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Networking 2 > FINAL - EVERYTHING > Flashcards

FINAL - EVERYTHING Flashcards

1
Q

what is multimedia?

A

two or more continuous media

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2
Q

what are the three broad categories of audio/video services?

A

streaming stored audio/video, streaming live audio/video, interactive audio/video

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3
Q

how does a client stream stored audio/video service?

A

downloads through the internet

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4
Q

how are audio/video services stored?

A

files are compressed and stored on server

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5
Q

what is digitization?

A

conversion of data into a stream of numbers

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6
Q

what is compression?

A

a coding process that will reduce the overall number of bits needed to represent information

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7
Q

what is sampling?

A

measuring analog signal at regular time intervals

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8
Q

what is it called when you sample amplitude (voltage)?

A

quantization

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9
Q

what is the nyquist theorum?

A

the idea that we need to sample the signal 2f times per second given the highest signal frequency ‘f’

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10
Q

what is pulse code modulation?

A

converting analog audio to compressed binary from sampling, quantization and encoding

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11
Q

what 3 questions do you need to decide when digitizing audio data?

A

sampling rate? how finely is the data quantized and is it uniform? file format?

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12
Q

what is the difference between predictive encoding and perceptual encoding?

A

predictive: difference in samples are encoded instead of the actual sampled values (typically used for speech)
perceptual: tries to mimic how people perceive sound (mp3)

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13
Q

what is the difference between predictive encoding and perceptual encoding?

A

predictive: difference in samples are encoded instead of the actual sampled values (typically used for speech)
perceptual: tries to mimic how people perceive sound (mp3)

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14
Q

what is the value of DC value in jpeg compression?

A

the average pixel value multiplied by a constant

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15
Q

what are AC values in jpeg compression?

A

changes in the pixel values - no change means AC = 0

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16
Q

why is jpeg called lossy compression? and what phase is responsible for this?

A

because some data is irreversibly lost, happens during quantization phase

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17
Q

what do you call a time ordered sequence of frames?

A

a video

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18
Q

what is spatial compression?

A

using JPEG or something close to compress each frame of a video

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19
Q

what is temporal compression?

A

removal of redundant frames

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20
Q

MPEG divides frames into what 3 categories?

A

i-frames, p-frames and b-frames

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21
Q

what is an i-frame?

A

independent frame not related to the previous frame or following frame, meant to represent an interval

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22
Q

what is the point of iframes?

A

they can stop cross origin domain policy, you can also load lots of different resources in an i-frame

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23
Q

what is a p-frame?

A

predicted frame - related to the previous i-frame or p-frame

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24
Q

what is a b-frame?

A

bidirectional frame - relates to previous or following frame

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25
Q

does the first approach for streaming stored audio/video involve streaming? whynot?

A

no because the entire file must be downloaded before the client sees any of it

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26
Q

what is the problem with the 2nd approach (web server + metafile)

A

both the browser and media player use HTTP services which run over TCP, this is totally fine for retrieving the metafile but TCP is not designed for audio/video file retrieval

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27
Q

why is TCP bad for audio/video files?

A

it re transmits lost or damaged segments which fucks up your stream

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28
Q

what protocol does a media server use and why?

A

UDP so lost and damaged segments are not retransmit

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29
Q

what is RTSP?

A

an out-of-band control protocol that can control the playing of audio/server

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30
Q

what is RTSP similar to?

A

second connection in FTP

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31
Q

what does RTSP not do?

A

define compression schemes, define encapsulation for transmission, restrict transportation method (udp tcp), restrict how media player buffers

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32
Q

what does RTSP do?

A

allows media player to control transmission, play pause fast forward rewind, messages use a different port number than media stream

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33
Q

what is an out of band protocol?

A

sends control data from a different connection then main data

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34
Q

what are the similarities between streaming stored audio/video and streaming live audio/video?

A

both sensitive to delay, both do not accept retransmission

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35
Q

what are the differences between streaming live and stored?

A

stored communication is unicast and on demand, live is multicast and live

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36
Q

what is the “jitter” phenomenon?

A

when packets of audio/video are transmitted and have different network delays –> you start playing packet 1 and it finished before packet 2 arrives

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37
Q

what is the purpose of a timestamp in real-time audio/video?

A

to solve the jitter problem by showing how a packet delay is relative to the previous packet

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38
Q

why do you need a playback buffer in real time interactive audio/video?

A

to store the data until they are played back based on the what the timestamps dictate

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39
Q

what else is needed other than a timestamp for real time traffic?

