2020 FRSecure CISSP Mentor Program - Class 6

2020 CISSP MENTOR
PROGRAM
May 4, 2020
-----------
Class 6 – May 4, 2020
Instructor:
• Brad Nigh, FRSecure Director of Professional Services & Innovation

CISSP® MENTOR PROGRAM – SESSION THREE
1
FRSECURE CISSP MENTOR PROGRAM LIVE
STREAM
#MissionBeforeMoney
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THANK YOU!
FRSECURE.COM/CISSP-MENTOR-PROGRAM

Great job so far! Keep it up, you can do this!
• We’ve completed chapters 1 – 4 so far.
• Arguably, the hardest part is behind us!
• Check-in.
• How many have read Chapter 1 - 4?
• Questions?
CISSP® MENTOR PROGRAM – SESSION SIX
2
WE’RE ALL BACK!
Let’s get on it!
OK, maybe 160 slides was a little ambitious.
We’re not going as fast tonight, but we’re still going fast.
134 slides tonight!

1. What type of sprinkler system would be best for a
datacenter?
A. Wet pipe
B. Dry pipe
C. Deluge
D. Pre-action
3
QUIZ…
Easy peezy – We’ll be switching up questions from other sources soon.

1. What type of sprinkler system would be best for an art
gallery?
A. Wet pipe
B. Dry pipe
C. Deluge
D. Pre-action
4
QUIZ…

2. What is the primary drawback in using dogs as a
perimeter control?
A. Training
B. Cost
C. Liability
D. Appearance
5
QUIZ…

2. What is the primary drawback in using dogs as a
perimeter control?
A. Training
B. Cost
C. Liability
D. Appearance
6
QUIZ…

3. The RSA algorithm is based on which one-way function?
A. Elliptic curves
B. Discrete logarithm
C. Frequency distribution
D. Factoring composite numbers into their primes
7
QUIZ…

3. The RSA algorithm is based on which one-way function?
A. Elliptic curves
B. Discrete logarithm
C. Frequency distribution
D. Factoring composite numbers into their
primes
8
QUIZ…

4. You are surfing the Web via a wireless network. Your
wireless connection becomes unreliable, so you plug
into a wired network to continue surfing. While you
changed physical networks, your browser required no
change.
What security feature allows this?
A. Abstraction
B. Hardware Segmentation
C. Layering
D. Process Isolation
9
QUIZ…

4. You are surfing the Web via a wireless network. Your
wireless connection becomes unreliable, so you plug
into a wired network to continue surfing. While you
changed physical networks, your browser required no
change.
What security feature allows this?
A. Abstraction
B. Hardware Segmentation
C. Layering
D. Process Isolation
10
QUIZ…

5. A criminal deduces that an organization is holding an
offsite meeting and has few people in the building,
based on the low traffic volume to and from the parking
lot, and uses the opportunity to break into the building
to steal laptops.
What type of attack has been launched?
A. Aggregation
B. Emanations
C. Inference
D. Maintenance Hook
11
QUIZ…

5. A criminal deduces that an organization is holding an
offsite meeting and has few people in the building,
based on the low traffic volume to and from the parking
lot, and uses the opportunity to break into the building
to steal laptops.
What type of attack has been launched?
A. Aggregation
B. Emanations
C. Inference
D. Maintenance Hook
12
QUIZ…

6. What is the most important goal of fire suppression
systems?
A. Preservation of critical data
B. Safety of personnel
C. Building integrity
D. Quickly extinguishing a fire
13
QUIZ…

6. What is the most important goal of fire suppression
systems?
A. Preservation of critical data
B. Safety of personnel
C. Building integrity
D. Quickly extinguishing a fire
14
QUIZ…

15
LET’S DO THIS!
Picking up where we left off.

• Network Architecture and Design
• Secure Network Devices and Protocols
• Secure Communications
16
WHAT ARE WE GOING TO COVER?
Agenda – Domain 4: Communication and Network Security
Starting on page 219 this evening
Great domain for the techies. A little more challenging for the “normal”
people…

Network Defense-in-Depth
• Assume that an attacker has already compromised your
perimeter.
• Network segmentation, isolation, etc.
• NSA Methodology for Adversary Obstruction (not testable, but
great guidance) - https://www.cdse.edu/documents/cdse/nsa-
methodology-for-adversary-obstruction.pdf
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LECTURE
Network Architecture and Design

perimeter.
18
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perimeter.
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Simplex, Half-Duplex, and Full-Duplex Communication
• Simplex communication is one-way, like a car radio tuned to a
music station.
• Half-duplex communication sends or receives at one time only
(not simultaneously), like a walkie-talkie.
• Full-duplex communications sends and receive simultaneously,
like two people having a face-to-face conversation.
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LECTURE
Fundamental Network Concepts

Baseband and Broadband
• Baseband networks have one channel, and can only send one
signal at a time
• Ethernet networks are baseband
• “100baseT” UTP cable means 100 megabit, baseband, and
twisted pair
• Broadband networks have multiple channels and can send
multiple signals at a time, like cable TV
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LECTURE

Analog & Digital
• Analog communications are a continuous wave of information
• Digital communications transfer data in bits: ones and zeroes
22
LECTURE

LANs, WANs, MANs, GANs, and PANs
• PANs are Personal Area Networks
• Typically a range of 100 meters or much less
• Low-power wireless technologies such as Bluetooth use PANs.
• LAN is a Local Area Network
• A comparatively small network
• Typically confined to a building or an area within one
• MAN is a Metropolitan Area Network
• Typically confined to a city, a zip code, a campus, or office park
• WAN is a Wide Area Network
• Typically covering cities, states, or countries
• GAN is a Global Area Network; a global collection of WANs.
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Circuit-Switched Networks
• A dedicated circuit or channel (portion of a circuit) is dedicated
between two nodes
• Can provide dedicated bandwidth to point-to-point connections
• Original voice networks were circuit-switched
• One drawback of circuit-switched networks: once a channel or
circuit is connected, it is dedicated to that purpose, even while no
data is being transferred
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Packet-Switched Networks
• Instead of using dedicated circuits, data is broken into packets,
each sent individually
• If multiple routes are available between two points on a network,
packet switching can choose the best route, and fall back to
secondary routes in case of failure
• Packets may take any path (and different paths) across a
network, and are then reassembled by the receiving node
• Missing packets can be retransmitted, and out of-order packets
can be re-sequenced.
• Unlike circuit-switched networks, packet-switched networks
make unused bandwidth available for other connections
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LECTURE

