Question

Consider a reliable data transfer protocol that does not use acknowledgements (ACKs) but instead uses negative acknowledgements (NAKs). A NAK is sent when a node observes a gap in the sequence numbers of the packets. NAKs and timeouts can both result in retransmissions. Suppose the sender has a lot of data to send and the end-to-end connection experiences few losses. Is a NAK-only protocol preferable to using ACKs? Why or why not?

Answer 1

ACK's is a abbriviation for acknowledgement,it is a protocol which lets you know,or which send a message when packet or parcel is reached to the destination,ACKs are useful in sliding window protocols,,it is the most common typ of protocol used, but this is a slow process,because for every packetit sends back a message,which makes the process slow, there fore using NAK'S which is also known as no acknowledgement or negative acknowledgement is good,as it dont give back any message.it is faster protocol.With a NAK-based protocol, a lost packet will only be detected when a subsequent packet is correctly received by the receiver (which will then notice a gap in the received sequence numbers). This means that with infrequent data transmissions, a NAK based protocol can have a long error recovery time. Hence, a NAK-only protocol would not be desirable in this case. On the other hand, if errors are rate and the data rate is high, an ACK-based scheme is not desirable as there is high overhead (for the ACKs).

if we see a case,like so many packets have been send to the receiver,but in between somehwere in between packets are stucked,and in path they are lost,and if we are using AKC we aill get an acknowledgement say that data is not received,but if we use NKC we will not know what had happed exactly,so in some case its better to use ACK than NKC.