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James F. Kurose, Keith W. Ross
Transport Layer
Question:14 | ISBN:9780132856201 | Edition: 6


Consider a reliable data transfer protocol that uses only negative acknowledg- ments. Suppose the sender sends data only infrequently. Would a NAK-only protocol be preferable to a protocol that uses ACKs? Why? Now suppose the sender has a lot of data to send and the end-to-end connection experiences few losses. In this second case, would a NAK-only protocol be preferable to a protocol that uses ACKs? Why?



If the sender sends the data infrequently (occasionally), then the NAK-only protocol is not preferred. It is good to use the protocol that uses ACKs.

  • The main disadvantage of NAK-only protocol is that it can detect that the packet has been lost only when the next packet is received by the receiver.
  • The NAK-only protocol realize the loss of packet after a long time when it receives the data packet with wrong sequence number as the sender sends the data packets occasionally.
  • When the receiver realize the packet loss, it sends NAK to the sender and the sender has to retransmit both the lost and next packet.
  • If the sender sends the data frequently, then the NAK-only protocol is preferred. The protocol that uses ACKs is not preferred as it require to send more number of acknowledgements.


When the sender sends data frequently and the data loss rate is very less, then a NAK-only protocol is preferable to a protocol that uses ACKs.

  • The receiver sends the NAK as it realizes the packet loss quickly as the data transmitted frequently.
  • Since the data loss is less, the number of NAK in NAK-only protocol is less when compared with protocol that uses ACKs.
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