Packet-Switched Networks
• Instead of using dedicated circuits, data is broken into packets,
each sent individually
• If multiple routes are available between two points on a network,
packet switching can choose the best route, and fall back to
secondary routes in case of failure
• Packets may take any path (and different paths) across a
network, and are then reassembled by the receiving node
• Missing packets can be retransmitted, and out of-order packets
can be re-sequenced.
• Unlike circuit-switched networks, packet-switched networks
make unused bandwidth available for other connections
26
LECTURE

Layered Design
• Models such as OSI and TCP/IP
• Each layer performs a specific function
• The complexity of each layer’s functionality is contained within
its layer
• Changes in one layer do not directly affect another: changing
your physical network connection from wired to wireless (at
Layer 1) has no effect on your Web browser (at Layer 7)
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LECTURE

Models and Stacks
• A network model is a description of how a network protocol suite
operates
• A network stack is a network protocol suite programmed in
software or hardware
• Protocol - set of rules that end points in a telecommunication
connection use when they communicate. Protocols specify
interactions between the communicating entities.
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LECTURE

The OSI Model
• OSI (Open System Interconnection) Reference Model is a layered
network model
• The model is abstract: we do not directly run the OSI model in our
systems
• Used as a reference point, so “Layer 1” (physical) is universally
understood
• Has seven layers
• Developed by International Organization for Standardization (ISO)
• Formally called “X.200: Information technology—Open Systems
Interconnection—Basic Reference Model.” - downloaded for free
at: http://www.itu.int/rec/T-REC-X.200-199407-I/en
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The OSI Model
network model
systems
understood
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The OSI Model
network model
systems
understood
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The OSI Model - Layer 1: Physical
• Describes units of data such as bits represented by energy (such
as light, electricity, or radio waves) and the medium used to carry
them (such as copper or fiber optic cables)
• Cabling standards such as Thinnet, Thicknet, and Unshielded
Twisted Pair (UTP) exist at layer 1, among many others
• Layer 1 devices include hubs and repeaters
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The OSI Model - Layer 1: Physical
• Describes units of data such as bits represented by energy (such
as light, electricity, or radio waves) and the medium used to carry
them (such as copper or fiber optic cables)
• Cabling standards such as Thinnet, Thicknet, and Unshielded
Twisted Pair (UTP) exist at layer 1, among many others
• Layer 1 devices include hubs and repeaters
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LECTURE

The OSI Model - Layer 2: Data link
• Handles access to the physical layer as well as local area
network communication
• An Ethernet card and its MAC (Media Access Control) address
are at Layer 2, as are switches and bridges.
• Divided into two sub-layers:
• Media Access Control (MAC) - transfers data to and from the
physical layer - touches Layer 1
• Logical Link Control (LLC) -handles LAN communications - touches
Layer 3
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The OSI Model - Layer 2: Data link
• Handles access to the physical layer as well as local area
network communication
• An Ethernet card and its MAC (Media Access Control) address
are at Layer 2, as are switches and bridges.
• Divided into two sub-layers:
• Media Access Control (MAC) - transfers data to and from the
physical layer - touches Layer 1
• Logical Link Control (LLC) -handles LAN communications - touches
Layer 3
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The OSI Model - Layer 3: Network
• Describes routing: moving data from a system on one LAN to a
system on another
• IP addresses and routers
• Protocols include IPv4 and IPv6, among others.
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The OSI Model - Layer 3: Network
• Describes routing: moving data from a system on one LAN to a
system on another
• IP addresses and routers
• Protocols include IPv4 and IPv6, among others.
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The OSI Model - Layer 4: Transport
• Handles packet sequencing, flow control, and error detection
• TCP and UDP are Layer 4 protocols
• Resending or re-sequencing packets
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The OSI Model - Layer 4: Transport
• Handles packet sequencing, flow control, and error detection
• TCP and UDP are Layer 4 protocols
• Resending or re-sequencing packets
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The OSI Model - Layer 5: Session
• Manages sessions, providing maintenance on connections
• Remote Procedure Calls (RPCs)
• A good way to remember the session layer’s function is
“connections between applications”
• Simplex, half-duplex, and full-duplex communication.
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LECTURE

The OSI Model - Layer 5: Session
• Manages sessions, providing maintenance on connections
• Remote Procedure Calls (RPCs)
• A good way to remember the session layer’s function is
“connections between applications”
• Simplex, half-duplex, and full-duplex communication.
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The OSI Model - Layer 6: Presentation
• Presents data to the application (and user) in a comprehensible
way
• Concepts include data conversion, characters sets such as
ASCII, and image formats such as GIF (Graphics Interchange
Format), JPEG (Joint Photographic Experts Group), and TIFF
(Tagged Image File Format)
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The OSI Model - Layer 6: Presentation
• Presents data to the application (and user) in a comprehensible
way
• Concepts include data conversion, characters sets such as
ASCII, and image formats such as GIF (Graphics Interchange
Format), JPEG (Joint Photographic Experts Group), and TIFF
(Tagged Image File Format)
43
LECTURE

The OSI Model - Layer 7: Application
• Where you interface with your computer application
• Web browser, word processor, and instant messaging clients
exist at Layer 7
• Protocols Telnet and FTP
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The OSI Model - Layer 7: Application
• Where you interface with your computer application
• Web browser, word processor, and instant messaging clients
exist at Layer 7
• Protocols Telnet and FTP
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The OSI Model
Many mnemonics exist to help remember the OSI model:
• “Please Do Not Throw Sausage Pizza Away” (Physical Data-Link
Network Transport Session Presentation Application)
• “Please Do Not Tell Sales People Anything.”
• “All People Seem to Need Data Processing”
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LECTURE

The OSI Model
Many mnemonics exist to help remember the OSI model:
• “Please Do Not Throw Sausage Pizza Away” (Physical Data-Link
Network Transport Session Presentation Application)
• “Please Do Not Tell Sales People Anything.”
• “All People Seem to Need Data Processing”
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LECTURE

The TCP/IP Model
• TCP/IP model (Transmission Control Protocol/Internet Protocol)
• Popular network model created by the United States Defense
Advanced Research Projects Agency in the 1970s (see:
http://www.isoc.org/internet/history/brief.shtml for more
information)
• A suite of protocols including UDP (User Datagram Protocol) and
ICMP (Internet Control Message Protocol), among many others
• Some sources use Link Layer in place of Network Access Layer,
and Network layer in place of Internet Layer
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LECTURE

