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Introduction to Networking > Chapter 3 > Flashcards

Chapter 3 Flashcards

1
Q

what is a network topology

A

a description of how a network is physically laid out and how signals travel from one device to another

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2
Q

All network designs today are based on what 4 basic physical topologies

A
  • bus
  • star
  • ring
  • point-to-point
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3
Q

What are the two categorizations of network topologies

A
  • Physical topology - the arrangment of cabling and how cables connect one device to another in a network
  • Logical topologies - the path data travels between computers on a network
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4
Q

What is physical bus topology

A

this is a continuous length of cable connecting one computer to another in a daisy-chain fashion

This is the simplest and at one time was the most common method for connecting computers

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5
Q

What are the weaknesses of physical bus topology

A
  • There’s a limit of 30 computers per cable segment
  • The maximum total length of cabling is 185 meters
  • Both ends of the bus must be terminated
  • Any break in the bus brings down the entire network
  • Adding or removing a machine brings down the entire network temporarily
  • Technologies using this topology are limited to 10 Mbps half-duplex communication since they use coaxial cabling
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6
Q

How does data travel in a physical bus

What is the term for signal travel across the medium and from device to device

A

Electrical pulses (signals) travel the cables lengths in all directions

Signal propagation

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7
Q

How does a signal stop in a physical bus?

A
  • the signal continues until it weakens to the point of fading out or until it is absorbed by a terminator
    • a terminator is an electrical component called a resistor that absorbs the signal instead of allowing it to bounce back up the wire
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8
Q

What happens to a signal if it is not terminated at the end of a wire

A

is bounces, or is “reflected”

signal bounce is the term used when electricity bounces off the end of a cable and back in the other direction

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9
Q

why can a Physical Bus only allow 30 computers, or up to 185 meters?

A
  • the signal becomes too weak and doesn’t make it to the next computer in the chain
  • As an electrical signal encounters each workstation along a daisy-chain some of its strength is absorbed by both the cabling and the connectors until the signal is eventually too weak to interpret
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10
Q

what is a Physical Star Topology

A

this is a configuration that uses a central (hub or switch) to connect computers

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11
Q

What are the advantages of a physical star topology

A
  • Much faster technologies than a bus
  • Centralized monitoring and management of network traffic are possible
  • easier network upgrades
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12
Q

what does using a central device such as in the physical star topology allow for

A

hubs and switches can include software that collects statistics about network traffic patterns and detect errors

As long as cabling and NICs support it, a star network can be easily updated by replacing the central device

If the number or workstations you need exceed the ports on the central device you can add another at any time

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13
Q

What is an extended Star topology

A

This is when several hubs or switches are connected. It’s simply an extension of a physical star.

Also sometimes referred to as a “hierarchical star”

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14
Q

What determines how data travels “logical topology” in a physical star

A

this is determined by the type of central device:

Hub = logical bus

switch = logical switching

MAU = logical ring

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15
Q

What is the disadvantage of a physical star

A

The central device represents a single point of failure. If this device fails the entire network goes down

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16
Q

What is a physical ring topology similar to and in what way

A

it’s like a bus:

Devices are daisy-chained to one another

Instead of terminating each end, the cabling is brought around from the last device back to the first device to form a ring

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17
Q

What is a physical ring topology most widely used for

What is the technology involved used for

A

to connect LANs. Uses a technology called Fiber Distributed Data Interface (FDDI)

FDDI was most often used as a “network backbone”, which is cabling used to communicate between LANs or between hubs and switches

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18
Q

How does data travel in Physical Ring Topology,

what happens if a station in the ring fails

A

Data travels unidirectionaly, if any station fails the ring ceases function and data can no longer be transferred.

