TCP segment structure 32 bits URG: urgent data countin (generally not used) source port #i dest port by bytes sequence number ACK: ACK of data valid acknowledgement number (not segments!) head not PSH: push data now Rused sf rcvr window size (generally not used checksum ptr urgent data bytes rcvr willing RST SYN. FIN Options(variable length) to accept connection estab (setup, teardown commands) applicaTion Internet data checksum (variable length) (as in UDP 3: Transport Layer 3b-23: Transport Layer 3b-2 TCP segment structure source port # dest port # 32 bits application data (variable length) sequence number acknowledgement number rcvr window size checksum ptr urgent data UAP RSF head len not used Options (variable length) URG: urgent data (generally not used) ACK: ACK # valid PSH: push data now (generally not used) RST, SYN, FIN: connection estab (setup, teardown commands) # bytes rcvr willing to accept counting by bytes of data (not segments!) Internet checksum (as in UDP)