NBA referee Dick Bavetta is working his 2,633rd consecutive game assignment, an ironman streak even longer than the one baseball Hall of Famer Cal Ripken Jr. complied.                                                                                                                        Bavetta officeiated the game Wednesday between the Knicks and Nets at Madison Square Garden,extending a streak durning which he has never missed an assignment since beginning his  career in 1975. He chalked up his streak to good health, a good work ethic he said all officials shared, and a fear of inconveniencing someone else if he had to take a day off.                                                                                                           The 74-year-old Bavetta has work 270 playoff ganes in 29 seasons, including 27 NBA Finals games,  three All-Star games and the 1992 Olympics.