluations of the network should be taken after the network has been
operational for a reasonable perdiod of time, the data from these eval.'s
should be compiled to make a report.
Periodic evaluations of a network are important maintenance and prevention
tools.
Evaluation reports indicate the networks strengths and weaknesses.
Lesson 66:
{Lesson 1}
Networking - Connecting of any collection of computers, printers,
routers, switches, and other devices for the purpose of communication
over some transmission medium.
Protocol - Formal description of a set of rules and conventions that
govern how devices on a network exchange information.
Local-area network (LAN) - High-speed, low-error data
network covering a relatively small geographic area. LANs connect
workstations, peripherals, terminals, and other devices in a single building
or other geographically limited area. LAN standards specify cabling and
signaling at the physical and data link layers of the OSI model. Ethernet,
FDDI, and Token Ring are widely used LAN technologies. Compare with
MAN and WAN.
Metropolitan-area network (MAN) - Network that spans a
metropolitan area. Generally, a MAN spans a larger geographic area than
a LAN, but a smaller geographic area than a WAN. Compare with LAN
and WAN.
Wide-area network (WAN) - Data communications network that
serves users across a broad geographic area and often uses transmission
devices provided by common carriers. Frame Relay, SMDS, and X.25
are examples of WANs. Compare with LAN and MAN.
Hardware - A term used in computing to refer to physical parts or
equipment.
Software - A term used in computing to refer to programs or
applications.
PC - Personal Computer
Standards - Set of rules or procedures that are either widely used or
officially specified. See also defacto standard.
Networking started with 'SneakerNet', networking computers was more
ecconomical and faster.
Hardware examples: routers, bridges
Software examples:
{Lesson 2}
OSI Reference Model - Open System Interconnection reference
model. Network architectural model developed by ISO and ITUT-T The
model consists of seven layers, each of which specifies particular network
functions such as addressing, flow control, error control, encapsulation,
and reliable message transfer. The highest layer (the application layer) is
closest to the user; the lowest layer (the physical layer) is closest to the
media technology. The lowest layer is implemented in hardware. The next
to lowest layer is implemented in hardware and software, while the upper
five layers are implemented only in software. The OSI reference model is
used universally as a method for teaching and understanding network
functionality.
Source - Network device that is sending data.
Destination - Network device that is receiving data.
Data (packets) - Logically grouped units of information that move between
computer systems
LAYER PURPOSE
-------------------------------------------------------------------------
Physical Layer 1 of the OSI reference model. The physical
layer defines the electrical, mechanical, procedural, and
functional specifications for activating, maintaining, and
deactivating the physical link between end systems
Data Layer 2 of the OSI reference model. This layer
provides reliable transit of data across a physical link.
The data link layer is
concerned with physical addressing, network topology, line
discipline, error notification, ordered delivery of
frames, and flow control. The IEEE has divided this layer
into two sublayers: the MAC sublayer and the LLC sublayer.
Sometimes simply called link layer.
Network Layer 3 of the OSI reference model. This layer provides
connectivity and path selection between two end systems.
The network layer is the layer at which routing occurs.
Transport Layer 4 of the OSI reference model. This layer is
responsible for reliable network communication between end
nodes. The transport layer provides mechanisms for the
establishment, maintenance, and termination of virtual
circuits, transport fault detection and recover, and
information flow control.
Session Layer 5 of the OSI reference model. This layer
establishes, manages, and terminates sessions between
applications and manages data exchange between
presentation layer entities.
Presentation Layer 6 of the OSI reference model. This layer ensures
that information sent by the application layer of one
system will be readable by the application layer of
another. The presentation layer is also concerned with the
data structures used by programs and therefore negotiates
data transfer syntax for the application layer.
Application Layer 7 of the OSI reference model. This layer provides
services to application processes (such as electronic
mail, file transfer, and terminal emulation) that are
outside of the OSI model. The application layer identifies
and establishes the availability of intended communication
partners (and the resources required to connect with
them), synchronizes cooperating applications, and
establishes agreement on procedures for error recovery and
control of data integrity.
{Lesson 3}
Layer 1 - #LINE 675 - 678
Coaxial - Cable consisting of a hollow outer cylindrical conductor that
surrounds a single inner wire conductor. Two types of coaxial cable are
currently used in LANs: 50-ohm cable, which is used for digital signaling,
and 75-ohm cable, which is used for analog signal and high-speed digital
signaling.
Twisted Pair - Transmission medium consisting of four or eight
insulated wires arranged by pairs in a regular spiral pattern. The wires can
be shielded or unshielded. Twisted pair is common in telephony
applications and is most common in data networks. See also STP and
UTP.
Fiber-optic - Physical medium capable of conducting modulated light
transmission. Compared with other transmission media, fiber-optic
cable is more expensive, but is not susceptible to electromagnetic
interference, and is capable of higher data rates. Sometimes called
optical fiber.
Media - Plural of medium. The various physical environments through
which transmission signals pass. Common networking media include
twisted-pair, coaxial and fiber-optic cable, and the atmosphere (through
which microwave, laser, and infrared transmission occurs). Sometimes
called physical media.
Things located at layer 1: wires, connectors, and voltages.
{Lesson 4}
ES - End system. Generally, an end-user device on a network.
Layer 2 - #LINE 680-687
NIC - Network interface card. Board that provides network
communication capabilities to and from a computer system. Also called an
adapter.
MAC address - Standardized data link layer address that is required
for every port or device that connects to a LAN. Other devices in the
network use these addresses to locate specific ports in the network and to
create and update routing tables and data structures. MAC addresses are
6 bytes long and are controlled by the IEEE. Also known as a hardware
address, a MAC-layer address, or a physical address.
Repeater - Device that regenerates and propagates electrical signals
between two network segments.
Some problems with large networks are that in ethernet architecture,
data is sent to all nodes.
Repeaters take weakened signals, clean them and retransmit them.
{Lesson 6}
Filter - Generally, a process or device that screens network traffic for
certain characteristics, such as source address, destination address, or
protocol, and determines whether to forward or discard that traffic based
on the established criteria.
Bit - Binary digit used in the binary numbering system. Can be 0 or 1.
Port - 1.) Interface on an internetworking device (such as a router). The
image shown here shows a cable plugged into the ports of two networking
devices. ; 2.) In IP terminology, an upper-layer process that is receiving
information from lower layers; 3.) To rewrite software or microcode so
that it will run on a different hardware platform or in a different software
environment than that for which it was originally designed; 4.) A female
plug on a patch panel which accepts the same size plug as an RJ45 jack.
Patch cords are used in these ports to cross connect computers wired to
the patch panel. It is this cross connection which allows the LAN to
function.
Segment - 1.) Section of a network that is bounded by bridges,
routers, or switches; 2.) In a LAN using a bus topology, a segment is a
continuous electrical circuit that is often connected to other such
segments with repeaters.
Collision - In Ethernet, the result of two nodes transmitting
simultaneously. The frames from each device impact and are damaged
when they meet on the physical media.
Collision domain - In Ethernet, the network area within which
frames that have collided are propagated. Repeaters and hubs propagate
collisions; LAN switches, bridges and routers do not.
Backoff - The retransmission delay enforced when a collision occurs.
Algorithm - Well-defined rule or process for arriving at a solution to a
problem. In networking, algorithms are commonly used to determine the
best route for traffic from a particular source to a particular
destination.
Bridge - Device that connects and passes packets between two
network segments that use the same communications protocol. Bridges
operate at the data link layer (layer 2) of the OSI reference model. In
general, a bridge will filter, forward, or flood an incoming frame based
on the MAC address of that frame.
A collison causes all offending devices to stop transmitting and wait a
time different from each other.
A bridge divides networks into segments by fowarding or not fowarding.
{Lesson 7}
Broadcast - Data packet that will be sent to all nodes on a network.
Broadcasts are identified by a broadcast address.
Broadcast Storm - Undesirable network event in which many
broadcasts are sent simultaneously across all network segments. A
broadcast storm uses substantial network bandwidth and, typically, causes
network time-outs.
IP address - 32-bit address assigned to hosts using TCP/IP. An IP
address belongs to one of five classes (A, B, C, D, or E) and is written
as 4 octets separated with periods (dotted decimal format). Each address
consists of a network number, an optional subnetwork number, and a host
number. The network and subnetwork numbers together are used for
routing, while the host number is used to address an individual host
within the network or subnetwork. A subnet mask is used to extract network
and subnetwork information from the IP address. Also called an Internet
address.
Layer 3 - #LINE 689-691
Bridges use MAC addresses to determine whether or not to foward.
Bridges are not effective at sending alot of data between segments.
There is another potential problem with using a
bridge. Bridges always spread and multiply a
special kind of data packet. These data packets
occur when a device on a network wants to
reach another device on the network, but does
not know the destination address of the device.
