self doubts

Question

A) Does digital signature provide privacy

B) when questions are asked like RIP uses TCP or UDP, SMTP uses what etc etc....how do we know if it requires TCP or UDP...its smtn we should know or is there a way to find it or something

C) Is Back off algo used oly by CSMA?

D) Assume sliding window protocol with window size W , seq number starting from 1 and whn sender send packet with seq num K it send ack as K + 1..which is correct

1.between two ack sender never sends more than 1 packet

2.sender must retransmit packet for every duplicate ack it receives

3.any new(previously unsent) packet  with seq number greater than W is sent by sender iff  a new(previously unseen) ack arrives

E) An ARP request packet include MAC address field and IP address of the receiver contains all 0's -true or false

F) what is hamming distance and to detect d errors the hamming distance should be?

Comments

A) privacy is broad term please define more clearly what you mean by that

F) to detect upto d error we require hamming distance of d+1 and to correct upto d errors we need hamming distance of 2d+1

C) It is used when channel is divided into slots and sender can only send at beginning of slot. Any algorithm that follow this can use backoff algorithm

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back off can be used by pure and slotted aloha? @tesla

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Back off algorithm is used where we can detect the collision and where we have to do retransmission after some time(decided by backoff algo) but aloha doesn't implement collision detection and here if packet got corrupt or lost then there acknowledgement will not be send and timer goes off and we do retransmission. So I think aloha don't use backoff algo.

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E) An ARP request packet include MAC address field and IP address of the receiver contains all 0's -

I think it is false bcz ARP request is broadcasting so the ip address of the receiver is set to limited broadcast address i.e all 1's

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@akb

But ARP is to find MAC using IP

so Ip address should be ther and MAC adress should be zero's na?

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I was wrong bcz see here target ip address is set to ip address of the host whose mac address we want to know

whereas

destination mac= All 1's 

Target MAC =All 0's

But Still answer of this is false as it doesn't contain all 0's.

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@akb

So for ARP request....MAC should be all 1's and ip address will be the ip of the target whose MAC is to be found right?