slides06

Question 1

Security in the IP

Answer 1

• Data in transit is readable as it is passed through the various machines on the path to the destination
• Many protocols used are not resistant to malicious interference
• Authentication mechanisms are weak to non-existent

Question 2

How many different wireless systems does your mobile phone support?

Answer 2

Satellite, Wireless Networking, wimax, wifi

Question 3

CSMA/CD

Answer 3

carrier sense, multiple access with collision detection

Question 4

fake delivery of bits? 1GB/s of actual data or not?

Answer 4

Due to layering encapsulation and other overheads, this is overwhelmingly not the rate of delivery of bits to the application you are running

Question 5

ethernet frame

Answer 5

Destination address
Source address
type
Data
crc: cyclic redundancy check, checksum check for corruption errors in the frame

Question 6

collision

Answer 6

If two hosts try to send simultaneously

Question 7

carrier sense

Answer 7

before they send data, a host listens to the Ethernet to see if
anyone else is using it at the moment

Question 8

collision detection

Answer 8

So each host continues to listen while transmitting to make sure there are no collisions (you write and listen atthe same time, if collison, w8 random time)

Question 9

CSMA/CD differs from Aloha

Answer 9

aloha doesnt solve hidden node problem, aloha doesnt scale, csma is distributed, aloha needs prior centralised knowledge

Question 10

categories of cables

Answer 10

6, last is expensive 5 is pop

Question 11

evolution of ethernet

Answer 11

vampire tap, bnc connector, hup and switch

Question 12

switch advantage

Answer 12

more throughput because full duplex but more complex

Question 13

why csmacd if swithces avoid collisions?

Answer 13

But buffers in the switch can fill up and then packets would have to be dropped by the switch