{Lesson 8}
Router - Network layer device that uses one or more metrics to
determine the optimal path along which network traffic should be
forwarded. Routers forward packets from one network to another based
on network layer information.
Network address - Network layer address referring to a logical,
rather than a physical, network device. Also called a protocol address.
Compare with MAC address.
Internet - Term used to refer to the largest global internetwork,
connecting tens of thousands of networks worldwide and having a "culture"
that focuses on research and standardization based on real-life use. Many
leading-edge network technologies come from the Internet community.
The Internet evolved in part from ARPANET. At one time, called the
DARPA Internet. Not to be confused with the general term internet.
Frame - Logical grouping of information sent as a data link layer unit
over a transmission medium. Often refers to the header and trailer, used
for synchronization and error control, that surround the user data
contained in the unit. The terms datagram, message, packet, and segment
are also used to describe logical information groupings at various layers
of the OSI reference model and in various technology circles.
Header - Control information placed before data when encapsulating
that data for network transmission.
Routing table - Table stored in a router or some other
internetworking device that keeps track of routes to particular network
destinations and, in some cases, metrics associated with those routes.
Encapsulation - The wrapping of data in a particular protocol
header. For example, Ethernet data is wrapped in a specific Ethernet
header before network transit. Also, when bridging dissimilar networks,
the entire frame from one network is simply placed in the header used by
the data link layer protocol of the other network.
Routing occurs at the network layer or layer 3 of the OSI model.
ROUTER BRIDGE
------------------------------------------------------------------
Network layer Data link layer
Uses IP address Uses MAC address
Connect Networks Connect Network Segments
{Lesson 9}
Dot address - Refers to the common notation for IP addresses in the
form <a.b.c.d> where each number a represents, in decimal, 1 byte of the
4-byte IP address. Also called dotted notation or four-part dotted
notation.
Byte - Term used to refer to a series of consecutive binary digits that are
operated upon as a unit (for example, an 8-bit byte).
1100,1010,0000,1111,1010,1010,0000,0001 = 202.15.170.1
{Lesson 11}
InterNIC - International Network Information Center. Organization that
serves the Internet community by supplying user assistance,
documentation, training, and other services.
Network number - Part of an IP address that specifies the network
to which the host belongs.
Host number - Part of an IP address that designates which node on
the subnetwork is being addressed. Also called a host address.
Class A networks have 16777214 possible IPs
Class B networks have 65533 possible IPs
Class C networks have 256 possible IPs
{Lesson 12}
Multicast - Single packets copied by the network and sent to a
specific subset of network addresses. These addresses are specified in the
destination address field. Compare with broadcast and unicast.
Network address - #LINE 840-842
Broadcast address - Special address reserved for sending a
message to all stations. Generally, a broadcast address is a MAC
destination address of all ones. Compare with multicast address and
unicast address.
Subnetwork - 1.) In IP networks, a network sharing a particular
subnet address. Subnetworks are networks arbitrarily segmented by a
network administrator in order to provide a multilevel, hierarchical routing
structure while shielding the subnetwork from the addressing complexity of
attached networks. Sometimes called a subnet. See also IP address,
subnet address, and subnet mask; 2.) In OSI networks, a collection of
ESs and ISs under the control of a single administrative domain and using a
single network access protocol.
Subnet address - Portion of an IP address that is specified as the
subnetwork by the subnet mask. See also IP address, subnet mask, and
subnetwork.
Subnet mask - 32-bit address mask used in IP to indicate the bits of
an IP address that are being used for the subnet address. Sometimes
referred to simply as mask. See also address mask and IP address.
The network address for 197.22.103.221 would be 197.22.103.0
The graphic represents a Class B network that has 8bits borrowed.
{Lesson 13}
Subnetworks are created by 'borrowing' bits from the host field.
Lesson 67:
{Lesson 14}
Routers use the subnetmask to determine which network to send data to.
Picture 1: A class B IP network with 3 subnetworks, 8 bits borrowed.
Picutre 2: "ANDing" is depicted, the way a router determines the IP of a
host on a subnetwork is ANDing the subnetmask and the host.
Picture 3: The picture shows a routers routing table and how it determines
that network to broadcast it to.
{Lesson 16}
ARP - Address Resolution Protocol. Internet protocol used to map an
IP address to a MAC address. Defined in RFC 826. Compare with
RARP.
RAM - Random-access memory. Volatile memory that can be read and
written by a microprocessor.
Header - Control information placed before data when encapsulating
that data for network transmission.
Frame - Logical grouping of information sent as a data link layer unit
over a transmission medium. Often refers to the header and trailer, used
for synchronization and error control, that surround the user data
contained
in the unit. The terms datagram, message, packet, and segment are also
used to describe logical information groupings at various layers of the
OSI
reference model and in various technology circles.
The picture represents a computers ARP tables.
The 'source' will have to look up the MAC address for the destination, if
it does not have it in its ARP tables, it would have to broadcast an ARP
request.
ARP Frame Structure: [FRAME HEADER|ARP MESSAGE(what is your MAC address)]
ARP is Address Resolution Protocol, it is used to lookup MAC address to
their IP's.
ARP reply fram structure: [MAC HEADER(mac dest,mac source)|IP HEADER(ip
dest,ip source)|ARP REPLY MESSAGE(here is my IP)]
{Lesson 17}
RARP - Reverse Address Resolution Protocol. Protocol in the TCP/IP
stack that provides a method for finding IP addresses based on MAC
addresses. Compare with ARP.
When a device on a network sees an ARP reply, the use it to update their
ARP tables.
RARP is Reverse ARP(address res. proto.), it is used to on diskless
workstations that have volitale memmory and cannot store their IP.
RARP request frame: [MAC HEADER(mac dest,mac source)|IP HEADER(dest
IP,null source)|RARP REQUEST(what is my IP)]
RARP reply frame: [MAC HEADER(mac dest,mac source)|IP HEADER(dest IP,
source IP)|RARP REPLY(here is your IP)]
When a diskless workstation recieves a RARP reply it copies its IP to
memmory and keeps there for as long as the session lasts.
Other devices ignore the RARP reply.
Diskless workstations must update their ARP tables to contact other
devices.
{Lesson 18}
Routers use ARP tables for multiple networks to determine where to route
data.
ARP tables on routers kept by routers are different from ARP tables kept
by other devices because they contain addresses for nodes on more than 1
network.
The router has two IP addresses and two MAC addresses because it connects
two different networks.
The routing table given maps destination IPs to ports because that is how
the router determines which port to send data.
Default gateways are where the routers send data thaXXXXX destination is
not inside the network.
Indirect routing is where the the routers send information destined to
be sent to a device outside the source's network, they strip the header
and replace it with that routers IP for the source and the final
destination as the destination.
{Lesson 19}
RIP - Routing Information Protocol. IGP supplied with UNIX BSD
systems. The most common IGP in the Internet. RIP uses hop count as a
routing metric. See also Enhanced IGRP, hop count, IGP, IGRP, and
OSPF.
IGRP - Interior Gateway Routing Protocol. IGP developed by Cisco to
address the problems associated with routing in large, heterogeneous
networks. Compare with Enhanced IGRP. See also IGP, OSPF, and
RIP.
OSPF - Open Shortest Path First. Link-state, hierarchical IGP routing
algorithm proposed as a successor to RIP in the Internet community.
OSPF features include least-cost routing, multipath routing, and load
balancing. OSPF was derived from an early version of the ISIS protocol.
See also Enhanced IGRP, IGP, IGRP,IS-IS, and RIP.
IGP - Interior Gateway Protocol. Internet protocol used to exchange
routing information within an autonomous system. Examples of common
Internet IGPs include IGRP, OSPF, and RIP. See also IGRP, OSPF, and
RIP.
EGP - Exterior Gateway Protocol. Internet protocol for exchanging
routing information between autonomous systems. Documented in RFC
904. Not to be confused with the general term exterior gateway
protocol. EGP is an obsolete protocol that has been replaced by BGP.
See also BGP.
Hop count - Routing metric used to measure the distance between a
source and a destination. RIP uses hop count as its sole metric. See also
hop and RIP.
Hop - Term describing the passage of a data packet between two
network nodes (for example, between two routers). See also hop
Static route - Route that is explicitly configured and entered into the
routing table. Static routes take precedence over routes chosen by
dynamic routing protocols.
Dynamic routing - Routing that adjusts automatically to network
topology or traffic changes. Also called adaptive routing.
Routing protocols define how information will be sent through routers and
networks, routed protocols are the information being sent through the
routers and network.
RIP stands for Routing Information Protocol, it uses hop count as the
metric to find the best route to send information.
The router would determine that the best path is through router 1, 2, and
3 since that contains the least amount of hops, then each router would
examine the packet, strip the header, replace it with its own and send it
to the next router which would do the same thing.
