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Course 2 - Bits and Bytes of Networking* > Week 1 - Introduction to Computer Networking > Flashcards

Week 1 - Introduction to Computer Networking Flashcards

1
Q

Define what is a “protocol”?

A

A defined set of rules/standards that computers must follow in order to communicate properly

(rules of delivering a piece of mail through a delivery system)

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2
Q

What does computer networking generally refer to?

A

the full scope of how computers communicate with each other

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3
Q

Why are network protocols important? 2

A
  1. computers can hear and understand each other with the same protocols
  2. repeat messages not fully delivered
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4
Q

What are the 5 layers of Networking of the TCP/IP model? Top to bottom

A
  1. Application
  2. Transport
  3. Networking
  4. Data Link
  5. Physical
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5
Q

What is the Physical Layer?

A

The physical devices that interconnect computers

The delivery truck (of bits of data)

(cables, connection points, and protocols for how signals are sent)

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6
Q

What is the Data Link Layer also known as? What protocol is introduced? What does it specify? What type of data transfer does it focus on?

A

Network interface layer

introduces first protocols (ethernet, wifi) and is responsible for specifying physical layer attributes and focuses on getting data to nodes on the same network/link.

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7
Q

What is the Network Layer? What device does it use and how? What protocol?

A

Internet Layer

Gets data from one node to another in different networks using routers. Uses common Internet Protocol

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8
Q

What does the Transport layer do? What are common protocols in this layer? Which is the unreliable delivery? What protocol does it use to get around?

A

Sorts out which clients and server programs are meant to get data

Common is TCP to deliver data reliably, uses IP to get around. UDP is also common but no reliable delivery.

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9
Q

What is UDP?

A

User Datagram Protocol

Unreliable delivery of data, delivers it everywhere

How delivery truck finds your specific house

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10
Q

What is the Application Layer? What does its protocols allow you to do?

A

Applications, directly interact with this layer. The protocols allow you to browse the web or send/receive data.

The actual package you can touch (interact with)

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11
Q

Out of the Cat cables, which is limited in range transporting data across long distances at high speeds?

A

Cat 6

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12
Q

What is crosstalk?

A

when an electrical pulse is detected on another cable causing an error in the transmission of data

receiving end can’t understand data causing it to be re-sent

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13
Q

Which is better and why? Cat 5 or Cat 5e?

A

Cat 5e is better as Cat 5 is older and more susceptible to crosstalk. Cat 5e is more reliable and faster.

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14
Q

What are Cat cables made of? What do they do?

A

Twisted copper wires inside a plastic insulator that send binary signals as voltage changes in 1s and 0s

(receiving end = interprets voltages into data using line coding)

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15
Q

What is the benefit of fiber optic cables distance-wise?

A

Can transport data across long distances at higher speed without potential data loss

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16
Q

What are point-to-point connections?

A

a single device is at the end of each cable

not for multiple computers to connect

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17
Q

What is a Hub? What layer is it? Can it inspect contents?

A

a physical layer device that allows multiple computers to interconnect on a single network (LAN)

No cannot inspect data, all computers end up receiving the data (congestion)

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18
Q

What is a network switch? What layer is it?

A

it’s a data link layer device that is like a hub but is able to inspect contents of ethernet data being sent to it from a computer to determine which system is meant to receive that data

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19
Q

Explain what routers do? What layer are they? What do they use to help them network?

A

Network layer

They forward data between independent networks using IP data and internal tables

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20
Q

How is a core ISP router different?

A

a core ISP router is able to handle more traffic and more complex traffic decisions

backbone of the internet

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21
Q

How do routers share global data with each other? How does it work?

A

BGP - Border Gateway Protocol

Lets them know the optimal path to forward traffic

Google Maps GPS of the world’s networks

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22
Q

What is a node?

A

a device connected to the internet

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23
Q

What is a server?

A

serves data to clients (customers) requesting that data (asking for food)

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24
Q

What is a client?

