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0. Ω System Design(Large scale systems)Ω > 1.4 Domain Name Systems > Flashcards

1.4 Domain Name Systems Flashcards

1
Q

What does DNS stand for?

A

Domain Name System

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2
Q

What are the two software components used in Windows Server 2008 DNS?

A
  • DNS server
  • DNS client (or resolver)
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3
Q

Why is DNS important for network users?

A

It maps user-friendly alphanumeric names to numeric IP addresses.

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4
Q

What layer of the TCP/IP reference model does DNS operate in?

A

Application layer

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5
Q

What is the default name resolution service in a Windows Server 2008 network?

A

Windows Server 2008 DNS

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6
Q

What is the role of the DNS Client service in Windows Server 2008?

A

It contacts a DNS server to resolve a network host name to an IP address.

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7
Q

How does Active Directory Domain Services (AD DS) utilize DNS?

A

It uses DNS to locate domain controllers for authentication and other operations.

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8
Q

What is the difference between DNS and WINS?

A

DNS is hierarchical while WINS is a flat namespace.

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9
Q

What does DHCP provide for Windows Server 2008 DNS?

A

Default support to register and update information for legacy DHCP clients in DNS zones.

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10
Q

What does a Domain Name System (DNS) do?

A

Translates a domain name to an IP address.

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11
Q

What are the types of DNS records?

A
  • NS record (name server)
  • MX record (mail exchange)
  • A record (address)
  • CNAME (canonical)
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12
Q

True or False: DNS servers can cache mappings.

A

True

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13
Q

What is a fully qualified domain name (FQDN)?

A

It uniquely identifies a host’s position within the DNS hierarchical tree.

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14
Q

What is the top of the DNS domain name hierarchy called?

A

Root domain

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15
Q

What type of domain is ‘microsoft.com’ considered?

A

Second-level domain

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16
Q

What is the purpose of a Start of Authority (SOA) record?

A

It identifies a primary DNS name server for the zone.

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17
Q

Fill in the blank: The DNS database consists of ______.

A

resource records (RRs)

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18
Q

What are common types of DNS resource records?

A
  • A
  • NS
  • MX
  • CNAME
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19
Q

What is the primary function of the DNS server?

A

To resolve domain names to IP addresses.

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20
Q

What can introduce delays when accessing a DNS server?

A

The need to contact the DNS server and potential propagation delays.

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21
Q

What are DNS top-level domains (TLDs)?

A

They indicate the type of organization or country/region.

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22
Q

True or False: DNS management is simple and straightforward.

A

False

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23
Q

What is the main disadvantage of DNS?

A

It can be complex to manage and is vulnerable to DDoS attacks.

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24
Q

What RFCs are foundational for DNS?

A
  • RFC 1034
  • RFC 1035
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25
Q

What is a subdomain?

A

Additional names derived from a registered second-level domain.

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26
Q

How does DNS support hierarchical names?

A

It allows registration of various data types in addition to host name-to-IP address mapping.

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27
Q

What does a CNAME record do?

A

Points a name to another name or to an A record.

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28
Q

What is the root domain of a DNS zone?

A

The specific domain name that anchors a zone.

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29
Q

What does a DNS server need to be considered authoritative for a name?

A

It must load the zone containing that name.

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30
Q

What is the first record in any zone file?

A

Start of Authority (SOA) RR.

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31
Q

What does the SOA RR identify?

A

A primary DNS name server for the zone.

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32
Q

What is DNS delegation?

A

Assigning responsibility for a portion of a DNS namespace to a different DNS server.

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33
Q

What resource record represents DNS delegation?

A

NS resource record.

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34
Q

What are the primary reasons to delegate a DNS namespace?

A
  • Need to delegate management to multiple organizations.
  • Need to distribute load among DNS servers.
  • Need to allow for a host’s organizational affiliation.
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35
Q

How does a DNS server facilitate delegation?

