Week 3 - Net

Question 1

What is global connectivity

Answer 1

connectivity between network clouds

Question 2

What layer is the IP router commonly situated on?

Answer 2

Network layer

Question 3

What is IP service referred to as?

Answer 3

Best Effort

Question 4

What does best effort mean?

Answer 4

whatever you get at the time of transmission

Question 5

Is IP connection-less or connection orientated?

Answer 5

connection less

Question 6

Some factors of the IP being connection-less?

Answer 6

• no connection set up
• send and forget
• unconfirmed
• unreliable
• data source is not constrained on transmisson
• no direct access, only access via transport protocol

Question 7

How is an IP address found?

Answer 7

A FQDN is looked up in the global directory service (DNS) and a corresponding IP address is found.

Question 8

What does an IP address identify as?

Answer 8

an interface on a host (ex, ethernet or wireless LAN) and not the host itself

Question 9

Give some uses of IP addresses?

Answer 9

identification – allows hosts to be unqiuely labelled
transport protocols - forms part of the identity of a transport packet flow
bound to an interface on an IP host - multiple interfaces, multiple IP addresses
used for routing and forwarding - discover network paths, transmit packets towards their destination.

Question 10

What does DNS stand for

Answer 10

domain name system

Question 11

what is the DNS

Answer 11

global distributed directory service, it maps domain names to IP addresses

Question 12

What are the DNS’ distributed services

Answer 12

• nameservers

- resolvers

Question 13

Describe DNS global system

Answer 13

• must be scalable
• distributed data and admin responsibility
• localised caching

Question 14

What is a DNS namespace?

Answer 14

• global distributed namespace
• nodes through a tree
• domain, single network or multiple
• DNS servers, servers for each domain

Question 15

What are the 3 DNS applications?

Answer 15

• nameservers
• resolvers
• protocol

Question 16

What are client applications in resolvers?

Answer 16

• host
• dig
• nslookup

Question 17

How does DNS name resolution work?

Answer 17

query to local server

• local server checks cache
• may query root server
• root server may redirect query

Question 18

Where does the authoritative answer in DNS name resolution come from?

Answer 18

domain server

Question 19

Where does the non-authoritative answer in DNS name resolution come from?

Answer 19

-from cache at local server

Question 20

What is the local server in name resolution? Describe.

Answer 20

• recursive
• queries other servers to resolve request
• result stored in cache
• resukt used to answer other queries
• TTL controls caching

Question 21

What is the local server within an organisation? Regarding DNS?

Answer 21

• recursive for local use

- iterative for others

Question 22

What is the root server in name resolution? Describe.

Answer 22

• iterative
• sends a referral to the requester
• referral gets closer to the actual server that holds the mapping
• not recursive due to load and security

Question 23

What is the root server within an organisation? Regarding DNS?

Answer 23

-for external users

Question 24

What is held in the TCP header?

Answer 24

source and destination port numbers

Question 25

what is held in the TCP payload?

Answer 25

data from the layer above

Question 26

Describe the TCP service?

Answer 26

- connection orientated - ordered - confirmed - reliable - byte-stream service

Question 27

What is the TCP protocol data structure?

Answer 27

segment header fornat

Question 28

What is the TCP algorithm protocol?

Answer 28

-FSM for protocol state -plus various algorithms for reliability, flow control, congestion control

Question 29

What does ACK stand for?

Answer 29

acknowledgement significant

Question 30

What does SYN stand for?

Answer 30

synchronise sequence numbers

Question 31

what does FIN stand for

Answer 31

no more data from sender

Question 32

Describe TCP connection set-up

Answer 32

- active open - 3 way handshake - passive open - local connection name - use SYN and SYN ACK

Question 33

describe TCP connection tear down?

Answer 33

- clean termination | - abortive termination uses RST flag

Question 34

Once TCP connection established, what does it follow?

Answer 34

-flow control and congestion control algorithms

Question 35

What is the 5 tuple for TCP endpoints?

Question 36

What are server port numbers?

Answer 36

- well known - 80 for HTTP - 443 for HTTPS

Question 37

What are client port numbers?

Answer 37

- typically ephemeral - allocated by OS - connection to same server will have different client port numbers

Question 38

What are causes on congestion?

Answer 38

- too many packets - buffer overflow in routers - unpredictable traffic patterns - time-of-day traffic

Question 39

What are the effects of congestion?

Answer 39

- higher end to end delay - lost packets - network instability - loss of service

Question 40

How does TCP congestion control work?

Answer 40

- start slow - send 1 segment, f successfully ACK'd send 2, then 4 then 8 - until a missing for delayed ACK then drop to hald and increase linearly

Question 41

What are TCP transmissions not protected from?

Answer 41

inspection forgery modification replay

Question 42

What are not security mechanisms?

Answer 42

reliability flow control congestion control

Question 43

When would you use UDP?

Answer 43

where reliability does not matter and delay does

Question 44

Why use UDP?

Answer 44

no end-to-end delay | control of data transmission rate

Question 45

Service description of UDP?

Answer 45

``` connectionless unconfirmed unrelaible datagram service - a thin layer on top of IP, uses best effort service ```

Question 46

UDP data structure protocol?

Answer 46

packet format

Question 47

UDP algorithm protocol?

Answer 47

simple send/recieve of independent packets

Question 48

What is the UDP endpoint 5 tuple?

Question 49

Main differences between TCP and UDP?

Answer 49

TCP - send and wait, reliable delivery, CO | UDP - send and hope, no flow control, no congestion control, CL

Question 50

What type of communication can UDP permit?

Answer 50

unicast | multicast

Question 51

What is multicast?

Answer 51

many|one to many - the destination IP address is a multicast group address - anyone can send to group - must be a member of group to receive

Question 52

What is QUIC?

Answer 52

Quick UDP Internet Connections | - based on UDP but with security, multiplexing etc

Question 53

What is multicast popular for?

Answer 53

LAN discovery protocols | - devices and services advertise their presence