IGRP is Interior Gateway Routing Protocol, it was developed by Cisco to
solve the problems with RIP.
EIGRP is Enhanced IGRP, it was designed by Cisco to increase IGRP's
effiency.
OSPF is Open Shortest Path First, a routing protocol with a multitude of
configurable metrics.
Static Routes are routes that do not changed and entered manually.
Dynamic Routes are determined by the routers to find the best routes.
Data packets are routed between different subnetworks by indirect routing,
they send the data to all nodes, a router sees that it has a path for it
and sends it out the port for that network. The source addresses are
stripped and replaced with the routers.
{Lesson 21}
Server - Node or software program that provides services to clients.
See also back end, client, and front end.
Adapter - Network interface card. Board that provides network
communication capabilities to and from a computer system. Also called an
adapter.
Hub - 1.) Generally, a term used to describe a device that serves as the
center of a star-topology network. 2.) Hardware or software device that
contains multiple independent but connected modules of network and
internetwork equipment. Hubs can be active (where they repeat signals
sent through them) or passive (where they do not repeat, but merely split,
signals sent through them). 3.) In Ethernet and IEEE 802.3, an Ethernet
multiport repeater, sometimes referred to as a concentrator.
Bus - Common physical signal path composed of wires or other media
across which signals can be sent from one part of a computer to another.
Sometimes called highway.
Hardware required to operate a LAN:
a) File server
b) NIC Cards
c) Adapters
d) Workstations
e) Networking Media
f) Hub
A hub is the central point in Star topology, it is also known as a
concentrator, all data going through the network goes through the hub. It
broadcasts the information the the network.
{Lesson 22}
EMI - Electromagnetic interference. Interference by electromagnetic
signals that can cause reduced data integrity and increased error rates on
transmission channels.
RFI - Radio frequency interference. Radio frequencies that create noise
that interferes with information being transmitted across unshielded
copper
cabling.
Cross talk - Interfering energy transferred from one circuit to another.
Ethernet - Baseband LAN specification invented by Xerox
Corporation and developed jointly by Xerox, Intel, and Digital Equipment
Corporation. Ethernet networks use CSMA/CD and run over a variety of
cable types at 10 Mbps. Ethernet is similar to the IEEE 802.3 series of
standards.
Backbone - The part of a network that acts as the primary path for
traffic that is most often sourced from, and destined for, other networks.
Thinnet - Term used to define a thinner, less expensive version of the
cable specified in the IEEE 802.3 10Base2 standard. Compare with
Cheapernet.
Cheapernet - Industry term used to refer to the IEEE 802.3 10Base2
standard or the cable specified in that standard. Compare with Thinnet.
Types of wires that use copper wires, such as STP, UTP, and coaxial cable
use pulses of electricity. Fiber optical cable uses pulses of light.
Some factors that can cause degradation of signals are RFI, EMI, and
flourescent lights.
EMI and RFI can be limited by shielding, cancelation, decreasing the size
of the conductors, and improve the insulation material.
The graphic depicts Cancelation.
Impedance is a complex electrical characteristic involving resistance, or
the opposition to the flow of electrons, and reactance, or the opposition
to canges in voltage and current.
Coaxial cable can run long distances without boosts than twisted pair, it
is less expensive than fiber-optic, and it is well known. But, coaxial is
think and difficult to work with.
{Lesson 23}
UTP - Unshielded twisted-pair. Four-pair wire medium used in a variety
of networks. UTP does not require the fixed spacing between connections
that is necessary with coaxial-type connections. There are five types of
UTP cabling commonly used: Category 1 cabling, Category 2 cabling,
Category 3 cabling, Category 4 cabling, and Category 5 cabling. Compare
with STP.
STP - Shielded twisted-pair. Two-pair wiring medium used in a variety
of network implementations. STP cabling has a layer of shielded insulation
to reduce EMI. Compare with UTP.
ARCnet - Attached Resource Computer Network. A 2.5-Mbps
token-bus LAN developed in the late 1970s and early 1980s by
Datapoint Corporation.
Token Ring - Token-passing LAN developed and supported by
IBM. Token Ring runs at 4 or 16 Mbps over a ring topology. Similar to
IEEE 802.5.
Polling - Access method in which a primary network device inquires, in
an orderly fashion, whether secondaries have data to transmit. The inquiry
occurs in the form of a message to each secondary that gives the
secondary the right to transmit.
Wiring closet - Specially designed room used for wiring a data or
voice network. Wiring closets serve as a central junction point for the
wiring and wiring equipment that is used for interconnecting devices.
Advantages of UTP:
A) UTP is easy to install, less expensive.
B) Small
Disadvantages of UTP:
A) More prone to intereference than anything else
The graphic depicts extended star topology.
Network architecture defines the rules of a network, and how the components
can interact and communicate. It can affect the choice of hardware because
different network architectures use different hardware devices.
Advantages of STP:
A) Better insulated than UTP.
Disadvantages of STP:
A) More expensive than UTP.
Advantages of OC(Fiber Optical):
A) Unaffected by EMI/RFI
B) Unaffected by crostalk
C) Can send data fastest
D) Can go farthest unboosted
E) Does not provide an entry for lighting strikes.
F) Thin
Disadvantages of OC:
A) Difficult to install
B) Expensive
{Lesson 24}
Journals are important because you keep the information you learn about the
job and, usually more important, information you learn on the job.
Four steps in designing a LAN are: study, selection and design,
implementation, and operation.
{Lesson 26}
The information you gather during investigation and analysis can affect
the choice of network media used, because some situautions may be more
effectively solved with UTP or STP and others with OC. Also, resource
constraints, such as budget, may prevent excessive use of OC.
Lesson 68:
{Lesson 27}
IEEE - Institute of Electrical and Electronics Engineers. Professional
organization whose activities include the development of communications
and network standards. IEEE LAN standards are the predominant LAN
standards today.
UL - Underwriters Laboratories. Independent agency within the United
States that tests product safety.
EIA - Electronic Industries Association. Group that specifies electrical
transmission standards. The EIA and TIA have developed numerous
well-known communications standards, including EIA/TIA-232 and
EIA/TIA-449. See also TIA.
TIA - Telecommunications Industry Association. Organization that
develops standards relating to telecommunications technologies. Together,
the TIA and the EIA have formalized standards, such as EIA/TIA-232, for
the electrical characteristics of data transmission. See also EIA.
IEEE 802.3 - IEEE LAN standard that specifies an implementation of
the physical layer and the MAC sublayer of the data link layer. IEEE
802.3 uses CSMA/CD access at a variety of speeds over a variety of
physical media. Extensions to the IEEE 802.3 standard specify
implementations for Fast Ethernet. Physical variations of the original IEEE
802.3 specification include 10Base2, 10Base5, 10BaseF, 10BaseT, and
10Broad36. Physical variations for Fast Ethernet include 100BaseT,
100BaseT4, and 100BaseX.
IEEE 802.5 - IEEE LAN standard that specifies an implementation of
the physical layer and MAC sublayer of the data link layer. IEEE 802.5
uses token passing access at 4 or 16 Mbps over STP cabling and is similar
to IBM Token Ring. See also Token Ring.
EIA/TIA-568 - Standard that describes the characteristics and
applications for various grades of UTP cabling. Since it originated,
additions have been made to this standard that include information on fiber
optic cable and link performance. The revised standard has been released
as EIA/TIA-568B. See EIA/TIA-568A. See also Category 1 cabling,
Category 2 cabling,Category 3 cabling, Category 4 cabling, Category
5 cabling, and UTP.
EIA/TIA-569 - Standard that defines and describes horizontal
pathways, telecommunications closets, backbone pathways, equipment
rooms, work stations, and entrance facilities for local area network
systems and, where applicable, the minimum requirements for them.
[CABLE CATEGORIES AND USES]
Category: Use:
1 used for telephone communications and is not suitable for
transmitting data.
2 cabling is capable of transmitting data at speeds up to 4
Mbps.
3 used in 10BaseT networks and can transmit data at speeds
up to 10 Mbps.
4 used in Token Ring networks and can transmit data at
speeds up to 16 Mbps.
5 used for running CDDI and can transmit data at speeds up
to 100 Mbps.
----------[ END OF LESSON 27 DEFINITIONS ]---------------
Standards important to networking media are: a) fire codes, b) building
codes, c) safety standards, and d) performance standards. Specifically,
IEEE 802.3 and 802.5, and EIA/TIA-568, and EIA/TIA-569.
Cabling specifications issued by the Underwriters Laboratories are
primarily concerned with safety standards, however, they also rate twisted
pair networking media for performance. In addition it is the Underwriters
Laboratories which established an identification program listing markings
for shielded and unshielded twisted pair networking media in order to
simplify the job of ensuring that materials used in LAN installations meet
specification.
