Week 8 - Net

Question 1

What does DHCP stand for?

Answer 1

Dynamic host configuration protocol

Question 2

What does DHCP allow?

Answer 2

automated address assignment

Question 3

Do clients have public or private addresses?

Answer 3

private, used with NAT

Question 4

Do clients need DNS entry?

Answer 4

No

Question 5

Do servers need a DNS entry?

Answer 5

Yes, as clients lookup the server address

Question 6

What is dynamic configuration?

Answer 6

automatically assigned address “leasing” from a pool of addresses

Question 7

Does DHCP use LAN or WAN?

Answer 7

LAN broadcast

Question 8

What is DHCP useful for?

Answer 8

• nomadic devices

- large number of hosts

Question 9

Process of DHCP?

Answer 9

• client broadcasts message
• both servers broadcast reply
• broadcast confirmation; server B chosen

Question 10

What is routing? In terms of an IP router?

Answer 10

– the process of discovering paths through the network,
gathering routing information, using a routing protocol
-– A metric value (a “cost”) is assigned to each route

Question 11

What is forwarding? In terms of an IP router?

Answer 11

– the process of transmitting packets using the discovered

routing information.

Question 12

What is forwarding? In terms of an IP host?

Answer 12

– discover locally available route(s) for destinations

– make local forwarding decisions.

Question 13

what is a destination

Answer 13

another network

Question 14

What is used to choose the route for forwarding?

Answer 14

longest prefix match

Question 15

How does longest prefix match work?

Answer 15

• apply network mask of routing entry to destination address in packet
• the longest mask that produces a match between the local forwarding entry and destination address is used

Question 16

What to use if no prefix matches?

Answer 16

default route

Question 17

what does NAT stand for?

Answer 17

network address translation

Question 18

What is NAT?

Answer 18

process where a network device, assigns a public address to a computer inside a private network

Question 19

What is the main use of NAT?

Answer 19

to limit the number of public IP addresses an organization or company must use, for both economy and security purposes.

Question 20

Describe some problems with NAT?

Answer 20

• lose end-to-end model
• makes end-to-end security harder
• single point of failure

Question 21

What does a firewall prevent?

Answer 21

• packets leaving site network

- packets entering site network

Question 22

where is a firewall situated?

Answer 22

border router

Question 23

What are some on the wire threats?

Answer 23

eavesdropping
traffic modification
- modification of genuine packets
man in the middle

Question 24

Explain symmetric cryptography?

Answer 24

single key
used for both encyprtion and decryption
must be known and kept secure by both parties

Question 25

explain public key cyrptography?

Answer 25

paired keys

different keys but complimentary

Question 26

What does a hash algorithm do?

Answer 26

creates a fixed size bit pattern from any input of bits

Question 27

properties of a hash algorithm?

Answer 27

• fixed size hash value as output
• cannot reporudce original message from hash
• Very low probability of
  producing two messages with
  the same hash.

Question 28

explain message authentication codes

Answer 28

sender sends message and MAC

reciever recieves message and MAC, and encrypts using their key and check if both MAC’s match to ensure no tampering

Question 29

how does digital checksum work?

Answer 29

Signature - public key:
– create hash
– encrypt with kS
– check at receiver using kP

Question 30

What does TLS stand for?

Answer 30

transport layer security

Question 31

What does TLS allow?

Answer 31

• client to authenticate server, and vise versa
• client and server to select crypto protocols for use over a communication session
• client and server to exchange keys securely
• confidential sessions between client and server