The TCP/IP Model
• TCP/IP model (Transmission Control Protocol/Internet Protocol)
• Popular network model created by the United States Defense
Advanced Research Projects Agency in the 1970s (see:
http://www.isoc.org/internet/history/brief.shtml for more
information)
• A suite of protocols including UDP (User Datagram Protocol) and
ICMP (Internet Control Message Protocol), among many others
• Some sources use Link Layer in place of Network Access Layer,
and Network layer in place of Internet Layer
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LECTURE

The TCP/IP Model - Network Access Layer
• Combines layers 1 (Physical) and 2 (Data Link) of the OSI model
• Describes Layer 1 issues such as energy, bits, and the medium
used to carry them (copper, fiber, wireless, etc.)
• Also describes Layer 2 issues such as converting bits into
protocol units such as Ethernet frames, MAC (Media Access
Control) addresses, and Network Interface Cards (NICs)
• Networks include:
• WAN - Wide Area Network
• LAN - Local Area Network
• Internet
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The TCP/IP Model - Internet Layer
• Aligns with the Layer 3 (Network) layer of the OSI model
• IP addresses and routing
• IPv4, IPv6, ICMP, and routing protocols (among others)
• IP (Internet Protocol) governs the Internet layer. (All packets go
through IP!)
• Best path determination and packet switching occur at this layer
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The TCP/IP Model - Host-to-host Transport Layer
• Sometimes called either “Host-to-Host” or, more commonly,
“Transport” alone
• Connects the Internet Layer to the Application Layer
• Where applications are addressed on a network, via ports
• TCP and UDP are the two Transport Layer protocols
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TCP - Transmission Control Protocol:
• Connection-oriented protocol.
• supports dialogues between source and destination.
• packages application information into segments.
• provides reliable full-duplex transmission.
• supports flow control that exchanges packets.
• windowing, acknowledgements.
• retransmission - resends anything not received.
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UDP - User Datagram Protocol:
• Connectionless protocol that exchanges datagrams.
• does not provide flow control.
• does not support windowing, acknowledgments or guaranteed
delivery.
• error processing and retransmission must be handled by other
protocols.
• unreliable.
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The TCP/IP Model - Application Layer
• Combines Layers 5 though 7 (Session, Presentation, and
Application) of the OSI mode
• Most of these protocols use a client-server architecture, where a
client (such as ssh) connects to a listening server (called a
daemon on UNIX systems) such as sshd
• Clients and servers use either TCP or UDP (and sometimes both)
as a Transport Layer protocol
• Protocols include SSH, Telnet and FTP, among many others
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LECTURE

• aka the Process Layer:
• Emphasis is on maximum flexibility for software developers.
• Handles all high level protocols:
• FTP, HTTP, SMTP [ TCP examples ]
• TFTP, SNMP, DHCP, DNS, BOOTP [ UDP examples ]
• Data representation, encoding and dialog control.
• Ensures data is properly packaged for the next layer.
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• aka the Process Layer:
• Emphasis is on maximum flexibility for software developers.
• Handles all high level protocols:
• FTP, HTTP, SMTP [ TCP examples ]
• TFTP, SNMP, DHCP, DNS, BOOTP [ UDP examples ]
• Data representation, encoding and dialog control.
• Ensures data is properly packaged for the next layer.
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Encapsulation
• Takes information from a higher layer and adds a header to it,
treating the higher layer information as data
• “One layer’s header is another layer’s data.”
• As the data moves down the stack in the TCP/IP model,
application layer data is encapsulated in a layer 4 TCP segment.
That TCP segment is encapsulated in a Layer 3 IP packet. That IP
packet is encapsulated in a Layer 2 Ethernet frame. The frame is
then converted into bits at Layer 1 and sent across the local
network.
• Data, segments, packets, frames, and bits are examples of
Protocol Data Units (PDUs)
• Reverse of encapsulation is called de-multiplexing (sometimes
called de-encapsulation)
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Encapsulation
network.
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Encapsulation
network.
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Network Access, Internet and Transport Layer Protocols
and Concepts
• TCP/IP is a protocol suite: including (but not limited to):
• IPv4 and IPv6 at Layer 3
• TCP and UDP at Layer 4
• A multitude of protocols at layers 5-7, including Telnet, FTP, SSH,
and many others
• Some protocols, such as IP, fit neatly into one layer (Internet).
Others, such as Address Resolution Protocol (ARP), help connect
one layer to another (Network Access to Internet in ARP’s case)
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LECTURE

MAC Addresses
• Unique hardware address of an Ethernet network interface card
(NIC)
• Typically “burned in” at the factory
• MAC addresses may be changed in software
• Burned-in MAC addresses should be unique
• Historically, MAC addresses were 48 bits long:
• Two halves: the first 24 bits form the Organizationally Unique
Identifier (OUI)
• Last 24 bits form a serial number (formally called an extension
identifier)
• Organizations that manufacture NICs, such as Cisco, Juniper, HP,
IBM, and many others, purchase 24-bit OUIs from the Institute of
Electrical and Electronics Engineers (IEEE), Incorporated
Registration Authority. A List of registered OUIs is available at
http://standards.ieee.org/regauth/oui/oui.txt
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MAC Addresses
• Unique hardware address of an Ethernet network interface card
(NIC)
• Typically “burned in” at the factory
• MAC addresses may be changed in software
• Burned-in MAC addresses should be unique
• Historically, MAC addresses were 48 bits long:
• Two halves: the first 24 bits form the Organizationally Unique
Identifier (OUI)
• Last 24 bits form a serial number (formally called an extension
identifier)
• Organizations that manufacture NICs, such as Cisco, Juniper, HP,
IBM, and many others, purchase 24-bit OUIs from the Institute of
Electrical and Electronics Engineers (IEEE), Incorporated
Registration Authority. A List of registered OUIs is available at
http://standards.ieee.org/regauth/oui/oui.txt
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EUI-64 MAC addresses
• IEEE created the EUI-64 (Extended Unique Identifier) standard for
64-bit MAC addresses
• OUI is still 24 bits, but the serial number is 40 bits
• Allows far more MAC addresses, compared with 48-bit
addresses
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IPv4
• Internet Protocol version 4, commonly called “IP”
• Fundamental protocol of the Internet
• Designed in the 1970s to support packet-switched networking
• Used for the ARPAnet, which later became the Internet
• IP is a simple protocol, designed to carry data across networks
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LECTURE