A

packet numbering for ordering purposes

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40
Q

real time traffic needs the support of what due to the fact that it used multimedia?

A

multi casting

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41
Q

what is “mixing”?

A

combining data from multiple streams into one

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42
Q

why is TCP bad for real time interactive traffic?

A

because it re transmits lost or damaged packets

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43
Q

is UDP suitable for real time interactive traffic?

A

not really because it lacks the ability to timestamp and order packets or mix them

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44
Q

what is RTP for?

A

real time traffic

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45
Q

what does RTP provide?

A

timestamping, sequencing, and mixing

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46
Q

what does RTP need to be used with?

A

UDP

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47
Q

how does encapsulation of packets work with RTP?

A

first encapsulated by RTP packet and then these packets are encapsulated in a UDP segment

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48
Q

what network layer does RTP operate in?

A

can be transport layer OR application layer

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49
Q

how is RTP used in the transport layer?

A

RTP libraries are used with languages in that layer to make RTP into a sublayer of the transport layer

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50
Q

how is RTP used in the application layer?

A

RTP packets are sent into a UDP socket interface

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51
Q

what is included in a RTP packet header to be encapsulated by a UDP segment?

A

data encoding, sequence number, timestamp

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52
Q

what does it mean if the P. and X. header fields are set in an RTP packet?

A

P - there is padding

X - extra extension header

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53
Q

what is the point of the CC and M field in RTP packets?

A

CC - how many contributors (mixing)

M - end of data

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54
Q

how many bits is the PT header field in RTP and what is it for?

A

8 bits - defines payload type

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55
Q

for the following RTP header fields, how many bits and how is it set?

  • sequence number
  • timestamp
  • ssrc
  • csrc
A

sequence number - 16 bits, first is random then incremented by 1 each time
timestamp - 32 bits, first is random then sum of past timestamps plus clock time for first bye produced
ssrc - 32 bits, defines identity of source (random # chosen by source)
csrc - 32 bits, defines # of sources (max 15)

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56
Q

what is RTCP

A

control protocol for RTP

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57
Q

when is RTCP used

A

when networking applications multicast to multiple receivers from one or more senders

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58
Q

how are RTP and RTCP packets distinguished from each other?

A

distinct port numbers

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59
Q

what do RTCP packets include?

A

sender and receiver ports

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60
Q

what are in RTCP sender report packets and what are they used for?

A

timestamp, allows receiver to synchronize RTP messages –> think audio and video synchronization

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61
Q

what are RTCP receiver reception packets for and what do they do?

A

passive participants, informs sender and other receivers of service quality

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62
Q

what are in RTCP source description packets?

A

email address, name of sender and application that generates RTP stream

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63
Q

what is the point of RTCP bye message?

A

shut down stream

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64
Q

what does an RTCP application specific message allow?

A

new message type definitions –> for when packet wants to use new applications

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65
Q

what is the restriction on RTP port numbers?

A

they must be an even number

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66
Q

where must the UDP port be that corresponds to an RTP packet?

A

immediately after the RTP port

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67
Q

what are the flow characteristics?

A

reliability, delay, jitter and bandwidth

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68
Q

what is the consequence of low reliability?

A

losing a packet or ack

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69
Q

what is responsible for lost packets in multimedia network apps?

A

network loss (congestion), end to end delay loss (packets arrive too late)

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70
Q

for multimedia application what range of delay makes a packet effectively useless?

A

100ms to 5 seconds

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71
Q

what causes jitter?

A

differing delay time between successive packets

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72
Q

what determines if jitter is high or low?

A

the difference between delays –> larger difference means higher jitter

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73
Q

what is packet marking need ed for?

A

for routers to distinguish between different classes; and treat packets accordingly

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74
Q

what are the tradeoffs when you change the size of the chunks in a group (n) for FEC simple scheme?

A

increase: less bandwidth waste, higher probability that 2 or more chunks are lost, longer playout delay
decrease: more lost packets can be recovered, more bandwidth waster

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75
Q

what is the disadvantage of interleaving for packet loss?

A

increases latency (need to sort out all the chunks in each packet)

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76
Q

what are the 3 different types of queuing?

A

FIFO, priority, weighted fair

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77
Q

In FIFO scheduling what happens if the arrival rate at the queue is higher than the processing rate?

A

the queue will fill up and new packets discarded

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78
Q

what is the condition of starvation for Priority scheduling?

A

when low priority queues never have the chance to be processed

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79
Q

how does the system process packet in weighted average scheduling?

