CIS 3043 –
Midterm #2 Review
Instructor: Sal Aurigemma
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Test Prep Suggestions
Use this presentation to narrow down the material.
Other concepts may certainly appear, but this should help focus your review
Read the book. You know… the textbook for this class. See syllabus if confused… yes, there is a syllabus, it’s on Harvey… yes, we use Harvey in this class.
Review all of the lecture slides. These are on Harvey under Course Content
Use the book to fill in any gaps and clarify concepts.
Did you know the text has some great questions throughout the material?
LAN vs WAN; major components
UTP: Distances, quality, how to read nomenclature
Clock cycle time, 1’s & 0’s on UTP vs fiber, regeneration
UTP propagation effects; fiber propagation effects
Ethernet Frame, field purposes, switching decisions
RSTP = IEEE nomenclature & why do we care?
VLAN = IEEE nomenclature & why do we care?
POE = how much power? Why do we care?
Components of 802.1X, why is it important?
Chapter 5
© 2013 Pearson
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RSTP = ieee 802.1w
VLAN = 802.1q
802.1x = port based access control
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5.24 Advanced Ethernet Capabilities
Power over Ethernet (POE)
Switches can supply power to devices via UTP.
(Wired telephone systems and USB ports already do this.)
Less expensive than
supplying power
separately.
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5.24 Advanced Ethernet Capabilities
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5.7 Physical layer standards
Physical layer standards govern
Connectors & plugs
Transmission media
Signaling
Great short answer question
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Transmission Media
4-pair U T P
8 copper wires organized as four pairs whose two wires are twisted around each other
Carries signals as voltage, etc. changes
Optical Fiber
Carries signal pulses through glass
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UTP Propagation Effects
Propagation Effect(s) Impact Installation Discipline
Attenuation Signal may become too low to be received properly. Limit cord distance to 100 m
Noise Random electromagnet energy in the wire (noise) adds to the signal and may produce errors.
Terminal crosstalk interference Interference by other wire pairs in the cord is crosstalk interference.
Crosstalk interference at the two ends where the wires are untwisted is terminal crosstalk interference. Major problem Limit untwisting of the wires to 1.25 cm (0.5 in)
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© 2013 Pearson
Great short answer question
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5.12 Ethernet Signaling Standards
Ethernet Signaling Standard Speed Cable Quality Category Maximum Cord Length
100BASE-TX 100 M b p s Cat 5e, 6, 6A 100 meters
1000BASE-T 1 G b p s Cat 5e, 6, 6A 100 meters
2.5GBASE- t to the power of a 2.5 G b p s Cat 5e, 6, 6A 100 meters
5GBASE-t to the power of a 5 G b p s Cat 5e, 6, 6A 100 meters
10GBASE-T 10 G b p s Cat 6 55 meters
10GBASE-T 10 G b p s Cat 6A 100 meters
a Developed in response to growing access point speeds.
Category (C a t) is a designation of U T P Quality
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LAN versus Carrier Fiber
Characteristic LAN Fiber Carrier WAN Fiber
Primary Distance Limitation Modal Dispersion Absorptive Attenuation
Quality Metric Modal Bandwidth (MHz-km) Not Applicable
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© 2013 Pearson
5.27 Failures and Backup Links (2 of 2)
802.1w
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5.28 Virtual L A N s (V L A N s)
V L A N s segregate traffic, creating security that can be broken but that is quite good.
802.1q
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5.29 Initial User Authentication with 802.1X
802.1X Authentication:
Supplicant must be verified by an authentication server before being allowed to use the workgroup switch to which it is attached.
Attacker cannot walk up to any Ethernet wall jack, plug in, and bypass the firewall
(Radius)
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5.29 Switch-To-Switch Security: 802.1A E
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Chapter 6 – Wireless I
Wireless propagation problems
802.11n vs 802.11ac
Frequency Hopping Spread Spectrum (FHSS) protocol
Wireless “media access” protocols
Non-overlapping channels in 2.4 GHz & 5 GHz
QAM
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6.5 Wireless Propagation Problems
Two forms of attenuation
Two grow worse at higher frequencies
Great short answer question
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6.15: Orthogonal Frequency Division Multiplexing
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6.17 Wi-Fi Wireless LAN with Multiple Access Points (3 of 3)
802.11r
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CSMA/CA is Mandatory
It is the default MAC method.
It is more efficient than RTS/CTS.
RTS/CTS
Is usually optional.
Is good if two or more client stations cannot hear each other.
It will prevent them from transmitting at the same time.
© 2013 Pearson
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Comparison
Great short answer question
Be able to break down CSMA/CA + ACK acronym to explain, basically how it works.
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Channel Bandwidth
Channel bandwidth is the highest frequency in a channel minus the lowest frequency.
An 88.0 MHz to 88.2 MHz channel has a bandwidth of 0.2 MHz (200 kHz).
Higher-speed signals need wider channel bandwidths.
6.10: Channel Bandwidth and Transmission Speed
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The 5 GHz Service Band
More bandwidth, so between 11 and 24 non-overlapping 20 MHz channels
Makes it easy to have nearby access points operate on non-overlapping channels
Increasing channel bandwidth in newer standards reduces the number of possible channels
6.11 2.4 GHz and 5 GHz Service Band
https://wifinigel.blogspot.com/2018/05/the-5ghz-problem-for-wi-fi-networks-dfs.html
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5GHz & Dynamic Frequency Selection (DFS)
Remember DFS from the Chapter 6 video?