A

requesting the data from the server (receiving food)

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25
Can nodes be both a server and a client?
Yes, almost all nodes are both at some point most aren't purely a server or client
26
Can individual computer programs on the same node be servers and clients to each other too?
Yes like Active Server Directory
27
What do you call a node that is a server but also a client? Which of the two?
It depends on its primary reason If it's to serve data to client, it's a server (like an email server, even though it's a client of a DNS server)
28
What could also occasionally be a server in your house?
A desktop (fetches data from servers so user can do their work)
29
How many wires are in a standard Cat 6 cable? How many pairs?
8 wires, 4 pairs
30
What is full duplexing?
When data is able to flow in both directions simultaneously
31
What is half-duplex? What layer is it?
A half duplex connection allows communication in both directions, but only one side can communicate at a time. Physical layer
32
What is simplex communication? on what medium? What layer is it?
1 way communication channel over a cable or radio signal Physical layer
33
What is EMI and RFI?
Electromagnetic interference Radio Frequency interference
34
What are FTP, STP, UTP cables?
FTP - foiled twisted pair STP - shielded twisted pair UTP - unshielded twisted pair
35
What is the least expensive type of Ethernet cable for home/business?
UTP unshielded twisted pair
36
Which two Ethernet cable types can exist together for extra protection against interference? Where is this most likely used?
STP and FTP in industrial environments where EMI/RFI is much higher than normal (more expensive option)
37
Which Ethernet cable is more used for Network tasks?
CAT cables
38
Which Ethernet cables are used for computer/router connections to hubs and Ethernet switches and which for server connections ---> Ethernet switches?
Straight through cables
39
When are crossover cables used?
1. connect an IT admin laptop directly to an Enterprise machine (server, switch, router, hub, etc) 2. Connecting 2 similar devices together (2 switches, 2 hubs, switch to hub, 2 routers, 2 PCs, router to PC)
40
What is Auto-MDI/MDIX technology? What do they stand for?
Technology on an Enterprise machine that can detect Ethernet connection types and select the correct wires to send/receive data Used to connect 2 computing devices to each other Auto Medium Dependent Interface Crossover (Auto-MDI/MDIX) technology
41
How do you connect crossover cables?
connection made between: 1. Ethernet port/NIC on the IT admin system 2. the management port of the Enterprise machine
42
What is NIC?
Network Interface Card
43
Difference between straight-through cables and crossover cables? What devices do they connect to?
Straight-through cables connect dissimilar devices and crossover cables connect similar devices
44
What is modulation?
varying electrical charges that carry bits of data over a cable
45
What is line coding?
converts binary digits into a sequence of bits (turns electrical charges into something the computer can understand) (digital data to digital signals)
46
What is a patch panel?
contains many network ports, main purpose
47
Which Ethernet TP cable is most common?
Unshielded Twisted Pair basic protection, least expensive
48
Which Ethernet TP cable uses braided aluminum and copper to encase 4 twisted pairs?
Shielded Twisted Pair uses braided aluminum and copper shielding
49
Which Ethernet TP cable uses a thin foil shield wrapped around bundle of TP wires?
Foiled Twisted Pair
50
Which TP cables can exist together in same cable for extra protection against interference?
STP and FTP
51
What is a collision domain?
A network segment where only one device can speak at a time (packets collide from congestion)
52
What is the Ethernet protocol?
protocol most widely used to send data across individual links
53
What does CSMA/CD do? What does it stand for?
Carrier Sense Multiple Access with Collision Detection (CSMA/CD) determines when a communication channel is clear so a device is free to transmit data
54
What happens if the CSMA/CD detects a data collision?
It stops sending data temporarily, waits a random interval of time and starts sending data again to avoid another collision
55
What is a MAC address and what is it attached to?
a globally unique identifier attached to an individual network node (like a computer, PlayStation, etc) (the address to a house)
56
How many bits in a MAC address?
48-bit number represented by 6 groupings (6 numbers in a group) of 2 hexadecimal numbers EX) 00 60 2F EX) 3A 07 BC
57
What is hexadecimal?
hexadecimal represents #s with a 16 digit range (the whole table 0-9 and A-F) EX) 01 68 7E EX) 2B 04 CD
58
What is an octet?
In computer networking, 8 bits (a byte) represented by a # 00 60 28 Each number is an octet/byte (48 bits in total)
59
What are the first 3 octets in a MAC address assigned by? And to who?
Assigned by the IEEE to individual network hardware manufacturers (institute of electrical and electronics engineers)
60
What are the last 3 octets of a MAC address assigned by?
Assigned any way a manufacturer would like with the condition that they only assign each possible address once to keep all MAC addresses globally unique
61
How does the Ethernet protocol use MAC addresses?
The Ethernet protocol uses MAC addresses: 1. to ensure the data it sends has an address for the machine that sent the data 2. an address for the machine that data is intended for
62