The markings on the cable shown tell the type of cable, what
specifications it met, and some indicate the brand.
Some advantages of using EIA/TIA standards are multi-vendor, multi-product
support, and they allow the LAN designer room for options and expansion.
The EIA/TIA standard addresses six elements of cabling for LAN systems.
These are horizontal cabling, telecommunications closets, backbone
cabling, equipment rooms, work areas, and entrance facilities.
EIA/TIA-568B defines horizontal cabling as that which runs from the
telecommunications outlet to the horizontal cross-connect. This element
includes the networking media that is run along a horizontal pathway, the
telecommunications outlet or connector, the mechanical terminations in the
wiring closet, and the patch cords or jumpers in the wiring closet.
For the EIA/TIA standards for horizontal cabling please see above "CABLE
CATEGORIES AND USES"
{Lesson 28}
-------------[LESSON 28 HAS NO DEFINITIONS]--------
Category 3 UTP cable:
Category 4 UTP cable:
Category 5 UTP cable:
Coaxial Cable:
OC:
STP cable:
{Lesson 29}
Topology - Physical arrangement of network nodes and media within
an enterprise networking structure.
Bus topology - Linear LAN architecture in which transmissions from
network stations propagate the length of the medium and are received by
all other stations. Compare with ring topology, star topology, and tree
topology.
Star topology - LAN topology in which end points on a network are
connected to a common central switch by point-to-point links. A ring
topology that is organized as a star implements a unidirectional closed-loop
star, instead of point-to-point links. Compare with bus topology.
Extended star topology - Star topology where a central hub is
connected by vertical cabling to other hubs that are dependent on it. See
hierarchical star topology.
Bus - Common physical signal path composed of wires or other media
across which signals can be sent from one part of a computer to another.
Sometimes called highway.
Highway - Same as Bus.
Terminator - Device that provides electrical resistance at the end of a
transmission line to absorb signals on the line, thereby keeping them from
bouncing back and being received again by network stations.
-----------[END OF LESSON 29 DEFINITIONS]------------
In a Bus topology, the signal is transmitted in both directions from the
workstation to all nodes on that network segment until it reaches a
terminator which absorbs the signal so it doesnt "bounce" back.
A signal is absorbed by a terminator when it reaches the end of the line
in Bus topology.
In Bus ethernet, collision detection is used, when a collison occurs the
NIC card issues a backoff which delays transmission for a different amount
of time for each device.
Advantages of Bus topology:
A) Low cost of installation.
B) Media doesnt pass through devices.
Disadvantages of Bus topology:
A) High cost of maintenance.
B) Hard to diagnois problems
C) If the cable breaks, the network is dysfunctional.
{Lesson 31}
Active hub - Multiported device that amplifies LAN transmission
signals.
Passive hub - A device used to connect the networking media. It has
no repeater functionality.
Concentrator - See hub.
-----------[END OF LESSON 31 DEFINITIONS]-----------
Star Topology is where networking media run from a central hub out to each
device attached to the network.
The graphic depicts simple star topology.
Advantages of Star Topology:
A) Easiest to design.
B) Easy to maintaing.
C) Easy to diagnois problems.
D) Easy to expand the network.
E) Only the device attached to the line is disabled if the line breaks.
Disadvantages of Star Topology:
A) Expensive to setup.
B) Hub can fail rendering network inoperable.
{Lesson 32}
Attenuation - Loss of communication signal energy.
-----------[END OF LESSON 32 DEFINITIONS]----------
When Horizontal cabling runs exceed the EIA/TIA-568B recommended max.
length the data they carry may become irrecognizable because of low power.
Repeaters can resolve this by taking in the weakened singals and cleaning
them and boosting them.
{Lesson 33}
Access method - 1.) Generally, the way in which network devices
access the network medium. 2.) Software within an SNA processor that
controls the flow of information through a network.
CSMA/CD - Carrier sense multiple access collision detect.
Media-access mechanism wherein devices ready to transmit data first
check the channel for a carrier. If no carrier is sensed for a specific period
of time, a device can transmit. If two devices transmit at once, a collision
occurs and is detected by all colliding devices. This collision subsequently
delays retransmissions from those devices for some random length of time.
CSMA/CD access is used by Ethernet and IEEE 802.3.
Connectionless - Term used to describe data transfer without the
existence of a virtual circuit. Compare with connection-oriented. See also
virtual circuit.
Best-effort delivery - Describes a network system that does not
use a sophisticated acknowledgment system to guarantee reliable delivery
of information.
Token passing - Access method by which network devices access
the physical medium in an orderly fashion based on possession of a small
frame called a token.
IEEE 802.3i - Physical variation of the original IEEE 802.3
specification that calls for using Ethernet type signaling over twisted pair
networking media. The standard sets the signaling speed at 10 megabits
per second using a baseband signaling scheme transmitted over twisted
pair cable employing a star or extended star topology.
10Base2 - Mbps baseband Ethernet specification using 50-ohm thin
coaxial cable. 10Base2, which is part of the IEEE 802.3 specification, has
a distance limit of 185 meters per segment.
10Base5 - 10-Mbps baseband Ethernet specification using standard
(thick) 50-ohm baseband coaxial cable. 10Base5, which is part of the
IEEE 802.3 baseband physical layer specification, has a distance limit of
500 meters per segment.
10BaseF - 10-Mbps baseband Ethernet specification that refers to the
10BaseFB, 10BaseFL, and 10BaseFP standards for Ethernet over
fiber-optic cabling.
10BaseT - 10-Mbps baseband Ethernet specification using two pairs
of twisted-pair cabling (Category 3, 4, or 5): one pair for transmitting data
and the other for receiving data. 10BaseT, which is part of the IEEE 802.3
specification, has a distance limit of approximately 100 meters per
segment.
10Broad36 - 10-Mbps broadband Ethernet specification using
broadband coaxial cable. 10Broad36, which is part of the IEEE 802.3
specification, has a distance limit of 3600 meters per segment.
Baseband - Characteristic of a network technology where only one
carrier frequency is used. Ethernet is an example of a baseband network.
Also called narrowband.
----------[END OF LESSON 33 DEFINITIONS]----------
Ethernet network architecture uses CSMA/CD to send data on the network,
CSMA/CD waits a specified amount of time of inactivity on the network and
transmits its data.
Token ring architecture uses Token passing as its access mothod.
Token passing doesn't work on Ethernet architecture because the physcial
layout is different, and because the networks use different standards.
{Lesson 36}
Punch tool - Spring-loaded tool used for cutting and connecting wire
in a jack or on a patch panel.
---------[END OF LESSON 36 DEFINITIONS]----------
Surface mounted jacks can be mounted to the wall by means of an
adhesive-backed box, or screw mounted box. They cannot be moved once they
are mounted.
The picture shows a stripped category 4 unsheilded
twisted pair line tha is to be punched down on the
RJ-45 jack.
Flush mounting:
A) Plaster Crumbles
B) If there is a wide, wooden baseboard. Avoid using first 2",
the walls bottom plate will block your box.
C) Use box or low-voltage mounting bracket?
Preparation:
Notes: A) Plaster:
I) Use hammer and chizel to remove plaster.
II) Put template over holes (equally overlapping 3 pieces of
lath at top and bottom).
III) Use utility knife to trim plaster.
IV) Using an electric saw, cut away the full lath strip that is
exposed in the center of the opening (alternating between
sides). Be careful when you do this. If you attempt to cut all
the way through one side before cutting into the other side
the saw will cause the lath to vibrate when you make the second
cut. This can cause the plaster around the opening to crack and
come loose.
B) Drywall:
I) Mount 12" - 18" above floor.
II) Put 2 holes in location.
III) Check for obstructions (insert wire and rotate).
IV) Determine size of hole (use template).
V) Test box fit.
VI) Use box or low-voltage mounting bracket?
C) Wood:
I) Trace outline.
II) Make starter holes at each corner.
III) Use saw to cut from corner to corner.
Mounting:
Box: A) Feed cable through opening.
B) Push box into wall opening.
C) Tighten screws.
Low-voltage mounting bracket:
A) Put bracket against opening (smooth side out).
B) Push top and bottom flanges toward back.
C) Push first one up and other down.
To begin laying in the wires, first strip the jacket from the end of the
cable. Try not to strip any more of the cable jacket than is necessary,
approximately 1 1/2" to 2". Lay the wires in the center of the
jack. Next, separate out each pair of twisted wires. Untwist this pair of
wires. Lay the blue wire in the slot to the left that is labeled in blue.