IPv4
• Requires a “helper protocol” called ICMP
• IP is connectionless and unreliable: it provides “best effort”
delivery of packets
• If connections or reliability are required, they must be provided by
a higher level protocol carried by IP, such as TCP
• Uses 32-bit source and destination addresses, usually shown in
“dotted quad” format, such as “192.168.2.4”
• 32-bit address field allows 232, or nearly 4.3 billion addresses
• Lack of IPv4 addresses is a fundamental problem: one of the
factors leading to the creation of IPv6, which uses 128-bit
addresses
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LECTURE

IPv4 - Key IPv4 Header Fields
• An IP header is 20 bytes long (with no options)
• Key fields are:
• Version: IP version (4 for IPv4)
• IHL: Length of the IP header
• Type of Service: sets the precedence of the packet
• Identification, Flags, Offset: used for IP fragmentation
• Time To Live: to end routing loops
• Protocol: embedded protocol (TCP, UDP, etc.)
• Source and Destination IP addresses
• (Optional) Options and padding
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IPv4 - Key IPv4 Header Fields
• An IP header is 20 bytes long (with no options)
• Key fields are:
• IHL: Length of the IP header
• Type of Service: sets the precedence of the packet
• Identification, Flags, Offset: used for IP fragmentation
• Time To Live: to end routing loops
• Protocol: embedded protocol (TCP, UDP, etc.)
• Source and Destination IP addresses
• (Optional) Options and padding
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IPv4 - IP Fragmentation
• If a packet exceeds the Maximum Transmission Unit (MTU) of a network
• May be fragmented by a router along the path
• MTU is the maximum PDU size on a network
• Fragmentation breaks a large packet into multiple smaller packets
• Typical MTU size for an IP packet is 1500 bytes
• IP Identification field (IPID) is used to re-associate fragmented packets (they will
have the same IPID)
• Flags are used to determine if fragmentation is allowed, and whether more
fragments are coming
• Fragment offset gives the data offset the current fragment carries: “Copy this
data beginning at offset 1480”
• Path MTU discovery uses fragmentation to discover the largest size packet
allowed across a network path
• If a large packet is sent with the DF (do not fragment) flag sent and a router with
a smaller MTU than the packet size will drop it, sending a “Fragmentation needed
and DF set” ICMP message
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IPv6
• Successor to IPv4
• Larger address space (128 bit addresses compared to IPv4’s 32
bits)
• Simpler routing
• Simpler address assignment
• Lack of IPv4 addresses was the primary factor that led to the
creation of IPv6
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LECTURE
Note - IPv6 address space is 2128; there are over 340 undecillion
(called 340 sextillion) total addresses, which is a 39-digit number in
decimal: 340,282,366, 920,938,463,463,374,607,431,768,211,456.

IPv6
• The IPv6 header is larger and simpler than IPv4
• Fields include:
• Traffic Class and Flow Label: used for QoS (Quality of Service)
• Payload Length: length of IPv6 data (not including the IPv6 header)
• Next header: next embedded protocol header
• Hop Limit: to end routing loops
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IPv6
• The IPv6 header is larger and simpler than IPv4
• Fields include:
• Traffic Class and Flow Label: used for QoS (Quality of Service)
• Payload Length: length of IPv6 data (not including the IPv6 header)
• Next header: next embedded protocol header
• Hop Limit: to end routing loops
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IPv6 Addresses and Autoconfiguration
• IPv6 hosts can statelessly autoconfigure a unique address,
omitting the need for static addressing or DHCP
• Stateless autoconfiguration takes the host’s MAC address and
uses it to configure the IPv6 address
• IPv6 addresses are 128 bits long, and use colons instead of
periods to delineate section
• One series of zeroes may be condensed into two colons (“::”).
• Stateless autoconfiguration removes the requirement for DHCP
(Dynamic Host Configuration Protocol)
• DHCP may be used with IPv6: this called “stateful
autoconfiguration”
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LECTURE

• The “ifconfig” (left) shows two IPv6 addresses:
• fc01::20c:29ff:feef:1136/64 (Scope:Global)
• fe80::20c:29ff:feef:1136/64 (Scope:Link)
• The first address (fc01::…) is a “global” (routable) address, used for
communication beyond the local network
• IPv6 hosts rely on IPv6 routing advertisements to assign the global
address
• The second address (fe80::…) is a link-local address, used for local
network communication only
• Systems assign link-local addresses independently, without the
need for an IPv6 router advertisement
• /64 is the network size in CIDR format; means the network prefix is
64 bits long: the full global prefix is fc01:0000:0000:0000
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• The host uses the following process to statelessly configure its
global address:
• Take the MAC address: 00:0c:29:ef:11:36
• Embed the “ffee” constant in the middle two bytes:
00:0c:29:ff:fe:ef:11:36
• Set the “Universal Bit”: 02:0c:29:ff:fe:ef:11:36
• Prepend the network prefix & convert to “:” format:
fc01:0000:0000:0000:020c:29ff:feef:1136
• Convert one string of repeating zeroes to “::”:
fc01::20c:29ff:feef:1136
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Note: systems may be “dual stack” and use both IPv4 and IPv6 simultaneously

IPv6 Security Challenges
• An IPv6-enabled system will automatically configure a link-local address
(beginning with fe80:…) without the need for any other ipv6-enabled
infrastructure. The host can communicate with other link-local
addresses on the same LAN. This is true even if the administrators are
unaware that IPv6 is now flowing on their network.
• ISPs are also enabling IPv6 service, sometimes without the customer’s
knowledge. Modern network tools, such as networked intrusion
detection systems, can “see” IPv6, but are often not configured to do so.
• Many network professionals have limited experience or understanding
of IPv6. From an attacker’s perspective, this can offer a golden
opportunity to launch attacks or exfiltrate data via IPv6.
• All network services that are not required should be disabled: this is a
fundamental part of system hardening. If IPv6 is not required, it should
be disabled
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Classful Networks (back to IPv4)
• Original IPv4 networks (before 1993) were “classful”
• Classified in classes A through E
• Class A through C were used for normal network use. Class D
was multicast, and Class E was reserved
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Classless Inter-Domain Routing
• CIDR allows for many network sizes beyond the arbitrary stateful network sizes.
• The Class A network 10.0.0.0 contains IP address that begins with 10: i.e.
10.3.96.223. In other words, 10.X.X.X is a Class A address. The first 8 bits of the
dotted-quad IPv4 address is the network (10); the remaining 24 bits are the host
address: 3.96.223 in the last pervious example
• CIDR notation for a Class A network is /8 for this reason: 10.0.0.0/8. The “/8” is
the netmask, which means the network portion is 8 bits long, leaving 24 bits for
the host
• The class C network of 192.0.2.0 contains any IP address that begins with
192.0.2: 192.0.2.177, 192.0.2.253, etc. That class C network is 192.0.2.0/24 in
CIDR format: the first 24 bits (192.0.2) describe the network; the remaining 8 bits
(177 or 253 in the previous example) describe the host
• Once networks are described in CIDR notation, additional routable network sizes
are possible
• If you only need 128 IP addresses, chop a Class C (/24) in half, resulting in two
/25 networks
• If you only need 64 IP addresses, chop a /24 network into quarters, resulting in
four /26 networks with 64 IP addressed each
78
LECTURE