A

round robin fashion with higher priority queues getting more processing relative to their priority weight

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80
Q

what is traffic shaping?

A

mechanism to control the amount and the rate of the traffic sent to the network

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81
Q

on what scheduling queue is the leaky bucket approach implemented on?

A

FIFO

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82
Q

in a token bucket approach if n = 100 and the host is idle for 100 tickets how many tokens are collected?

A

10000

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83
Q

what is the problem with the leaky bucket approach to traffic shaping

A

it limits the output rate to the average of bursty traffic

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84
Q

what is the difference between an access link and a trunk link?

A

access links are assigned to one specific vlan whereas trunk links carry multiple vlans

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85
Q

what are some reasons for grouping devices into vlans?

A

service need, protocol, physical proximity

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86
Q

each switch port can be assinged to _______ vlan(s), each switch port can be assigned to _____ vlan(s)

A

multiple, only one

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87
Q

where are dynamically assigned Vlan ports stored?

A

in virtual membership policy servers

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88
Q

what is the area between switches called?

A

switch fabric

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89
Q

what is the area between switches called?

A

switch fabric

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90
Q

what is frame tagging in Vlans?

A

when the switch appended a Vlan ID to each frame

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91
Q

which switch appends the Vlan ID? which switch removes it?

A

first switch in the path, last switch in the path

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92
Q

what happens is a tag is not removed from a frame before it is sent to non-vlan-capable devices?

A

the device won’t be able to understand the frame

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93
Q

what is cisco’s proprietary protocol called for tag formatting?

A

inter switch link (ISL) protocol

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94
Q

what are the benefits of using switches to create Vlans over using routers to create distinct networks?

A

easier to administer, less expensive, higher performance (less latency)

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95
Q

what are the disadvantages of using switches to create Vlans over using routers to create distinct networks?

A

Vlan may be tied to a specific vendor

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96
Q

what are routes needed for despite advances in switch technology?

A

filter WAN traffic, route traffic between distinct networks, route packets between Vlans

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97
Q

what is trunking?

A

when you connect two switches together

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98
Q

when is trunking useful?

A

when trying to configure Vlans that span multiple switches

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99
Q

what is the vendor for inter switch link?

A

cisco

100
Q

what trunking protocol is IEEEE standard?

A

802.1Q

101
Q

what do switches use to dynamically configure trunk ports?

A

dynamical trunking protocol

102
Q

what is VTP?

A

virtual trunking protocol

103
Q

what is the purpose of VTP?

A

to maintain Vlan configuration consistency throughout the network

104
Q

how does VTP execute its purpose?

A

by synchronizing VTP configurations among switches in VTP domain

105
Q

what are the 3 VTP modes?

A

server, client, transparent

106
Q

what does a server mode VTP switch allow you to do ?

A

change the configuration information and broadcast it to other VTP devices

107
Q

what does a client mode vtp switch allow you to do?

A

receive changes from a VTP server and pass to other VTP switches but you cannot modify the VLAN configuration

108
Q

what does a transparent mode VTP switch allow you to do?

A

you don’t receive configuration information from other switches, you simply pass it back to other switches, you can alos modify VLAN config but only apply the changes to local switch (not sent)

109
Q

why does transparent mode exist?

A

to prevent issues when moving a switch between environment due to the fact that it may have a higher revision number then existing switches in new network

110
Q

what is the default mode for switches?

A

server

111
Q

what command allows you to change the mode of switches?

A

vtp mode command

112
Q

what command allows you to view the current mode of switch?

A

show vtp status command

113
Q

what are the STP (spanning tree protocol) requirements?

A

one root bridge / network
one root port / non root bridge
one designated port / segment

114
Q

why are spanning trees necessary?

A

to solve the problems that arise when networks implement redundant paths between devices using multiple switches

115
Q

what are the problems associated with redundant paths between segments?

A

broadcast storms, multiple frame transmission, MAC address database instabilitiy

116
Q

what does the STA (spanning tree algorithm) do?

A

automatically discovers the network topology and creates single optimum path through network

117
Q

what are the different types of bridges in STP

A

root bridge, designated bridge, backup bridge

118
Q

what does a backup bridge do?

A

it listens to network traffic and build a bridge database but does not forward packets. it can also take over for root bridge if it fails

119
Q

what special packets do bridges send?

A

bridge protocol data units

120
Q

what are the 5 states a port can being in during a STA configuration process?

