Sussex bowl Durham out for 131 to complete a 132-run victory on day four at Chester-le-Street.
Ryan Pringle, Jack Burnham and Stuart Poynter will remain at Durham for 2018 after agreeing new deals.
Philip Salt's maiden first-class half-century on day three sees Sussex set Durham 264 to win at Chester-le-Street.
Graham Clark's unbeaten 73 ensures Durham close just 25 runs behind Sussex on day two at Chester-le-Street.
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With his contract up at the end of the season, Durham's record first-class wicket-taker Graham Onions ponders the future.
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How to get into cricket - physical exertion with a chess-like element in matches which range from half an hour to five days.