Pace IT - Network Devices (part 1)

Instructor, PACE-IT Program – Edmonds Community College
Areas of expertise Industry Certifications
 PC Hardware
 Network Administration
 IT Project Management
 Network Design
 User Training
 IT Troubleshooting
Qualifications Summary
Education
 M.B.A., IT Management, Western Governor’s University
 B.S., IT Security, Western Governor’s University
Entrepreneur, executive leader, and proven manger
with 10+ years of experience turning complex issues
into efficient and effective solutions.
Strengths include developing and mentoring diverse
workforces, improving processes, analyzing
business needs and creating the solutions
required— with a focus on technology.

PACE-IT.
– Hubs, bridges, and switches.
– Modems.
– Routers.

The Open System
Interconnect (OSI) model
was developed as a way to
help disparate computing
systems communicate with
each other.
It is composed of seven layers that work together in
order for communication to occur. Network devices tend
to fall within the first three of those layers. Layer 1—the
Physical Layer—deals with how bits are converted to
the appropriate signal and placed on the network. Layer
2—the Data Link Layer—is concerned more concerned
with making sure the appropriate host is reached on the
network. Finally, Layer 3—the Network Layer—is all
about making sure the right network is reached.
Network devices I.

Network devices I.
– The hub.
» Operates at Layer 1 of the OSI model.
• It is only concerned with physically placing the signal on the
network.
» All devices that connect to hubs are in the same collision domain
and broadcast domain.
• Collision domains are areas where network traffic can collide and
cause problems.
• Broadcast domains are network segments where broadcast
traffic is heard by all of the devices on the network.
» A hub functions as a concentrator/repeater in that it doesn’t care
where the signal comes from or where it is going.
» A hub only operates in half-duplex.
• It can be sending or receiving, but not both at the same time.
» All of the network’s bandwidth is shared by all of the devices
connected to the network.
• This sharing of the bandwidth effectively reduces the amount of
bandwidth that is available to devices.
• As the size of the network increases, the performance of the
network will be reduced.

Network devices I.
– The bridge.
» Bridges connect different LAN segments together (by creating a
bridge between them) and break up collision domains.
• They can also bridge different types of network media and
different types of network transmissions (e.g., Ethernet to
token ring and/or wireless to Ethernet).
» They have a limited amount of ports.
– The wireless access point (WAP).
• A specific type of network bridge that bridges wireless
network segments with wired network segments.
» Operates in half-duplex mode by using a method called carrier
sense multiple access with collision avoidance (CSMA/CA).
• With CSMA/CA, devices will listen to the line. If there is no
traffic on the line, the device is free to transmit. If there is
traffic on the line, the device waits a random period of time
and then listens in on the line again.
• While WAPs do not break up collision domains, collisions are
avoided by the use of CSMA/CA.

Network devices I.
– The switch.
» It is similar to a hub, but it is also much smarter than a hub.
• It utilizes an application-specific integrated circuit (ASIC) chip.
• The ASIC has specific programing that allows the switch to
learn what devices are on the network and which ports they
are connected to on the switch.
» Because they know which devices are on the segment and
where they are located, they can operate in full-duplex.
• Full-duplex is when a device can send and receive signals at
the same time.
• With full-duplex, all of the devices receive all of the possible
network bandwidth all of the time. They do not share the
bandwidth as in the case of a hub.
» Switches break up collisions domains. Each port on a switch is
its own collision domain.
» Switches do not break up broadcast domains. All devices
connected to a switch will receive network broadcasts.

Network devices I.
– The modem.
» The term “modem” is actually short for modulator/demodulator.
• It was originally developed to take the digital signal coming
from a node and convert it to an analog signal (modulating the
signal) to be placed on the wire. In return, it would accept an
analog signal from the wire and convert it (demodulating the
signal) to a digital signal that the node could understand.
» They were originally developed to create connections between
network segments via the public switched telephone network
(PSTN) using the plain old telephone system (POTS).
» Cable modems can be used to connect network segments to
the Internet by translating the network signal into a format that
can be handled by the cable network.
» A modem is not a router.

Network devices I.
– The router.
» It is responsible for connecting different networks together.
• It uses special programing to keep track of different networks
and the best possible paths to reach those networks.
» It is not concerned with what hosts are connected to networks.
» They are found at the edges of the network.
» They can connect different types of media together (e.g.,
Ethernet to serial and/or Ethernet to fiber optic).
» Routers break up collision domains.
» Routers break up broadcast domains. Because network
broadcasts are for a specific single network, they cannot pass
through a router interface.
• When a router receives a network broadcast, it just drops the
broadcast (it ignores the broadcast).

Network devices I.
Hubs work at Layer 1 of the OSI model and function as a
concentrator/repeater. Every packet the hub receives is propagated out all
of its ports. Bridges work at Layer 2 of the OSI model. They are used to
connect network segments together. They can also be used to change
network media. A WAP is a specific type of bridge used to bridge wireless
and wired networks. Switches work at Layer 2 of the OSI model. The ASIC
allows them to know where and what devices are connected to them. The
bridge and the switch break up collision domains.
Topic
Hubs, bridges, and switches.
Summary
“Modem” stands for modulator/demodulator. Modems operate at Layer 1 of
the OSI model. Originally, they translated a digital network signal into an
analog signal that the PSTN could handle and reversed the process when
required. Cable modems translate the network signal into a format that the
cable network can handle.
Modems.
Routers work at Layer 3 of the OSI model. They are used to connect
networks together. They do not care what hosts are connected to a
network—just where that network is located and how to get to it. Routers
break up both collision domains and broadcast domains.
Routers.

This workforce solution was 100 percent funded by a $3 million grant awarded by the
U.S. Department of Labor's Employment and Training Administration. The solution was
created by the grantee and does not necessarily reflect the official position of the U.S.
Department of Labor. The Department of Labor makes no guarantees, warranties, or
assurances of any kind, express or implied, with respect to such information, including
any information on linked sites and including, but not limited to, accuracy of the
information or its completeness, timeliness, usefulness, adequacy, continued availability
or ownership. Funded by the Department of Labor, Employment and Training
Administration, Grant #TC-23745-12-60-A-53.
PACE-IT is an equal opportunity employer/program and auxiliary aids and services are
available upon request to individuals with disabilities. For those that are hearing
impaired, a video phone is available at the Services for Students with Disabilities (SSD)
office in Mountlake Terrace Hall 159. Check www.edcc.edu/ssd for office hours. Call
425.354.3113 on a video phone for more information about the PACE-IT program. For
any additional special accommodations needed, call the SSD office at 425.640.1814.
Edmonds Community College does not discriminate on the basis of race; color; religion;
national origin; sex; disability; sexual orientation; age; citizenship, marital, or veteran
status; or genetic information in its programs and activities.

Pace IT - Network Devices (part 1)

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Pace IT - Network Devices (part 1)