Physical

Question 1

why do we need different types of addresses?

Answer 1

at application layer we may want addresses to be understandable so need to convert between addresses

Question 2

Why does ethernet needs addresses?

Answer 2

to be unique on the network

Question 3

why cant we assign them manually or get the manifucaturer to number each card?

Answer 3

if we bought from different manufacturers they might have the same number

Question 4

what do part 1 of ethernet addresses mean?

Answer 4

uniquely identifies the manufacturer (needs central control)

Question 5

what do part 2 of ethernet addresses mean?

Answer 5

uniquely identifies the card (controlled by manufacturer

Question 6

How many bit MAC address does ethernet use?

Answer 6

48

Question 7

what do IP addresses need to identify?

Answer 7

network
machine

Question 8

are IP address split in 2 as well?

Answer 8

yes

Question 9

How do IP layer send packets across ethernet?

Answer 9

if the machines are on the same local network they can be sent directly to that machine

Question 10

what happens if they are not on the same local network?

Answer 10

we need to convert an IP adddress into MAC address

Question 11

How do we convert IP into MAC address?

Answer 11

computer maintains a table in memory that maps IP to ethernet MAC address

Question 12

but how do we populate the table?

Answer 12

we use ARP (address resolution protocol)

Question 13

what does ARP contain?

Answer 13

the algorithm used
e.g packets sent, the response to receiving one, how theyre sent
how packets are formulated
e.g which bits of data contain IP address

Question 14

what do we do if we want to send smth to machine B but dont know its MAC address?

Answer 14

we can use a broadcase packet and send a packet to ALL machines

Question 15

how does broadcast packet work?

Answer 15

it uses a special address (all binary ones)

Question 16

How do we get a computer to talk to another?

Answer 16

use RS232

Question 17

What is RS232?

Answer 17

consists of transmit pin, receive pin, ground
connect transmit to other receive pin and vice versa and ground to ground

Question 18

What is point-to-point link?

Answer 18

connects 2 computers together to communicate

Question 19

What type of transfer does RS232 use?

Answer 19

serial transfer - sent bit by bit

Question 20

what else is transmitted in RS232?

Answer 20

many parameters e.g how fast data is transmitted

Question 21

what does Asynchronous mean?

Answer 21

sender transmits when it wants, not synchronised with the receiver

Question 22

Whats the difference between serial and parallel transfer

Answer 22

parallel sends all at once while serial sends bits one after another at regular intervels

Question 23

what happens after serial transfer?

Answer 23

receiver peices them back together

Question 24

what needs to known for serial transfer to work?

Answer 24

the first bit received
how many bits are sent
how fast theyre sent

Question 25

why do we need to know first bit in serial transfer?

Answer 25

start bit and stop bit is used to identify start and end of each character

Question 26

what are the values of start and stop bit

Answer 26

0 and 1(line is kept at 1 until next character is sent)

Question 27

how does transmission of a character work in serial transfer?

Answer 27

it always begins with transition from a 1 to a 0
8 transmitted bits later it will return to 1 again

Question 28

what happens if it doesnt return 1

Answer 28

we have a framing error and need to resynchronise