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19
Q

How does FDDI transfer data

A

Fiber Distributed Data Interface

uses dual ring (data travels in both directions)

one ring failure will not break the network

Operates using fiber-optic cable at 100 Mpbs

Extended star topologies with Gigabit Ethernet has largely replaced FDDI

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20
Q

What is Point-to-Point topology

A

this is format in which data has a direct link between two devices

Mostly used in WANs

Wireless bridge

used to connect two computers

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21
Q

What is Point-to-Multipoint topology

A

also known as (PMP) this means that a central device communicates with two or more other devices

All communication goes through the central device

often used in WANs where a main office has connections to several branch offices via a router

A single connection is made from the router to a switching device that directs traffic to the correct branch office

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22
Q

What is Mesh Topology

A

this means that each device is connected to every other device in a network

the purpose of creating a mesh topology is to ensure that if one or more connections fail, there’s another path for reaching all devices on the network

Expensive due to multiple interfaces and cabling

Found in large WANs and internetworks

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23
Q

What are logical topologies

A
  • These are how data travels from computer to computer
  • They are sometimes the same as physical topology
    • In a physical bus and physical ring, the logical topology mimics the physical arrangement of cables
    • For physical star, electronics in central device determine logical topology
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24
Q

What are the three logical topologies and what are the network technologies and physical topologies associated with them?

A
  • Bus
    • Ethernet
      • bus or star
    • Wireless LANs
      • star
  • Ring
    • Token ring
      • Star
    • FDDI
      • Ring
  • Switched
    • Ethernet
      • Star
25
Q

What are example of LAN technologies

A

Ethernet, 802.11 wireless, Token Ring

26
Q

What are examples of WAN technologies

A

Frame relay, FDDI, ATM

27
Q

What is an unshielded twisted pair

A

an unshielded twisted pair or (UTP) is:

The most common media type in LANs

made up of 4 pairs of copper wires each twisted together

Comes in numbered categories

28
Q

What is Fiber-optic cabling

A

Fiber-optic cabling uses thin strands of glass to carry pulses of light long distances and at high data rates

29
Q

What is Coaxial Cable

A

this is obsolete as a LAN medium but it is used as the network medium for internet access via cable modem

30
Q

What are the two ways network technologies can use media to transmit signals

A

Baseband - sends digital signals in which each bit of data is represented by a pulse of electricity or light. Sent at a single fixed frequency and no other frames can be sent along with it

Broadband - uses analog techniques to encode binary 1s and 0s across a continuous range of values. Signals flow at a particular frequency and each frequency represents a channel of data

31
Q

Ethernet is the ___ ___ LAN technology

Easy to install and support with a ___ ___ factor

supports a broad range of speeds: 10 ___ to 10 ___

Can operate in physical ___ or physical ___ and logical ___ or ___ ___ topology

Most NICs/hubs/switches can operate at multiple speeds: 10/100/1000

Underlying technology is the same

A

Ethernet is the most popular LAN technology

Easy to install and support with a low cost factor

supports a broad range of speeds: 10 mbps to 10 Gbps

Can operate in physical bus or physical star and logical bus or switched local topology

Most NICs/hubs/switches can operate at multiple speeds: 10/100/1000

Underlying technology is the same

32
Q

What is Ethernet 2 frame type

A

frame type used by TCP/IP

TCP/IP has become the dominant network protocol in LANs so supporting multiple frame types has become unnecessary

33
Q

What are ethernet frames composed of

A

Destination MAC, Source MAC, Type, Data, FCS

34
Q

What is Carrier Sense Multiple Access with Collision Detection (CSMA/CD)

A
  • Carrier Sense - Listen before send - must hear silence
  • Multiple Access - If two or more stations hear silence, multiple stations may transmit at the same time
  • Collision Detection - If two or more stations transmit, a collision occurs and is detected by the NIC; all stations must retransmit
35
Q

What is a collision domain

A

The extent to which signals in an ethernet bus topology network are propagated is called a collision domain

36
Q

What does the term “best-effort delivery system” mean when referring to Ethernet

A
  • Like the post-office; you hope it gets there but there is no acknowledgement either way
  • Network protocols and applications ensure delivery
  • Only collisions are automatically retransmitted
37
Q