What does it mean when a network segment is a collision domain?
all devices on that segment receive all communication across the entire segment also: network congestion collision of data packets 1 device can transmit data at a time
63
What 2 sections are MAC addresses split into?
1. OUI (organizationally unique identifier) - first 3-hexa bytes/octets of MAC address assigned by the IEEE to individual hardware manufacturer's 2. The manufacturer uses the last 3-hexa bytes to generate unique MAC addresses for every interface.
64
What does OUI stand for in MAC addresses?
Organizationally Unique Identifier
65
What are the 3 types of Ethernet transmissions?
1. Unicast 2. Multicast frame 3. Broadcast using a broadcast address
66
What is a broadcast address? How do they look?
It's a special destination used by the broadcast Ethernet transmission to send data to every device on a LAN. The Ethernet broadcast address is all F's (set to 1s)
67
Why are Ethernet broadcast addresses used?
So devices can learn more about each other (like their MAC address)
68
How many addresses receive the Unicast Ethernet transmission?
1, always meant for one receiving address
69
How do Ethernet transmissions work by looking at a special bit in the MAC address? 2 different types of transmissions looked at
1. If first octet's least significant bit is set to 0, means the ethernet frame is UNICAST and intended for only the destination address (sent to all devices on CD, but only received and processed by the intended destination) 2. If the first octet's least significant bit is set to 1, it means you're dealing with a MULTICAST frame.
70
What did the Ethernet protocol use to solve the data collision issue?
using a technique known as CSMA/CD Carrier Sense Multiple Access with Collision Detection
71
What is a benefit of twisted wires?
Reduces noise and is less susceptible to cross talk
72
What sort of applications use twisted pair cabling technology?
audio, security, alarm, network Ethernet cables
73
What happens in the area between two parallel wires that are carrying current in opposite directions?
a magnetic field is created
74
What does MAC stand for?
Media Access Control
75
In what layer do MAC address work in?
The data link layer
76
What are the differences between Unicast, Multicast, and Broadcast addresses? 3 What do they send?
1. Unicast: The packet is sent to a single destination (one-to-one) 2. Multicast: The packet is sent to a set (group) of hosts that can be on different networks (one to many) 3. Broadcast: The packet is sent to an entire network (one to all) with a broadcast address
77
Why are Ethernet broadcast addresses used?
So devices can learn more about each other (like their MAC address)
78
What is a data packet?
general concept of data sent from A to B, no specific layer
79
What are data packets at an Ethernet level called? What are they?
Ethernet Frames collection of highly structured info presented in a specific order
80
How do Ethernet frames work with physical layer network interfaces?
The network interfaces convert the streams of bits into meaningful data (vice versa)
81
Are all sections of an Ethernet frame mandatory?
Almost all are mandatory and most have a fixed size
82
What are the 8 sections of an Ethernet frame?
1. Preamble 2. SFD (start frame delimiter) 3. Destination MAC address 4. Source MAC address 5. VLAN header 6. Ether-type 7. Payload 8. FCS (frame check sequence)
83
What is a preamble? Can it be split?
First section of an Ethernet frame and can be split into 2 sections 1. First 7 bytes act as buffer and synchronize the internal clocks frames use (regulates data speed) 2. SFD
84
What is SFD in the preamble? What does it do?
signals to receiving device that the preamble is over and the actual frame contents will now follow Start Frame Delimiter
85
What is the Ether-type field?
describes the protocol of the contents of the frame (2 bytes long)
86
What could we also find instead of an Ether-type field in a frame?
VLAN header (indicates the frame is a VLAN frame) Ether-type field follows it
87
How are frames with VLAN delivered?
Only delivered out of a switch interface configured to relay that specific VLAN tag
88
What is a VLAN?
Virtual LAN technique that lets you have multiple LANs operating on the same physical equipment
89
What do VLANs separate?
separate different groups of traffic and devices (IP phones on one VLAN, all desktops on another, etc)
90
What data does the data payload transport? (46-1500 bytes long)
Everything from the higher layers (IP, Transport, Application) that isn't a header
91
What does FCS stand for?
Frame Check Sequence
92
What is the FCS (frame check sequence) in an Ethernet frame?
a 4 byte number that represents a checksum value for the entire frame
93
How is a checksum value calculated?
performs a CRC (cyclical redundancy check) against the frame Performing a CRC against a set of data should give you the same checksum number every time
94
What does the CRC do?
CRC Cyclical Redundancy Check Included in an Ethernet frame so receiving network interface can see if it received corrupted data
95
When does a network device throw out the data received?
When the checksum number it calculated does not match the frame check sequence number that was attached to the end of the frame
96
Does Ethernet perform data recovery?
No, only performs data integrity checks
97
Why are MAC addresses useful?
Using MAC addresses prevents the network segment from becoming a collision domain

Course 2 - Bits and Bytes of Networking* (15 decks)

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