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What does ACK number of 1000 in TCP means| ISRO 2015

Q   An ACK  number of 1000 in TCP always means that

option 

a) 999 bytes have been successfully received.

b) 1000 bytes have been successfully received.

c) 1001 bytes have been successfully received.

d) none of the above

3Comments
Arul @innovwelt
17 Jun 2016 11:50 pm

D) None of the above

 

The ACK number tells the sender that the sequence number of the "next" packet should be 1000.

It does not mean that 999/1000/1001 bytes have been already received. Since, the initialialization of sequence number is done randomly, we cannot predict the number of bytes received already.

 

Hradesh @hradeshpatel
18 Jun 2016 07:41 am

sir..basically my doubt is first of all we given ACK ...but i think that the difference between ACK is represent flag or ack is represent acknowlegment number....in question confusing

2-   Tcp uses intially on connection establishment phase choosen random seqeuence number at the both side sender as well as receiver ..but ack sends both side ... and it's  tell that next expected sequence number...if 999 is not received why are u send ack 1000...

 

shivanisrivarshini @shivanisrivarshini
18 Jun 2016 11:47 am

When receiver receives the packet say 999 then i need to intimate the sender that it received so as intimation says that send 1000 packet or I am expecting 1000 packet

If 999 packet is lost no matter of sending ACK to sender and based on protocol if packet is lost sender comes to know and resend it AGAIN............

UNTILL THE PACKET REACHED TO RECEIVER THEIR IS NOTHING LIKE SENDING  ACK FOR ASKING 1000 PACKET TO SENDER