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Unit Eight Project
Running Head: UNIT Eight PROJECT
Unit Eight Project
Dale Henderson
Kaplan University
IT283-02 Networking with TCP/IP
Anthony Stabile
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Unit Eight Project
 Table 9-1, match the function on the right with the correct IEEE sublayer of the data link layer.
Sublayer
A. LLC
B. MAC
Function
A Provides an interface to
upper layer
B Controls the placement of
frame on the medium
A Remains relatively
independent of the physical
equipment
B Adds a frame delimiter
B Provides a unique source and
destination address
 Concept Questions
1. Why has Ethernet been so successful?

Simplicity and ease of maintenance

Ability to incorporate new technologies

Reliability

Low cost of installation and upgrade
2. What functions does data encapsulation provide?

Frame delimiting

Addressing

Error detection
3. How does Ethernet handle error detection?

The sending node calculates a Cyclic Redundancy Check (CRC) of the
bits in the frame. The node places the CRC result in the Frame
Check Sequence (FCS) field in the trailer part of the Ethernet
frame. After receiving a frame, a receiving node calculates its
own CRC to compare to the one in the frame. If the two CRC results
match, the recipient assumes that the frame arrived without error.
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Vocabulary Exercising: Matching
Term
Description
a. 10BASE5
b. 10BASE2
c. Hub
d. Half duplex
e. Full duplex
f. Switch
D Only one station at a time
can transmit
C Concentrates connections,
allowing the network to see a
group of nodes as a single unit
B Uses 185 meters of thin
coaxial cable
F Isolates each port and sends
a frame only to its proper
destination (if the destination
is known)
E Both ends of connection can
send at the same time
A Uses 500 meters of thick
coaxial cable
 Concept Questions
1. Compare and contrast half duplex and full duplex

Half-duplex – Only one station could successfully
transmit at a time.
Full-duplex – having a connection that can carry both
transmitted and received signals at the same time, have
enabled the development of 1-Gbps Ethernet beyond.
2. What aspects of Ethernet has remained relativity
unchanged over the years, and what aspects have changed?

The ability to migrate the original implementation of
Ethernet to current and future Ethernet implementation
is based on the practically unchanged structure of the
Layer 2 frame. Physical media and MAC continually
evolved, but the Ethernet frame header and trailer have
essentially
remained
constant
through
the
many
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generations of Ethernet. Ethernet’s simplicity and ease
of use and installation have remained unchanged. The
Ethernet frame has remained relatively unchanged.
Ethernet is still usually connected in a star topology,
but the center of the star is a switch rather than a
hub these days. The cabling for Ethernet has evolved
from coaxial to unshielded twisted pair to fiber-optic.
Unshielded twisted pair is still widely used. Fiberoptic is reserved mostly for data centers, links
between switches, and high-end devices.
 Vocabulary Exercise: Matching
Field
A. Preamble
B. Start of frame delimiter
C. Destination address
D. Source address
E. Length/type
F. Data
G. Frame check sequence
Definition
G. Used for error detection
A. Used for synchronization
B. Specifies the number of
bytes in the data part of the
frame or specifies the type
of data (the upper-layer
protocol)
F. Carries the upper-layer
data
E. Tells other devices on the
network that a frame is
coming along the medium
D. Specifies the frame’s
sender
C. Specifies the frame’s
intended recipient
 Multiple- Choice Questions
1. What is the maximum size of an Ethernet frame according
to the IEEE 802.3ac standard?

A. 1522 bytes
2. What is the minimum size of an Ethernet frame?

D. 64 bytes
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3. What does a receiving device do if it receives a frame
that is less than the allowed minimum size or greater
than the allowed maximum size?

B. The receiving device drops the frame
4. How does a recipient device know if the sender used the
Length/Type field to specify a length or a type?

D. The recipient bases the decision on whether it’s
been configured for Ethernet II or IEEE 802.3
5. Why is padding sometimes added to the data part of an
Ethernet frame?

B. To ensure the frame is at least 64 bytes.
6. What happens if a frame arrives damaged?

A. The recipient calculates a CRC that differs from the
CRC in the FCS field and drops the frame.
7. How long is a MAC address?

C. 48 bits
 Concept Questions
1. Compare and Contrast MAC addresses with IP addresses

MAC addresses operate at the OSI data link layer (Layer
2). Layer 2 addresses are used only for local delivery
when transporting a frame across a local medium. These
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addresses use a flat addressing scheme and do not
indicate on what network a device is located. If a
device is moved to another network, its Layer 2 address
does not need to change. IP addresses operate at the
OSI network layer (Layer 3). Layer 3 addresses are
carried from source to destination host across an
internetwork. Layer 3 addresses use a hierarchical
addressing scheme and indicate a network number and
host identifier.
2. Compare and contrast unicast, broadcast, and multicast
communications at the MAC sublayer

Unicast – the unique address used when a frame is sent
from a single transmitting device to a single
destination device

Broadcast – uses a special address that allows all
nodes to accept and process the frame

Multicast – allows a source device to send a packet to
a group of devices.
 Vocabulary Exercise: Completion

1. Because devices using coaxial or hub-based Ethernet
send their messages on a shared medium, a carrier sense
multiple access collision detect (CSMA/CD) is used to
determine if the medium is already in use before a
sender transmits.
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2. When a device detects that no other computer is
sending a frame, the device waits if it has something
to send. All devices that have messages to send must
listen before transmitting.