Lay the second wire of this pair in the slot to the right that is labeled
in blue and white. Next, notice that the color used to code the next
slot on the right side of the jack is green. Locate the twisted pair that
contains the green wire. Untwist this pair of wires until enough is free
to work with. Lay the green wire in the slot to the right that is labeled
in green. Lay the second wire of this pair in the slot to the left that is
labeled in green and white. Continue in this fashion until all of the
wires have been matched to their corresponding color-coded slots in the
jack.
Wires are punched down in an RJ45 jack using a punch-down tool. Begin by
positioning the blade on the outside of the jack. After you have
completed punching down all the wires, place the clips on the jack and
tighten them.
{Lesson 38}
Cut sheet - A rough diagram indicating where cable runs are located
and the numbers of rooms they lead to.
EIA/TIA-606 - Administration standard for the telecommunications
infrastructure of commercial buildings. It includes the following
administration areas: terminations, media, pathways, spaces, and bounding
and grounding.
----------[END OF LESSON 38 DEFINITIONS]----------
Proper handling of cat. 5 UTP cable:
A) Strip only as much as required.
B) Maintain the twists as much as possible.
C) Never bend cable of 90degrees.
D) Use cable ties to cinch cables that run the same path together.
E) Don't pinch or kink cables.
F) Never exceed 25lbs of pull.
G) Secure the cable well.
To document cable runs use a cut sheet, which is a rough diagram that
shows where the cable runs are and the room numbers that they go to.
Labels on cables: Labeled at faceplat, housing or connection. Also can
be connector.
The picture is of a faceplate that is labled at the outlet.
{Lesson 39}
Raceway - Wall-mounted channel with a removable cover used to
support horizontal cabling.
Decorative raceway - Type of wall-mounted channel with
removable cover used to support horizontal cabling. Decorative raceway is
big enough to hold two cables.
Gutter - Type of wall-mounted channel with removable cover used to
support horizontal cabling. Gutter is big enough to hold several cables.
Tie-wraps - Plastic ties used for holding cables together or for holding
cables in place.
Ladder rack - Metal ladder that can be suspended from the ceiling. It
is used to support cable.
Telepole - Telescoping pole with a hook at one end. It is used to get
cable across a ceiling or attic quickly.
Fish tape - Retractable coil of steel tape used to guide cable through a
wall from above or below.
------------[END OF LESSON 39 DEFINITIONS]---------
Mounting cable on a wall, in a raceway:
A) It can be mounted with either adhesive backing or with screws.
B) lay the cable inside it.
C) Attache the top that is provided.
In a dropped ceiling:
A) Dont lay cable on ceiling, provide other means of support.
I) Use gutters or tie-wraps to keep wires together.
II) Use a ladder rack to hold wires.
B) Use a telepole to help string wires.
A gutter is a type of raceway, it is used to hold wires. Benefits of
using include that it holds wires well, and it is large enough to hold
several cables. Disadvantages of it include that even though it can hold
several cables, it has a limited number of cables that can be run through
it.
The picture shown is a staple gun, it is used to staple items to drywall
and wood. It should not be used to staple cables.
To fish cable through a wall:
A) From above:
I) Locate the wall's top plate.
II) Drill a 0.75" hole through the top plate.
III) Feed fish tape through the hole.
IV) Have a second person hook the tape on to the wire.
V) Have that person strip back about 1" of the jacket.
VI) Have that person bend wires around the hook of the fish tape.
VII) Use electrical tape to secure cable to fish tape.
VIII) Pull wire through hole.
B) From below:
I) Drill a 0.125" hole at an angle near the baseboard.
II) Mark the spot with a hanger.
III) Locate the wire in the basement.
IV) Mark a spot where the wall is located (2.25" from hole).
V) Drill a 0.75" hole.
Lesson 69:
{Lesson 41}
<----------[NO DEFINTIONS FOR LESSON 41]---------->
To string cable using a:
A) Telepole:
I) Extend pole.
II) Hook the cable to the end.
III) Pull cable across.
B) Pull string:
I) Attach multiple cables to the string.
II) Pull.
C) Fish tape:
I) Locate the wall's top plate.
II) Drill a 0.75" hole through the top plate.
III) Feed fish tape through the hole.
IV) Have a second person hook the tape on to the wire.
V) Have that person strip back about 1" of the jacket.
VI) Have that person bend wires around the hook of the fish tape.
VII) Use electrical tape to secure cable to fish tape.
VIII) Pull wire through hole.
Us
{Lesson 42}
MDF - Main distribution facility - Primary communications room for a
building. Central point of a star networking topology where patch panels,
hub, and router are located.
IDF Intermediate distribution facility - Secondary communications room
for a building using a star networking topology. The IDF is dependent on
the MDF.
Patch panel - An assembly of pin locations and ports which can be
mounted on a rack or wall bracket in the wiring closet. Patch panels act
like switchboards that connect workstations cables to each other and to
the outside.
Pin location - A color-coded slot on a patch panel. Cable wires are
punched down using a punch tool to make an electrical connection that
allows the network to function.
Port - 1.) Interface on an internetworking device (such as a router) 2.)
In IP terminology, an upper-layer process that is receiving
information from lower layers; 3.) To rewrite software or microcode so
that it will run on a different hardware platform or in a different
software environment than that for which it was originally designed; 4.) A
female plug on a patch panel which accepts the same size plug as an RJ45
jack. Patch cords are used in these ports to cross connect computers wired
to the patch panel. It is this cross connection which allows the LAN to
function.
<----------[END OF LESSON 42 DEFINITIONS]---------->
MDF's are the primary distribution facilities, the IDF's connect
to them.
A patch panel is located in a wiring closet, it is used to connect
devices.
To lay wires in a patch pannel, lay the wires in the patch pannel starting
from the left to the lowest unused one. Punch the wires down using a
punch down tool.
{Lesson 43}
TDR - Time domain relfectometer. Device capable of sending signals
through a network medium to check cable continuity, length, and other
attributes. TDRs are used to find physical layer network problems.
Time-domain reflectometry Technique of sending an electrical
signal down a cable and then timing the signal's reflection back from the
end of the cable.
Wire map - Feature provided by most cable testers. Used to test
twisted pair cable installations, it shows which wire pairs connect to
what pins on the plugs and sockets.
Signal injector - Device used to measure attenuation of a signal on a
network.
<----------[END OF LESSON 43 DEFINITIONS]---------->
A cable test can test to check that all the wires are in their correct
sequence. They can be used to test signal degradation.
If connections are bad at the telecommunications outlet, the response a
TDR will read the distance as shorter distances.
Wire maps can detect if the connections are in the wrong order, or crossed
pairs.
The graphic shows split pairs.
A signal injector measures attenuation of a signal.
Common causes of near-end cross talk:
A) Crossed pairs
B) Twisted pairs that have become untwisted
C) Cables pulled to tightly or bent at more than 90.
A noise level text can detect interference and narrow what the
interference is caused by.
"
When a cable tester is used to take a noise
reading on the cable, all cables should be
disconnected from the computer equipment.
Generally speaking, high reading levels, indicate
a problem. A simple way to locate the precise
source is to try unplugging electrical devices
until the source of the noise is found. However,
be aware that this does not always work.
"
{Lesson 44}
<------------[NO DEFINTIONS IN LESSON 44]---------->
To build an ethernet star topology LAN:
A) Determine the needs of your company for present and 5yrs in the future.
B) Locate a central point for the MDF.
C) Run the horiz. cabling from the MDF to the workstation outlet.
{Lesson 46}
<------------[NO DEFINTIONS IN LESSON 46]---------->
EIA/TIA-569 specifies that there be a minimum of one wiring closet per floor
and states that additional wiring closets should be provided for each area
up to 1000 square meters when the floor area served exceeds 1000 square
meters or the horizontal cabling distance exceeds 90 meters.
Wiring closets must have suffcient power and HVAC (heating, vent., A/C) and
must adhere to the guidlines governing the types of walls, floors, and ceiling
acceptable temprature and humidty.
All interior walls on which equipment will be mount should be covered with
0.75" plywood that is raised away from the underlying wall a min of 1.75".
If the wiring closet has a PBX, it should be covered from the floor to the
ceiling with 0.75" plywood and a min of 15 feet of wall space for terminations
and equip. The ceiling should not be dropped or false for security reasons.
MDF's floors must be able to bear a min. of 250lb/ft^2. IDF's floors should
be able to bear 100lb/ft^2. Where possible rooms should have raised floors,
if they cannot have a raised floor there should be a 12" ladder rack to
support all proposed equipment and cable.
No water or steam pipes should run through or above the room (except a
sprinkler if required by fire codes). Relative humidity should remain
between 30% and 50%. The temprature should maintian aprrx. 70F when
fully operational.
A wall switch to turn the room lighting on and off should be immediately
inside the door. Fluorescent lightng should be avoided.
