How does Iago plot to have cassio demoted in act 2?

In Act 2, Iago devises a plan to have Cassio demoted from his position as Othello's lieutenant by getting him drunk and causing a brawl. He starts by convincing Cassio to drink heavily with him at a local tavern. As Cassio becomes increasingly intoxicated, Iago begins to goad him into making remarks that could be seen as disrespectful or insubordinate towards Othello. At the same time, Iago arranges for Roderigo, who is also resentful of Cassio's position, to be present and witness Cassio's behavior. When Cassio eventually becomes belligerent and engages in a drunken brawl with Roderigo, Iago orchestrates the situation so that Othello witnesses the commotion. Othello is angered and disappointed by Cassio's behavior and, as a result, demotes him from his position. Ultimately, Iago's plot to have Cassio demoted is successful and further sets in motion his larger plan to manipulate Othello and destroy his marriage to Desdemona.