A

By using NS RRs to identify DNS servers for each zone.

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36
Q

What types of zones can represent the same portion of the DNS namespace?

A
  • Primary
  • Secondary
  • Stub
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37
Q

What is a primary zone in DNS?

A

A zone where all updates for records are made.

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38
Q

What is a secondary zone?

A

A read-only copy of the primary zone.

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39
Q

What is a stub zone?

A

A read-only copy of the primary zone containing only the resource records identifying authoritative DNS servers.

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40
Q

What is zone transfer?

A

The process of replicating a zone file to multiple DNS servers.

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41
Q

What is the role of the master DNS server in zone transfer?

A

It is the source of the zone information during a transfer.

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42
Q

What are the two types of zone file replication?

A
  • Full zone transfer (AXFR)
  • Incremental zone transfer (IXFR)
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43
Q

What is a recursive DNS query?

A

A query that forces a DNS server to respond with either a failure or success response.

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44
Q

What is an iterative DNS query?

A

A query where the DNS server responds with the best local information it has.

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45
Q

What is the Time-to-Live (TTL) in a resource record?

A

The length of time used by DNS servers to cache information before expiring it.

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46
Q

What happens if the TTL is set too short?

A

Increased utilization of DNS servers and network traffic.

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47
Q

What is the impact of setting the TTL to zero?

A

Significant impact on DNS server performance due to constant querying for expired data.

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48
Q

What type of updates does Windows Server 2008 support for the DNS database?

A

Both static and dynamic updates.

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49
Q

What does the DNS Client service architecture illustrate?

A

Name resolution and update operations.

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50
Q

What does the DNS Server service architecture illustrate?

A

Administration tools and the Windows Management Instrumentation (WMI) interface.

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51
Q

What does DNS stand for?

A

Domain Name Service

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52
Q

What is the primary purpose of DNS?

A

To identify resources on networks

53
Q

In what year was the Domain Name System introduced?

A

November 1983

54
Q

At which OSI layer does DNS operate?

A

Application layer

55
Q

What port does DNS use?

56
Q

Which RFCs define the DNS protocol?

A
  • RFC 1034
  • RFC 1035
57
Q

What is the primary function of the Domain Name System?

A

To translate domain names to numerical IP addresses

58
Q

What is a DNS name server?

A

A server that stores the DNS records for a domain

59
Q

What types of records are commonly stored in the DNS database?

A
  • SOA
  • A and AAAA
  • MX
  • NS
  • PTR
  • CNAME
60
Q

What does SOA stand for in DNS records?

A

Start of Authority

61
Q

True or False: DNS is intended to be a general-purpose database.

62
Q

What does DNSSEC stand for?

A

Domain Name System Security Extensions

63
Q

What protocol did the Domain Name System originally use for transport?

A

User Datagram Protocol (UDP)

64
Q

How does the DNS function as a ‘phone book’ for the Internet?

A

By translating human-friendly hostnames into IP addresses

65
Q

What is the maximum length of a full domain name in DNS?

A

253 characters

66
Q

What is the root zone in the DNS structure?

A

The top of the domain name hierarchy

67
Q

What is the LDH rule in domain names?

A

Labels may only contain letters, digits, and hyphen

68
Q

What system allows for the use of non-ASCII characters in domain names?

A

Internationalizing Domain Names in Applications (IDNA)

69
Q

What is the role of authoritative name servers?

A

To provide definitive answers to DNS queries

70
Q

What are the two types of authoritative name servers?

A
  • Primary server
  • Secondary server
71
Q

What is a ‘lame delegation’ in DNS?

A

When a name server is designated as authoritative for a domain it does not have data for

72
Q

What is the process called when a DNS resolver queries multiple servers to obtain an answer?

A

Iterative resolution

73
Q

What is the purpose of caching in DNS?

A

To improve efficiency and reduce traffic on root servers

74
Q

What does the AA bit in DNS responses indicate?