Ethernet detects damaged frames, how does this occur

A

There is an error checking code in a frame’s trailer called a Cyclic Redundancy Check (CRC)

Uses CRC to determine that data is unchanged

If a frame is detected as damaged, it is discarded with no notification

38
Q

Ethernet on hubs works only in what mode

A

Half duplex

39
Q

How are Ethernet standards expressed

A
  • XBaseY
    • X designates speed of transmission
    • Y specifies type of media (T = twisted pair, FX = fiber optic)
40
Q

Describe the following Ethernet Standard: 10BaseT

A
  • uses two of the four wire pairs
  • Runs over category 3 or higher UTP cabling
  • Highly susceptible to collisions and is obsolete
41
Q

Describe the following Ethernet Standard: 40 Gigabit and 100 Gigabit Ethernet

A

Very high cost is still prohibitive

Adoption has been slow

Fiber-optic cabling is primary medium

Although there are provisions to use special copper assemblies over short distances

42
Q

What is 802.11 wireless networking also referred to as

can be found in most towns and in those cases it is called what?

A

Wireless Fidelity (Wi-Fi)

a hotspot

43
Q

what are the two modes in which Wi-Fi can operate

A
  • Infrastructure - use central access point (AP)
  • Ad hoc - no central device; data travels from device to device like a bus
    • sometimes called peer-to-peer mode
44
Q

what is the Wi-Fi access method

A

sending station can’t hear if another station begins transmitting so they cannot use the CSMA/CD access method that ethernet uses

Wi-Fi devices use carrier sense multiple access with collision avoidance (CSMA/CA)

uses request-to-send/clear-to-send (RTS/CTS) packets and acknoledgements

With this extra “chatter” actual throughput is essentially cut in half

45
Q

Describe the following type of signal interference: Absorption

A

Solid objects absorb radio signals, causing them to attenuate (weaken)

46
Q

Describe the following type of signal interference: Refraction

A

The bending of a radio signal as it passes from a medium of one density through a medium of a different density

47
Q

Describe the following type of signal interference: Diffraction

A

the altering of a wave as it tries to bend around an object

48
Q

Describe the following type of signal interference: Reflection

A

Occurs when a signal hits a dense, reflective material, resulting in signal loss

49
Q

Describe the following type of signal interference: Scattering

A

When a signal changes direction in unpredictable ways, causing a loss in signal strength

50
Q

What is signal-to-noise ratio

A
  • the amount of noise compared with the signal strength
    • Noise can come from equipment, other wireless devices, and other wireless networks
51
Q

What is throughput

A

The actual amount of data transferred - not counting erros and acknowledgements

52
Q

what is goodput

A

Actual application-to-application data transfer speed

53
Q

What is overhead

A

Packet frame headers, acknowledgements, and retransmissions

54
Q

What are Wi-Fi encryption protocols

A

Wired equivalent privacy (WEP), Wi-Fi Protected Access (WPA), and WPA2

Not all devices support all three protocols

Older devices might only support WEP and/or WPA

55
Q

What are the physical and logical topologies for a Token Ring network?

A

They have a Star Physical topology with a ring logical topology

56
Q

How does a Token Ring Network operate?

A
  • A token is passed along the network
    • Only the station with the token can transmit
    • Frames are acknowledged and token is released
    • no collisions
    • Obsolete
57
Q

What is Fiber Distributed Data Interface Technology

topology, speed, cabling and so on

A

This uses a physical and logical ring topology

uses a token passing method with dual rings for redundancy

Transmits at 100 mbps and can include up to 500 nodes over a distance of 60 miles

uses only fiber optic cable

Obsolete on new networks

58
Q

What are the 4 primary physical topologies

A

bus

star

ring

point-to-point

59
Q

What are the 3 primary logical topologies

A

bus, ring, switched

Introduction to Networking (6 decks)

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