3. If a device detects a signal from another device, it
waits before attempting to transmit.

4. When no traffic is detected, a device transmits its
message. While transmitting, the device continues to
listen for traffic from another device. If another
device is sending at the same time, a collision has
occurred.

5. If a collision happens, the sending devices
continues to send for the time it takes to send a jam
signal and then jamming signal sending. The devices
invoke a backoff algorithm that causes them to wait a
random amount of time before trying to send again.
 Concept Questions
1. What is interframe spacing, and why does Ethernet use
it?

It is the time measured from the last bit of the FCS
field of one frame to the first bit of the Preamble of
the next frame. After a frame has been sent, all
devices on a 10-Mbps Ethernet network are required to
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wait a minimum of 96 bit times (9.6 microseconds)
before any device can transmit its next frame.
2. Why is the backoff timing random when an Ethernet
collision occurs?

After a collision occurs and all devices allow the
cable to become idle (each waits the full interframe
spacing), the devices whose transmissions collided
must wait an additional and potentially progressively
longer period of time before attempting to retransmit
the collided frame.
 Vocabulary Exercise: Completion
1. 10BASE-T uses two pairs of a four-pair cable and is
terminated at each end with an eight-pin RJ-45 connector. The
pair connected to pins 1 and 2 is used for transmitting, and
the pair connected to pins 3 and 6 is used for receiving.
2. Replacing hubs with switches in 10BASE-T networks has
greatly increased the throughout available to these networks
and has helped Ethernet maintain its longevity in the LAN
market. The 10BASE-T links connected to a switch can support
either half-duplex or full-duplex operation.
3. The most popular implementations of 100 Mbps Ethernet are
100BASE-TX, which uses Category 5 or later UTP cable, and
100BASE-FX, which uses fiber-optic cable.
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4. 1000BASE-T Ethernet provides full-duplex transmission using
all four pairs in Category 5 or later UTP cable.
5. The two fiber versions of Gigabit Ethernet are 1000BASE-SX
and 1000BASE-LX. Fiber-optic cabling offers better noise
immunity than UTP, a smaller physical size, and higher
distances and bandwidth.
6. A difference between 1000BASE-SX and 1000BASE-LX is the
link media, connectors, and wavelength of the optical signal.
7. The IEEE 802.3ae standard was adapted to include 10-Gbps,
full-duplex transmission over fiber-optic cable, 10-Gigabit
Ethernet is evolving for use not only in LANs, but also in
MANs and WANs.
8. Although Gigabit Ethernet is now widely available and 10Gigabit products are becoming more available, the IEEE and the
10-Gigabit Ethernet Alliance are working on 40-, 100-, and
even 160-Gbps standards.
 Vocabulary Exercise: Matching
Term
a. Hub
b. Switch
Characteristic
B. Divides collision domains
A Forwards received bits out
every port
B Supports full-duplex
communication
A Simplifies network cabling
but doesn’t have any
performance benefits
A When many nodes that
transmits frequently are
connected to the device,
latency increases, because
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each node must wait for an
opportunity to transmit
B Provides an alternative to
contention-based Ethernet
B Maintains a table that maps
each MAC address to a port
 Vocabulary Exercise: Completion
1. A switch selectively forwards an individual frame that
it receives on a port to the port where the destination
node is connected.
2. Switches use store-and-forward switching, whereby the
switch receives an entire frame, checks the FCS for errors,
and forwards the frame to the appropriate port.
3. A switch maintains a table, called the MAC table, which
matches a MAC address with the port used to connect the
node with that address.
Concept Question
 List and describe the five basic operations of an Ethernet
LAN switch.

Learning. A switch populates the MAC table by learning
which port it should use to reach each MAC address. As
a frame enters the switch, the switch examines the MAC
source address. If no entry exists in the table for
this address, the switch creates a new entry that
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pairs the source address with the port on which the
frame arrived. The switch can now use this mapping to
forward frames to the node with the MAC address in the
table entry.

Aging. A switch tracks how long an entry has been in
the MAC table. If the entry reaches a certain age
without being refreshed by a new frame from the same
node on the same port, the entry is removed.

Flooding. If a switch has not yet learned which port
it should use to forward a frame to a destination, the
switch sends the frame to all ports, except the port
on which the frame arrived.

Selective forwarding. A switch examines the
destination MAC address in a frame and forwards the
frame out the appropriate port.

Filtering. After a switch has learned the address or
addresses that map to a port, it filters frames from
going out that port that include a destination address
that is not mapped to the port.
 Multiple-Choice Questions
1. What is a basic job of ARP?

A. Resolve IPv4 addresses to MAC addresses
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2. If a node has recently sent a frame to another node,
where is the mapping of IPv4
address to MAC address stored?

B. ARP cache
3. When a node has not recently sent a frame to another
node, how does the node discover the correct MAC address
to use for the IPv4 address of the destination node?

C. The sender monitors traffic until it discovers
the correct MAC address to use.
4. What type of header does an ARP frame contain?

A. IP
5. When an Ethernet transmitter sends to a destination not
on its local network, what MAC destination address does
it use, and how does it discover this address?

A. The transmitter uses the MAC address of the
destination, which it discovers with an ARP request.
6. What is the destination address in the frame when a node
sends an ARP request to find the MAC address associated
with a known IP address?

B. The address of the local router interface
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References
Dean, Tamara. (2009). Network+ Guide to Networks.
Boston: Course Technology, Cengage Learning.
Dye, McDonald, Rufi. (2010). Network Fundamentals: CCNA
Exploration Companion Guide. Indianapolis: Cisco Press.
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