MDFs must have atleast 1 duplex power outlet every 10'. IDFs must have atleast
2 per wall.
The door should be atleast 3' wide and should swing open out of the room and
lock from the outside.
All wires leaving the room should leave via 4" conduits.
POP is point of presence, it is where the line that will connect the
network to the internet is located.
{Lesson 47}
Catchment area - Zone that falls within area that can be served by
an internetworking device such as a hub.
<----------[END OF LESSON 47 DEFINTIONS]---------->
You determine the catchment area to a) locate which computers will use
which wiring closets, and b) determine where additional wiring closets
will need to be located.
A scale model of a building is depicted in the picture.
The location and number of wiring closets needed is determined using
EIA/TIA specifications of one per floor minimum, and within a radius
supported in the catchement zone.
{Lesson 49}
Backbone - The part of a network that acts as the primary path for
traffic that is most often sourced from, and destined for, other networks.
Backbone cabling - Cabling that provides interconnections
between wiring closets, wiring closets and the POP, and between buildings
that are part of the same LAN.
Vertical cabling - Backbone cabling. See backbone cabling.
Hierarchical star topology - Extended star topology where a
central hub is connected by vertical cabling to other hubs that are
dependent on it. See extended star topology.
HCC - Horizontal cross-connect. Wiring closet where the horizontal
cabling connects to a patch panel which is connected by backbone cabling
to the main distribution facility.
MCC Main cross-connect. Wiring closet that serves as the most central
point in a star topology and where LAN backbone cabling connects to the
Internet.
ICC Intermediate cross-connect. IDF that connects the horizontal
cross-connect to the main cross-connect. See horizontal cross-connect.
See main cross-connect.
<----------[END OF LESSON 49 DEFINTIONS]---------->
Multi-building or multi-floored LAN's would require more than one wiring
closet, also large buildings.
Backbone cabling is used to connect wiring closets.
EIA/TIA-568 specifies four types of networking media that can be used for
backbone cabling:
100 ohm UTP
150 ohm STP
50 ohm Coaxial Cable (not recommened)
62.5/125 micron optical fiber, single fiber.
Hierarchical star topology is when an MDF connects to an IDF and other
IDF's are connected to that IDF.
HCC's are horiz. cross connects, they connect a patch pannels to MDF's
ICC's are used to connect IDF's to MDF's, MCC are the main wiring closets.
{Lesson 51}
AC - Alternating current. Electrical current that reverses its direction
regularly and continually. It is the form of electrical power found in
residential and commercial buildings.
DC - Direct Current. Electrical current that travels in only one
direction. Direct current is generally used in electronic circuits.
Ground - Electrically neutral contact point.
Conductor - Any material with a low resistance to electrical current.
Any material capable of carrying an electrical current. See insulator.
Insulator - Any material with a high resistance to electrical current. See
conductor.
Safety ground wire - Circuit wire that connects to a local earth
ground and the chassis of an electrical appliance or device via an
electrical outlet and plug. It is used to ensure that no voltage potential
exists between the chassis of the electrical device and the earth ground.
Neutral wire - Circuit wire that is connected to an earth ground at the
power plant and at the transformer.
Hot wire - Ungrounded lead wire that connects the transformer and
electrical devices or appliances via an electrical outlet and power plug.
<----------[END OF LESSON 52 DEFINITIONS]---------->
Electrical devices are ground in computer devices using a ground wire.
A safety grounds are where shocks are redirected.
A neutral wire is where current flows after leaving the application.
A hot wire is where the current flows from the power plant.
A safety ground is a short path to ground that electricity can take rather
than shocking the users.
Some large buildings require more than one ground.
{Lesson 52}
<----------[NO DEFINTIONS FOR LESSON 52]---------->
If the ground wire for devices in one location has a slightly different
potential to the common and hot wires than the ground wire for devices in
the second location, the closed circuit produced by the use of UTP cable
will allow electrical current to flow from the negative source to the
positive source. Anyone touching the chassis of a device on the network
could receive a nasty shock in such a scenario.
When multiple buildings are to be networked, it is highly desirable to use
fiber-optic cable as the backbone to avoid dangerous circuits between
buildings.
UTP cable can facilitate lightning by absorbing excess voltage and catch
fire inside the building.
Lesson 70:
{Lesson 53}
<-----[LESSON 53 DEFS END]----->
To develop a wiring plan for Ethernet extended star topology, determin
where all your nodes are and which hubs they are connected to (using
cachement area) and eliminate unnessicary hubs if possible.
{Lesson 54}
Digital signal - Language of computers comprising only two states, on
and off which are indicated by a series of voltage pulses.
Signal reference ground - Reference point used by computing devices to
measure and compare incoming digital signals to.Reference point used by
computing devices to measure and compare incoming digital signals to.
<-----[LESSON 54 DEFS END]----->
The distance between the POP and the MDF can impact the selection of
networking media, because if the distance is longer than specific type of
cable can run unboosted, that type of cabel cant be used.
If there is a multiple earth grounds are present, then copper lines may
not be an option because there wouldnt be a common signal refernce ground.
ICC's are intermediate cross connects, they are used between the MDF and
an IDF.
HCC's are horizontal cross connects, they are used between an distribution
facilite and a workstation.
{Lesson 56}
<-----[LESSON 56 DEFS END]----->
Data is transmited over a network using digital signals by converting the
the binary representation of the data into the presence or absence of
voltage (1 and 0 respectively).
When there is a link between the the electrical ground and the signal
reference ground, the data may be come corrupted and unrecognizable.
Electrical noise can effect digital signals by interefering with
transmission and making the signal unrezognizable.
In order to avoid the problem of electrical noise
described above, it is important to work closely
with your electrical contractor and the power
company. This will enable you to get the best
and shortest electrical ground. One way to do
this is to investigate the costs of getting a single
power transformer dedicated to your LAN
installation area.
{Lesson 57}
Normal mode - Term used to describe problems between the hot
and neutral wires on a power line. See common mode.
Common mode - Term used to describe problems involving either
the hot or neutral wires and the safety ground wire on a power line. See
normal mode.
UPS - Uninterruptable power supply. Backup device designed to
provide an uninterrupted power source in the event of a power failure.
They are commonly installed on al file servers and wiring hubs.
Surge - Any voltage increase above 110 % of the normal voltage
carried by a power line. See sag, spike, and oscillation.
Spike - Any power impulse lasting between .5 and 100 microseconds
and possessing an amplitude over 100 % of peak power line voltage. See
surge, sag, and oscillation.
Sag - Any decrease of below 80% in the normal voltage carried by a
power line. A sag is sometimes referred to as a brownout. See surge,
spike, and oscillation.
Oscillation - Secondary signal on top of the 60-Hz waveform. It has a
magnitude that ranges from 15 % to 100 % of the normal voltage carried
on the power line. See surge, spike, and sag.
Ground loop - Arrangement that exists when a multi-path connection
exists between computers. Usually this occurs when computers are
connected to each other through a ground wire and when computers are
attached to the same network using twisted pair cable.
<-----[LESSON 57 DEFS END]----->
Common causes of surges and spikes are lightning strikes and the cycling
of office equipment.
A spike or a surge can literally wreak havoc on
any type of sensitive electronic equipment
including networking devices. Consequences of
electrical surges and spikes can be severe.
Possibilities include lockups, loss of memory,
problems in retrieving data, altered data and
garbling.
A surge supressor should be placed on all devices on the network to avoid
ground loops.
The problem of sags and brownouts can only be addressed with a UPS
(uninteruptible power supply).
The only way to solve Oscillation is to rewire.
The picture shows a typcial ground loop.
{Lesson 58}
MOV - Metal oxide varistor. Voltage clamping surge suppressor capable
of absorbing large currents without damage.
<-----[LESSON 58 DEFS END]----->
The surge suppressor shown in picture 2 is the best placement.
At a minimum every network file server should
be provided with power backup. If power wiring
hubs are required, then they must also be
supported with power backup. Finally, in
extended star topology networks where
internetworking devices such as bridges and
routers are used, power backup must be
provided to them as well in order to avoid
failures in the system.
UPSs can handle short power outages of a few minutes.
A backup generator should be used if power is needed for extended periods
of time beyond what a UPS can provide.
A number of vendors have developed UPS. You
will find that these differ in the following ways:
the power storage capacity of the batteries, the
power delivery capability of the inverter, and
whether the inverter is designed to operate all
the time or only when the input voltage reaches
a specific level.
Offline UPSs monitor the power and if it drops they switch to batteries.
Online UPSs sendpower to the UPS batteries keeping them charged and draw
power from them at all times.
{Lesson 59}
<-----[LESSON 59 DEFS END]----->
MOV surge suppressors are wall mounted devices usually.
