TCP Header (Cont)
Checksum (16 bits): covers the segment + pseudo header. Protection from mis-delivery.
Urgent pointer (16 bits): Points to the byte following urgent data. Lets receiver know how much data it should deliver right away.
Options (variable): Max segment size (does not include TCP header, default 536 bytes), Window scale factor, Selective Ack permitted, Timestamp, No-Op, End-of-options