RFC 1918 Addressing
• RFC 1918 addresses are private IPv4 addresses
• Used for internal traffic that does not route via the Internet
• Allows conservation of IPv4 addresses
• Three blocks of IPv4 addresses are set aside for RFC 1918:
• 10.0.0.0-10.255.255.255 (10.0.0.0/8)
• 172.16.0.0-172.31.255.255 (172.16.0.0/12)
• 192.168.0.0-192.168.255.255 (192.168.0.0/16)
• Any public Internet connection using un-translated RFC1918 addresses
as a destination will fail
• Internet traffic sent with an un-translated RFC 1918 source address will
never return
• RFC stands for “Request for Comments,” a way to discuss and publish
standards on the Internet
• More information about RFC 1918 is available at: http://www.rfc-
editor.org/rfc/rfc1918.txt
79
LECTURE
Note - Memorizing RFC numbers is
not generally required for the exam;
RFC 1918 addresses are an exception
to that rule.

Network Address Translation
• Used to translate IP addresses
• Frequently used to translate RFC1918 addresses as they pass from
intranets to the Internet
• Three types of NAT are:
• Static NAT
• Makes a one-to-one translation between addresses, such as
192.168.1.47→192.0.2.252
• Pool NAT (also known as dynamic NAT)
• Reserves a number of public IP addresses in a pool
• Addresses can be assigned from the pool, and then returned.
• Port Address Translation (PAT, also known as NAT overloading)
• Typically makes a many-to-one translation from multiple private
addresses to one public IP address
• Common solution for homes and small offices: multiple internal
devices such as laptops, desktops and mobile devices share one public
IP address
80
LECTURE

ARP and RARP
ARP is the Address Resolution Protocol
• Used to translate between Layer 2 MAC addresses and Layer 3 IP
addresses
• Resolves IPs to MAC addresses by asking “Who has IP address
192.168.2.140, tell me,” for example. An example of an ARP reply
is “192.168.2.140 is at 00:0c:29:69:19:66.”
• 10.23.51.960019 arp who-has 192.168.2.140 tell 192.168.2.4
• 10.23.51.960019 arp reply 192.168.2.140 is-at
00:0c:29:69:19:66
• Any local system could answer the ARP request, including an
attacker. Secure networks should consider hard-coding ARP
entries for this reason.
81
LECTURE

ARP and RARP
• RARP is used by diskless workstations to request an IP address
• A node asks “Who has MAC address at 00:40:96:29:06:51, tell
00:40:96:29:06:51
• 05:30:01.495795 ARP, Reverse Request who-is 00:40:96:29:06:51
tell 00:40:96:29:06:51
• A RARP server answers with the node’s IP address.
82
LECTURE

Unicast, Multicast, and Broadcast Traffic
• Unicast – one to one communication
• Multicast – one to many communication
• Broadcast – one to all communication
83
LECTURE

Limited and Directed Broadcast Addresses
• Broadcast traffic is sent to all stations on a LAN
• There are two types of IPv4 broadcast addresses:
• Limited broadcast
• Limited broadcast address is 255.255.255.255
• “limited” because it is never forwarded across a router
• Directed broadcast
• Also called net-directed
• Broadcast address of the 192.0.2.0/24 network is 192.0.2.255
(the host portion of the address is all “1”s in binary, or 255)
• Called “directed” broadcast, because traffic to these addresses
may be sent from remote networks (it may be “directed”).
84
LECTURE

Layer 2 Broadcast
• Reaches all nodes in a “broadcast domain”
• A switch is an example of a broadcast domain
• The Ethernet broadcast address is MAC address
“FF:FF:FF:FF:FF:FF”
• Traffic on an Ethernet switch is received by all
connected nodes
85
LECTURE

Promiscuous Network Access
• Accesses all unicast traffic on a network segment
• Systems such as Networked Intrusion Detection Systems (NIDS) require
promiscuous network access in order to monitor all traffic on a network
• Network nodes normally only “see” unicast traffic sent directly to them
• Accessing unicast traffic sent to other nodes requires two things:
• A network interface card (NIC) configured in promiscuous mode
• The ability to access other unicast traffic on a network segment.
• Devices such as switches provide traffic isolation, so that each host
will only receive unicast traffic sent to it (in addition to broadcast
and multicast traffic)
• A hub, switch SPAN port, or TAP is typically used to provide
promiscuous network access.
86
LECTURE

TCP
• Reliable Layer 4 protocol
• Uses a three-way handshake to create reliable connections
across a network
• Can reorder segments that arrive out of order, and retransmit
missing segments
87
LECTURE

Key TCP Header Fields
• A TCP header is 20 bytes long (with no options)
• Important fields include:
• Source and Destination port
• Sequence and Acknowledgement Numbers: Keep full-duplex
communication in sync
• TCP Flags
• Window Size: Amount of data that may be sent before
receiving acknowledgement
88
LECTURE

Key TCP Header Fields
• A TCP header is 20 bytes long (with no options)
• Important fields include:
• Source and Destination port
• Sequence and Acknowledgement Numbers: Keep full-duplex
communication in sync
• TCP Flags
• Window Size: Amount of data that may be sent before
receiving acknowledgement
89
LECTURE

TCP Ports
• TCP connects from a source port to a destination port, such as
from source port 51178 to destination port 22
• The TCP port field is 16 bits, allowing port numbers from 0 to
65535
• There are two types of ports:
• Reserved - 1023 or lower
• Ephemeral - 1024-65535
• Common services such as HTTP use well-known ports
• The Internet Assigned Numbers Authority (IANA) maintains a list
of well-known ports at http://www.iana.org/assignments/port-
numbers
• Most Linux and UNIX systems have a smaller list of well-known
ports in /etc/services
90
LECTURE