A

disabled, blocking, listening, learning, forwarding

121
Q

what is the command for disabling a spanning tree on a selected VLAN?

A

no spanning-tree vlan “number”

122
Q

what is the command for forcing a switch to be the root of spanning tree

A

spanning-tree vlan “number” root primary

123
Q

what is the command to show spanning tree configuration formation?

A

show spanning-tree

124
Q

a computer that can act as both a server and/or client is called a?

A

peer

125
Q

a p2p system with no dedicated server is known as?

A

a pure p2p system

126
Q

what makes peer to peer networks more reliable then other networks?

A

no central point of failure

127
Q

what does having a ton of peers do for resource management?

A

workload can be spread out and the peers themselves provide a ton of resources and power

128
Q

how is system utilization maximized in p2p systems?

A

computer that are connected but idle can still provide their resources

129
Q

how is a p2p network scalable?

A

peers can be freely added to the network

130
Q

what assumptions are ring systems generally built on?

A

that machines are all on a nearby network and owned by a single organization

131
Q

what is the best known hierarchical system on the internet?

A

domain name service

132
Q

what is the NTP protocol and what is its topology?

A

protocol for synchronizing clocks of computer systems over networks - hierarchical

133
Q

what is the most “pure” decentralized system used in practice?

A

gnutella

134
Q

list the criteria for evaluating topologies:

A

manageability, information coherence, extensibility , fault tolerance, resistant to legal/public intervention, security, scalability

135
Q

what is the common architecture for web applications?

A

centralized + ring

136
Q

what is the best architecture for p2p networks?

A

centralized + decentralized

137
Q

explain the napster model

A

members (client) downloads software package and installs locally, napster central computer maintains directories of music files of members who are currently logged in to the system, when a user requersts a file the central computer connects them with a members computer that has that file in their directory, the target file is downloaded directly between member computers bypassing central computer

138
Q

why was napster shut down?

A

because it maintained a central directory of users

139
Q

what will a gnutella network structure have at its core after a significant amount of time has passed?

A

a high speed computer

140
Q

what is a freeloader in p2p networks?

A

someone who only downloads and doesn’t share any files (ME!)

141
Q

what is a torrent?

A

a collaborative file sharing process?

142
Q

what do you call the set of all peers that take part in a torrent?

A

a swarm

143
Q

what is a seed?

A

a peer in a swarm that has the complete content file

144
Q

what is a leech?

A

a peer that has a part of the file and wants to download the rest

145
Q

what is a tracker?

A

a central node that tracks the operation of the swarm

146
Q

what are the contents of a torrent file?

A

file name, # of chunks (size), checksum, IP address of tracker and peers and such

147
Q

what are a peers neighbors?

A

other peers whose addresses the new peer receives when it accesses the tracker

148
Q

what does bit torrent protocol and policies around fairness try and prevent?

A

overloading a peer with requests from other peers

149
Q

what peers are in the unchoked group?

A

the peers that the current peer has concurrently connected to and is continuously downloading/uploading too

150
Q

what peers are in the chocked group?

A

the peers that he current peer is not currently connected to but may connect to in the future

151
Q

how does bittorrent allow new peers to join which do not have a piece to share? what is this action called?

A

every 30 seconds the system randomly promotes a peer out of the choked group and into the unchocked group regardless of its uploading rate - optimistic unchoking

152
Q

what is the rarest-first strategy in piece sharing between peers?

A

peers try to first download the pieces with fewest repeated copies among the neighbors so that they are circulated faster

153
Q

what layer are p2p protocols constructed in?

A

the application layer

154
Q

what do p2p networks always support?

A

some type of message-routing capability

155
Q

what is the collection of peer connections in a p2p network called?

A

a p2p overlay

156
Q

a network that is built on top of another network is called what?

A

an overlay network

157
Q

what is the most common technique for structuring p2p overaly networks?

A

distributed hash tables

158
Q

most DHT implementations have what address space size?

A

2^160

159
Q

What is a cryptographic hash function that DHT uses and why does it use these types of hash functions?

A

SHA-1 because they are collision resistant

160
Q

which method of storing objects do DHT typically use and why is it superior?

A

indirect method, efficiency

161
Q

is it guaranteed that an object can be found if it exists in an unstructured overlay?

A

no

162
Q

how are nodes organized in unstructured overlay networks?

A

in random graphs

163
Q

what is the impact of increasing the degree of a peer in a graph

A

the peer will require more storage, but the diameter of the overlay will be reduced (more connection = more density = less spread out = smaller diameter)

164
Q

how is endless message circulation prevented when flooding is used?