A

The server is providing authoritative answers

75
Q

Fill in the blank: The DNS database is conventionally stored in a _______.

76
Q

Who developed the first ARPANET directory?

A

Elizabeth Feinler

77
Q

What is the function of the WHOIS directory?

A

To retrieve information about resources, contacts, and entities

78
Q

What are the top-level domains (TLDs) in DNS?

A

The right-most labels in domain names, such as .com or .edu

79
Q

What is the role of the Internet Engineering Task Force in the context of DNS?

A

To publish specifications for DNS protocols

80
Q

What does the term ‘zone’ refer to in DNS?

A

A subdomain under the administrative control of a name server

81
Q

How many levels can the tree of domain subdivisions have?

A

Up to 127 levels

82
Q

What is the role of root name servers in the DNS?

A

Root name servers are involved in only a relatively small fraction of all requests.

83
Q

What are recursive and caching name servers used for?

A

To improve efficiency, reduce DNS traffic, and increase performance in end-user applications.

84
Q

What is the purpose of DNS cache servers?

A

They store DNS query results for a period of time determined by the time-to-live (TTL) of the domain name record.

85
Q

What is a DNS resolver?

A

The client side of the DNS responsible for initiating and sequencing queries for resource resolution.

86
Q

Define a non-recursive query.

A

A query where a DNS resolver queries a DNS server that provides a record without querying other servers.

87
Q

What is a recursive query?

A

A query where a DNS resolver queries a single DNS server that may query other servers on behalf of the requester.

88
Q

What is the difference between iterative and recursive queries?

A

In iterative queries, each server refers the client to the next server until resolved, while recursive queries are fully resolved by one server.

89
Q

What are glue records?

A

Records that provide the IP address of an authoritative name server mentioned in a delegation to break circular dependencies.

90
Q

How does record caching work in DNS?

A

It stores results of name resolution locally with a time to live (TTL) to reduce load on DNS servers.

91
Q

What is a reverse DNS lookup?

A

A query of the DNS for domain names when the IP address is known.

92
Q

What is the format for storing IP addresses in reverse lookups for IPv4?

A

IP addresses are stored in reverse-ordered octet representation in PTR records under in-addr.arpa.

93
Q

What happens if a DNS resolver does not find a record?

A

It may cache the negative result based on the TTL of the SOA record.

94
Q

What is the typical structure of a DNS message?

A

Each DNS message consists of a header and four sections: question, answer, authority, and additional.

95
Q

What is the significance of the TTL in DNS records?

A

TTL indicates how long the information remains valid before needing to be refreshed.

96
Q

What are some common DNS record types?

A
  • A
  • AAAA
  • MX
  • TXT
97
Q

What is dynamic DNS (DDNS)?

A

It updates a DNS server with a client IP address on-the-fly.

98
Q

True or False: The DNS protocol uses different formats for queries and responses.

99
Q

What is the function of MX records in DNS?

A

They provide a mapping between a domain and a mail exchanger.

100
Q

Fill in the blank: A _______ is a combination of the name server and IP address.

A

glue record

101
Q

What are authoritative name servers?

A

Servers that provide DNS records for which they are responsible.

102
Q

How does a DNS resolver handle requests?

A

It checks its cache first, then queries designated DNS servers if the answer is not found.

103
Q

What is the function of the identification field in a DNS message header?

A

It matches responses with queries.

104
Q

What is DNSSEC?

A

A security extension for DNS that adds support for cryptographically signed responses

DNSSEC helps protect against certain types of attacks such as DNS cache poisoning.

105
Q

What is the purpose of the TYPE field in a Resource Record (RR)?

A

Indicates the format of the data and its intended use

Examples include A records for IPv4 addresses, NS records for name servers, and MX records for mail servers.

106
Q

What does the CLASS field in a Resource Record specify?

