Week 8

Question 1

What are Domain Names?

Answer 1

Devices are labeled with numeric IP addresses

Domain names are names for the numeric IP addresses

Question 2

What is a DNS?

Answer 2

DNS translates human-readable domain names into machine readable IP addresses

Question 3

What is Shared Hosting?

Answer 3

An IP address mapped to multiple host names

Question 4

What are the 4 DNS requirements?

Answer 4

Scalability

Efficiency

Reliability

Maintainability

Question 5

What does the scalability part of the DNS mean?

Answer 5

Hierarchial Design:

Root

Top Level Domain

Second Level Domain

Third Level Domain

Question 6

What does the Redundancy part of the DNS mean?

Answer 6

Each logical root server refers to multiple physical ones

Question 7

What does the Reliability part of the DNS mean?

Answer 7

No single point of failure

Question 8

What are Root DNS servers?

Answer 8

Top Level, represented by (.)

First point of contact if a DNS resolver can’t resolve a name

Question 9

What are Top-Level Domain Servers?

Answer 9

Organizational
(com, org, edu, gov, net)

or

Geographical
(uk,us,eg,sp,de)

Managed by ICANN (Internet Corporation for Assigned Names and Numbers)

Question 10

What are Authoritative Servers?

Answer 10

Hold the complete data for a domain’s DNS records

Source of DNS responses

To ensure maintainability authoritative servers must be updated automatically

Question 11

What are Sub-domains?

Answer 11

Web addresses may utilise multiple subdomains separated by periods (pronounced “dot) in a hierarchical fashion

Each domain manages its subdomains

Question 12

What is DNSSEC?

Answer 12

Attackers exploit vulnerabilities in the DNS - it doesn’t check for credentials before accepting an answer

DNSSEC adds a layer of trust on top of DNS

Question 13

What does DNSSEC use?

Answer 13

Asymmetric Encryption

Hash Functions

Question 14

What is Asymmetric Encryption?

Answer 14

Uses pair of keys (private and public)

Using encryption key as the public key (private communication)

Using decryption key as public key

Question 15

What are Hash Functions?

Answer 15

Hash function takes data of arbitrary size, M, and returns a fixed-size number, H(M)

Question 16

How is a Digital Signature created?

Answer 16

DNS Data is put through hash function which gets hash value

Then encrypted with private key to make digital signature which is then attached to DNS data

Which makes Signed DNS Data (DNS data + digital signature)

Question 17

How is a DNS Response verified?

Answer 17

DNS is put through hash function to get Hash Value

Encrypted Hash decrypted with public key to get Hash Value

If Hash Values are equal then DNS Response is Verified

Question 18

What is the Hourglass Model?

Answer 18

Internet Protocols have an hourglass shape

Question 19

What are the 2 protocols the transport layer provides?

Answer 19

Transmission Control Protocol (TCP)

The User Datagram Protocol (UDP)

Question 20

How is information sent in networking?

Answer 20

Information is sent by combining headers (supplemental data) and payloads (the actual contents that you wish to send)

Question 21

How is application level data used? (hint: chopped)

Answer 21

Application level data is chopped up into smaller pieces. TCP pairs up each such piece of data with a TCP header to form segments

Question 22

What are Networking Ports?

Answer 22

Ports are used to map data to the correct process

Some port numbers are reserved for use by specific application layer protocols, eg. port 80 for HTTP

Question 23

What are all the features of TCP services?

Answer 23

Connection-oriented communication

End-to-end communication

Complete reliability

Full duplex communication

A stream interface

Reliable connection startup

Graceful connection shutdown

Question 24

What is Connection-Oriented Communication?

Answer 24

TCP provides connection oriented communication - an application sets up a connection, uses it, and tears it down

Question 25

What is End-to-end communication?

Answer 25

TCP provides end-to-end communication - a connection has exactly two endpoints

Question 26

What is Complete Reliability?

Answer 26

Data will be received exactly as sent even if that means resending

Question 27

What is Full-Duplex Communication?

Answer 27

Data may be sent and received simultaneously

Question 28

What is a Stream Interface?

Answer 28

A continuous stream of data is sent and received

Question 29

What is Reliable Connection Startup?

Answer 29

TCP provides reliable connection start-up through a three-way handshake - communication always starts properly

Question 30

Why are Sequence Numbers important?

Answer 30

If all connections start numbering segments from the same number, the receiver might confuse segments from different sequential connections

Question 31

What is Graceful Connection Shutdown?

Answer 31

TCP provides Graceful Connection shutdown through a four-way handshake - communication always finishes properly

Question 32

What are the 4 fields of the UDP Header?

Answer 32

Source Port

Destination Port

Length

Checksum

Question 33

What are the 4 Services of the UDP?

Answer 33

Connectionless communication

End-to-end communication

Best-effort reliability

A message interface

Question 34

What is Connectionless Communication?

Answer 34

Application does not set up or tear down a connection

Question 35

What is End-to-end communication?

Answer 35

Connection has exactly 2 endpoints

Question 36

What is Best Effort Reliability?

Answer 36

Data may be lost, duplicated or delayed

Question 37

What is a Message Interface?

Answer 37

Individual data items are sent and recieved

Question 38

What are the benefits of TCP vs UDP?

Answer 38

TCP provides full reliability, with high latency

UDP provides best effort reliability with minimal latency