D-Link DES-3326 User Manual page 107

24-port NWay Ethernet Switch User's Guide
contain are. If there are 100 octets of data in each packet, the
first packet is numbered 0, the second 100, the third 200, etc.
To insure that the data in a packet is received uncorrupted, TCP
adds the binary value of all the octets in the packet and writes
the sum in the checksum field. The receiving TCP recalculates
the checksum and if the numbers are different, the packet is
dropped.
Figure 5-12. TCP Packet Header
When packets have been successfully received, TCP sends an
acknowledgement. This is simply a packet that has the
acknowledgement number field filled in.
An acknowledgement number of 1000 indicates that all of the
data up to octet 1000 has been received. If the transmitting TCP
does not receive an acknowledgement in a reasonable amount of
time, the data is resent.
Switch Management and Operating Concepts
91