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ADVNET MAY > Predict Exam Questions > Flashcards

Predict Exam Questions Flashcards

(90 cards)

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1
Q

What guarantees does TCP provide?

A

Reliable, ordered, and error-checked delivery of data.

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2
Q

What guarantees does UDP provide?

A

None — it’s connectionless and does not guarantee delivery or order.

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3
Q

Which protocol is better for streaming video: TCP or UDP?

A

UDP — it tolerates some loss and has lower latency.

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4
Q

Which protocol is better for sending emails: TCP or UDP?

A

TCP — email protocols require reliable delivery.

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5
Q

What is the main benefit of using UDP over TCP?

A

Lower overhead and faster delivery for real-time data.

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6
Q

Why might you choose TCP over UDP?

A

To ensure data arrives intact, in order, and with error-checking.

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7
Q

Does UDP have congestion control?

A

No, UDP does not have built-in congestion control.

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8
Q

Which protocol uses a three-way handshake to establish a connection?

A

TCP.

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9
Q

Which protocol is commonly used for DNS queries?

A

UDP.

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10
Q

Why does DNS sometimes use TCP?

A

For larger responses (over 512 bytes) or zone transfers.

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11
Q

What is TCP’s window scaling used for? (sliding window mechanism)

A

To manage the flow of unacknowledged data between sender and receiver.

(keeps track of how many bytes (or frames) have been sent but not yet ACKed)

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12
Q

What does TCP use to detect lost packets?

A

Acknowledgements (ACKs) and timeouts.

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13
Q

What is selective acknowledgement (SACK)?

A

An extension that allows TCP to acknowledge non-contiguous packets.

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14
Q

What is the purpose of TCP window scaling?

A

To allow larger window sizes in high-bandwidth networks.

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15
Q

How does TCP avoid congestion?

A

By adjusting the congestion window using algorithms like slow start and congestion avoidance.

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16
Q

What is cumulative acknowledgement in TCP?

A

Acknowledging the last byte received in order.

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17
Q

Why are delayed ACKs used in TCP?

A

To reduce the number of small packets sent.

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18
Q

How does TCP ensure data is delivered in order?

A

By using sequence numbers and reordering data at the receiver.

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19
Q

What is the initial congestion window in TCP used for?

A

To control the amount of data sent at the start of a connection.

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20
Q

Why does TCP use retransmission?

A

To resend lost or corrupted packets.

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21
Q

What is network latency?

A

The time it takes for a data packet to travel from source to destination.

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22
Q

What is the bandwidth-delay product?

A

The amount of data that can be in transit in a network.

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23
Q

Why is TCP inefficient in long fat networks?

A

Its default window size limits throughput over high-delay links.

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24
Q

How can you improve TCP performance over long distances?

A

Enable window scaling.
Could use larger buffers, but could cause Bufferbloat. So use with Active Queue Management. (AQM)