A

message identifiers and TLL values

165
Q

what is the iterative deepening or expanding ring?

A

when the TTL starts small for a flooding search and is increased by a small amount if the search stops until the query returns successfully or the entire network has been queried

166
Q

what is the benefit of random walk when compared with flooding?

A

greatly reduces the message overhead

167
Q

structured overlay lay networks have routing mechanisms that are?

A

deterministic and guarantee the ability to locate objects in the overaly

168
Q

what are the challenges associated with having an adaptive (peers can join and leave) structured overlay network?

A

distributing responsibility to nodes that are joining, redistributing responsibility of nodes that are leaving

169
Q

what is the format of the key based routing that structured overlays use?

A

object id’s are mapped to peer address and object request are routed to nearest peer in peer address space

170
Q

what are P2P systems using key based routing called?

A

distributed object location and routing systems

171
Q

what are three DOLR DHT protocols?

A

pastry, kademlia, chords

172
Q

in pastry keys are store in the node whose ID is closest in terms of what?

A

number (numerical)

173
Q

what is the common “m” value for pastry?

A

128

174
Q

a new node in pastry ring needs what?

A

to know at least on node that should be close to it

175
Q

if a node is not responding to probe messages what is assumed?

A

that is has failed or departed

176
Q

given a node X what nodes will test it for liveliness?

A

the nodes in X’s leaf set

177
Q

what is the key difference between pastry and kademlia?

A

in pastry nodes are routed based on how numerically close nodes are to each other whereas kademlia routes nodes based on the physical distance (bitwise exclusive or) between nodes

178
Q

what information does kademlia keep for each node?

A

id and routing table - no leaf set

179
Q

what is the point of k-buckets in kademlia?

A

allows nodes to use alternative nodes when a node leaves or the network fails

180
Q

what is a row in a kademlia routing table referred to as?

A

a k-bucket

181
Q

what does the network security model 1 require us to do?

A
  1. design algorithm for security transformation
  2. generate secret key information (session keys)
  3. develop methods to distribute secret inro
  4. specify a protocol
182
Q

what does the network security model 2 require us to do?

A

select gatekeeper function to identify users, implement security controls for users

183
Q

if a protocol is not flawed then its implementations are also not flawed?

A

false

184
Q

what is cryptography about?

A

controlling access to information

185
Q

key generation, encryption and decryption are examples of what?

A

access control algorithms, computations

186
Q

what is a cipher?

A

something that is used to encrypt plaintext

187
Q

what is the result of encryption?

A

ciphertext

188
Q

how can you recover plaintext from cipher text?

A

decrypt

189
Q

what is used to configure a cryptosystem (cipher)

A

a key

190
Q

what is the difference between a symmetric key cryptosystem and a public key cryptosystem?

A

symmetric - uses the same key to encrypt and decrypt

public - uses a public key to encrypt and a private key to decrypt

191
Q

computational complexity grows with what?

A

input size

192
Q

what complexity is considered infeasible?

A

super polynomial time

193
Q

what is polynomial time?

A

O(n)

194
Q

what is in super polynomial time?

A

O(2^n), O(2^squrt(n))

195
Q

what is kreckhoff’s principle?

A

that crypto algorithms are not secret

196
Q

why do we assume that crypto algorithms are not secret?

A

experience –> they are weak when exposed, the never remain secret, better to find weakness before hand

197
Q

what is the general idea for IFF (identify friend or foe)?

A

a challenge (random number) is sent to unknown entity, if the entity can encrypt the challenge using the expected key then it was a friend if not then its a foe

198
Q

what is the main concern of authentication on a standalone computer?

A

an attack on the authentication software

199
Q

on a network what can attackers do?

A

passively observers message, replay messages, perform active attacks

200
Q

what are active attacks?

A

inserting, deleting or changing messages

201
Q

what is a replay attack?

A

when an attacker uses information that it read passively from an exchange between entities to pose as one of the entities

202
Q

what is a nonce?

A

a number used once

203
Q

why is a nonce used in the context of challenge response?

A

for “freshness”

204
Q

what is a man in the middle attack?

A

when “trudy” knows the thing you are trying to encrypt and what it looks like when it is encrypted she can figure out the key used for encryption and its game over

205
Q

is one way authentication with a symmetric key secure?

A

yes

206
Q

is mutual authentication (challenger response) secure?

A

no - “alice” could be “trudy”

207
Q

are 2 one way authentications a secure method of mutual authentication?