Socket Pairs
• A socket is a combination of an IP address and a TCP or UDP
port on one node
• A socket may “listen” (wait for a connection)
• A socket pair is then “established” during a connection
• A socket pair describes a unique connection between two nodes:
• Source port
• Source IP
• Destination port
• Destination IP
• Netstat output:
91
LECTURE

TCP Flags
• The original six TCP flags are:
• URG: Packet contains urgent data
• ACK: Acknowledge received data
• PSH: Push data to application layer
• RST: Reset (tear down) a connection
• SYN: Synchronize a connection
• FIN: Finish a connection (gracefully)
• Two new TCP flags were added in 2001:
• CWR (Congestion Window Reduced)
• ECE (Explicit Congestion Notification Echo)
92
LECTURE

The TCP handshake
• TCP uses a three-way handshake to establish a reliable connection
• The connection is full duplex, and both sides synchronize (SYN) and
acknowledge (ACK) each other
• Exchange of these four flags is performed in three steps: SYN, SYN-ACK,
ACK
• The client chooses an initial sequence number, set in the first SYN
packet
• The server also chooses its own initial sequence number, set in the
SYN/ACK packet
• Each side acknowledges each other’s sequence number by incrementing
it: this is the acknowledgement number
• Once a connection is established, ACKs typically follow for each
segment
• The connection will eventually end with a RST (reset or tear down the
connection) or FIN (gracefully end the connection)
93
LECTURE

The TCP handshake
• TCP uses a three-way handshake to establish a reliable connection
• The connection is full duplex, and both sides synchronize (SYN) and
acknowledge (ACK) each other
• Exchange of these four flags is performed in three steps: SYN, SYN-ACK,
ACK
• The client chooses an initial sequence number, set in the first SYN
packet
• The server also chooses its own initial sequence number, set in the
SYN/ACK packet
• Each side acknowledges each other’s sequence number by incrementing
it: this is the acknowledgement number
• Once a connection is established, ACKs typically follow for each
segment
• The connection will eventually end with a RST (reset or tear down the
connection) or FIN (gracefully end the connection)
94
LECTURE

UDP
• User Datagram Protocol
• A simpler and faster cousin to TCP
• No handshake, session, or reliability
• Informally called “Send and Pray”
• Has a simpler and shorter 8-byte header
• Fields include:
• Source IP
• Destination IP
• Packet length (header and data)
• Simple (and optional) checksum - if used, the checksum provides limited
integrity to the UDP header and data
• Operates at Layer 4
• Commonly used for applications that are “lossy” (can handle some
packet loss), such as streaming audio and video
• Also used for query-response applications, such as DNS queries.
95
LECTURE

ICMP
• Internet Control Message Protocol
• Helper protocol that helps Layer 3 (IP)
• ICMP is used to troubleshoot and report error
conditions
• No concept of ports, but instead uses types and
codes
• Commonly-used ICMP types are echo request and
echo reply (used for ping) and time to live exceeded in
transit (used for traceroute)
96
LECTURE

ICMP
• Internet Control Message Protocol
• Helper protocol that helps Layer 3 (IP)
• ICMP is used to troubleshoot and report error
conditions
• No concept of ports, but instead uses types and
codes
• Commonly-used ICMP types are echo request and
echo reply (used for ping) and time to live exceeded in
transit (used for traceroute)
97
LECTURE

ICMP - Ping
• Named after sonar used to “ping” submarines
• Sends an ICMP Echo Request to a node and listens for an ICMP
Echo Reply
• Designed to determine whether a node is up or down
• Attackers use ICMP to map target networks; many sites filter
types of ICMP such as Echo Request and Echo Reply
• An unanswered ping (an ICMP Echo Request with no Echo Reply)
does not mean a host is down. The node may be down, or the
node may be up and the Echo Request or Echo Reply may have
been filtered at some point.
98
LECTURE

ICMP - Traceroute
• Uses ICMP Time Exceeded messages to trace a network route
• The Time to Live field is used to avoid routing loops: every time a packet
passes through a router, the router decrements the TTL field. If the TTL
reaches zero, the router drops the packet and sends an ICMP Time
Exceeded message to the original sender
• Client’s traceroute client sends a packet to the server with a TTL of 1.
The router A decrements the TTL to 0, drops the packet, and sends an
ICMP Time Exceeded message to the client. Router A is now identified.
• The client then sends a packet with a TTL of 2 to the server. Router A
decrements the TTL to 1 and passes the packet to router B. Router B
decrements the TTL to 0, drops it, and sends an ICMP Time Exceeded
message to the client. Router B is now identified.
• This process continues until the server is reached
• Most traceroute clients (such as UNIX and Cisco) send UDP packets
outbound
99
LECTURE

ICMP - Traceroute
• Uses ICMP Time Exceeded messages to trace a network route
• The Time to Live field is used to avoid routing loops: every time a packet
passes through a router, the router decrements the TTL field. If the TTL
reaches zero, the router drops the packet and sends an ICMP Time
Exceeded message to the original sender
• Client’s traceroute client sends a packet to the server with a TTL of 1.
The router A decrements the TTL to 0, drops the packet, and sends an
ICMP Time Exceeded message to the client. Router A is now identified.
• The client then sends a packet with a TTL of 2 to the server. Router A
decrements the TTL to 1 and passes the packet to router B. Router B
decrements the TTL to 0, drops it, and sends an ICMP Time Exceeded
message to the client. Router B is now identified.
• This process continues until the server is reached
• Most traceroute clients (such as UNIX and Cisco) send UDP packets
outbound
100
LECTURE

Application Layer TCP/IP Protocols and Concepts
• TCP/IP’s Application Layer - combines the
Presentation, Session, and Application Layers of the
OSI model
• Only standardizes communication and depends upon
the underlying transport layer protocols to establish
host-to-host data transfer channels and manage the
data exchange
101
LECTURE

Telnet
• Provides terminal emulation over a network
• “Terminal” means text-based VT100-style terminal access
• Telnet servers listen on TCP port 23
• Weak because it provides no confidentiality: all data transmitted
during a telnet session is plaintext, including the username and
password used to authenticate to the system
• Also has limited integrity: attackers with write access to a
network can alter data, or even seize control of Telnet sessions
• Secure Shell (SSH) provides secure authentication,
confidentiality, and integrity and is a recommended replacement
for Telnet.
102
LECTURE