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25
What causes high latency?
Physical distance, propagation delay, processing delays, and queueing.
26
What is RTT?
Round-Trip Time — time for a signal to go to the destination and back.
27
Why does latency affect user experience?
It delays interactions, especially in real-time applications.
28
How does TCP measure latency?
Using round-trip time estimates.
29
How can latency be reduced?
Optimising routing, reducing hops, and using faster physical media.
30
How does TCP's congestion window react to high latency?
It grows more slowly, which can reduce throughput.
31
What is the purpose of the Domain Name System (DNS)?
To map human-readable domain names to IP addresses.
32
What type of DNS record maps a domain name to an IPv4 address?
A record.
33
What type of DNS record maps a domain name to an IPv6 address?
AAAA record.
34
What does an MX record specify?
The mail server responsible for accepting email for the domain.
35
What is a CNAME record used for?
It maps one domain name to another (alias).
36
What is a TXT record used for?
To store human-readable text, often for domain verification or SPF records.
37
What does TTL stand for in DNS?
Time To Live — how long a DNS record can be cached.
38
Why might you choose a low TTL value like 60 seconds?
To allow quick propagation of changes.
39
Why might you choose a high TTL value like 86400 seconds?
To reduce DNS traffic and improve performance.
40
What happens when a TTL expires?
The DNS record is removed from cache and must be re-queried.
41
What is a recursive DNS server?
A server that resolves DNS queries by querying other servers on behalf of the client.
42
What is an authoritative DNS server?
A server that holds the actual DNS records for a domain.
43
What is a glue record?
A record that provides the IP address of a nameserver when delegating a zone.
44
Why are glue records important?
They prevent circular dependency issues in DNS resolution.
45
What is the root of the DNS hierarchy?
The root zone, represented as a dot ('.').
46
What is label compression in DNS packets?
A way to reduce packet size by referencing earlier labels.
47
What flag in a DNS packet indicates authoritative data?
The AA (Authoritative Answer) flag.
48
What is bailiwick checking?
A security check to ensure additional data matches the expected domain zone.
49
What is cache poisoning?
Injecting false DNS data into a cache to redirect users.
50
How does DNSSEC help prevent cache poisoning?
By signing DNS records cryptographically.
51
Why should recursive and authoritative DNS servers be separated?
To reduce attack surface (I.e. keep cache and zone files record separate) so in case of recursive cache server poisoning, authoritive server is not at risk of serving false malicious records to everyone. Also stops recursive server from slowing down authoritative server.
52
What is a stealth primary DNS server?
A hidden master server not listed in NS records.
53
Why use a stealth primary server?
To protect the master server behind a firewall.
54
Why should you avoid using CNAMEs for service mapping?
They complicate caching and add extra DNS lookups.
55
What might happen if glue records are outdated?
Clients may not be able to resolve the domain.
56
What is an SOA record in DNS?
Start of Authority — defines the main parameters of a DNS zone.
57
What does the SOA serial number represent?
A version number that changes with each zone update.
58
What happens if a secondary server can't reach the primary for too long?
It stops serving the zone after the expire interval.
59
What does the 'refresh' value in SOA specify?
How often a secondary server checks for updates.
60
What should you do if you find yourself manually editing zone files?
Reconsider — automation is preferred to avoid errors.
61
What is DHCP used for?
Automatically assigning IP addresses and configuration to devices.
62
What does SLAAC stand for?
Stateless Address Autoconfiguration.
63
What are the main types of IP address allocation?
Static allocation, DHCP, and SLAAC.
64
What is a benefit of using static addressing?
Predictability and manual control.
65
What is a downside of static addressing?
Scalability and manual configuration burden.
66
What is a benefit of DHCP?
Centralised control and easy reconfiguration.
67
What is a downside of DHCP?
Dependency on DHCP server availability.
68
How does SLAAC generate addresses?
By combining the network prefix with the device's interface ID.
69
What does RFC4941 define?
Temporary random IPv6 addresses to enhance privacy.
70
What does RFC7217 define?
Stable, opaque IPv6 addresses that don't expose MACs.
71
How does a basic DHCP exchange work?
The client broadcasts a discover, server replies with offer, client requests, and server acknowledges.
72
What problem arises if a DHCP server is split across buildings and the link breaks?
Clients may receive conflicting addresses or fail to get configuration.
73
How can DHCP be made more reliable?
Use failover pairs or relays and manage lease conflicts.
74
What can happen if a DHCP client reconnects to a different server?
It might be assigned a different address unless configuration ensures consistency.
75
Why are lease durations important in DHCP?
They determine how often clients must renew their addresses.
76
What is a DHCP relay?
A device that forwards DHCP requests from clients to a central server.
77
Why are short DHCP leases useful?
They allow fast IP recycling and adapt to dynamic networks.
78
Why are long DHCP leases useful?
They reduce DHCP traffic and keep IPs stable.
79
What type of address does DHCPv6 assign?
IPv6 addresses and other configuration information.
80
How does DHCP help prevent duplicate IP addresses?
By tracking leases and ensuring assigned addresses are unique.
81
What is subnetting?
Dividing a larger IP network into smaller, manageable sub-networks.
82
Why use subnetting?
To improve routing efficiency and better organise IP address space.
83
What does CIDR stand for?
Classless Inter-Domain Routing.
84
What does the '/16' in 147.188.0.0/16 mean?
The first 16 bits are the network prefix.
85
How many /24 subnets are in a /16 block?
256
86
What’s the usable host range of a /24 subnet?
254 usable addresses (from .1 to .254).
87
What is a broadcast address in IPv4?
The address with all host bits set to 1.
88
What happens if you assign the network or broadcast address to a host?
It can cause communication issues or conflict.
89
How would you divide 147.188.0.0/16 into 100 subnets?
Create /23 subnets to allow ~512 addresses each.
90
What tool helps visualise subnet boundaries and sizes?
A subnet calculator.

ADVNET MAY (4 decks)

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