TCP Packet

Explanation for a few header fields:
Src/Dst Ports - Source and destination port numbers used for TCP virtual addressing. (See discussion on network applications.)
Seqno - Sequence numbers used to reassemble packets into the right order.
Ack - Acknowledgement field used for indicating that a packet has made it, for example.
Cksum - Checksum used to verify whether the packet is dammaged.
Data - This is usually application data.