The 20-year-old Wales international has played nine Premier League games for Palace this season.
Former Eagles and Ipswich defender David Wright told BBC Radio Suffolk: "He's a very good player, very intelligent. He finds pockets of space in between lines very well.
"He picks the ball up and can break lines, he has a real good burst on him and can get at the back four. I think it will be a really good signing.
"He really impressed me when he came through as a young lad. He's small in terms of stature but is very quick and strong."
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