FTP
• Used to transfer files to and from servers
• FTP has no confidentiality or integrity and should not be used to transfer sensitive data over
insecure channels
• FTP uses two ports:
• The control connection (where commands are sent) is TCP port 21
• “Active FTP” uses a data connection (where data is transferred) which originates from TCP port 20
• The two socket pairs (the next two examples use arbitrary ephemeral ports):
• Client:1025→Server:21 (Control Connection)
• Server:20→Client: 1026 (Data Connection)
• Client:1025→Server:21 (Control Connection)
• Client 1026→Server:1025 (Data Connection)
• The data connection originates from the server, in the opposite direction of the control channel.
Many firewalls will block the active FTP data connection for this reason, breaking Active FTP.
Passive FTP addresses this issue by keeping all communication from client to server:
• The FTP server tells the client which listening data connection port to connect to; the client then
makes a second connection. Passive FTP is more likely to pass through firewalls cleanly, since it
flows in classic client-server direction.
103
LECTURE

TFTP
• Trivial File Transfer Protocol
• UDP port 69
• Simple way to transfer files; often used for saving
router configurations or “bootstrapping” (downloading
an operating system) via a network by diskless
workstations
• No authentication or directory structure: files are read
from and written to one directory, usually called
/tftpboot.
• No confidentiality or integrity
104
LECTURE

SSH
• Designed as a secure replacement for Telnet, FTP, and the UNIX
“R” commands (rlogin, rshell, etc)
• Provides confidentiality, integrity, and secure authentication,
among other features
• Includes SFTP (SSH FTP) and SCP (Secure Copy) for transferring
files
• Can also be used to securely tunnel other protocols, such as
HTTP
• SSH servers listen on TCP port 22 by default
• SSH version 1 was the original version, which has since been
found vulnerable to man-in-the middle attacks
• SSH version 2 is the current version of the protocol, and is
recommended over SSHv1, or Telnet, FTP, etc.
105
LECTURE

SMTP, POP, and IMAP
• SMTP is the Simple Mail Transfer Protocol
• Used to transfer email between servers
• Servers listen on TCP port 25
• POPv3 (Post Office Protocol) and IMAP (Internet
Message Access Protocol) are used for client-server
email access, which use TCP ports 110 and 143,
respectively
106
LECTURE

DNS
• Domain Name System
• A distributed global hierarchical database that translates names
to IP addresses, and vice versa
• Uses both TCP and UDP: small answers use UDP port 53; large
answers (such as zone transfers) use TCP port 53
• Authoritative name servers provide the “authoritative” resolution
for names within a given domain
• Recursive name servers will attempt to resolve names that it
does not already know
• Caching name servers will temporarily cache names previously
resolved
107
LECTURE

DNS
• Domain Name System
• A distributed global hierarchical database that translates names
to IP addresses, and vice versa
• Uses both TCP and UDP: small answers use UDP port 53; large
answers (such as zone transfers) use TCP port 53
• Authoritative name servers provide the “authoritative” resolution
for names within a given domain
• Recursive name servers will attempt to resolve names that it
does not already know
• Caching name servers will temporarily cache names previously
resolved
108
LECTURE

DNS Weaknesses
• DNS uses the unreliable UDP protocol for most requests, and
native DNS provides no authentication. The security of DNS relies
on a 16-bit source port and 16-bit DNS query ID. Attackers who
are able to blindly guess both numbers can forge UDP DNS
responses.
• A DNS cache poisoning attack is an attempt to trick a caching
DNS server into caching a forged response. If bank.example.com
is at 192.0.2.193, and evil.example.com is at 198.18.8.17, an
attacker may try to poison a DNS server’s cache by sending the
forged response of “bank.example.com is at 198.18.8.17.” If the
caching DNS name server accepts the bogus response, it will
respond with the poisoned response for subsequent
bank.example.com requests (until the record expires).
109
LECTURE

DNSSEC
• Domain Name Server Security Extensions provides
authentication and integrity to DNS responses via the
use of public key encryption
• DNSSEC does not provide confidentiality: it acts like a
digital signature for DNS responses
• See http://www.kb.cert.org/vuls/id/800113 for more
details on the improved cache poisoning attack and
defenses
110
LECTURE

DNSSEC
• Domain Name Server Security Extensions provides
authentication and integrity to DNS responses via the
use of public key encryption
• DNSSEC does not provide confidentiality: it acts like a
digital signature for DNS responses
• See http://www.kb.cert.org/vuls/id/800113 for more
details on the improved cache poisoning attack and
defenses
111
LECTURE

HTTP and HTTPS
• HTTP (Hypertext Transfer Protocol) - Used to transfer
unencrypted Web-based data
• HTTPS (Hypertext Transfer Protocol Secure) -
transfers encrypted Web-based data via SSL/TLS
• HTTP uses TCP port 80
• HTTPS uses TCP port 443
112
LECTURE

BOOTP and DHCP
• BOOTP is the Bootstrap Protocol
• Used for bootstrapping via a network by diskless systems
• Many system BIOSs now support BOOTP directly, allowing the BIOS to load
the operating system via a network without a disk
• Startup occurs in two phases:
• Use BOOTP to determine the IP address and OS image name
• Use TFTP to download the operating system
• DHCP is Dynamic Host Configuration Protocol
• Designed to replace and improve on BOOTP by adding additional features
• Allows more configuration options, as well as assigning temporary IP
address leases to systems
• Systems can be configured to receive IP address leases, DNS servers, and
default gateways, among other information.
• Both BOOTP and DHCP use the same ports:
• UDP port 67 for servers
• UDP port 68 for clients
113
LECTURE

Layer 1 Network Cabling
• Simplest part of the OSI model
• Fundamental network cabling terms to understand:
• Electro Magnetic Interference (EMI) is interference caused
by magnetism created by electricity
• Any unwanted signal (such as EMI) on a network cable is
called noise
• Crosstalk occurs when a signal crosses from one cable to
another
• Attenuation is the weakening of signal as it travels further
from the source
114
LECTURE

Layer 1 Network Cabling - Twisted Pair Cabling
Unshielded Twisted Pair (UTP)
• Uses pairs of wire twisted together
• Twisting them together dampens the magnetism and
makes cabling less susceptible to EMI
115
LECTURE

