Bits & Bytes: Week 4, I (Network Services)

Question 1

This is a globally distributed network service that resolved strings of letters into IP addresses

Answer 1

Domain Name System

Question 2

A(n) ____________ can change but keep the same ____________

Answer 2

IP address; domain name

Question 3

If a website has multiple servers across the world, a ____________ might resolve to a different ____________ depending on which server is closest to the client.

Answer 3

Domain name; IP address

Question 4

The process of using DNS to turn a domain name into an IP address is known as this.

Answer 4

Name resolution

Question 5

According to the course, what are the four parts of a standard, modern network configuration? (Hint: DIGS)

Answer 5

1. DNS Server
2. IP Address
3. Gateway for a host
4. Subnet Mask

Question 6

What are the five primary types of DNS servers? (Hint: CARRoT)

Answer 6

1. Caching name servers
2. Authoritative name servers
3. Recursive name servers
4. Root name servers
5. TLD name servers

Question 7

These two types of DNS servers, often provided by an ISP or local network, store known domain name lookups (for a certain amount of time)

Answer 7

Caching and Recursive name servers

Question 8

True or false: A DNS server can only fulfil one type of duty at a time.

Answer 8

False; Any given DNS server can fulfil many roles at once.

Question 9

What type of DNS server performs full DNS resolution requests?

Answer 9

the Recursive name server

Question 10

This is a value in seconds that can be configured by the owner of a domain name for how long a server can cache an entry before it is discarded and a new, full resolution search must be performed again

Answer 10

DNS TTL

Question 11

In general, how long is a DNS TTL?

Answer 11

A few minutes to a few hours at most

Question 12

This is when a DNS server starts a brand new process, without relying on any cached data, turn a domain name into an IP address.

Answer 12

Full Recursive Resolution

Question 13

What is the name for a technique that’s used to route traffic to different destinations depending on factors such as location, network congestion, or link health?

Answer 13

Anycast

Question 14

How many root name servers (or root name authorities) exist across the globe?

Answer 14

13

Question 15

Why are DNS TTL times generally shorter now than they were in the past?

Answer 15

There is more internet bandwidth available to perform new DNS lookups as the internet has grown faster and in size

Question 16

ACRONYM:

TLD

Answer 16

Top Level Domain

Question 17

What is the top of the hierarchical DNS name resolution system called? What are some examples of this?

Answer 17

Top Level Domain

Ex: .com, .org, .net, .gov, .edu

Question 18

ACRONYM:

ANS

Answer 18

Authoritative name server

Question 19

What is the flow of traffic between servers when a DNS lookup is performed?

Answer 19

User requests domain name from local Caching/Recursive name server which asks Root Name Server who sends TLD location back to Caching/Recursive which then asks TLD name server who sends ANS location back to Caching/Recursive Server which then asks ANS who finally provides corresponding IP address

Question 20

Why must all full DNS resolutions go through a strictly regulated and controlled series of hierarchical lookups to get the correct responses?

Answer 20

In order to protect against malicious parties redirecting network traffic and stealing data.

Question 21

What is an example of an application layer service that uses UDP instead of TCP?

Answer 21

DNS

Question 22

Why is a DNS request an ideal candidate for UDP’s connectionless protocol?

Answer 22

A DNS request and response can usually fit into one UDP datagram

Question 23

How many TCP packets would a DNS resolution request require? How many UDP packets?

Answer 23

44; 8

Question 24

Responding to incoming address lookups is the sole purpose of this.

Answer 24

a DNS server

Question 25

Performing lookups and repeating unsuccessful lookups is the sole purpose of this.

Answer 25

a DNS Resolver

Question 26

When a DNS lookup response doesn’t fit in a single UDP datagram, a DNS name server would respond with a packet explaining that the response is too large. How does the DNS client address this situation?

Answer 26

The DNS client would have to establish a TCP connection in order to perform the lookup.