Special Edition Using TCP/IP, Second Edition

Problems in the TFTP Specification

Although the file transfer process is a simple implementation, complications arise when duplicate data packets and acknowledgements are retransmitted due to a delay in acknowledgements. For example, if an acknowledgement from a client is delayed, the server retransmits a duplicate packet. In addition, the client retransmits another acknowledgement for the previous packet if the next packet to be received does not arrive within its timer specified limit because it is possible that the acknowledgement previously sent did not reach the server. Now, the duplicate packet sent by the server is also acknowledged by the client resulting in the receipt of two acknowledgements by the server. For each acknowledgement ...