DFS documents reference specific requirements for anything within 35km (21 miles) of Doppler Radar (TDWR) locations. Radar systems protected by the DFS standard come in many forms, including radar on boats, radars for TV weather stations, and military radars.
Non-DFS channels at 40MHz:
36 , 44, 149, and 157
DFS becomes a bigger issue at wider channel bandwidth (802.11ac Wave 2)
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Be able to describe, in basic terms, what is DFS, why it matters, when it matters most, and how to deal with it.
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Today’s Main 802.11 Wi-Fi Transmission Standards
802.11n
Operates in both the 2.4 G H z and 5 G H z bands
40 M H z channels but drops back to 20 M H z if it senses interference
MIMO
802.11a c
Add channel bandwidths of 80 M H z or 160 M H z
Therefore much higher speeds than 802.11n
Can only operate in the 5 G H z band because will not fit in the 2.4 G H z band
However, because channels are wider, there are fewer channels in the 5 G H z service band
Multi-user MIMO capable
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6.21 Number of Channels in the 5 G H z Unlicensed Radio Band
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6.22 Characteristics of Major 802.11 Wi-Fi Standards (1 of 3)
Characteristic 802.11n Dual Band 802.11ac
Rated Speed 100 M b p s to 600 M b p s 433 M b p s to 6.9 G b p s
Common Throughput 2018 300 M b p s 1.5 G b p s
Status Widely used Widely used and dominates sales
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Standard Channels in 5 GHz Band in the USA
802.1g NA (2.4 GHz only)
802.11a 20-25
802.1n 20-25 at 20 MHz
8-12 at 40 MHz
802.1ac 4-6 at 80 MHz
1-2 at 160 MHz
Copyright © 2015 Pearson Education, Inc.
6.21 Major 802.11 Wi-Fi Standards
Wider channels means fewer channels
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6.23: MIMO
© 2013 Pearson
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Access point transmits two signals in the same channel—one from Antenna A and
one from Antenna B.
These are called spatial streams.
MIMO Benefits
MIMO brings higher speeds because it can send more information in a channel.
MIMO also brings longer propagation distances for technical reasons we will not discuss.
© 2013 Pearson
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6.23: MIMO (Multiple Input/Multiple Output)
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WiFi Digital Modulation (QAM)
Quadrature Amplitude Modulation
How do we measure 1’s and 0’s in:
UTP: voltages
Fiber: light pulses
WiFi: Radio wave phase and amplitude
Awesome video explanation here
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Chapter 7
Almost everything in 802.11 Security
Drive-by-Hackers vs War Drivers
Unprotected vs Rogue Access Points
WEP, WPA, WPA2, WPS
PSK vs 802.1X modes
PSK operational risks
Evil Twin Access Points
BlueTooth vs 802.11
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Pre-Shared Key (PSK) Mode
(Personal Mode) 802.1X Mode
(Enterprise Mode)
Environment Home, Business few WAPs Companies with multiple WAPs
Uses a Central Authentication Server? No. The WAP does all the authentication work. Yes
Authentication Knowledge of Pre-Shared Key (PSK is a fancy way of saying “WiFi password”) Credentials on 802.1x authentication server
Technical Security Technologically strong, but weak human security can compromise the technological security Technically extremely strong but can be defeated by rogue access points and evil twin attacks
Operational threats Mismanaging the PSK Rouge WAPs, MitM evil-twin attacks
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7.4 802.11i Modes of Operation
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802.11 Core Security Standards
WEP Initial core security standard.
Easily cracked today.
NEVER USE!!!!
WPA Has been partially cracked.
Excuse to use: Large installed base makes upgrading the entire network to 802.11i expensive. [No longer a valid excuse for most companies]
802.11i (WPA2) Today’s preferred standard.
Extremely strong.
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7.7 Operational Security Threats in P S K Initial Authentication Mode (1 of 3)
Three weaknesses of PSK
Unauthorized disclosure of the PSK
PSK changes after employee leaves are laborious (if you remember)
Weak PSKs are easy to crack or guess
Great short answer question
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Wireless Protected Setup (WPS)
Created by Wi-Fi Alliance to make PSK setup easier
User enters an 8-digit PIN for a particular access point
Unfortunately, easily cracked and should be turned off on the access point if possible
Copyright © 2015 Pearson Education, Inc.
Don’t use WPS
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© 2013 Pearson
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7.6: 802.11i and WPA in Pre-Shared Key Mode
Great short answer question
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802.11i Only Protects from Some Threats
Other Threats Must Also Be Addressed
Rogue Access Points
Evil Twin Access Points
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802.11i Security is Not Enough
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Virtual Private Networks (VPNs)
End-to-end encryption with a pre-shared client-server secret
The secret is never transmitted so cannot be intercepted.
© 2013 Pearson
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7.8: Using a VPN to Counter Evil Twins
Great short answer question
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7.8 802.1X Initial Authentication Mode (3 of 4)
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The Bluetooth info in the text is very good to know, but will not be testable for CIS 3043.
You will be required to answer one question regarding Bluetooth communication:
Since Bluetooth operates in the 2.4GHz frequency range, as does 802.11g/n, how does Bluetooth ensure there is no interference?
Answer: FHSS and AFH (and describe briefly what they mean)
Copyright © 2015 Pearson Education, Inc.
Deviation from Text
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a
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