Casson's volume conjecture for ideal triangulations

Let $M$ be a hyperbolic $3$-manifold with toroidal boundary and let $X$ be an ideal triangulation of $M$. Suppose the space of angle structures $\mathscr A_X$ is non-empty. Casson conjecture.

$$\sup\{\operatorname{Vol}(\alpha)\mid\alpha\in\mathscr A_X\}\leq\operatorname{Vol}(M).$$

This conjecture asserts that a non-geometric ideal triangulation cannot have angle-structure volume exceeding the hyperbolic volume of the manifold; the source gives no resolution.