A

The class code of the record, typically set to IN for Internet

Other classes include Chaos (CH) and Hesiod (HS).

107
Q

What are wildcard DNS records?

A

Records that specify names starting with an asterisk, *, to match multiple subdomains

They generate resource records within a DNS zone by substituting whole labels.

108
Q

What is the function of the UPDATE DNS opcode?

A

Used to add or remove resource records dynamically from a zone database

Useful for registering network clients in DNS when they become available.

109
Q

What transport protocols does DNS use?

A

User Datagram Protocol (UDP) and Transmission Control Protocol (TCP)

UDP is used for queries, while TCP is used for larger responses and zone transfers.

110
Q

What is DNS over TLS (DoT)?

A

An IETF standard for encrypted DNS using TLS to protect the entire connection

DoT servers listen on TCP port 853.

111
Q

What does DNS over HTTPS (DoH) do?

A

Tunnels DNS query data over HTTPS, which transports HTTP over TLS

It uses TCP port 443 to appear similar to web traffic.

112
Q

What are the privacy properties of DNS over QUIC (DoQ)?

A

Similar to DoT with latency characteristics of classic DNS over UDP

RFC 9250 describes this method.

113
Q

What is DNSCrypt?

A

A protocol that introduces DNS encryption on the downstream side of recursive resolvers

Clients encrypt query payloads using servers’ public keys.

114
Q

What is DNS cache poisoning?

A

A vulnerability where false data is distributed to caching resolvers

This can redirect legitimate requests to malicious hosts.

115
Q

What is an IDN homograph attack?

A

A type of spoofing where visually similar characters can mislead users

For example, paypal.com vs paypa1.com.

116
Q

What is DNSMessenger?

A

A cyber attack technique that uses DNS to communicate with malware

It exploits DNS TXT records to send commands to infected systems.

117
Q

What are the main approaches to counter privacy issues with DNS?

A
  • VPNs
  • Tor
  • Proxies and public DNS servers

These methods aim to protect user privacy from local ISP surveillance.

118
Q

Who oversees domain name registration?

A

The Internet Corporation for Assigned Names and Numbers (ICANN)

ICANN accredits domain name registrars and oversees the name and number systems of the Internet.

119
Q

What is a registrant in the context of domain names?

A

A person or organization that requests domain registration

Registrant information is published using the WHOIS protocol.

120
Q

What is a thick registry approach in domain name registration?

A

A model where WHOIS data is maintained in central registries

Most Generic top-level domain (gTLD) registries have adopted this approach.

121
Q

What is the maximum TTL for a Resource Record?

A

About 68 years (2^31 - 1 seconds)

TTL stands for time-to-live and indicates how long a record is valid.

122
Q

What does DENIC stand for?

A

German NIC

DENIC is the central registry for the .de domain in Germany.

123
Q

What is the thick registry approach?

A

Keeping WHOIS data in central registries instead of registrar databases

Adopted by most Generic top-level domain (gTLD) registries since about 2001.

124
Q

Which top-level domains use a thin registry model?

A

COM and NET

In this model, basic WHOIS data is held by the domain registry.

125
Q

What basic WHOIS data is held by domain registries like GoDaddy and VeriSign?

A

Registrar and name servers

This information is part of the thin registry model for COM and NET domains.

126
Q

What is the role of the Public Interest Registry?

A

Exclusively manages the ORG domain

ORG domain registrants use this registry specifically.

127
Q

What are network information centers (NIC)?

A

Organizations that function as both registries and registrars

They provide access to WHOIS datasets in addition to registering domain names.

128
Q

What is a registry-registrar model?

A

A method where the registry manages the domain name database and relationships with registrars

Used by top-level domain registries for COM, NET, and ORG.

129
Q

In the registry-registrar model, who are the customers of the registrar?

A

Registrants (users of a domain name)

Sometimes includes additional subcontracting of resellers.

0. Ω System Design(Large scale systems)Ω (19 decks)

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