A

no - man in the middle attack

208
Q

is symmetric key mutual authentication secure?

A

yes apparently

209
Q

can you use the same key pair for encryption and signing for pubic keys?

A

no

210
Q

what is perfect forward secrecy?

A

prevents trudy from decrypting recorded ciphertext at a later time, even if Trudy get Kab or other secrets

211
Q

what is used to ensure perfect forward secrecy with public key authentication?

A

sessions key

212
Q

what is a session key?

A

a key that is used and then forgotten

213
Q

what is diffie hellman?

A

a key exchange algorithm to establish a shared symmetric key

214
Q

what does the diffie hellman algorithm rely on?

A

the difficulty in solving the discrete logarithm problem

215
Q

explain the deffie hellman process

A

alice and bob chose secret values and agree on values for the prime and generator, they take each other’s values and calculate g^(value)mod(p) and send the result to each other, they then use their own secret value that same formula where g = value received from other party to get a shared secret value to be used as a symmetric key

216
Q

how does a man in the middle diffie helman attack work?

A

trudy switches out the secret values passed between alice and bob with her own

217
Q

how do you prevent MIM attack with diffie hellman?

A

encrypt DH exchange with symmetric key or public key and then sign DH values with private key

218
Q

what do timestamps allow in security protocols?

A

a reduction in the number of messages (a nonce both sides know in advance)

219
Q

what must you allow for when issuing timestamps?

A

clock skew

220
Q

is sign and encrypt with nonce secure?

A

yes

221
Q

is encrypt and sign with nonce secure?

A

yes

222
Q

is sign and encrypt with timestamp secure

A

yes

223
Q

is encrypt and sign with timestamp secure

A

NO! - but trudy must ask within clock skew

224
Q

for mutual authentication with public key is encrypt and sign with timestamp secure?

A

yes

225
Q

where is the socket layer situated?

A

between the application and transport layers

226
Q

what protocol is used for most secure transaction over the internet?

A

SSL

227
Q

describe the simplified SSL protocol

A

alice asks bob to talk securely and sends him a list of ciphers she has plus a nonce, bob responds with his certificate and selects one of alices ciphers and sends it along with his nonce, alice sends “S” that she generated along with a hash that has been encrypted with “k”, this hash keeps a record of all previous message along with a literal string CLNT, bob responds with a similar hash, boom auth complete

228
Q

how many ssl keys are there? and what are they for

A

6

  • 2 for encryption
  • 2 for integrity
  • 1 IV (?)
229
Q

why is there one key for sending and one for receiving in SSL for each key type?

A

it helps to prevent certain types of replay attacks

230
Q

how is mutual authentication possible in simplified ssl protocol?

A

the server (bob) can send a certificate request to the client (alice) in message 2

231
Q

is an SSL connection the same an SSL session?

A

no, once an SSL session is established you don’t need to go through the entire protocol again to establish a new connection

232
Q

what must both sides know in order to establish a new connection given an existing SSL session?

A

the session ID

233
Q

are there any public key operations when establishing a new connection given an existing SSL session?

A

no

234
Q

where isIPSec located?

A

at the network layer

235
Q

what are the problems with IPSec

A

complex as fuck, over engineered, flawed, not very interoperable

236
Q

what are the two parts in IPSec?

A

Internet key exchange and ESP/AH (encapsulating security payload, authentication header)

237
Q

how many version of IKE phase 1 are there?

A

8 fucking bullshit phases

238
Q

how many key options are there in IKE

A

4

239
Q

what are the two different IKE modes?

A

main mode and aggressive mode

240
Q

what is the difference between the IKE digital signature main mode and aggressive mode?

A

in aggressive mode there is not attempt to disguise the identities of alice or bob

241
Q

T/F: alice and bobs identities in main mode are protected from all attackers

A

F : only protected from passive attackers, active attackers can still find out

242
Q

what is the problem with symmetric key in main mode?

A

alices ID must be IP address

243
Q

what happens in symmetric key aggressive mode?

A

not trying to hide identities means IP address doesn’t need to be Alice’s ID –> solves issue

244
Q

what is the problem with public key encryption for IPSec ( in both modes)

A

trudy can compute valid keys and proofs

245
Q

what is unique about the public key encryption aggressive mode

A

it hides Id’s

246
Q

what is plausible deniability in the context of IPSec public encryption mode?

A

alice and bob can deny that any conversation took place since trudy can “create” conversations

Networking 2 (1 decks)

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