Syslog message data

each log message from my EdgeRouter as below:

Sep2500:10:3270.164.4.1Sep2507:10:34Mill-gatewaykernel: [block-default-A]IN=eth2OUT=eth1MAC=fc:ec:da:03:c0:ae:d4:ca:6d:73:97:dd:08:00src=138.68.229.70DST=70.164.6.19LEN=1452TOS=0x00PREC=0x00TTL=52ID=36149DFPROTO=TCPSPT=4444DPT=37458WINDOW=486RES=0x00ACKPSHURGP=0MARK=0x64800000

Is there any source that explain log message in details? (e.g I dont understand WINDOW, RES, MARK,...)

Thanks for your help.