{Lesson 61}
SNMP - Simple Network Management Protocol. Network management
protocol used almost exclusively in TCP/IP networks. SNMP provides a
means to monitor and control network devices, and to manage
configurations, statistics collection, performance, and security.
CMIP - Common Management Information Protocol. OSI network
management protocol created and standardized by ISO for the monitoring
and control of heterogeneous networks.
MIB - Management Information Base. Database of network management
information that is used and maintained by a network management
protocol such as SNMP or CMIP. The value of a MIB object can be
changed or retrieved using SNMP or CMIP commands. MIB objects are
organized in a tree structure that includes public (standard) and private
(proprietary) branches.
MIB collection - Polling technique used by the SNMP protocol to
gather information needed to monitor the network.
MIB reporting - Technique used by the CMIP protocol to obtain
information needed to monitor the network. It is dependent upon network
devices to initiate reports regarding their status to a central monitoring
station on the network.
Network analyzer - Network monitoring device that maintains
statistical information regarding the status of the network and each device
attached to it. More sophisticated versions using artificial intelligence can
detect, define, and fix problems on the network.
<-----[LESSON 61 DEFS END]----->
An inventory allows you to take stock of all of
the network's hardware and software. Ideally,
this information should be obtained when the
hardware and software is purchased and before
it is set up. This will save you time and effort
and reduce the amount of inconvenience
experienced by network end users.
The graphic shows information that would be present in a facility audit.
Where all the nodes are, room number, IP and MAC addresses.
A facility audit allows you to note where
everything is. It should include the cabling,
work stations, printers, and internetworking
devices such as hubs, bridges, and routers. In
short, it should provide detailed information
about the location of all of the network's
components. Ideally, all of this information
should have been recorded at the time the LAN
was installed.
An operational audit allows you to view the
day-to-day activity on the LAN. It requires the
use of specialized software and hardware. In
addition to a network monitor, an operational
audit may also include the use of devices such
as a network analyzer, a time domain reflectors,
breakout boxes, power meters, and an oscillator.
Devices such as network monitors and analyzers
use specialized software to perform their
functions.
SNMP sends a query to each work station and each station responds with its
status.
MIB collection is shown in the graphic.
MIB reporting is shown in the graphic.
{Lesson 62}
<-----[LESSON 62 DEFS END]----->
An efficiency audit will allow you to determine
that the network is performing to its potential.
Like the operational audit, this audit is best
performed once the network has begun to
provide services to its clients. It, too, will need
to be performed using the network management
tools discussed.
A security audit reviews what the security
requirements of the network are and what kind
of software and hardware security system best
meets them. Only observation and experience in
how the network and its clients use and access
data will provide you with the information
needed to complete this audit.
Notwork analyzers offers a more sophisticated level of service than
a network monitor can. In fact, in some instances
these devices are so sophisticated and
intelligent that they not only detect and identify
problems such as bottlenecks, they fix them as
well.
Requests for help should be documented in five parts:
1) Assign an ID # to the request
2) Prelim. information (who, time, method of report)
3) On-site information (power on site, temp, humidity)
4) Information regarding how it was fixed, on-site or taken to shop.
5) Summary of all work done, type of problem (hw/sw/user)
Heirachy of troubleshooting procedures:
A) Check user
B) Check hardware
C) Check software
{Lesson 63}
<-----[LESSON 63 DEFS END]----->
Periodic evaluations of the network are
important maintenance and prevention tools that
can help ensure that it continues to operate at
an acceptable level.
Procedure for changing the system:
A) Reviewers review request
B) Reviewers submit change requests to network admin
C) Network admin implements changes if neccisary.
A request for change should be considered an evolving document because it
can be changed at anytime the adminstrator feels that the system is not
preforming at itz peak potential.
##########################################################################
#### END OF SEMESTER 1 (11/02/98) ########################################
##########################################################################
The network model was divided into layers to:
A) Reduce complexity
B) Standardize interfaces
C) Facilitate modular engineering
D) Ensure interoperable technology
E) Accelerates evolution
F) Simplifies teaching and learning
Layers of the OSI model and their functions:
Application - The application layer
provides network services to user
applications. For example, a word
processing application is serviced by file
transfer services at this layer.
Presentation - This layer provides data
representation and code formatting. It
ensures that the data that arrives from the
network can be used by the application,
and it ensures that information sent by the
application can be transmitted on the
network.
Session - This layer establishes, maintains,
and manages sessions between
applications.
Transport - This layer segments and
reassembles data into a data stream. This
layer uses the TCP protocol.
Network - This layer determines the best
way to move data from one place to
another. The router operates at this layer.
This layer uses the Internet Protocol
addressing scheme.
Data Link - This layer provides physical
transmission across the medium. It
handles error notification, network
topology, and flow control. This layer
uses the Media Access Control (MAC)
address.
Physical - This layer provides the
electrical, mechanical, procedural, and
functional means for activating and
maintaining the physical link between
systems. This layer uses the physical
media like twisted pair, coaxial, and
fiber-optic cable.
|
\|/
7) Application -> Network processes to application
6) Presentation -> Data representation
5) Session -> Interhost communication
4) Transport -> End-to-end connections
3) Network -> Addresses and best path
2) Data link -> Access to media
1) Physical -> Binary transmission
Each layer's protocol exchanges information with other systems on the same
layer. Each layer provides it serverices to higher/lower layers.
Steps in data encapsulation:
1) Data
2) [Segment Header] + [Data]
3) [Network Header] + [Segment Header] + [Data]
4) [Frame Header] + [Network Header] + [Segment Header] + [Data] +
[Frame Trailer]
5) Converted to binary.
During encapsulation, the network header is added to the data after the
segment header.
Lesson 2:
Ethernet was the first of the major LAN technologies, it runs the largest
number of LANs; Token ring from IBM, it followed Ethernet and is now
widely used in a large # of IBM networks; FDDI, high speed also using reng
topology is now a popular campus LAN.
Lesson 3:
Blah
Lesson 4:
Charectaristics of a WAN:
A) The network operates beyond the local
LAN’s geographic scope. It uses the
services of carriers such as Regional Bell
Operating Companies (RBOCs), Sprint,
and MCI.
B) WANs use serial connections of various
types to access bandwidth over wide-area
geographies.
C) By definition, the WAN connects devices
separated by wide areas. WAN devices
include:
Routers that offer many services
including internetworking and
WAN interface ports.
Switches that connect to WAN
bandwidth for voice, data, and
video communication.
Modems that interface voice-grade
services; channel service
units/digital service units
(CSU/DSU) that interface T1/E1
services; Terminal
Adapters/Network Termination 1
(TA/NT1) that interface Integrated
Services Digital Network (ISDN)
services.
Communication servers that
concentrate dialin and dial-out user
communication.
WAN - Wide-area network. Data communications network that serves users
across a broad geographic area and often uses transmission devices
provided by common carriers. Frame Relay, SMDS, and X.25 are
examples of WANs. Compare with LAN and MAN.
PTT - Post, Telephone, and Telegraph. Government agency that provides
telephone services. PTTs exist in most areas outside North America and
provide both local and long-distance telephone services.
ITU-T - International Telecommunication Union Telecommunication
Standardization Sector (ITU-T) (formerly the Committee for Internatiional
Telegraph and Telephone ([CCITT]). An international organization that
develops communication standards. See also CCITT.
ISO - International Organization for Standardization. International
organization that is responsible for a wide range of standards, including
those relevant to networking. ISO developed the OSI reference model, a
popular networking reference model.
IETF - Internet Engineering Task Force. Task force consisting of over 80
working groups responsible for developing Internet standards. The IETF
operates under the auspices of ISOC. See also ISOC.
EIA - Electronic Industries Association. Group that specifies electrical
transmission standards. The EIA and TIA have developed numerous
well-known communications standards, including EIA/TIA-232 and
EIA/TIA-449. See also TIA.
DTE - data terminal equipment. Device at the user end of a user-network
interface that serves as a data source, destination, or both. DTE connects
to a data network through a DCE device (for example, a modem) and
typically uses clocking signals generated by the DCE. DTE includes such
devices as computers, protocol translators, and multiplexers. Compare with
DCE.
DCE - Data communications equipment (EIA expansion) or data
circuit-terminating equipment (ITU-T expansion). The devices and
connections of a communications network that comprise the network end
of the user-to-network interface. The DCE provides a physical connection
to the network, forwards traffic, and provides a clocking signal used to
synchronize data transmission between DCE and DTE devices. Modems
and interface cards are examples of DCE. Compare with DTE.
CSU - Channel service unit. Digital interface device that connects end-user
equipment to the local digital telephone loop. Often referred to together
with DSU, as CSU/DSU. See also DSU.
DSU - Data service unit. Device used in digital transmission that adapts the
physical interface on a DTE device to a transmission facility such as T1 or
E1. The DSU is also responsible for such functions as signal timing. Often
referred to together with CSU, as CSU/DSU. See also CSU.
