vector clocks A, B, C, D are trying to set a date. Alice starts off (Wed, (A:1)) (Tue, (A:1,B:1)) (Tue, (A:1,B:1,D:1)) (Thu, (A:1,C:1)) -> Conflict (A:1,C:1) did not descencd from (A:1,B:1,D:1) Descend Each marker in vclk2 must have corresponding or greater marker than in vclk1 Resolve (Thu, (A:1, B:1, C:1, D:2)) problems width of vector clock grows with number of actors, or clients. keep growth under control with timestamp to prune old clocks revisited Actor Some entity in the system that makes an update to an object