• Cables are classified by categories according to rated
speed
• Tighter twisting results in more dampening:
• Category 6 UTP cable designed for gigabit networking has
far tighter twisting than a Category 3 fast Ethernet cable
• Cisco Press also has a good summary at
http://www.ciscopress.com/articles/article.asp?p=31276
116
LECTURE

speed
117
LECTURE

speed
118
LECTURE

Layer 1 Network Cabling - Coaxial Cabling
• Coaxial cables are often used for satellite and cable
TV service
• More resistant to EMI, allows higher bandwidth and
longer connections compared with twisted pair cable.
• Two older types of coaxial cable are Thinnet and
Thicknet, used for Ethernet bus networking.
119
LECTURE

Layer 1 Network Cabling - Coaxial Cabling
• Coaxial cables are often used for satellite and cable
TV service
• More resistant to EMI, allows higher bandwidth and
longer connections compared with twisted pair cable.
• Two older types of coaxial cable are Thinnet and
Thicknet, used for Ethernet bus networking.
120
LECTURE

Layer 1 Network Cabling - Fiber Optic Network Cable
• Uses light to carry information
• Can be used to transmit via long distances: past 50 miles
• Advantages are speed, distance, and immunity to EMI
• Disadvantages include cost and complexity
• Multimode fiber carrier
• Uses multiple modes (paths) of light, resulting in light dispersion
• Used for shorter distances
• Single-mode fiber
• Uses a single strand of fiber, and the light uses one mode (path) down the center of the
fiber
• Used for long-haul, high-speed networking
• Multiple signals may be carried via the same fiber using Wavelength Division
Multiplexing (WDM)
• Multiple light “colors” are used to transmit different channels of information on the
same fiber
• Combined speeds of over a terabit/second can be achieved when WDM is used to carry
10-gigabits per color
121
LECTURE

Layer 1 Network Cabling - Fiber Optic Network Cable
• Uses light to carry information
• Can be used to transmit via long distances: past 50 miles
• Advantages are speed, distance, and immunity to EMI
• Disadvantages include cost and complexity
• Multimode fiber carrier
• Uses multiple modes (paths) of light, resulting in light dispersion
• Used for shorter distances
• Single-mode fiber
• Uses a single strand of fiber, and the light uses one mode (path) down the center of the
fiber
• Used for long-haul, high-speed networking
• Multiple signals may be carried via the same fiber using Wavelength Division
Multiplexing (WDM)
• Multiple light “colors” are used to transmit different channels of information on the
same fiber
• Combined speeds of over a terabit/second can be achieved when WDM is used to carry
10-gigabits per color
122
LECTURE

LAN Technologies and Protocols - Ethernet
• Most common local area networking technology
• Transmits network data in frames
• Originally used a physical bus topology, and later
added support for physical star
• Describes Layer 1 issues such as physical medium
and Layer 2 issues such as frames
• Baseband (one channel)
123
LECTURE

• Most common local area networking technology
• Transmits network data in frames
• Originally used a physical bus topology, and later
added support for physical star
• Describes Layer 1 issues such as physical medium
and Layer 2 issues such as frames
• Baseband (one channel)
124
LECTURE

• Carrier Sense Multiple Access (CSMA) addresses collisions
• Carrier Sense Multiple Access with Collision Detection (CSMA/CD):
• 1. Monitor the network to see if it is idle
• 2. If the network is not idle, wait a random amount of time
• 3. If the network is idle, transmit
• 4. While transmitting, monitor the network
• 5. If more current is detected than sent, another station must also be
sending a) Send Jam signal to tell all nodes to stop transmitting b) Wait a
random amount of time before retransmitting
• CSMA/CD is used for systems that can send and receive simultaneously,
such as wired Ethernet
• CSMA/CA (Collision Avoidance) is used for systems such as 802.11
wireless that cannot send and receive simultaneously
• CSMA/CA relies on receiving an acknowledgement from the receiving
station: if no acknowledgement is received, there must have been a
collision, and the node will wait and retransmit
125
LECTURE

LAN Technologies and Protocols - ARCNET &
Token Ring
• ARCNET (Attached Resource Computer Network) and
Token Ring are two legacy LAN technologies
• Pass network traffic via tokens
• Possession of a token allows a node to read or write
traffic on the network
• No collisions - Predictable network behavior
• ARCNET ran at 2.5 mbps and popularized the star
topology
• The last version of Token Ring ran at 16 mbps using a
physical star/logical ring topology
126
LECTURE

LAN Technologies and Protocols - FDDI
• Fiber Distributed Data Interface
• Legacy LAN technology
• Logical network ring via a primary and secondary
counter-rotating fiber optic ring
• Secondary ring was typically used for fault tolerance
• A single FDDI ring runs at 100 megabits
• Uses a “token bus,” a different token-passing
mechanism than Token Ring
127
LECTURE

LAN Physical Network Topologies - Bus
• Connects network nodes in a string
• Each node inspects the data as it passes along the
bus
• Fragile: should the network cable break anywhere
along the bus, the entire bus would go down
128
LECTURE

LAN Physical Network Topologies - Tree
• Also called hierarchical network
• A network with a root node, and branch nodes that are
at least three levels deep (two levels would make it a
star)
• The root node controls all tree traffic
• Legacy network design; the root node was often a
mainframe
129
LECTURE

LAN Physical Network Topologies - Tree
• Also called hierarchical network
• A network with a root node, and branch nodes that are
at least three levels deep (two levels would make it a
star)
• The root node controls all tree traffic
• Legacy network design; the root node was often a
mainframe
130
LECTURE

LAN Physical Network Topologies - Ring
• Connects network nodes in a ring
• Logical ring, physical star
• MAU/MSAU
131
LECTURE

LAN Physical Network Topologies - Star
• The dominant physical topology for LANs
• First popularized by ARCNET, and later adopted by
Ethernet
• Each node is connected directly to a central device
such as a hub or a switch
132
LECTURE

LAN Physical Network Topologies - Star
• The dominant physical topology for LANs
• First popularized by ARCNET, and later adopted by
Ethernet
• Each node is connected directly to a central device
such as a hub or a switch
133
LECTURE

LAN Physical Network Topologies - Mesh
• Interconnects network nodes to each other
• Full mesh and partial mesh
• Superior availability and are often used for highly
available (HA) server clusters
134
LECTURE

Technical, but not too technical.
Please try to catch up in your reading.
• We left off on page 253 in the book.
• Wednesday (5/6) we’ll finish this chapter and domain.
• Come with questions!
Have a great evening, talk to you Wednesday!
135
WE MADE IT THROUGH SESSION #6!

2020 FRSecure CISSP Mentor Program - Class 6

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