EIA/TIA-232 - Common physical layer interface standard, developed by
EIA and TIA, that supports unbalanced circuits at signal speeds of up to 64
kbps. Closely resembles the V.24 specification. Formerly known as
RS-232.
EIA/TIA-449 - Popular physical layer interface developed by EIA and
TIA. Essentially, a faster (up to 2 Mbps) version of EIA/TIA-232 capable
of longer cable runs. Formerly called RS-449. See also EIA-530.
V.24 - ITU-T standard for a physical layer interface between DTE and
DCE. V.24 is essentially the same as the EIA/TIA-232 standard. See also
EIA/TIA-232.
V.35 - ITU-T standard describing a synchronous, physical layer protocol
used for communications between a network access device and a packet
network. V.35 is most commonly used in the United States and in Europe,
and is recommended for speeds up to 48 Kbps.
X.21 - ITU-T standard for serial communications over synchronous digital
lines. The X.21 protocol is used primarily in Europe and Japan.
G.703/G.704 - ITU-T electrical and mechanical specifications for
connections between telephone company equipment and DTE using BNC
connectors and operating at E1 data rates.
EIA-530 - Refers to two electrical implementations of EIA/TIA-449:
RS-422 (for balanced transmission) and RS-423 (for unbalanced
transmission). See also RS-422, RS-423, and EIA/TIA-449.
HDLC - High-Level Data Link Control. Bit-oriented synchronous data
link layer protocol developed by ISO. Derived from SDLC, HDLC
specifies a data encapsulation method on synchronous serial links using
frame characters and checksums. See also SDLC.
Frame Relay - Industry-standard, switched data link layer protocol that
handles multiple virtual circuits using HDLC encapsulation between
connected devices. Frame Relay is more efficient than X.25, the protocol
for which it is generally considered a replacement. See also X.25.
PPP - Point-to-Point Protocol. A successor to SLIP, PPP provides
router-to-router and host-to-network connections over synchronous and
asynchronous circuits. See also SLIP.
ISDN - Integrated Services Digital Network. Communication protocol,
offered by telephone companies, that permits telephone networks to carry
data, voice, and other source traffic. See also BISDN, BRI, N-ISDN, and
PRI.
Lesson 5:
Noted: Network address = IP Address.
Routed protocol - Protocol that can be routed by a router. A router must
be able to interpret the logical internetwork as specified by that routed
protocol. Examples of routed protocols include AppleTalk, DECnet, and
IP.
Routing protocol - Protocol that accomplishes routing through the
implementation of a specific routing algorithm. Examples of routing
protocols include IGRP, OSPF, and RIP.
Header - Control information placed before data when encapsulating that
data for network transmission. Compare with trailer. See also PCI.
Queue - 1.) Generally, an ordered list of elements waiting to be processed.
2.) In routing, a backlog of packets waiting to be forwarded over a router
interface.
Hop - Term describing the passage of a data packet between two network
nodes (for example, between two routers). See also hop count.
Path switching:
Sent with dest IP of final dest and MAC address of router as dest, router
changes MAC address to MAC addr of next hop (final dest or not)
Routers are capable of supporting multiple
independent routing protocols and maintaining
routing tables for several routed protocols
concurrently. This capability allows a router to
deliver packets from several routed protocols over
the same data links.
Static route - Route that is explicitly configured and entered into the
routing table. Static routes take precedence over routes chosen by dynamic
routing protocols.
Dynamic routing - Routing that adjusts automatically to network topology
or traffic changes. Also called adaptive routing.
Stub network - Network that has only a single connection to a router.
Default route - Routing table entry that is used to direct frames for which
a next hop is not explicitly listed in the routing table.
IGRP, using Equal Cost Load Balancing, when there are multiple paths,
splits the traffic equally. Using unequal cost load balancing, the
traffic can be split asymetrically.
Bandwidth - The difference between the highest and lowest frequencies
available for network signals. The term is also used to describe the rated
throughput capacity of a given network medium or protocol.
Delay - The time between the initiation of a transaction by a sender and
the first response received by the sender. Also, the time required to move a
packet from source to destination over a given path.
Reliability - Ratio of expected to received keepalives from a link. If the
ratio is high, the line is reliable. Used as a routing metric.
Hop count - Routing metric used to measure the distance between a
source and a destination. RIP uses hop count as its sole metric. See also
hop and RIP.
Cost - Arbitrary value, typically based on hop count, media bandwidth, or
other measures, that is assigned by a network administrator and used to
compare various paths through an internetwork environment. Cost values
are used by routing protocols to determine the most favorable path to a
particular destination: the lower the cost, the better the path. Sometimes
called path cost. See also routing metric.
Distance vector routing algorithm - Class of routing algorithms that
iterate on the number of hops in a route to find a shortest-path spanning
tree. Distance vector routing algorithms call for each router to send its
entire routing table in each update, but only to its neighbors. Distance
vector routing algorithms can be prone to routing loops, but are
computationally simpler than link state routing algorithms. Also called
Bellman-Ford routing algorithm. See also link state routing algorithm and
SPF.
Link state routing algorithm - Routing algorithm in which each router
broadcasts or multicasts information regarding the cost of reaching each of
its neighbors to all nodes in the internetwork. Link state algorithms create a
consistent view of the network and are therefore not prone to routing
loops, but they achieve this at the cost of relatively greater computational
difficulty and more widespread traffic (compared with distance vector
routing algorithms). Compare with distance vector routing algorithm.
Convergence - The speed and ability of a group of internetworking
devices running a specific routing protocol to agree on the topology of an
internetwork after a change in that topology.
Loop - Route where packets never reach their destination, but simply cycle
repeatedly through a constant series of network nodes.
Count to infinity - Problem that can occur in routing algorithms that are
slow to converge, in which routers continuously increment the hop count to
particular networks. Typically, some arbitrary hop-count limit is imposed to
prevent this problem.
To avoid infinite loops, a max. hop count is enforced.
Holddown - State into which a route is placed so that routers will neither
advertise the route nor accept advertisements about the route for a specific
length of time (the holddown period). Holddown is used to flush bad
information about a route from all routers in the network. A route is
typically placed in holddown when a link in that route fails.
LSA - Link-state advertisement. Broadcast packet used by link-state
protocols that contains information about neighbors and path costs. LSAs
are used by the receiving routers to maintain their routing tables. Sometimes
called a link-state packet (LSP).
IS-IS - Intermediate System-to-Intermediate System. OSI link-state
hierarchical routing protocol based on DECnet Phase V routing whereby
ISs (routers) exchange routing information based on a single metric to
determine network topology. Compare with Integrated IS-IS. See also
ES-IS and OSPF.
The balanced hybrid routing protocol uses
distance vectors with more accurate metrics to
determine the best paths to destination networks.
However, it differs from most distance vector
protocols by using topology changes to trigger
routing database updates.
Ex of hybrid routing proto. IS-IS and EIGRP
File server - Node or software program that provides services to clients.
See also back end, client, and front end.
Routers are active and intelligent network
nodes and thus can participate in managing the
network. Routers manage networks by providing
dynamic control over resources and supporting
the tasks and goals for internetworks:
connectivity, reliable performance, management
control, and flexibility.
Lesson 14:
Access lists restrict access to systems by protocol, saddr, daddr, sport,
dport.
Access list - 1.) List kept by Cisco routers to control access to or from
the router for a number of services (for example, to prevent packets with a
certain IP address from leaving a particular interface on the router). 2.)
Command that creates an entry in a standard traffic filter list.
Access lists are evaluated from the top to the bottom. Upon reaching a
matching statement no futher checking is done.
Access rules are steup in Config mode.
syntax: access-list ACCESS# [permit|deny] [test conditions]
Adding rules to interfaces is done in interface config mode
syntax: ip access-group ACCESS# [in|out]
test conditions = 'source mask' for standard access lists
test conditions = 'proto source mask dest mask [operator operand][established]
operator = lt,gt,eq,neq
operand = port number
established = allows filtering after clearing ack bit
Access lists use 0's to mean matching.
172.30.16.0 mask: 0.0.15.255 = 0.0.0.0
172.30.31.255 mask: 0.0.15.255 = 0.0.15.255
any is the abbrv. for '0.0.0.0 255.255.255.255'
host is th eabbrv for '0.0.0.0' as mask
Named access lists (Cisco IOS 11.2+)
ip access-list [standard|extended] name
[no] [permit|deny] [test conditions (see above)]
Access lists can act as firewalls
show ip <interface> Shows if any access lists are applied to an interface.
show access-lists Shows access lists and their rules
Cisco.Defs.txt is my "Engineer's Notebook" from Certified Advanced Networking Semesters I and II. |