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CS2003 > Week 3 - Net > Flashcards

Week 3 - Net Flashcards

1
Q

What is global connectivity

A

connectivity between network clouds

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2
Q

What layer is the IP router commonly situated on?

A

Network layer

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3
Q

What is IP service referred to as?

A

Best Effort

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4
Q

What does best effort mean?

A

whatever you get at the time of transmission

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5
Q

Is IP connection-less or connection orientated?

A

connection less

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6
Q

Some factors of the IP being connection-less?

A
  • no connection set up
  • send and forget
  • unconfirmed
  • unreliable
  • data source is not constrained on transmisson
  • no direct access, only access via transport protocol
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7
Q

How is an IP address found?

A

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

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8
Q

What does an IP address identify as?

A

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

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9
Q

Give some uses of IP addresses?

A

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.

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10
Q

What does DNS stand for

A

domain name system

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11
Q

what is the DNS

A

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

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12
Q

What are the DNS’ distributed services

A
  • nameservers

- resolvers

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13
Q

Describe DNS global system

A
  • must be scalable
  • distributed data and admin responsibility
  • localised caching
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14
Q

What is a DNS namespace?

A
  • global distributed namespace
  • nodes through a tree
  • domain, single network or multiple
  • DNS servers, servers for each domain
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15
Q

What are the 3 DNS applications?

A
  • nameservers
  • resolvers
  • protocol
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16
Q

What are client applications in resolvers?

A
  • host
  • dig
  • nslookup
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17
Q

How does DNS name resolution work?

A

query to local server

  • local server checks cache
  • may query root server
  • root server may redirect query
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18
Q

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

A

domain server

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19
Q

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

A

-from cache at local server

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20
Q

What is the local server in name resolution? Describe.

A
  • recursive
  • queries other servers to resolve request
  • result stored in cache
  • resukt used to answer other queries
  • TTL controls caching
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21
Q

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

A
  • recursive for local use

- iterative for others

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22
Q

What is the root server in name resolution? Describe.

A
  • 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
23
Q

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

A

-for external users

24
Q

What is held in the TCP header?

A

source and destination port numbers

25
Q

what is held in the TCP payload?

A

data from the layer above

26
Q

Describe the TCP service?

A
  • connection orientated
  • ordered
  • confirmed
  • reliable
  • byte-stream service
27
Q

What is the TCP protocol data structure?

A

segment header fornat

28
Q

What is the TCP algorithm protocol?

A

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

29
Q

What does ACK stand for?

A

acknowledgement significant

30
Q

What does SYN stand for?

A

synchronise sequence numbers

31
Q

what does FIN stand for

A

no more data from sender

32
Q

Describe TCP connection set-up

A
  • active open - 3 way handshake
  • passive open
  • local connection name
  • use SYN and SYN ACK
33
Q

describe TCP connection tear down?

A
  • clean termination

- abortive termination uses RST flag

34
Q

Once TCP connection established, what does it follow?

A

-flow control and congestion control algorithms

35
Q

What is the 5 tuple for TCP endpoints?

A
36
Q

What are server port numbers?

A
  • well known
  • 80 for HTTP
  • 443 for HTTPS
37
Q

What are client port numbers?

A
  • typically ephemeral
  • allocated by OS
  • connection to same server will have different client port numbers
38
Q

What are causes on congestion?

A
  • too many packets
  • buffer overflow in routers
  • unpredictable traffic patterns
  • time-of-day traffic
39
Q

What are the effects of congestion?

A
  • higher end to end delay
  • lost packets
  • network instability
  • loss of service
40
Q

How does TCP congestion control work?

A
  • 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
41
Q

What are TCP transmissions not protected from?

A

inspection
forgery
modification
replay

42
Q

What are not security mechanisms?

A

reliability
flow control
congestion control

43
Q

When would you use UDP?

A

where reliability does not matter and delay does

44
Q

Why use UDP?

A

no end-to-end delay

control of data transmission rate

45
Q

Service description of UDP?

A 
connectionless
unconfirmed
unrelaible
datagram service
- a thin layer on top of IP, uses best effort service
46
Q

UDP data structure protocol?

A

packet format

47
Q

UDP algorithm protocol?

A

simple send/recieve of independent packets

48
Q

What is the UDP endpoint 5 tuple?

A
49
Q

Main differences between TCP and UDP?

A

TCP - send and wait, reliable delivery, CO

UDP - send and hope, no flow control, no congestion control, CL

50
Q

What type of communication can UDP permit?

A

unicast

multicast

51
Q

What is multicast?

A

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
52
Q

What is QUIC?

A

Quick UDP Internet Connections

- based on UDP but with security, multiplexing etc

53
Q

What is multicast popular for?

A

LAN discovery protocols

- devices and services advertise their presence

CS2003 (17 decks)

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